Digestive system

@article{dogiel1903das,
    author = "Dogiel, A. S.",
    title = "Das Periphere Nervensystem des Amphioxus (Branchiostoma Lanceolatum)",
    year = "1903",
    journal = "Beiträge und Referate zur Anatomie und Entwickelungsgeschichte",
    url = "https://doi.org/10.1007/bf02110551",
    doi = "10.1007/bf02110551",
    number = "1",
    openalex = "W2005412999",
    pages = "145-213",
    volume = "21"
}

@inproceedings{barrington1936proteolytic1,
    author = "Barrington, E. J. W",
    title = "Proteolytic digestion and the problem of the pancreas in Lampetra",
    year = "1936",
    booktitle = "Proceedings of the Royal Society, London B, v. 121, p. 221-232",
    note = "talkorigins\_source = {true}; raw\_reference = {Barrington, E. J. W., 1936, Proteolytic digestion and the problem of the pancreas in Lampetra: Proceedings of the Royal Society, London B, v. 121, p. 221-232.}"
}

In view of the interest of Amphioxus as a primitive Chordate type, and its wide use in zoological teaching, it is remarkable that so little should be known of the structure and physiology of its digestive system. The early treatise of Delage and Hérouard (1898) gives little information concerning the mid-gut and the so-called “liver” beyond referring to their green colour, which is ascribed without further elucidation to the presence of secretory granules, while the hind-gut “ne présente rien de particular”. Pietschmann (1929), in his recent excellent account of the Cephalochorda, can give little further information. The epithelium of the “ liver” and “ stomach” are described as composed of ciliated cells with granulated cytoplasm, but no suggestion of regional differentiation in the various parts of these organs is given. Of the function of the hinder region of the alimentary system nothing can be said beyond a reference to the spiral movement imparted to the food by the ilio-colon ring, while Hammar’s statement, based on an embryological study (1898), that the “liver” is homologous with the liver of the higher Chordata, is accepted without question. The essentially physiological monograph of Franz (1927 b)is equally uninformative. It is, then, evident that this alimentary system demands a complete investigation both from the structural and functional points of view, and it has, in fact, been impossible to deal with all the problems which have suggested themselves. In its present form the work provides a description of the ciliary mechanisms of the post-pharyngeal regions of the gut, together with some account of the cytology of the epithelium and of the digestive enzymes secreted by it, and discusses in the light of this description the probable mode of operation of the mechanisms and the function of the various parts of the system; in conclusion, the homology of the “liver” is discussed, and a new interpretation of this organ suggested. It is hoped to undertake in the near future a comparative study of the cytology of the alimentary canal of the lower Chordata, and the cytological portion of the present work is therefore not to be regarded as exhaustive.

@article{barrington1937vi,
    author = "Barrington, Ernest James William",
    title = "VI - The digestive system of Amphioxus (Branchiostoma) Lanceolatus",
    year = "1937",
    journal = "Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences",
    abstract = "In view of the interest of Amphioxus as a primitive Chordate type, and its wide use in zoological teaching, it is remarkable that so little should be known of the structure and physiology of its digestive system. The early treatise of Delage and Hérouard (1898) gives little information concerning the mid-gut and the so-called “liver” beyond referring to their green colour, which is ascribed without further elucidation to the presence of secretory granules, while the hind-gut “ne présente rien de particular”. Pietschmann (1929), in his recent excellent account of the Cephalochorda, can give little further information. The epithelium of the “ liver” and “ stomach” are described as composed of ciliated cells with granulated cytoplasm, but no suggestion of regional differentiation in the various parts of these organs is given. Of the function of the hinder region of the alimentary system nothing can be said beyond a reference to the spiral movement imparted to the food by the ilio-colon ring, while Hammar’s statement, based on an embryological study (1898), that the “liver” is homologous with the liver of the higher Chordata, is accepted without question. The essentially physiological monograph of Franz (1927 b)is equally uninformative. It is, then, evident that this alimentary system demands a complete investigation both from the structural and functional points of view, and it has, in fact, been impossible to deal with all the problems which have suggested themselves. In its present form the work provides a description of the ciliary mechanisms of the post-pharyngeal regions of the gut, together with some account of the cytology of the epithelium and of the digestive enzymes secreted by it, and discusses in the light of this description the probable mode of operation of the mechanisms and the function of the various parts of the system; in conclusion, the homology of the “liver” is discussed, and a new interpretation of this organ suggested. It is hoped to undertake in the near future a comparative study of the cytology of the alimentary canal of the lower Chordata, and the cytological portion of the present work is therefore not to be regarded as exhaustive.",
    url = "https://doi.org/10.1098/rstb.1937.0013",
    doi = "10.1098/rstb.1937.0013",
    number = "553",
    openalex = "W2042849178",
    pages = "269-312",
    volume = "228",
    references = "doi101098rspb19360049"
}

