Feeding mechanisms

@misc{openalexw2583380307,
    author = "Orton, JH",
    title = "The mode of feeding of Crepidula, with an account of the current-producing mechanism in the mantle cavity, and some remarks on the mode of feeding in gastropods and lamellibranchs.",
    year = "1912",
    booktitle = "Plymouth Marine Science Electronic Archive (The Marine Biological Association (MBA), Plymouth Marine Laboratory (PML) and the Sir Alister Hardy Foundation for Ocean Science (SAHFOS).)",
    openalex = "W2583380307"
}

SUMMARY The mode of feeding in Amphioxus is effected by– (1) The maintenance of a stream of water through the pharynx by rows of lateral cilia on the gill-bars. (2) The throwing out of mucus from the endostyle on to the gill-bars to serve for entrapping food-particles. (3) The collection of food-particles by rows of cilia on the pharyngeal surface of the gill-bars; these cilia woraSkip the foodparticles with mucus into cylindrical masses and transport such masses dorsally into the dorsal groove which carries the collected masses backwards into the digestive tract. Thus the ciliary mechanisms on a gill-bar of Amphioxus are exactly the same as those on the gill-filaments of some Lamellibranchs, as Pecten, and some Gastropods, as Crepidula. A subsidiary mode of food-collection is effected in the buccal cavity of Amphioxus by the ciliated tract known as the wheel organ, and Hatchek's pit, which supplies mucus for entrapping food-particles. These particles are passed on to the peri-pharyngeal bands which, conduct them in turn into the dorsal groove. The gill of Amphioxus functions mainly as a feeding organ and a water pump, and probably not at all as an organ for aerating the blood. The mode of feeding in Ascidians is almost exactly the same as that described above for Amphioxus. Food-collection, however, in Ascidians is effected by cilia on the papillae and similar outgrowths on the gill, and is also helped in some forms by transverse waving of the longitudinal bars, by which process the food is pushed as well as lashed towards the dorsal region of the pharynx.

@article{orton1913the,
    author = "Orton, J. H.",
    title = "The Ciliary Mechanisms on the Gill and the Mode of Feeding in Amphioxus, Ascidians, and Solenomya togata",
    year = "1913",
    journal = "Journal of the Marine Biological Association of the United Kingdom",
    abstract = "SUMMARY The mode of feeding in Amphioxus is effected by– (1) The maintenance of a stream of water through the pharynx by rows of lateral cilia on the gill-bars. (2) The throwing out of mucus from the endostyle on to the gill-bars to serve for entrapping food-particles. (3) The collection of food-particles by rows of cilia on the pharyngeal surface of the gill-bars; these cilia woraSkip the foodparticles with mucus into cylindrical masses and transport such masses dorsally into the dorsal groove which carries the collected masses backwards into the digestive tract. Thus the ciliary mechanisms on a gill-bar of Amphioxus are exactly the same as those on the gill-filaments of some Lamellibranchs, as Pecten, and some Gastropods, as Crepidula. A subsidiary mode of food-collection is effected in the buccal cavity of Amphioxus by the ciliated tract known as the wheel organ, and Hatchek's pit, which supplies mucus for entrapping food-particles. These particles are passed on to the peri-pharyngeal bands which, conduct them in turn into the dorsal groove. The gill of Amphioxus functions mainly as a feeding organ and a water pump, and probably not at all as an organ for aerating the blood. The mode of feeding in Ascidians is almost exactly the same as that described above for Amphioxus. Food-collection, however, in Ascidians is effected by cilia on the papillae and similar outgrowths on the gill, and is also helped in some forms by transverse waving of the longitudinal bars, by which process the food is pushed as well as lashed towards the dorsal region of the pharynx.",
    url = "https://doi.org/10.1017/s0025315400006706",
    doi = "10.1017/s0025315400006706",
    number = "1",
    openalex = "W2036476667",
    pages = "19-49",
    volume = "10"
}

@article{orton1913the1,
    author = "Orton, J. H",
    title = "The ciliary mechanisms on the gill and the mode of feeding in Amphioxus, Ascidians and Solenomyo togato",
    year = "1913",
    journal = "Journal of the Marine Biological Association of the United Kingdom, v. 10, p. 19-49",
    note = "talkorigins\_source = {true}; raw\_reference = {Orton, J. H., 1913, The ciliary mechanisms on the gill and the mode of feeding in Amphioxus, Ascidians and Solenomyo togato: Journal of the Marine Biological Association of the United Kingdom, v. 10, p. 19-49.}"
}

The results of the writer's investigations on the ciliary mechanisms on the gills of Mollusca and Amphioxus (1 and 2) gave rise to the suggestion that similar mechanisms might probably also occur in Brachiopods, for it is a well-known fact that Brachiopods—like some Molluscs and Amphioxus—feed on the smaller organisms which are to be found floating in the sea. Owing to the kindness of Dr. H. C. Williamson, of Aberdeen, I have been able to examine living Crania which were obtained by dredging in Loch Fyne, and living Terebratula have also been obtained from Naples. An investigation of the living gill-filaments—or lophophoral cirri, as they are frequently termed in this group—showed that the ciliary mechanisms on these filaments are essentially the same as those occurring on the gill-filaments of Amphioxus, Lamellibranchs, some Gastropods, and most Ascidians. As it was found that existing accounts of the mode of feeding in Brachiopods are vague and incomplete the following description of the process has been written.

@article{doi101017s0025315400007803,
    author = "ORTON, J. H.",
    title = "On Ciliary Mechanisms in Brachiopods and some Polychætes, with a Comparison of the Ciliary Mechanisms on the Gills of Molluscs, Protochordata, Brachiopods, and Cryptocephalous Polychætes, and an Account of the Endostyle of Crepidula and its Allies.",
    year = "1914",
    journal = "Journal of the Marine Biological Association of the United Kingdom",
    abstract = "The results of the writer's investigations on the ciliary mechanisms on the gills of Mollusca and Amphioxus (1 and 2) gave rise to the suggestion that similar mechanisms might probably also occur in Brachiopods, for it is a well-known fact that Brachiopods—like some Molluscs and Amphioxus—feed on the smaller organisms which are to be found floating in the sea. Owing to the kindness of Dr. H. C. Williamson, of Aberdeen, I have been able to examine living Crania which were obtained by dredging in Loch Fyne, and living Terebratula have also been obtained from Naples. An investigation of the living gill-filaments—or lophophoral cirri, as they are frequently termed in this group—showed that the ciliary mechanisms on these filaments are essentially the same as those occurring on the gill-filaments of Amphioxus, Lamellibranchs, some Gastropods, and most Ascidians. As it was found that existing accounts of the mode of feeding in Brachiopods are vague and incomplete the following description of the process has been written.",
    url = "https://doi.org/10.1017/s0025315400007803",
    doi = "10.1017/s0025315400007803",
    openalex = "W2083317234",
    references = "doi10108000222937008696201, doi101242jcss2552171, doi105281zenodo16214581, openalexw2583380307, openalexw622144126, orton1913the"
}

Abstract The mechanism of ciliary movement has been extensively studied from the morphological point of view, and although there is a general consensus of opinion as to the structure of the “ciliary apparatus,” there is no adequate account of the functions of the various parts of the mechanism. The material used for this work has been the gills of Mytilus edulis, and has already been described (Orton, 27). It is entirely due to the movement of the cilia that an efficient stream of water is kept passing on to the face of the gill, and that the food is moved up to the mouth of the animal. By means of carmine particles the existence of these currents is easily detected by the naked eye.

@article{doi101098rspb19220007,
    author = "Gray, J.",
    title = "The mechanism of ciliary movement",
    year = "1922",
    journal = "Proceedings of the Royal Society of London Series B Containing Papers of a Biological Character",
    abstract = "Abstract The mechanism of ciliary movement has been extensively studied from the morphological point of view, and although there is a general consensus of opinion as to the structure of the “ciliary apparatus,” there is no adequate account of the functions of the various parts of the mechanism. The material used for this work has been the gills of Mytilus edulis, and has already been described (Orton, 27). It is entirely due to the movement of the cilia that an efficient stream of water is kept passing on to the face of the gill, and that the food is moved up to the mouth of the animal. By means of carmine particles the existence of these currents is easily detected by the naked eye.",
    url = "https://doi.org/10.1098/rspb.1922.0007",
    doi = "10.1098/rspb.1922.0007",
    openalex = "W2163421883"
}

The food of the oyster consists of minute plants, plant detritus, and animals filtered from the water passing through the gills. In turbid waters much sand and other inorganic matter is accumulated along with the food particles. Bivalve molluscs which live in muddy waters possess highly complicated systems of ciliary tracts with the aid of which some separation of food from dirt does occur. In the oyster this mechanism consists partly in the gills, but mainly in the palps. Water borne particles on striking the gills are entangled in mucus and carried by the cilia of the gill epithelium: (a) ventrad to the groove formed by the ventral margins of the gill lamellae; or, (b) dorsad to the dorsal groove which passes along the bases of the gill filaments. In these grooves the mucus covered particles are whipped into slime strings which are then carried anteriorly to the posterior margins of the palps. At this point the material may either pass between the deeply grooved and heavily ciliated faces of the palps, and thence toward the mouth, or failing this is pushed off onto the mantle ventrad the edges of the palps. At intervals the material accumulated here is expelled from the mantle chamber by water forced out by quick contractions of the adductor muscle. When relatively large masses of collected particles are brought to the palps most of these are rejected and pass off onto the mantle as Kellogg has shown. A larger proportion of the material brought to the palps by the dorsal groove is accepted than that which arrives via the ventral groove. Observation shows that the larger particles, chiefly sand grains, are consigned mainly to the ventral groove.

@article{doi103181003797272184,
    author = "Nelson, Thurlow C.",
    title = "The mechanism of feeding in the oyster.",
    year = "1923",
    journal = "Experimental Biology and Medicine",
    abstract = "The food of the oyster consists of minute plants, plant detritus, and animals filtered from the water passing through the gills. In turbid waters much sand and other inorganic matter is accumulated along with the food particles. Bivalve molluscs which live in muddy waters possess highly complicated systems of ciliary tracts with the aid of which some separation of food from dirt does occur. In the oyster this mechanism consists partly in the gills, but mainly in the palps. Water borne particles on striking the gills are entangled in mucus and carried by the cilia of the gill epithelium: (a) ventrad to the groove formed by the ventral margins of the gill lamellae; or, (b) dorsad to the dorsal groove which passes along the bases of the gill filaments. In these grooves the mucus covered particles are whipped into slime strings which are then carried anteriorly to the posterior margins of the palps. At this point the material may either pass between the deeply grooved and heavily ciliated faces of the palps, and thence toward the mouth, or failing this is pushed off onto the mantle ventrad the edges of the palps. At intervals the material accumulated here is expelled from the mantle chamber by water forced out by quick contractions of the adductor muscle. When relatively large masses of collected particles are brought to the palps most of these are rejected and pass off onto the mantle as Kellogg has shown. A larger proportion of the material brought to the palps by the dorsal groove is accepted than that which arrives via the ventral groove. Observation shows that the larger particles, chiefly sand grains, are consigned mainly to the ventral groove.",
    url = "https://doi.org/10.3181/00379727-21-84",
    doi = "10.3181/00379727-21-84",
    openalex = "W2333935753"
}

@article{yonge1926ciliary,
    author = "Yonge, C. M.",
    title = "Ciliary Feeding Mechanisms in the Thecosomatous Pteropods.",
    year = "1926",
    journal = "Journal of the Linnean Society of London, Zoology",
    url = "https://doi.org/10.1111/j.1096-3642.1926.tb02174d.x",
    doi = "10.1111/j.1096-3642.1926.tb02174d.x",
    number = "245",
    openalex = "W2006877939",
    pages = "417-429",
    volume = "36"
}

Previous work on the structure and function of the alimentary system in the Lamellibranchs (Yonge (1923, 1925, 1926a, 1926b)) showed that the many peculiarities which they exhibit appear to be correlated with the highly developed ciliary feeding mechanisms on the gills and palps, as a result of the action of which only the smallest particles are passed into the œsophagus and stomach. This latter organ is concerned chiefly with sorting the particles, the larger ones being passed directly into the mid-gut and the smaller ones entering the ducts of the digestive diverticula (“liver” or “hepatopancreas”), where they are digested intracellularly. The food is largely of a vegetable nature and the digestive processes are concerned especially with the disposal of carbohydrates. There are present, free in the lumen of the gut, in the epithelium and in the surrounding tissues, great numbers of phagocytes which actively ingest food particles. Their presence, also, appears to be correlated with the finely divided nature of the food and the fact that, but for the digestive action of these phagocytes, particles of food, unless sufficiently fine to enter the ducts of the digestive diverticula, can only be digested if composed of starch or glycogen. The only extracellular digestive enzymes in the gut of the Lamellibranchs, namely, those set free by the dissolution in the stomach of the head of the crystalline style, act exclusively on these two carbohydrates. Owing to their deep water habitat, the Septibranchs have been little studied, but Pelseneer (1891,1911) and Plate (1897) have reported, on the evidence of the stomach contents, that they are carnivorous, while all investigators who have worked upon them have shown that in structure both the food collecting and digestive organs of the Septibranchs are quite distinct from those of the other Lamellibranchs. Gills are absent, their place being taken by the muscular septum, the labial palps are very small and the gut is provided with a muscular coating of a thickness unknown in the other Lamellibranchs, where the finely divided food is carried through the gut exclusively by ciliary activity, and so muscle for peristalsis is unnecessary.