@article{barrington1938the2,
    author = "Barrington, E. J. W",
    title = "The digestive system of Amphioxus ( Branchiostoma) lanceolatus",
    year = "1938",
    journal = "Philosophical Transactions of the Royal Society, London B, v. 228, p. 269-311",
    note = "talkorigins\_source = {true}; raw\_reference = {Barrington, E. J. W., 1938, The digestive system of Amphioxus ( Branchiostoma) lanceolatus: Philosophical Transactions of the Royal Society, London B, v. 228, p. 269-311.}"
}

This paper is concerned with the system of neurons which lies in the walls of the atrium of Branchiostoma. The system is found on the parietal and ventral walls of the atrium, as well as round the gut, and it is therefore thought preferable to speak of it as the atrial nervous system rather than the autonomic (enteric) system (Boeke). The neurons are shown to lie in or immediately below the atrial epithelium, which is of ectodermal origin. Special attention is given to the innervation of the gut and its diverticulum, of the atrio-coelomic funnels, and of the atrioporal region. Evidence as to the effector and receptor elements of the system is discussed. It has central connexions, and it is suggested that its activities play an important part in the animal’s behaviour.

@article{holmes1953the,
    author = "Holmes, William",
    title = "The Atrial Nervous System of Amphioxus (Branchiostoma)",
    year = "1953",
    journal = "Journal of Cell Science",
    abstract = "This paper is concerned with the system of neurons which lies in the walls of the atrium of Branchiostoma. The system is found on the parietal and ventral walls of the atrium, as well as round the gut, and it is therefore thought preferable to speak of it as the atrial nervous system rather than the autonomic (enteric) system (Boeke). The neurons are shown to lie in or immediately below the atrial epithelium, which is of ectodermal origin. Special attention is given to the innervation of the gut and its diverticulum, of the atrio-coelomic funnels, and of the atrioporal region. Evidence as to the effector and receptor elements of the system is discussed. It has central connexions, and it is suggested that its activities play an important part in the animal’s behaviour.",
    url = "https://doi.org/10.1242/jcs.s3-94.28.523",
    doi = "10.1242/jcs.s3-94.28.523",
    number = "28",
    openalex = "W2113571363",
    pages = "523-535",
    volume = "S3-94",
    references = "dogiel1903das, doi1010970000188819470500000035, doi101111j1469185x1952tb01361x, doi10230720025486, doi105962bhltitle49162"
}

The Acrania possess an histologically complex peripheral nervous system, the atrial nervous system, lying just under the epithelium lining the atrium and covering the various organs within it. The system contains both sensory and motor components, and is especially rich in peripheral sensory cell bodies. It is in connexion with the central nervous system by way of the dorsal root nerves. Most of the motor axons entering the system pass to the cross-striated pterygial muscle flooring the atrium, others pass to the cross-striated trapezius muscles, and there is also a large ciliarymotor component, which controls the action of the lateral ciliary tracts of the gill bars. Unipolar sensory neurons are abundant upon the surface of the pterygial muscle, and are also found upon the parietal walls of the atrium. Multipolar sensory neurons are abundant upon the foregut and its diverticulum. The hindgut (outside the atrium) is more sparsely innervated, but occasional multipolar sensory neurons occur there. The multipolar neurons of the foregut and diverticulum appear to be in connexion one with another asynaptically, but their axons pass to the central nervous system. Similar sensory neurons of several types are found in the richly innervated atrio-coelomic funnels. The function of the atrial nervous system is not yet entirely understood, but it is probable that it is mainly concerned with the regulation of the feeding process, and with spawning. It is concluded that the system is not evidently homologous with the ‘sympathetic’ systems of the craniates, and that it is unwise at present to attempt to homologize the visceral nervous systems of the two groups.

@article{bone1961the,
    author = "Bone, Quentin",
    title = "The organization of the atrial nervous system of amphioxus (Branchiostoma lanceolatum (Pallas))",
    year = "1961",
    journal = "Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences",
    abstract = "The Acrania possess an histologically complex peripheral nervous system, the atrial nervous system, lying just under the epithelium lining the atrium and covering the various organs within it. The system contains both sensory and motor components, and is especially rich in peripheral sensory cell bodies. It is in connexion with the central nervous system by way of the dorsal root nerves. Most of the motor axons entering the system pass to the cross-striated pterygial muscle flooring the atrium, others pass to the cross-striated trapezius muscles, and there is also a large ciliarymotor component, which controls the action of the lateral ciliary tracts of the gill bars. Unipolar sensory neurons are abundant upon the surface of the pterygial muscle, and are also found upon the parietal walls of the atrium. Multipolar sensory neurons are abundant upon the foregut and its diverticulum. The hindgut (outside the atrium) is more sparsely innervated, but occasional multipolar sensory neurons occur there. The multipolar neurons of the foregut and diverticulum appear to be in connexion one with another asynaptically, but their axons pass to the central nervous system. Similar sensory neurons of several types are found in the richly innervated atrio-coelomic funnels. The function of the atrial nervous system is not yet entirely understood, but it is probable that it is mainly concerned with the regulation of the feeding process, and with spawning. It is concluded that the system is not evidently homologous with the ‘sympathetic’ systems of the craniates, and that it is unwise at present to attempt to homologize the visceral nervous systems of the two groups.",
    url = "https://doi.org/10.1098/rstb.1961.0002",
    doi = "10.1098/rstb.1961.0002",
    number = "704",
    openalex = "W2013764007",
    pages = "241-269",
    volume = "243",
    references = "doi101002ar1090650110, doi101002cne901150105, doi101002jmor1050540103, doi101017s002531540001170x, doi1010381791345a0, doi101111j146363951956tb00047x, doi101111j1469185x1952tb01361x, doi101113expphysiol1958sp001305, doi105962bhltitle140340, doi105962bhltitle82144, holmes1953the"
}