@book{openalexw2059329361,
    author = "Yonge, C. M.",
    title = "Structure and function of the organs of feeding and digestion in the septibranchs, Cuspidaria and Poromya",
    year = "1928",
    booktitle = "ERA",
    abstract = "Previous work on the structure and function of the alimentary system in the Lamellibranchs (Yonge (1923, 1925, 1926a, 1926b)) showed that the many peculiarities which they exhibit appear to be correlated with the highly developed ciliary feeding mechanisms on the gills and palps, as a result of the action of which only the smallest particles are passed into the œsophagus and stomach. This latter organ is concerned chiefly with sorting the particles, the larger ones being passed directly into the mid-gut and the smaller ones entering the ducts of the digestive diverticula (“liver” or “hepatopancreas”), where they are digested intracellularly. The food is largely of a vegetable nature and the digestive processes are concerned especially with the disposal of carbohydrates. There are present, free in the lumen of the gut, in the epithelium and in the surrounding tissues, great numbers of phagocytes which actively ingest food particles. Their presence, also, appears to be correlated with the finely divided nature of the food and the fact that, but for the digestive action of these phagocytes, particles of food, unless sufficiently fine to enter the ducts of the digestive diverticula, can only be digested if composed of starch or glycogen. The only extracellular digestive enzymes in the gut of the Lamellibranchs, namely, those set free by the dissolution in the stomach of the head of the crystalline style, act exclusively on these two carbohydrates. Owing to their deep water habitat, the Septibranchs have been little studied, but Pelseneer (1891,1911) and Plate (1897) have reported, on the evidence of the stomach contents, that they are carnivorous, while all investigators who have worked upon them have shown that in structure both the food collecting and digestive organs of the Septibranchs are quite distinct from those of the other Lamellibranchs. Gills are absent, their place being taken by the muscular septum, the labial palps are very small and the gut is provided with a muscular coating of a thickness unknown in the other Lamellibranchs, where the finely divided food is carried through the gut exclusively by ciliary activity, and so muscle for peristalsis is unnecessary.",
    openalex = "W2059329361"
}

ABSTRACT The gills of Pecten have been the subject of much study, their structure being particularly described by Ridgewood (1903), Kellogg (1915), and Dakin (1909). However, there are structures of profound physiological importance present in the gills which apparently have so far remained unnoticed, while data are lacking concerning the neuromuscular mechanism which leads to a definite and orderly distribution of food material on the gill surfaces. Further, there are only casual references to the sensory reactions of the gill, without which an adequate understanding of their function is impossible. My own observations disagree with those of Kellogg (1915), who writes, ‘Extensive movements of the gills of Yoldia have been described by Drew (1899) and the writer (1890) in which organs there are well-developed muscles, but in the Pecten gill and others also capable of extensive movements such muscles are absent.’

@article{doi101242jcss273291365,
    author = "Setna, S. B.",
    title = "The Neuro-muscular mechanism of the gill of Pecten",
    year = "1930",
    journal = "Journal of Cell Science",
    abstract = "ABSTRACT The gills of Pecten have been the subject of much study, their structure being particularly described by Ridgewood (1903), Kellogg (1915), and Dakin (1909). However, there are structures of profound physiological importance present in the gills which apparently have so far remained unnoticed, while data are lacking concerning the neuromuscular mechanism which leads to a definite and orderly distribution of food material on the gill surfaces. Further, there are only casual references to the sensory reactions of the gill, without which an adequate understanding of their function is impossible. My own observations disagree with those of Kellogg (1915), who writes, ‘Extensive movements of the gills of Yoldia have been described by Drew (1899) and the writer (1890) in which organs there are well-developed muscles, but in the Pecten gill and others also capable of extensive movements such muscles are absent.’",
    url = "https://doi.org/10.1242/jcs.s2-73.291.365",
    doi = "10.1242/jcs.s2-73.291.365",
    openalex = "W2599841425"
}

ABSTRACT Seven main types of Lamellibranch gills and their food currents, together with a number of varieties, have been described. These are shown summarily and comprehensively in the composite diagram in Text-fig. 18.

@article{doi101242jcss279315375,
    author = "Atkins, D.",
    title = "On the Ciliary Mechanisms and Interrelationships of Lamellibranchs: PART III: Types of Lamellibranch Gills and their Food Currents",
    year = "1937",
    journal = "Journal of Cell Science",
    abstract = "ABSTRACT Seven main types of Lamellibranch gills and their food currents, together with a number of varieties, have been described. These are shown summarily and comprehensively in the composite diagram in Text-fig. 18.",
    url = "https://doi.org/10.1242/jcs.s2-79.315.375",
    doi = "10.1242/jcs.s2-79.315.375",
    openalex = "W2525963645",
    references = "doi101002jmor1050260403, doi101038112861a0, doi101093oxfordjournalsmollusa064002, doi1023071535718, doi1023071535734, doi1023071536130, doi1026515rzsiv19i21920162756, doi103181003797272184"
}

1. Ciliary currents concerned with rejection of sediment from the mantle cavity of pectinibranch Prosobranchia consist of A, currents carrying heavier particles to the inhalent opening; B, currents carrying medium particles across the floor of the mantle cavity; C, currents carrying fine particles over and between the gill filaments for later consolidation by the mucus from the hypobranchial gland. Material in currents B and C is rejected from the exhalent opening. 2. The feeding currents in ciliary feeding Prosobranchia represent modifications of these rejection currents. 3. In Vermetus novae-hollandiae currents B and C only are modified, material being passed to the mouth region, where it is mixed with mucus from the large pedal gland, by way of a food groove. 4. In Crepidula fornicata and other Calyptraeidae all currents are modified for feeding and there is an endostyle for mucus secretion.

@article{doi101017s0025315400012364,
    author = "Yonge, C. M.",
    title = "Evolution of Ciliary Feeding in the Prosobranchia, with an Account of Feeding in Capulus Ungaricus",
    year = "1938",
    journal = "Journal of the Marine Biological Association of the United Kingdom",
    abstract = "1. Ciliary currents concerned with rejection of sediment from the mantle cavity of pectinibranch Prosobranchia consist of A, currents carrying heavier particles to the inhalent opening; B, currents carrying medium particles across the floor of the mantle cavity; C, currents carrying fine particles over and between the gill filaments for later consolidation by the mucus from the hypobranchial gland. Material in currents B and C is rejected from the exhalent opening. 2. The feeding currents in ciliary feeding Prosobranchia represent modifications of these rejection currents. 3. In Vermetus novae-hollandiae currents B and C only are modified, material being passed to the mouth region, where it is mixed with mucus from the large pedal gland, by way of a food groove. 4. In Crepidula fornicata and other Calyptraeidae all currents are modified for feeding and there is an endostyle for mucus secretion.",
    url = "https://doi.org/10.1017/s0025315400012364",
    doi = "10.1017/s0025315400012364",
    openalex = "W1972197389"
}

ABSTRACT Certain Lamellibranchs have the latero-frontal tract composed of large complex ‘cilia’, here called eu-latero-frontal cilia, together with subsidiary ones, termed pro-latero-frontal cilia. This type of latero-frontal tract occurs in some or all of the three families of Protobranchs (there is some doubt as to the presence of pro-latero-frontal cilia in all the families), and in the Mytilidae and probably the Trigoniidae (fixation too imperfect for the identification of pro-latero-frontal cilia) among the Filibranchs, and in all the marine families of Eulamellibranchs obtainable at Plymouth, and in the fresh-water families, Dreissensiidae, Sphaeriidae, Unionidae, Mutelidae, and Aetheriidae. A fist of the species investigated is given. Other Lamellibranchs, which were previously considered as lacking latero-frontal cilia, have been found to possess small ones only, difficult of observation, termed micro-latero-frontal cilia. These occur in the Arcidae, Anomiidae, Pteriidae, Pectinidae, Spondylidae, Limidae, Pinnidae, and are inferred to be present in the Amussiidae, Vulsellidae, and Isognomonidae, in which eu-latero-frontal cilia are certainly absent. A list of the species examined is given. In one family, the Ostreidae, moderate-sized latero-frontal cilia, termed anomalous latero-frontal cilia, together with subsidiary ones, termed para-latero-frontal cilia are present. In bivalves having eu-latero-frontal cilia the arrangement of the various ciliary tracts, frontal, latero-frontal, and lateral is fairly constant, notable exceptions being a Protobranch, Nuculana, and a Filibranch, Trigonia. In bivalves having micro-latero-frontal cilia the arrangement of the various tracts seems more or less constant. The homology of the various types of latero-frontal cilia is discussed. The composition of the latero-frontal ciliated tracts has been found to be a stable character, and, as it is correlated with other characters, has taxonomic value. It is suggested that the variations in the constitution of the latero-frontal tracts tend to show that Ridewood’s (1903) classification does not express genetic affinities, as he himself conceded, nor does Pelseneer’s (1911) entirely, and that Pel-seneer’s order Filibranchia, and Ridewood’s orders Eleutherorhabda and Synaptorhabda are not monophyletic. Families possessing micro-latero-frontal cilia appear to be closely related, and form a group, which, with certain modifications, corresponds to ‘the Aviculidae and their allies’, or the ‘sedentary’ branch of Lamellibranchs, previously established by the palaeontologists, Jackson and Douville respectively, largely on shell characters. Thus the constitution of the latero-frontal tracts of the gill filaments supports the findings of palaeontologists with regard to this group. Unfortunately neither Jackson nor Douville proposed a formal name for the group. The relationship of forms with micro-latero-frontal cilia, and the evolution within the group of the eulamellibranchiate or synaptorhabdic gill are discussed. One family, the Ostreidae, which must be included on account of its relationship with either the Pteriacea or Pectinaeea (based on other evidence) has moderatesized, or anomalous latero-frontal cilia together with para-latero-frontal cilia. The anomalous latero-frontal cilia differ in certain respects from the large cilia characteristic of the majority of the Lamellibranchia, and are presumed to have arisen independently. Common characters of the group characterized by the possession of micro-latero-frontal cilia, in addition to the form of the latero-frontal cilia, are: (1) shell characters of the prodissoconch, Arcidae excepted; (2) byssal fixation; (3) considerable free posterior region to the gill axes; (4) considerable development of muscles in the gill axes, Ostreidae excepted; (5) method of division of the pallial cavity, Ostreidae excepted; (6) gills without a supra-axial extension to the outer demibranch; (7) presence of longitudinal currents at the free ventral edge of both inner and outer demibranchs; and of opposed frontal currents on all lamellae and frequently on the same filament, Pinnidae excepted; (8) absence of pallial sutures, Pinnidae and Ostreidae excepted; (9) inner fold of the mantle margin characteristically well developed, especially in swimming forms; (10) insertion of the retractor muscles of the mantle margin at a considerable distance from the shell edge, Arcidae excepted; (11) tendency for members, except the Ostreidae, to lie on the right valve; (12) abdominal sense organs on the posterior adductor muscle; and (13) intercommunication of the auricles, Anomiidae excepted., Two groups of the Lamellibranchia are proposed provisionally, namely Group I, Macrociliobranchia, including the orders Protobranchia (Pelseneer), Filibranchia (emended to include only the Mytilacea and Trigoniacea), Eulamellibranchia (Pelseneer, 1911), and Septibranchia (Pelseneer); and Group II, Microciliobranchia, with the order Pseudolamellibranchia, emended to include the sub-orders Arcacea (excluding the Trigoniidae), Anomiacea, Pteriacea, Pectinacea, and Ostreacea. The Macrociliobranchia will need revision, for it is very probable that the Filibranchia (emended), if not the Eulamellibranchia, are still not monophyletic.

@article{doi101242jcss280319345,
    author = "Atkins, D.",
    title = "On the Ciliary Mechanisms and Interrelationships of Lamellibranchs.: PART VII: Latero-frontal Cilia of the Gill Filaments and their Phylogenetic Value",
    year = "1938",
    journal = "Journal of Cell Science",
    abstract = "ABSTRACT Certain Lamellibranchs have the latero-frontal tract composed of large complex ‘cilia’, here called eu-latero-frontal cilia, together with subsidiary ones, termed pro-latero-frontal cilia. This type of latero-frontal tract occurs in some or all of the three families of Protobranchs (there is some doubt as to the presence of pro-latero-frontal cilia in all the families), and in the Mytilidae and probably the Trigoniidae (fixation too imperfect for the identification of pro-latero-frontal cilia) among the Filibranchs, and in all the marine families of Eulamellibranchs obtainable at Plymouth, and in the fresh-water families, Dreissensiidae, Sphaeriidae, Unionidae, Mutelidae, and Aetheriidae. A fist of the species investigated is given. Other Lamellibranchs, which were previously considered as lacking latero-frontal cilia, have been found to possess small ones only, difficult of observation, termed micro-latero-frontal cilia. These occur in the Arcidae, Anomiidae, Pteriidae, Pectinidae, Spondylidae, Limidae, Pinnidae, and are inferred to be present in the Amussiidae, Vulsellidae, and Isognomonidae, in which eu-latero-frontal cilia are certainly absent. A list of the species examined is given. In one family, the Ostreidae, moderate-sized latero-frontal cilia, termed anomalous latero-frontal cilia, together with subsidiary ones, termed para-latero-frontal cilia are present. In bivalves having eu-latero-frontal cilia the arrangement of the various ciliary tracts, frontal, latero-frontal, and lateral is fairly constant, notable exceptions being a Protobranch, Nuculana, and a Filibranch, Trigonia. In bivalves having micro-latero-frontal cilia the arrangement of the various tracts seems more or less constant. The homology of the various types of latero-frontal cilia is discussed. The composition of the latero-frontal ciliated tracts has been found to be a stable character, and, as it is correlated with other characters, has taxonomic value. It is suggested that the variations in the constitution of the latero-frontal tracts tend to show that Ridewood’s (1903) classification does not express genetic affinities, as he himself conceded, nor does Pelseneer’s (1911) entirely, and that Pel-seneer’s order Filibranchia, and Ridewood’s orders Eleutherorhabda and Synaptorhabda are not monophyletic. Families possessing micro-latero-frontal cilia appear to be closely related, and form a group, which, with certain modifications, corresponds to ‘the Aviculidae and their allies’, or the ‘sedentary’ branch of Lamellibranchs, previously established by the palaeontologists, Jackson and Douville respectively, largely on shell characters. Thus the constitution of the latero-frontal tracts of the gill filaments supports the findings of palaeontologists with regard to this group. Unfortunately neither Jackson nor Douville proposed a formal name for the group. The relationship of forms with micro-latero-frontal cilia, and the evolution within the group of the eulamellibranchiate or synaptorhabdic gill are discussed. One family, the Ostreidae, which must be included on account of its relationship with either the Pteriacea or Pectinaeea (based on other evidence) has moderatesized, or anomalous latero-frontal cilia together with para-latero-frontal cilia. The anomalous latero-frontal cilia differ in certain respects from the large cilia characteristic of the majority of the Lamellibranchia, and are presumed to have arisen independently. Common characters of the group characterized by the possession of micro-latero-frontal cilia, in addition to the form of the latero-frontal cilia, are: (1) shell characters of the prodissoconch, Arcidae excepted; (2) byssal fixation; (3) considerable free posterior region to the gill axes; (4) considerable development of muscles in the gill axes, Ostreidae excepted; (5) method of division of the pallial cavity, Ostreidae excepted; (6) gills without a supra-axial extension to the outer demibranch; (7) presence of longitudinal currents at the free ventral edge of both inner and outer demibranchs; and of opposed frontal currents on all lamellae and frequently on the same filament, Pinnidae excepted; (8) absence of pallial sutures, Pinnidae and Ostreidae excepted; (9) inner fold of the mantle margin characteristically well developed, especially in swimming forms; (10) insertion of the retractor muscles of the mantle margin at a considerable distance from the shell edge, Arcidae excepted; (11) tendency for members, except the Ostreidae, to lie on the right valve; (12) abdominal sense organs on the posterior adductor muscle; and (13) intercommunication of the auricles, Anomiidae excepted., Two groups of the Lamellibranchia are proposed provisionally, namely Group I, Macrociliobranchia, including the orders Protobranchia (Pelseneer), Filibranchia (emended to include only the Mytilacea and Trigoniacea), Eulamellibranchia (Pelseneer, 1911), and Septibranchia (Pelseneer); and Group II, Microciliobranchia, with the order Pseudolamellibranchia, emended to include the sub-orders Arcacea (excluding the Trigoniidae), Anomiacea, Pteriacea, Pectinacea, and Ostreacea. The Macrociliobranchia will need revision, for it is very probable that the Filibranchia (emended), if not the Eulamellibranchia, are still not monophyletic.",
    url = "https://doi.org/10.1242/jcs.s2-80.319.345",
    doi = "10.1242/jcs.s2-80.319.345",
    openalex = "W1898333710",
    references = "doi101093oxfordjournalsmollusa064002, doi101098rspb19220007, doi101242jcss273291365, doi105962bhltitle16341, doi105962bhltitle83559, openalexw2059329361, openalexw2221217307, openalexw2417875044, openalexw3184762063, orton1913the"
}

@article{jørgensen1949feedingrates,
    author = "JØRGENSEN, C. BARKER",
    title = "Feeding-Rates of Sponges, Lamellibranchs and Ascidians",
    year = "1949",
    journal = "Nature",
    url = "https://doi.org/10.1038/163912a0",
    doi = "10.1038/163912a0",
    number = "4154",
    openalex = "W2090263512",
    pages = "912-912",
    volume = "163",
    references = "doi101111j174817161943tb02058x, doi1023071537654"
}

@article{dodd1950ciliary,
    author = "DODD, J. M.",
    title = "Ciliary Feeding Mechanisms in Anuran Larvæ",
    year = "1950",
    journal = "Nature",
    url = "https://doi.org/10.1038/165283a0",
    doi = "10.1038/165283a0",
    number = "4190",
    openalex = "W2075230306",
    pages = "283-283",
    volume = "165",
    references = "doi101002jmor1050770204, doi101017s0080456800035584, jørgensen1949feedingrates"
}

SUMMARY A description is given of the structure and function of the feeding organs in various aquatic invertebrate filter feeders (suspension feeders), especially in such forms as have also been used in experiments on feeding rate, on efficiency of feeding organs in retaining particles of different sizes, etc. Sponges ingest indiscriminately particles with and without food value. Particles that are too big to enter through the pores of the surface may be phagocytized by the cells of the epithelium. In primitive sponges with large flagellated chambers intake and digestion of food particles is mainly performed by the choanocytes, whereas in highly developed sponges a large part of the particles are phagocytized by the walls of the incurrent canals before they reach the flagellated chambers. The tube‐living polychaete Serpulimorpha are suspension feeders. They feed by means of the ciliated branchial crown which surrounds the mouth. The burrowing, tube‐living Chaetopterus variopedatus feeds by filtering water through a mucus bag. A similar feeding method has also been described in Nereis diversicolor. Within the Echiuroidea Urechis caupo likewise feeds by means of a mucus net. The net is attached to the walls of the burrow in which the worm is living. In suspension‐feeding lamellibranchs the gills both propel and filter the water. Most investigators assume that the filtration is performed mainly by the laterofrontal cilia of the gill filaments, whereas MacGinitie states that during normal feeding, water is filtered through sheets of mucus which cover the surfaces of the gills. A variety of sorting devices, especially on the gills, are developed in different lamellibranchs. Sorting is performed according to size, shape and density of particles. Qualitative sorting has, however, also been demonstrated in the oyster. Filter‐feeding habits have been adopted independently by several gastropod families, both sessile and free‐living. As in the lamellibranchs, it is generally the cleansing mechanisms of the unmodified gill and of the mantle cavity that have been developed into food‐collecting mechanisms. In Crepidula and other highly specialized suspension‐feeding Prosobranchia the filtering of the water is performed by mucus sheets, which are continuously carried over the gill surface. In vermetids from still water the importance of the gill as a food‐collecting organ is reduced, but long mucus threads, produced by the pedal gland and floating freely in the water, are used to catch food particles which adhere to the mucus. In suspension‐feeding copepods a filter chamber is enclosed between the ventral body wall and the maxillae which project ventroanteriorly. The maxillae carry long plumose setae extending antero‐medially towards the mouth and forming the lateral walls of the filter chamber. The feeding currents are produced chiefly by rapid vibratory movements of the antennae. Most if not all of the filter‐feeding copepods can feed in other ways too, e.g. by scraping or by catching larger food. Tunicates possessing a branchial sac feed by means of mucus sheets, which are produced by the endostyle and continuously carried across the inside of the branchial wall towards the dorsal lamina. Here the sheets are rolled up into a food string which is transported down into the oesophagus. The ciliary through‐current is thus filtered by the mucus sheets. In Doliolida and Salpida, where the branchial sac is reduced or absent, the feeding mucus is formed into a net which is supported by the peripharyngeal grooves. The net is continuously carried backwards, especially by the cilia of the oesophagus which twist the mucus net into a string. In Salpida the through‐current is produced by contractions of circular muscles in the body wall. Most appendicularians do not directly inspire the surrounding water, but concentrate the suspended food particles in external trap‐like filters. Amphioxus feeds similarly to tunicates, with well‐developed branchial sac. Sponges effectively strain 0–5‐1μ1 particles from the feeding current. The mucus nets of Chaetopterus and Urechis retain large protein molecules completely. Adsorption to the mucus is of negligible importance for the retention of proteins. In Mytilus and Ostrea the critical particle size was found to range round about 1–3μ. In different species and stages of filter‐feeding copepods the minimum distances between the barbs of the setae of the filters vary from 1–5 to 8‐2μ. Ascidians retain completely particles of 1 μ, but only inefficiently proteins such as haemoglobin and haemocyanin. Measurements of filtration rates in sponges vary from 45 to 170 ml./hr./mg. nitrogen. Pressures in the flagellated chambers range from o‐8 mm. water in primitive species with large chambers, to a maximum of 4 mm. in species with small spherical chambers. Veligers of O. edulis have been found to filter on an average 800 ml./hr./mg. nitrogen; adult O. virginica 19–48 ml./hr./mg. nitrogen; young Mytilus edulis 120–160 ml.; and medium‐sized to large M. californianus 5–8 ml./hr./mg. nitrogen. The optimum temperature for water propulsion in M. californianus varies with the mean temperature of the surroundings. The mussels maintain under natural conditions about the same pumping rate in all localities irrespective of the differences which may exist in mean temperatures. A quantity of o‐1 g./l. of silt, calcium carbonate, or kaolin depressed the pumping rate of Ostrea virginica by about 50%, and 1 g./l. by more than 80%. Sperm of O. virginica carries a substance, diantlin, which stimulates the flow rate. A correlation has been observed in O. virginica between rate of water propulsion and the concentration of a carbohydrate factor in the water. This factor is stated to be probably a mixture of rhamnoside and dehydro‐ascorbic acid. It is found in amounts ranging from 2 to 100 mg./l. Calanus fintnarchicus filters some 20 ml./hr./mg. dry weight, and Centropages hamatus some 85 ml./hr./mg. dry weight. Calanus is about 20 times as big as Centropages. Ciona intestinalis, weighing about 2–6 g., filtered no ml./hr./mg. nitrogen, and Molgula sp. (0–5 g.) 150 ml./hr./mg. nitrogen. Urechis feeds on an average about 13 min./hr. Lamellibranchs, copepods, and probably also sponges and ascidians, feed practically continuously when food is present in the water. Most sponges, lamellibranchs and ascidians filter 13–16 1. of water for each millilitre of oxygen taken up, and copepods 4–9 1. Suspension feeders, which filter about 15 l./ml. oxygen uptake, can cover their food requirements for maintenance and optimal growth when 0–15‐0‐20 mg. of utilizable organic matter is available per litre of water. The amount of organic matter in solution in unpolluted sea water is fairly constant, the measurements varying from 2‐2 to 4–6 mg./l. in different localities and depths. About one‐third to one‐half of the dissolved matter is ‘protein’. This fraction of the organic matter in the sea is probably not accessible as food to the filter feeders. Phytoplankton organic matter in sea water varies from zero to more than 3 mg./l. Representative seasonal variations of coastal waters are 60–1160/μg./l. in the English Channel, 30–480μ/1. on Georges Bank, 6–920μg./l. off Miami, Florida. The amounts of organic matter contained in the phytoplankton in coastal waters, where all the suspension feeders so far investigated live, are therefore sufficient to cover the food requirements of suspension feeders during parts of the year. The amounts of phytoplankton may be even 10–20 times the amounts required for optimal growth, if 151. are filtered for each millilitre of oxygen intake. When production is low, however, the amounts of phytoplankton may be too small to provide enough food even for maintenance. During such periods detritus may be of importance as a food source. Suspension feeders living at great depths in the oceans, where the average content of particulate detritus is about 25 jug./l., must be able to filter some 100 1. of water or more for each millilitre of oxygen consumed.

@article{doi101111j1469185x1955tb01546x,
    author = "Jørgensen, Christian",
    title = "QUANTITATIVE ASPECTS OF FILTER FEEDING IN INVERTEBRATES",
    year = "1955",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "SUMMARY A description is given of the structure and function of the feeding organs in various aquatic invertebrate filter feeders (suspension feeders), especially in such forms as have also been used in experiments on feeding rate, on efficiency of feeding organs in retaining particles of different sizes, etc. Sponges ingest indiscriminately particles with and without food value. Particles that are too big to enter through the pores of the surface may be phagocytized by the cells of the epithelium. In primitive sponges with large flagellated chambers intake and digestion of food particles is mainly performed by the choanocytes, whereas in highly developed sponges a large part of the particles are phagocytized by the walls of the incurrent canals before they reach the flagellated chambers. The tube‐living polychaete Serpulimorpha are suspension feeders. They feed by means of the ciliated branchial crown which surrounds the mouth. The burrowing, tube‐living Chaetopterus variopedatus feeds by filtering water through a mucus bag. A similar feeding method has also been described in Nereis diversicolor. Within the Echiuroidea Urechis caupo likewise feeds by means of a mucus net. The net is attached to the walls of the burrow in which the worm is living. In suspension‐feeding lamellibranchs the gills both propel and filter the water. Most investigators assume that the filtration is performed mainly by the laterofrontal cilia of the gill filaments, whereas MacGinitie states that during normal feeding, water is filtered through sheets of mucus which cover the surfaces of the gills. A variety of sorting devices, especially on the gills, are developed in different lamellibranchs. Sorting is performed according to size, shape and density of particles. Qualitative sorting has, however, also been demonstrated in the oyster. Filter‐feeding habits have been adopted independently by several gastropod families, both sessile and free‐living. As in the lamellibranchs, it is generally the cleansing mechanisms of the unmodified gill and of the mantle cavity that have been developed into food‐collecting mechanisms. In Crepidula and other highly specialized suspension‐feeding Prosobranchia the filtering of the water is performed by mucus sheets, which are continuously carried over the gill surface. In vermetids from still water the importance of the gill as a food‐collecting organ is reduced, but long mucus threads, produced by the pedal gland and floating freely in the water, are used to catch food particles which adhere to the mucus. In suspension‐feeding copepods a filter chamber is enclosed between the ventral body wall and the maxillae which project ventroanteriorly. The maxillae carry long plumose setae extending antero‐medially towards the mouth and forming the lateral walls of the filter chamber. The feeding currents are produced chiefly by rapid vibratory movements of the antennae. Most if not all of the filter‐feeding copepods can feed in other ways too, e.g. by scraping or by catching larger food. Tunicates possessing a branchial sac feed by means of mucus sheets, which are produced by the endostyle and continuously carried across the inside of the branchial wall towards the dorsal lamina. Here the sheets are rolled up into a food string which is transported down into the oesophagus. The ciliary through‐current is thus filtered by the mucus sheets. In Doliolida and Salpida, where the branchial sac is reduced or absent, the feeding mucus is formed into a net which is supported by the peripharyngeal grooves. The net is continuously carried backwards, especially by the cilia of the oesophagus which twist the mucus net into a string. In Salpida the through‐current is produced by contractions of circular muscles in the body wall. Most appendicularians do not directly inspire the surrounding water, but concentrate the suspended food particles in external trap‐like filters. Amphioxus feeds similarly to tunicates, with well‐developed branchial sac. Sponges effectively strain 0–5‐1μ1 particles from the feeding current. The mucus nets of Chaetopterus and Urechis retain large protein molecules completely. Adsorption to the mucus is of negligible importance for the retention of proteins. In Mytilus and Ostrea the critical particle size was found to range round about 1–3μ. In different species and stages of filter‐feeding copepods the minimum distances between the barbs of the setae of the filters vary from 1–5 to 8‐2μ. Ascidians retain completely particles of 1 μ, but only inefficiently proteins such as haemoglobin and haemocyanin. Measurements of filtration rates in sponges vary from 45 to 170 ml./hr./mg. nitrogen. Pressures in the flagellated chambers range from o‐8 mm. water in primitive species with large chambers, to a maximum of 4 mm. in species with small spherical chambers. Veligers of O. edulis have been found to filter on an average 800 ml./hr./mg. nitrogen; adult O. virginica 19–48 ml./hr./mg. nitrogen; young Mytilus edulis 120–160 ml.; and medium‐sized to large M. californianus 5–8 ml./hr./mg. nitrogen. The optimum temperature for water propulsion in M. californianus varies with the mean temperature of the surroundings. The mussels maintain under natural conditions about the same pumping rate in all localities irrespective of the differences which may exist in mean temperatures. A quantity of o‐1 g./l. of silt, calcium carbonate, or kaolin depressed the pumping rate of Ostrea virginica by about 50\%, and 1 g./l. by more than 80\%. Sperm of O. virginica carries a substance, diantlin, which stimulates the flow rate. A correlation has been observed in O. virginica between rate of water propulsion and the concentration of a carbohydrate factor in the water. This factor is stated to be probably a mixture of rhamnoside and dehydro‐ascorbic acid. It is found in amounts ranging from 2 to 100 mg./l. Calanus fintnarchicus filters some 20 ml./hr./mg. dry weight, and Centropages hamatus some 85 ml./hr./mg. dry weight. Calanus is about 20 times as big as Centropages. Ciona intestinalis, weighing about 2–6 g., filtered no ml./hr./mg. nitrogen, and Molgula sp. (0–5 g.) 150 ml./hr./mg. nitrogen. Urechis feeds on an average about 13 min./hr. Lamellibranchs, copepods, and probably also sponges and ascidians, feed practically continuously when food is present in the water. Most sponges, lamellibranchs and ascidians filter 13–16 1. of water for each millilitre of oxygen taken up, and copepods 4–9 1. Suspension feeders, which filter about 15 l./ml. oxygen uptake, can cover their food requirements for maintenance and optimal growth when 0–15‐0‐20 mg. of utilizable organic matter is available per litre of water. The amount of organic matter in solution in unpolluted sea water is fairly constant, the measurements varying from 2‐2 to 4–6 mg./l. in different localities and depths. About one‐third to one‐half of the dissolved matter is ‘protein’. This fraction of the organic matter in the sea is probably not accessible as food to the filter feeders. Phytoplankton organic matter in sea water varies from zero to more than 3 mg./l. Representative seasonal variations of coastal waters are 60–1160/μg./l. in the English Channel, 30–480μ/1. on Georges Bank, 6–920μg./l. off Miami, Florida. The amounts of organic matter contained in the phytoplankton in coastal waters, where all the suspension feeders so far investigated live, are therefore sufficient to cover the food requirements of suspension feeders during parts of the year. The amounts of phytoplankton may be even 10–20 times the amounts required for optimal growth, if 151. are filtered for each millilitre of oxygen intake. When production is low, however, the amounts of phytoplankton may be too small to provide enough food even for maintenance. During such periods detritus may be of importance as a food source. Suspension feeders living at great depths in the oceans, where the average content of particulate detritus is about 25 jug./l., must be able to filter some 100 1. of water or more for each millilitre of oxygen consumed.",
    url = "https://doi.org/10.1111/j.1469-185x.1955.tb01546.x",
    doi = "10.1111/j.1469-185x.1955.tb01546.x",
    openalex = "W2069246071",
    references = "doi101002jmor1050260403, doi101017s0025315400007803, doi101017s0025315400009681, doi101017s002531540001170x, doi101017s0025315400052875, doi101038165734b0, doi101086399023, doi101242jcss279315375, doi101242jcss280319345, doi1023071438975, doi1023071537438, jørgensen1949feedingrates, openalexw1579846885, openalexw3170347765, orton1913the, yonge1926ciliary"
}

@article{atkins1956ciliary,
    author = "ATKINS, D.",
    title = "Ciliary Feeding Mechanisms of Brachiopods",
    year = "1956",
    journal = "Nature",
    url = "https://doi.org/10.1038/177706a0",
    doi = "10.1038/177706a0",
    number = "4511",
    openalex = "W1980010812",
    pages = "706-707",
    volume = "177",
    references = "doi101017s0025315400007803, doi101038164367b0"
}

Summary Large living specimens of Lingula unguis (L.) were collected below lowwater mark of neap‐tides in the Johore Strait, Singapore. The location of the inhalant and exhalant water currents, the subdivision of the mantle chamber into one median exhalant and two lateral inhalant chambers, and the mode of formation of the water currents by ciliary action are described. The structure, and also the ciliary feeding and cleansing mechanisms, of the brachia and of the cirri are described. The frontal cilia on the adlabial cirri are arranged in five adjacent antagonistic longitudinal tracts. Three tracts beat towards the brachial groove and alternate with two tracts beating in the opposite direction. The frontal cilia on the ablabial cirri are arranged in three tracts, a median tract beating towards the brachial groove flanked by tracts beating away from it. The lateral tracts on both series of cirri beat transversely across the cirri from the frontal surface towards the abfrontal surface; the abfrontal tracts beat distally. Lingula unguis is adapted for life on sheltered muddy beaches in its mode of feeding. Small quantities of fine particles are accepted, larger quantities of finely divided matter and coarse particles are rejected. To a considerable extent Lingula selects water‐borne particles, which are not bound into mucous threads until they reach the safety of the brachial groove. Food particles were collected (a) along the outer margins of the brachial fold, (b) on those frontal tracts of both adlabial and ablabial cirri, that beat towards the brachial groove, and (c) by mass movement of water‐borne particles into the brachial groove. All food particles accepted into the brachial groove were carried to the mouth. Due to different conditions in Werent parts of the inhalant stream of water, groups of cirri may operate in unison to effect the acceptance of food particles in one part of a brachium while at the same time other cirri cause the rejection of material. Rejection mechanisms include (1) dislodgment of particles already entangled on the frontal surface by strong adverse water currents, (2) themass movement of water‐borne particles away from the brachial groove, (3) the shutting of the brachial groove by the brachial fold, and (4) the rejectionof large objects by muscular movements of the cirri. The ciliary cleansing mechanisms of the mantle and of the body wall are described. Comparisons are made with Crania and with Neothyris.

@article{chuang1956the,
    author = "CHUANG, S. H.",
    title = "THE CILIARY FEEDING MECHANISMS OF LINGULA UNGUIS (L.) (BRACHIOPODA)",
    year = "1956",
    journal = "Proceedings of the Zoological Society of London",
    abstract = "Summary Large living specimens of Lingula unguis (L.) were collected below lowwater mark of neap‐tides in the Johore Strait, Singapore. The location of the inhalant and exhalant water currents, the subdivision of the mantle chamber into one median exhalant and two lateral inhalant chambers, and the mode of formation of the water currents by ciliary action are described. The structure, and also the ciliary feeding and cleansing mechanisms, of the brachia and of the cirri are described. The frontal cilia on the adlabial cirri are arranged in five adjacent antagonistic longitudinal tracts. Three tracts beat towards the brachial groove and alternate with two tracts beating in the opposite direction. The frontal cilia on the ablabial cirri are arranged in three tracts, a median tract beating towards the brachial groove flanked by tracts beating away from it. The lateral tracts on both series of cirri beat transversely across the cirri from the frontal surface towards the abfrontal surface; the abfrontal tracts beat distally. Lingula unguis is adapted for life on sheltered muddy beaches in its mode of feeding. Small quantities of fine particles are accepted, larger quantities of finely divided matter and coarse particles are rejected. To a considerable extent Lingula selects water‐borne particles, which are not bound into mucous threads until they reach the safety of the brachial groove. Food particles were collected (a) along the outer margins of the brachial fold, (b) on those frontal tracts of both adlabial and ablabial cirri, that beat towards the brachial groove, and (c) by mass movement of water‐borne particles into the brachial groove. All food particles accepted into the brachial groove were carried to the mouth. Due to different conditions in Werent parts of the inhalant stream of water, groups of cirri may operate in unison to effect the acceptance of food particles in one part of a brachium while at the same time other cirri cause the rejection of material. Rejection mechanisms include (1) dislodgment of particles already entangled on the frontal surface by strong adverse water currents, (2) themass movement of water‐borne particles away from the brachial groove, (3) the shutting of the brachial groove by the brachial fold, and (4) the rejectionof large objects by muscular movements of the cirri. The ciliary cleansing mechanisms of the mantle and of the body wall are described. Comparisons are made with Crania and with Neothyris.",
    url = "https://doi.org/10.1111/j.1096-3642.1956.tb00468.x",
    doi = "10.1111/j.1096-3642.1956.tb00468.x",
    number = "2",
    openalex = "W1983606715",
    pages = "167-189",
    volume = "127",
    references = "doi101017s0025315400007803, doi101098rstl18580034, doi101126science16414901b, doi101242jcss279314181, doi101242jcss279315375, doi101242jcss280319345, doi101508300037918, doi105479si00963801572314261, doi105962bhltitle14915, doi105962bhltitle56810"
}

The Megathyridae Allan 1940 is a family of brachiopods in which the adult lophophore is of simple design, bilobed (schizolophous) in Argyrotheca and four-lobed (ptycholophous) in Megathyris. Little is known of feeding mechanisms in the family. H´erouard (1877), finding it difficult or impossible to observe the feeding currents of living brachiopods, constructed artificial lophophores of lead piping with fine perforations corresponding to the position of attachment of the filaments. Through these he forced water, while the artificial lophophores were immersed in a bowl of water. He assumed, wrongly, that the result would be similar to the action produced by cilia vibrating in water. His remarks on the working of an artificial lophophore resembling that of Megathyris (= Argiope) were transcribed by Morgan (1883) without making it clear that the observations were not his own and were not made on the living animal. Apart from HÉerouard's work on artificial lophophores, the only reference to feeding in a member of the Megathyridae is that of Shipley (1883) who merely mentioned that in Argyrotheca the arrangement of the cilia is adapted to bring particles into the ciliated groove and thence to the mouth. Thus an examination of the method of feeding of the Megathyridae was considered desirable, and was made possible in the first instance through the kindness of M. Paul Bourgis, then, in 1955, on the staff of the Laboratoire Arago, Banyuls-surMer. He sent two small consignments of living Argyrotheca cor data (Risso), A. cuneata (Risso) and Megathyris detruncata (Gmelin), received on the 28 October and 24 December 1955.

@article{doi101017s0025315400013485,
    author = "Atkins, D.",
    title = "The ciliary feeding mechanism of the Megathyridae (Brachiopoda), and the growth stages of the lophophore",
    year = "1960",
    journal = "Journal of the Marine Biological Association of the United Kingdom",
    abstract = "The Megathyridae Allan 1940 is a family of brachiopods in which the adult lophophore is of simple design, bilobed (schizolophous) in Argyrotheca and four-lobed (ptycholophous) in Megathyris. Little is known of feeding mechanisms in the family. H´erouard (1877), finding it difficult or impossible to observe the feeding currents of living brachiopods, constructed artificial lophophores of lead piping with fine perforations corresponding to the position of attachment of the filaments. Through these he forced water, while the artificial lophophores were immersed in a bowl of water. He assumed, wrongly, that the result would be similar to the action produced by cilia vibrating in water. His remarks on the working of an artificial lophophore resembling that of Megathyris (= Argiope) were transcribed by Morgan (1883) without making it clear that the observations were not his own and were not made on the living animal. Apart from HÉerouard's work on artificial lophophores, the only reference to feeding in a member of the Megathyridae is that of Shipley (1883) who merely mentioned that in Argyrotheca the arrangement of the cilia is adapted to bring particles into the ciliated groove and thence to the mouth. Thus an examination of the method of feeding of the Megathyridae was considered desirable, and was made possible in the first instance through the kindness of M. Paul Bourgis, then, in 1955, on the staff of the Laboratoire Arago, Banyuls-surMer. He sent two small consignments of living Argyrotheca cor data (Risso), A. cuneata (Risso) and Megathyris detruncata (Gmelin), received on the 28 October and 24 December 1955.",
    url = "https://doi.org/10.1017/s0025315400013485",
    doi = "10.1017/s0025315400013485",
    openalex = "W2009344834",
    references = "atkins1956ciliary, doi101002jmor1051050302, doi101017s0025315400006123, doi101017s0025315400015630, doi101038122472b0, doi101111j109636421958tb00702x, doi105479si00963801572314261, openalexw2172375356, openalexw634017756, openalexw637354097"
}

All major types of lophophore in branehiopods, except the ptyeholophe, are represented among the growth stages of the five species described here. The basic ciliary mechanisms are uniform, and similar to those known in other species. The mantle cavity is always divided by the lophophore into inhalant and exhalant chambers with separate apertures; but the arrangement may change radically during ontogeny with the increasing complexity of the lophophore, which is attributed to a dimensional relation between food-collecting capacity and metabolic requirements. The limited variety of lophophoral arrangements is taken to reflect an inherent limitation imposed by the basic structure and function of lophophores. The feeding mechanisms are compared briefly with those of other filter-feeding animals.

@article{doi101111j109636421962tb01626x,
    author = "Rudwick, Martin J. S.",
    title = "Filter-feeding mechanisms in some brachiopods from New Zealand",
    year = "1962",
    journal = "Journal of the Linnean Society of London Zoology",
    abstract = "All major types of lophophore in branehiopods, except the ptyeholophe, are represented among the growth stages of the five species described here. The basic ciliary mechanisms are uniform, and similar to those known in other species. The mantle cavity is always divided by the lophophore into inhalant and exhalant chambers with separate apertures; but the arrangement may change radically during ontogeny with the increasing complexity of the lophophore, which is attributed to a dimensional relation between food-collecting capacity and metabolic requirements. The limited variety of lophophoral arrangements is taken to reflect an inherent limitation imposed by the basic structure and function of lophophores. The feeding mechanisms are compared briefly with those of other filter-feeding animals.",
    url = "https://doi.org/10.1111/j.1096-3642.1962.tb01626.x",
    doi = "10.1111/j.1096-3642.1962.tb01626.x",
    openalex = "W2009022303",
    references = "atkins1956ciliary, doi101017s0016756800059173, doi101017s0016756800061720, doi101017s0025315400007803, doi101017s0025315400013485, doi101017s0025315400015630, doi1010381911021a0, doi101098rstl18580034, doi101126science671741491a, openalexw634017756, openalexw637354097"
}

Larvae of the neotropical frogs Phyllomedusa are distinctive in that they feed normally in mid‐water on phytoplankton, maintaining neutral buoyancy by means of an independently beating tail filament. The feeding mechanism of larval Phyllomedusa trinitatis was studied morphologically and experimentally. The primary feeding mechanism involves a buccal rasp which may in some circumstances render food into small particles, a pumping mechanism which forces water through the buccal cavity and the gill filters, an entanglement system which traps particles in mucous strings produced in special organs, and the formation of mucous cords which transport particles to the oesophagus. In mid‐water feeding and surface feeding the buccal rasp serves only its other function in preventing backflow of the respiratory stream. The primary feeding mechanism is discussed and compared with schemes proposed for Rana temporaria and R. agilis. Little agreement exists between these schemes and that which is here proposed. It is concluded that the primary feeding mechanism is the same in the three forms but that there are behavioural differences in feeding generally. Some comment is made on the primary feeding mechanism in the Microhylidae.

@article{doi101111j146979981969tb01699x,
    author = "Kenny, Julian S.",
    title = "Feeding mechanisms in anuran larvae",
    year = "1969",
    journal = "Journal of Zoology",
    abstract = "Larvae of the neotropical frogs Phyllomedusa are distinctive in that they feed normally in mid‐water on phytoplankton, maintaining neutral buoyancy by means of an independently beating tail filament. The feeding mechanism of larval Phyllomedusa trinitatis was studied morphologically and experimentally. The primary feeding mechanism involves a buccal rasp which may in some circumstances render food into small particles, a pumping mechanism which forces water through the buccal cavity and the gill filters, an entanglement system which traps particles in mucous strings produced in special organs, and the formation of mucous cords which transport particles to the oesophagus. In mid‐water feeding and surface feeding the buccal rasp serves only its other function in preventing backflow of the respiratory stream. The primary feeding mechanism is discussed and compared with schemes proposed for Rana temporaria and R. agilis. Little agreement exists between these schemes and that which is here proposed. It is concluded that the primary feeding mechanism is the same in the three forms but that there are behavioural differences in feeding generally. Some comment is made on the primary feeding mechanism in the Microhylidae.",
    url = "https://doi.org/10.1111/j.1469-7998.1969.tb01699.x",
    doi = "10.1111/j.1469-7998.1969.tb01699.x",
    openalex = "W2025020900",
    references = "dodd1950ciliary"
}

Abstract The cilia lining the stigmata of the branchial sac of an ascidian circulate water through the animal. These stigmatal cilia are under nervous control; when either siphon is stimulated, both siphons close by muscular contractions and at the same time the stigmatal cilia stop beating simultaneously in all parts of the branchial sac. Spontaneous ciliary arrests may also occur, with or without associated closure of the siphons. Elements of the branchial nervous system that run in the gill bars are assumed to be concerned in coordination of the ciliary arrests. The majority of the branchial nerve fibres emerge dorsally from the visceral nerves that form the posterior brain roots, although nerves are also believed to enter the branchial sac along its anterior margin. No cell bodies could be found in the branchial nerves or in the visceral nerves, so that the cell bodies of the branchial nerve fibres are assumed to lie in the central nervous system. The branchial nerve fibres form a peripheral conducting net extending throughout the branchial sac. Branches of these nerve fibres terminate in contact with some of the ciliated cells; cell-to-cell conduction (through close junctions?) probably spreads excitation to the other ciliated cells. Nerve-nerve junctions appear to be more sensitive to curare than those between nerves and ciliated cells. Electrical recordings from the branchial sac, obtained with suction electrodes, show that arrest of the cilia is accompanied by electrical activity, and that prolonged arrest is maintained by trains of regular pulses. Intracellular microelectrodes in the ciliated cells indicate that these cells have a negative resting potential of 30-40 mV, and that a ciliary arrest is associated with a positive-going spike of 45-50 mV. The externally recorded ‘ciliary arrest potentials’ probably represent the coordinated depolarization of many ciliated cells. The rhythmical character of the trains of pulses presumably depends on pacemaker activity; this is not localized, since intact organisms or isolated small portions of the branchial sac are capable of generating similar trains of pulses. During the arrest response the stigmatal cilia first perform a reverse beat, then maintain the reverse position for several seconds before slowly relaxing and after several more seconds recommencing to beat with progressively increasing amplitude. The duration of the arrest response varies in media with different concentrations of the common cations, and also varies in response to repetitive stimulation, in a manner which suggests that the depolarization of the ciliated cells is associated with an influx of Ca2+, so that the ciliary control here may have some close parallels with that described for Paramecium.

@article{doi101098rspb19740058,
    author = "Mackie, G. O. and Paul, D. H. and Singla, C. M. and Sleigh, M. A. and Williams, Daphne",
    title = "Branchial innervation and ciliary control in the ascidian Corella",
    year = "1974",
    journal = "Proceedings of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract The cilia lining the stigmata of the branchial sac of an ascidian circulate water through the animal. These stigmatal cilia are under nervous control; when either siphon is stimulated, both siphons close by muscular contractions and at the same time the stigmatal cilia stop beating simultaneously in all parts of the branchial sac. Spontaneous ciliary arrests may also occur, with or without associated closure of the siphons. Elements of the branchial nervous system that run in the gill bars are assumed to be concerned in coordination of the ciliary arrests. The majority of the branchial nerve fibres emerge dorsally from the visceral nerves that form the posterior brain roots, although nerves are also believed to enter the branchial sac along its anterior margin. No cell bodies could be found in the branchial nerves or in the visceral nerves, so that the cell bodies of the branchial nerve fibres are assumed to lie in the central nervous system. The branchial nerve fibres form a peripheral conducting net extending throughout the branchial sac. Branches of these nerve fibres terminate in contact with some of the ciliated cells; cell-to-cell conduction (through close junctions?) probably spreads excitation to the other ciliated cells. Nerve-nerve junctions appear to be more sensitive to curare than those between nerves and ciliated cells. Electrical recordings from the branchial sac, obtained with suction electrodes, show that arrest of the cilia is accompanied by electrical activity, and that prolonged arrest is maintained by trains of regular pulses. Intracellular microelectrodes in the ciliated cells indicate that these cells have a negative resting potential of 30-40 mV, and that a ciliary arrest is associated with a positive-going spike of 45-50 mV. The externally recorded ‘ciliary arrest potentials’ probably represent the coordinated depolarization of many ciliated cells. The rhythmical character of the trains of pulses presumably depends on pacemaker activity; this is not localized, since intact organisms or isolated small portions of the branchial sac are capable of generating similar trains of pulses. During the arrest response the stigmatal cilia first perform a reverse beat, then maintain the reverse position for several seconds before slowly relaxing and after several more seconds recommencing to beat with progressively increasing amplitude. The duration of the arrest response varies in media with different concentrations of the common cations, and also varies in response to repetitive stimulation, in a manner which suggests that the depolarization of the ciliated cells is associated with an influx of Ca2+, so that the ciliary control here may have some close parallels with that described for Paramecium.",
    url = "https://doi.org/10.1098/rspb.1974.0058",
    doi = "10.1098/rspb.1974.0058",
    openalex = "W1982720788",
    references = "doi101017s002531540001170x"
}

We enumerate the five basic mechanisms by which any biological or manmade filter can remove particles from a fluid. These mechanisms are: (1) direct interception, (2) inertial impaction, (3) gravitational deposition, (4) motile-particle deposition, and (5) electrostatic attraction. For these mechanisms we present dimensionless indexes that indicate which measurable characteristics of the filter, the particles, and the flow affect the intensity of particle capture. By comparing the magnitudes of these indexes it is possible to determine the main mechanism a filter is using to capture particles. Awareness of these mechanisms and their interrelationships will provide insights for those investigating the efficiency of various modes of filter feeding and the mechanisms of size-selective suspension feeding.

@article{doi101086283227,
    author = "Rubenstein, Daniel I. and Koehl, M. A. R.",
    title = "The Mechanisms of Filter Feeding: Some Theoretical Considerations",
    year = "1977",
    journal = "The American Naturalist",
    abstract = "We enumerate the five basic mechanisms by which any biological or manmade filter can remove particles from a fluid. These mechanisms are: (1) direct interception, (2) inertial impaction, (3) gravitational deposition, (4) motile-particle deposition, and (5) electrostatic attraction. For these mechanisms we present dimensionless indexes that indicate which measurable characteristics of the filter, the particles, and the flow affect the intensity of particle capture. By comparing the magnitudes of these indexes it is possible to determine the main mechanism a filter is using to capture particles. Awareness of these mechanisms and their interrelationships will provide insights for those investigating the efficiency of various modes of filter feeding and the mechanisms of size-selective suspension feeding.",
    url = "https://doi.org/10.1086/283227",
    doi = "10.1086/283227",
    openalex = "W2016949116",
    references = "doi101111j1469185x1955tb01546x, doi1023071540326"
}

Most accounts on suspension feeding assume that mechanical, sievelike filters retain particles from the ambient water Fluid mechanical aspects have been neglected. Suspension feeding is characterized by very low Reynolds numbers. This implies that water processing and particle retention are exclusively determined by viscous forces. Modern filtration theory can therefore be applied to hypotheses on suspension feeding involving mechanical filters. The resistance to water flow through such filters was found to correspond to pressure drops across the filters of about 0.1 to 0.4 mm H,O in flagellates, ciliates, sponges, and ascidians; and of > l mm H,O in copepods and bivalves. These theoretical pressure drops are consistent with the function as filters of ciliate membranelles, pseudopodial collars in flagellates and sponges, and ascidian mucus filters. Ciliary and flagellar water transport operate at very low pressures The pressure drops calculated for copepod second maxillae and bivalve laterofrontal cirri seem to be incompatible with the roles as filters traditionally ascribed to these structures. Recent studies indicate that sievelike models have to b e abandoned in explaining particle retention in copepods and bivalves. Particles seem to be captured by means of mechanisms that do not imply physical interception of the suspended particles Copepods seem to have adopted mechanisms, based on viscous forces, that direct food particles in the surrounding water toward the second maxillae, which eventually capture the parcel of water that contains the particle. In the bivalve gill capture of suspended particles implies transfer from the currents passing through the gill via the interfilamentary spaces to the frontal surface currents along the filaments. Complex patterns of flow arise where the 2 systems of currents meet at the entrance to the interfilamentary spaces. The patterns are characterized by steep velocity gradients which may act on suspended particles and cause them to enter the surface currents, i.e. to b e captured. It remains to be ascertained to what extent fluid mechanics operate in the capture of particles in other metazoan ciliary feeders

@article{doi103354meps011089,
    author = "Jørgensen, CB",
    title = "Fluid mechanical aspects of suspension feeding",
    year = "1983",
    journal = "Marine Ecology Progress Series",
    abstract = "Most accounts on suspension feeding assume that mechanical, sievelike filters retain particles from the ambient water Fluid mechanical aspects have been neglected. Suspension feeding is characterized by very low Reynolds numbers. This implies that water processing and particle retention are exclusively determined by viscous forces. Modern filtration theory can therefore be applied to hypotheses on suspension feeding involving mechanical filters. The resistance to water flow through such filters was found to correspond to pressure drops across the filters of about 0.1 to 0.4 mm H,O in flagellates, ciliates, sponges, and ascidians; and of > l mm H,O in copepods and bivalves. These theoretical pressure drops are consistent with the function as filters of ciliate membranelles, pseudopodial collars in flagellates and sponges, and ascidian mucus filters. Ciliary and flagellar water transport operate at very low pressures The pressure drops calculated for copepod second maxillae and bivalve laterofrontal cirri seem to be incompatible with the roles as filters traditionally ascribed to these structures. Recent studies indicate that sievelike models have to b e abandoned in explaining particle retention in copepods and bivalves. Particles seem to be captured by means of mechanisms that do not imply physical interception of the suspended particles Copepods seem to have adopted mechanisms, based on viscous forces, that direct food particles in the surrounding water toward the second maxillae, which eventually capture the parcel of water that contains the particle. In the bivalve gill capture of suspended particles implies transfer from the currents passing through the gill via the interfilamentary spaces to the frontal surface currents along the filaments. Complex patterns of flow arise where the 2 systems of currents meet at the entrance to the interfilamentary spaces. The patterns are characterized by steep velocity gradients which may act on suspended particles and cause them to enter the surface currents, i.e. to b e captured. It remains to be ascertained to what extent fluid mechanics operate in the capture of particles in other metazoan ciliary feeders",
    url = "https://doi.org/10.3354/meps011089",
    doi = "10.3354/meps011089",
    openalex = "W2113366633",
    references = "doi101111j146363951981tb00616x, jørgensen1949feedingrates"
}

The apparent diversity of suspension feeding animals is, in one sense, more apparent than real. Virtually all suspension feeders capture particles from the water at low Reynolds numbers with cylindrical filtering elements, so, at the level of the filtering elements, flow patterns are identical and viscous forces dominate the situation. Six particle capture mechanisms are likely to be operating alone or in combination: (1) scan and trap (isolation of a parcel of fluid containing the particle), (2) sieving, (3) direct interception, (4) inertial impaction, (5) gravitational deposition, and (6) diffusive deposition. To insure that all variables relevant to the suspension feeding process are recorded, future work on suspension feeding should report the diameter and spacing of the filtering elements, flow speeds, diameter of particles available and captured, particle settling velocities, particle mobility (active or passive), and particle surface properties.

@article{doi101093icb24171,
    author = "LaBarbera, Michael",
    title = "Feeding Currents and Particle Capture Mechanisms in Suspension Feeding Animals",
    year = "1984",
    journal = "American Zoologist",
    abstract = "The apparent diversity of suspension feeding animals is, in one sense, more apparent than real. Virtually all suspension feeders capture particles from the water at low Reynolds numbers with cylindrical filtering elements, so, at the level of the filtering elements, flow patterns are identical and viscous forces dominate the situation. Six particle capture mechanisms are likely to be operating alone or in combination: (1) scan and trap (isolation of a parcel of fluid containing the particle), (2) sieving, (3) direct interception, (4) inertial impaction, (5) gravitational deposition, and (6) diffusive deposition. To insure that all variables relevant to the suspension feeding process are recorded, future work on suspension feeding should report the diameter and spacing of the filtering elements, flow speeds, diameter of particles available and captured, particle settling velocities, particle mobility (active or passive), and particle surface properties.",
    url = "https://doi.org/10.1093/icb/24.1.71",
    doi = "10.1093/icb/24.1.71",
    openalex = "W2072787745",
    references = "doi1010160022098171900542, doi1010160022098181901118, doi101093icb153717, doi101139z78290, doi1023071540326"
}

Filter characteristics have been determined and compared in ciliary and mucus-net filter feeders. The ciliary feeders include the polychaete Sabella penicillus, the brachiopod Terebratulina retuso, the marine bivalves Monia squama, Cardiurn glaucum, and Petricola pholadiformis, and the freshwater bivalves Dreissena polymorpha, Unio pictamrn, and Anodonta cygnea. The mucus-net feeders are the polychaete Chaetopterus variopedatus, the gastropod Crepidula fomicata, and the ascidians Sfyela clava, Ciona intestinalis, Ascidia virginia, Ascidia obliqua, and Ascidia mentula. Efficiencies of particle retention as a function of particle size was determined by counting of particles in samples of inhalant and exhalant water. The lower threshold for efficient particle retention varied from about 6 p m in T. retuso to about 1 p n in D. polyrnorpha. Mucus nets efficiently retained particles down to 1 to 2 pm. Filter feeding is characterized by processing of water at low pressures (5 l mm H,O). Mechanisms of water processing and particle retention in brachiopods and bivalves are compared. It is concluded that laminar flow of through-currents and surface-currents in brachiopods is consistent with the hypothesis of capture of suspended particles by means of viscous forces acting upon the particles in the zone of contact between the 2 flow systems.

@article{doi103354meps015283,
    author = "Jørgensen, CB and Kørboe, T and Møhlenberg, F and Riisgård, Hans Ulrik",
    title = "Ciliary and mucus-net filter feeding, with special reference to fluid mechanical Characteristics",
    year = "1984",
    journal = "Marine Ecology Progress Series",
    abstract = "Filter characteristics have been determined and compared in ciliary and mucus-net filter feeders. The ciliary feeders include the polychaete Sabella penicillus, the brachiopod Terebratulina retuso, the marine bivalves Monia squama, Cardiurn glaucum, and Petricola pholadiformis, and the freshwater bivalves Dreissena polymorpha, Unio pictamrn, and Anodonta cygnea. The mucus-net feeders are the polychaete Chaetopterus variopedatus, the gastropod Crepidula fomicata, and the ascidians Sfyela clava, Ciona intestinalis, Ascidia virginia, Ascidia obliqua, and Ascidia mentula. Efficiencies of particle retention as a function of particle size was determined by counting of particles in samples of inhalant and exhalant water. The lower threshold for efficient particle retention varied from about 6 p m in T. retuso to about 1 p n in D. polyrnorpha. Mucus nets efficiently retained particles down to 1 to 2 pm. Filter feeding is characterized by processing of water at low pressures (5 l mm H,O). Mechanisms of water processing and particle retention in brachiopods and bivalves are compared. It is concluded that laminar flow of through-currents and surface-currents in brachiopods is consistent with the hypothesis of capture of suspended particles by means of viscous forces acting upon the particles in the zone of contact between the 2 flow systems.",
    url = "https://doi.org/10.3354/meps015283",
    doi = "10.3354/meps015283",
    openalex = "W1971107871",
    references = "doi101007bf00386593, doi1010160022098171900542, doi101016s0003936580800091, doi10108000785326197810425487, doi101111j109636421962tb01626x, doi101111j146363951981tb00616x, doi101128aem335122512281977, doi103354meps001055, doi103354meps005291, doi103354meps011089, doi104319lo19812661062, openalexw1549886310"
}

The dominance of Paleozoic articulate brachiopods in once-muddy environments may be explained by an array of mechanisms and structures that reject nonfood particles, in some cases without interruption of feeding: (1) behavioral flexibility of the lophophore and its individual filaments; (2) persistent, variable-speed rejection currents on the mantle, which sometimes concentrate pseudofeces in topographically controlled vortices; (3) costae and alae (which have many other probable functions); (4) inhalant currents elevated above substrate; (5) marginal setae. Some mantle currents parallel (and presumably augment) lophophore feeding currents; others diverge up to 90° to provide rejection while feeding continues. Contrary to previous reports, the lateral cilia seem to be involved in rejection and may reverse. Repeated claims for the superiority of the gill of suspension-feeding bivalves over the “weak” individual filaments of the lophophore are probably false. In suspension-feeding bivalves, simultaneous feeding and rejection are likely to be hindered by fused gill elements and mucus-trapping of food. The energetically efficient articulates are predicted to have a competitive advantage over suspension-feeding bivalves when oxygen or food is limiting, as, for example, after a bolide impact.

@article{doi101017s0094837300013634,
    author = "Thayer, Charles W.",
    title = "Are brachiopods better than bivalves? Mechanisms of turbidity tolerance and their interaction with feeding in articulates",
    year = "1986",
    journal = "Paleobiology",
    abstract = "The dominance of Paleozoic articulate brachiopods in once-muddy environments may be explained by an array of mechanisms and structures that reject nonfood particles, in some cases without interruption of feeding: (1) behavioral flexibility of the lophophore and its individual filaments; (2) persistent, variable-speed rejection currents on the mantle, which sometimes concentrate pseudofeces in topographically controlled vortices; (3) costae and alae (which have many other probable functions); (4) inhalant currents elevated above substrate; (5) marginal setae. Some mantle currents parallel (and presumably augment) lophophore feeding currents; others diverge up to 90° to provide rejection while feeding continues. Contrary to previous reports, the lateral cilia seem to be involved in rejection and may reverse. Repeated claims for the superiority of the gill of suspension-feeding bivalves over the “weak” individual filaments of the lophophore are probably false. In suspension-feeding bivalves, simultaneous feeding and rejection are likely to be hindered by fused gill elements and mucus-trapping of food. The energetically efficient articulates are predicted to have a competitive advantage over suspension-feeding bivalves when oxygen or food is limiting, as, for example, after a bolide impact.",
    url = "https://doi.org/10.1017/s0094837300013634",
    doi = "10.1017/s0094837300013634",
    openalex = "W2475664597",
    references = "chuang1956the, doi1010160022098185902229, doi101016b9780127514048500177, doi101086284025, doi101098rspb19790086, doi101126science2034379458, doi101126science2164542173, doi101126science2304722167, doi1023071441916, doi1023072406301, openalexw1549886310"
}

Models of particle encounter efficiency borrowed from aerosol fil- tration theory have revolutionised ideas about mechanisms of suspension-feeding (a form of hydrosol filtration), although they continue to be under-utilised in generating predictions concerning feeding ecology and morphological evolution and in guiding quantitative experimentation. As a complementary tool we model encounter rate, demonstrated with parameterisations ofthe same particle-encounter mechanisms. The rate models include specific encounter geometry, absent from the prevalent efficiency indices, which is used to refine estimates of the absolute and relative effectiveness of the various encounter mechanisms. Using rate (as opposed to effi- ciency and in accord with optimal foraging theory) as the dependent variable yields very different predictions for optimisation schemes. For example, a larger collector radius reduces encounter efficiency for most mechanisms, but it either increases or leaves unaffected encounter rate. Similarly, an increase in advection velocity often reduces encounter efficiency, but it increases encounter rate for most mechanisms

@article{openalexw76963690,
    author = "Shimeta, Jeff and Jumars, Peter A.",
    title = "Physical mechanisms and rates of particle capture by suspension-feeders",
    year = "1991",
    journal = "Oceanography and Marine Biology/Oceanography and marine biology - an annual review",
    abstract = "Models of particle encounter efficiency borrowed from aerosol fil- tration theory have revolutionised ideas about mechanisms of suspension-feeding (a form of hydrosol filtration), although they continue to be under-utilised in generating predictions concerning feeding ecology and morphological evolution and in guiding quantitative experimentation. As a complementary tool we model encounter rate, demonstrated with parameterisations ofthe same particle-encounter mechanisms. The rate models include specific encounter geometry, absent from the prevalent efficiency indices, which is used to refine estimates of the absolute and relative effectiveness of the various encounter mechanisms. Using rate (as opposed to effi- ciency and in accord with optimal foraging theory) as the dependent variable yields very different predictions for optimisation schemes. For example, a larger collector radius reduces encounter efficiency for most mechanisms, but it either increases or leaves unaffected encounter rate. Similarly, an increase in advection velocity often reduces encounter efficiency, but it increases encounter rate for most mechanisms",
    openalex = "W76963690",
    references = "doi1010160022098171900542, doi101093icb153717, doi1023071540326, doi103354meps015283"
}

@article{stokes1995ciliary,
    author = "Stokes, M. D. and Holland, N. D.",
    title = "Ciliary Hovering in Larval Lancelets (=Amphioxus)",
    year = "1995",
    journal = "The Biological Bulletin",
    url = "https://doi.org/10.2307/1542300",
    doi = "10.2307/1542300",
    number = "3",
    openalex = "W2121451173",
    pages = "231-233",
    volume = "188",
    references = "doi101017s002211207000215x, doi101038044202a0, doi1010381841849a0, doi101098rstb19940059, doi101111j146363951995tb00986x, doi101111j1469185x1989tb00471x, doi101242jcss254215279, doi101242jcss27228551, openalexw1482353918, openalexw20166170"
}

Richard A. Tankersley, Multipurpose Gills: Effect of Larval Brooding on the Feeding Physiology of Freshwater Unionid Mussels, Invertebrate Biology, Vol. 115, No. 3, Symposium: Recent Advances in the Study of Invertebrate Feeding Biodynamics (Summer, 1996), pp. 243-255

@article{doi1023073226934,
    author = "Tankersley, Richard A.",
    title = "Multipurpose Gills: Effect of Larval Brooding on the Feeding Physiology of Freshwater Unionid Mussels",
    year = "1996",
    journal = "Invertebrate Biology",
    abstract = "Richard A. Tankersley, Multipurpose Gills: Effect of Larval Brooding on the Feeding Physiology of Freshwater Unionid Mussels, Invertebrate Biology, Vol. 115, No. 3, Symposium: Recent Advances in the Study of Invertebrate Feeding Biodynamics (Summer, 1996), pp. 243-255",
    url = "https://doi.org/10.2307/3226934",
    doi = "10.2307/3226934",
    openalex = "W2318133690",
    references = "doi101242jcss279315375"
}

The energy cost for various ciliary filter feeders shows that useful pump work constitutes 0.3–1.1% of the total metabolic expenditure. The ‘water processing potential’ (liters of water pumped per milliliter O 2 consumed by the animal) is a useful tool for characterizing filter feeding and adaptation to the environment. The six types of ciliary‐capture mechanisms (collar sieving, cirral trapping, ciliary sieving, ciliary downstream collecting, ciliary upstream collecting, mucus‐net sieving) are reviewed as well as the aerosol/hydrosol filtration theory. A brief overview of fluid mechanical principles and tools for studying ciliary functions is given.

@article{doi104319lo20014640882,
    author = "Riisgård, Hans Ulrik and Larsen, Poul S.",
    title = "Minireview: Ciliary filter feeding and bio‐fluid mechanics—present understanding and unsolved problems",
    year = "2001",
    journal = "Limnology and Oceanography",
    abstract = "The energy cost for various ciliary filter feeders shows that useful pump work constitutes 0.3–1.1\% of the total metabolic expenditure. The ‘water processing potential’ (liters of water pumped per milliliter O 2 consumed by the animal) is a useful tool for characterizing filter feeding and adaptation to the environment. The six types of ciliary‐capture mechanisms (collar sieving, cirral trapping, ciliary sieving, ciliary downstream collecting, ciliary upstream collecting, mucus‐net sieving) are reviewed as well as the aerosol/hydrosol filtration theory. A brief overview of fluid mechanical principles and tools for studying ciliary functions is given.",
    url = "https://doi.org/10.4319/lo.2001.46.4.0882",
    doi = "10.4319/lo.2001.46.4.0882",
    openalex = "W2140876002",
    references = "doi1010079781461252146, doi101007978364281863930, doi1010160021999177901000, doi101016s0169534798013652, doi101086283227, doi101098rspa19510218, doi101146annurevfl09010177002011, doi1015159780691212975, doi1023071540270, doi105860choice324494, orton1913the, riisgard1999filter"
}

@article{gonzalez2009the,
    author = "GONZALEZ, PAUL and CAMERON, CHRISTOPHER B.",
    title = "The gill slits and pre-oral ciliary organ of Protoglossus (Hemichordata: Enteropneusta) are filter-feeding structures",
    year = "2009",
    journal = "Biological Journal of the Linnean Society",
    url = "https://doi.org/10.1111/j.1095-8312.2009.01332.x",
    doi = "10.1111/j.1095-8312.2009.01332.x",
    number = "4",
    openalex = "W2145362624",
    pages = "898-906",
    volume = "98",
    references = "doi101007bf02458306, doi101016s0092867403004690, doi101038nature06967, doi101073pnas9794469, doi101093oxfordjournalsmolbeva004134, doi101371journalpbio0040291, doi105860choice324494, openalexw2138825607, openalexw234888846, openalexw70084438"
}

Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with the environment, and may explain both size-dependent and spatio-temporal differences in distributions of various feeding types as well as other aspects of the biology of zooplankton (mating behaviour, predator defence strategies).

@article{doi101111j1469185x201000148x,
    author = "Kiørboe, Thomas",
    title = "How zooplankton feed: mechanisms, traits and trade-offs",
    year = "2010",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with the environment, and may explain both size-dependent and spatio-temporal differences in distributions of various feeding types as well as other aspects of the biology of zooplankton (mating behaviour, predator defence strategies).",
    url = "https://doi.org/10.1111/j.1469-185x.2010.00148.x",
    doi = "10.1111/j.1469-185x.2010.00148.x",
    openalex = "W1969980650",
    references = "doi1010079781461235446, doi101007bf02112126, doi1010160022098171900542, doi101111j146979981983tb05071x, doi104319lo20014640882, doi104319lo20095441210, doi105860choice265651"
}

A large number of suspension-feeding aquatic animals (e.g. bivalves, polychaetes, ascidians, bryozoans, crustaceans, sponges, echinoderms, cnidarians) have specialized in grazing on not only the 2 to 200 μm phytoplankton but frequently also the 0.5 to 2 μm free-living bacteria, or they have specialized in capturing larger prey, e.g. zooplankton organisms. We review the different particle capture mechanisms in order to illustrate the many solutions to the common problem of obtaining nourishment from a dilute suspension of microscopic food particles. Despite the many differences in morphology and living conditions, particle capture mechanisms may be divided into 2 main types. (1) Filtering or sieving (e.g. through mucus nets, stiff cilia, filter setae), which is found in passive suspension feeders that rely on external currents to bring suspended particles to the filter, and in active suspension feeders that themselves produce a feeding flow by a variety of pump systems. Here the inventiveness of nature does not lie in the capture mechanism but in the type of pump system and filter pore-size. (2) A paddle-like flow manipulating system (e.g. cilia, cirri, tentacles, hair-bearing appendages) that acts to redirect an approaching suspended particle, often along with a surrounding 'fluid parcel', to a strategic location for arrest or further transport. Examples include (1) sieving (e.g. by microvilli in sponge choanocytes, mucus nets in polychaetes, acidians, and salps among others), filter setae in crustaceans, 'ciliary sieving' by stiff laterofrontal cilia in bryozoans and phoronids; and (2) 'cirri trapping' in mussels and other bivalves with eu-laterofrontal cirri, ciliary 'catch-up' in bivalve and gastropod veliger larvae, some polychaetes, entroprocts, and cycliophores. These capture mechanisms may involve contact with a particle, and possibly mechanoreception or chemore-ception, or may include redirection of particles by the interaction of multiple currents (e.g. in scallops and other bivalves without eu-laterofrontal cirri). Based on the review, we discuss the current physical and biological understanding of the capture process and suggest a number of specific problems related to particle capture, which may be solved in the future using advanced theoretical, computational and experimental techniques.

@article{doi103354meps08755,
    author = "Riisgård, Hans Ulrik and Larsen, Poul S.",
    title = "Particle capture mechanisms in suspension-feeding invertebrates",
    year = "2010",
    journal = "Marine Ecology Progress Series",
    abstract = "A large number of suspension-feeding aquatic animals (e.g. bivalves, polychaetes, ascidians, bryozoans, crustaceans, sponges, echinoderms, cnidarians) have specialized in grazing on not only the 2 to 200 μm phytoplankton but frequently also the 0.5 to 2 μm free-living bacteria, or they have specialized in capturing larger prey, e.g. zooplankton organisms. We review the different particle capture mechanisms in order to illustrate the many solutions to the common problem of obtaining nourishment from a dilute suspension of microscopic food particles. Despite the many differences in morphology and living conditions, particle capture mechanisms may be divided into 2 main types. (1) Filtering or sieving (e.g. through mucus nets, stiff cilia, filter setae), which is found in passive suspension feeders that rely on external currents to bring suspended particles to the filter, and in active suspension feeders that themselves produce a feeding flow by a variety of pump systems. Here the inventiveness of nature does not lie in the capture mechanism but in the type of pump system and filter pore-size. (2) A paddle-like flow manipulating system (e.g. cilia, cirri, tentacles, hair-bearing appendages) that acts to redirect an approaching suspended particle, often along with a surrounding 'fluid parcel', to a strategic location for arrest or further transport. Examples include (1) sieving (e.g. by microvilli in sponge choanocytes, mucus nets in polychaetes, acidians, and salps among others), filter setae in crustaceans, 'ciliary sieving' by stiff laterofrontal cilia in bryozoans and phoronids; and (2) 'cirri trapping' in mussels and other bivalves with eu-laterofrontal cirri, ciliary 'catch-up' in bivalve and gastropod veliger larvae, some polychaetes, entroprocts, and cycliophores. These capture mechanisms may involve contact with a particle, and possibly mechanoreception or chemore-ception, or may include redirection of particles by the interaction of multiple currents (e.g. in scallops and other bivalves without eu-laterofrontal cirri). Based on the review, we discuss the current physical and biological understanding of the capture process and suggest a number of specific problems related to particle capture, which may be solved in the future using advanced theoretical, computational and experimental techniques.",
    url = "https://doi.org/10.3354/meps08755",
    doi = "10.3354/meps08755",
    openalex = "W2063850008",
    references = "doi101016jjembe200403002, doi10108000785326197810425487, doi101086283227, doi10108800344885729096601, doi101093icb153717, doi101111j146363951987tb00892x, doi101111j1469185x1955tb01546x, doi101139z78290, doi1023071352661, doi1023071540270, doi1023071540326, doi103354meps015283, doi103354meps045217, doi105860choice270306, openalexw2076004673, openalexw628103700, orton1913the"
}

@incollection{candiani2015detection,
    author = "Candiani, Simona and Garbarino, Greta and Pestarino, Mario",
    title = "Detection of mRNA and microRNA Expression in Basal Chordates, Amphioxus and Ascidians",
    year = "2015",
    booktitle = "Neuromethods",
    url = "https://doi.org/10.1007/978-1-4939-2303-8\_14",
    doi = "10.1007/978-1-4939-2303-8\_14",
    openalex = "W2478715418",
    pages = "279-292",
    references = "doi101002dvdy20847, doi101002dvdy20956, doi101016016895259090008t, doi101016jydbio200703009, doi101038nature02871, doi101038nature07415, doi101038nmeth843, doi101111j1525142x201000452x, doi101126science1064921, doi101126science1114519"
}

Suspension feeders (SFs) evolved a high diversity of mechanisms, sometimes with remarkably convergent morphologies, to retain plankton, detritus and man-made particles with particle sizes ranging from less than 1 µm to several centimetres. Based on an extensive literature review, also including the physical and technical principles of solid-liquid separation, we developed a set of 18 ecological and technical parameters to review 35 taxa of suspension-feeding Metazoa covering the diversity of morphological and functional principles. This includes passive SFs, such as gorgonians or crinoids that use the ambient flow to encounter particles, and sponges, bivalves or baleen whales, which actively create a feeding current. Separation media can be flat or funnel-shaped, built externally such as the filter houses in larvaceans, or internally, like the pleated gills in bivalves. Most SFs feed in the intermediate flow region of Reynolds number 1-50 and have cleaning mechanisms that allow for continuous feeding. Comparison of structure-function patterns in SFs to current filtration technologies highlights potential solutions to common technical design challenges, such as mucus nets which increase particle adhesion in ascidians, vanes which reduce pressure losses in whale sharks and changing mesh sizes in the flamingo beak which allow quick adaptation to particle sizes.

@article{doi101098rsif20210741,
    author = "Hamann, Leandra and Blanke, Alexander",
    title = "Suspension feeders: diversity, principles of particle separation and biomimetic potential",
    year = "2022",
    journal = "Journal of The Royal Society Interface",
    abstract = "Suspension feeders (SFs) evolved a high diversity of mechanisms, sometimes with remarkably convergent morphologies, to retain plankton, detritus and man-made particles with particle sizes ranging from less than 1 µm to several centimetres. Based on an extensive literature review, also including the physical and technical principles of solid-liquid separation, we developed a set of 18 ecological and technical parameters to review 35 taxa of suspension-feeding Metazoa covering the diversity of morphological and functional principles. This includes passive SFs, such as gorgonians or crinoids that use the ambient flow to encounter particles, and sponges, bivalves or baleen whales, which actively create a feeding current. Separation media can be flat or funnel-shaped, built externally such as the filter houses in larvaceans, or internally, like the pleated gills in bivalves. Most SFs feed in the intermediate flow region of Reynolds number 1-50 and have cleaning mechanisms that allow for continuous feeding. Comparison of structure-function patterns in SFs to current filtration technologies highlights potential solutions to common technical design challenges, such as mucus nets which increase particle adhesion in ascidians, vanes which reduce pressure losses in whale sharks and changing mesh sizes in the flamingo beak which allow quick adaptation to particle sizes.",
    url = "https://doi.org/10.1098/rsif.2021.0741",
    doi = "10.1098/rsif.2021.0741",
    openalex = "W4210367689",
    references = "doi1010160022098181901118, doi101016jjembe200403002, doi101017s0094837300013634, doi101038ngeo2108, doi101039d0ew00397b, doi101086283227, doi101098rsif20060127, doi101098rsif20210741, doi101098rsos140317, doi101111j146363951981tb00616x, doi101111j1469185x201000148x, doi101134s0031030107050073, doi101146annureven25010180000535, doi104319lo19943920395, doi105860choice501224, nielsen2007on"
}

The minimum size of particles being efficiently captured in the gills of filter-feeding bivalves differs between mussels with well-developed laterofrontal cirri (lfc) and scallops having only simple pro-laterofrontal cilia (pro-lfc). The presence of branching compound lfc increases the particle retention efficiency below the lower limit of about 4 µm for 100% retention, whereas the simple pro-lfc cilia in scallops are less efficient with decreasing retention efficiency for particles smaller than about 7 µm. To understand the particle capture mechanisms in bivalves, attention must be paid to the ciliary structures and water flow in flat gills (mussels) versus plicate gills (scallops, oysters). Here, we briefly review the literature on particle capture mechanisms in filter-feeding marine bivalves with large lfc (mussels, clams), short lfc (oysters), and with only pro-lfc (scallops), and then we describe our present understanding of these processes. This is carried out along with comments on a long-lasting and current controversy on particle-capture mechanisms in filter-feeding bivalves. We rebut the hypothesis of “hydrosol filtering” proposed by Ward et al. (1998), where the approach angle of a particle towards the gill is 30° and the particle is captured by direct interception with a gill filament, whereas lfc generate “zones of blocked through-flow”. No further test of the hydrosol hypothesis has so far been made, but nevertheless, it has been cited in many publications over the last 25 years.

@article{riisgård2026ciliary,
    author = "Riisgård, Hans Ulrik and Larsen, Poul S.",
    title = "Ciliary Structures and Particle-Capture Mechanisms in Marine Filter-Feeding Bivalves",
    year = "2026",
    journal = "Journal of Marine Science and Engineering",
    abstract = "The minimum size of particles being efficiently captured in the gills of filter-feeding bivalves differs between mussels with well-developed laterofrontal cirri (lfc) and scallops having only simple pro-laterofrontal cilia (pro-lfc). The presence of branching compound lfc increases the particle retention efficiency below the lower limit of about 4 µm for 100\% retention, whereas the simple pro-lfc cilia in scallops are less efficient with decreasing retention efficiency for particles smaller than about 7 µm. To understand the particle capture mechanisms in bivalves, attention must be paid to the ciliary structures and water flow in flat gills (mussels) versus plicate gills (scallops, oysters). Here, we briefly review the literature on particle capture mechanisms in filter-feeding marine bivalves with large lfc (mussels, clams), short lfc (oysters), and with only pro-lfc (scallops), and then we describe our present understanding of these processes. This is carried out along with comments on a long-lasting and current controversy on particle-capture mechanisms in filter-feeding bivalves. We rebut the hypothesis of “hydrosol filtering” proposed by Ward et al. (1998), where the approach angle of a particle towards the gill is 30° and the particle is captured by direct interception with a gill filament, whereas lfc generate “zones of blocked through-flow”. No further test of the hydrosol hypothesis has so far been made, but nevertheless, it has been cited in many publications over the last 25 years.",
    url = "https://doi.org/10.3390/jmse14030251",
    doi = "10.3390/jmse14030251",
    number = "3",
    openalex = "W7125705367",
    pages = "251",
    volume = "14"
}