Abstract In order to clarify the morphology of the circulatory system of amphioxus the blood vessels were investigated using modern techniques of light and electron microscopy. The pattern of circulation in amphioxus is forward ventrally and backwards dorsally. In addition, circulating corpuscles, usually associated with the blood of higher chordates, are absent. The circulatory system of amphioxus consists of well defined contractile vessels and vascular spaces or sinuses within a connective tissue matrix. The contractile vessels have a discontinuous endothelial lining resting on a basal lamina and are enclosed by a simple layer of contractile myoepithelial cells. Discontinuous endothelial linings occur throughout the vascular tree, including major and minor afferent and efferent vessels and blood sinuses. This is in contrast to higher animals where the endothelium forms a more or less continuous lining along the inner surface of the boundary layer. It is suggested that the endothelial cells of amphioxus, like the endothelial cells in capillaries of higher chordates, most likely play a role in the physiology of the circulatory system by removing residues of filtration from the basal lamina, thereby facilitating an exchange of materials to and from the surrounding tissues.

@article{doi101002jmor1051390403,
    author = "Möller, Peter C. and Philpott, Charles W.",
    title = "The circulatory system of Amphioxus (Branchiostoma floridae) I. Morphology of the major vessels of the pharyngeal area",
    year = "1973",
    journal = "Journal of Morphology",
    abstract = "Abstract In order to clarify the morphology of the circulatory system of amphioxus the blood vessels were investigated using modern techniques of light and electron microscopy. The pattern of circulation in amphioxus is forward ventrally and backwards dorsally. In addition, circulating corpuscles, usually associated with the blood of higher chordates, are absent. The circulatory system of amphioxus consists of well defined contractile vessels and vascular spaces or sinuses within a connective tissue matrix. The contractile vessels have a discontinuous endothelial lining resting on a basal lamina and are enclosed by a simple layer of contractile myoepithelial cells. Discontinuous endothelial linings occur throughout the vascular tree, including major and minor afferent and efferent vessels and blood sinuses. This is in contrast to higher animals where the endothelium forms a more or less continuous lining along the inner surface of the boundary layer. It is suggested that the endothelial cells of amphioxus, like the endothelial cells in capillaries of higher chordates, most likely play a role in the physiology of the circulatory system by removing residues of filtration from the basal lamina, thereby facilitating an exchange of materials to and from the surrounding tissues.",
    url = "https://doi.org/10.1002/jmor.1051390403",
    doi = "10.1002/jmor.1051390403",
    openalex = "W2143598529",
    references = "doi10100797836429105483, doi101083jcb171208, doi101083jcb202313, doi101083jcb231101, doi101083jcb351213, doi101083jcb372244, doi101083jcb372277, doi101083jcb44475, doi101083jcb92409, doi10310910520296009114754, doi105962bhltitle6856"
}

@article{moller1973the,
    author = "Moller, Peter C. and Philpott, Charles W.",
    title = "The circulatory system of amphioxus (Branchiostoma floridae)",
    year = "1973",
    journal = "Zeitschrift f�r Zellforschung und mikroskopische Anatomie",
    url = "https://doi.org/10.1007/bf00307456",
    doi = "10.1007/bf00307456",
    number = "1",
    openalex = "W2060753319",
    pages = "135-141",
    volume = "143",
    references = "doi101001jama197403230160059035, doi101002jmor1051390403, doi1010160076687955010203, doi101073pnas476802, doi101083jcb13155, doi101083jcb61113, doi101083jcb92409, doi101201b2184685, openalexw1498836585, openalexw1513425511"
}

@article{moller1974fine,
    author = "Moller, PeterC. and Ellis, RichardA.",
    title = "Fine structure of the excretory system of Amphioxus (Branchiostoma floridae) and its response to osmotic stress",
    year = "1974",
    journal = "Cell and Tissue Research",
    url = "https://doi.org/10.1007/bf00224314",
    doi = "10.1007/bf00224314",
    number = "1",
    openalex = "W2083401012",
    volume = "148",
    references = "doi101002jmor1051390403, doi101007bf00336662, doi101016s0022532069900331, doi101083jcb171208, doi101083jcb202313, doi10117711114, doi101242jeb313424, doi10310910520296009114754, doi105962bhltitle55924, nakao1965the, openalexw2047767613"
}

@inproceedings{welsch1975the3,
    author = "Welsch, U",
    title = "The fine structure of the pharynx, cryptopodocytes and digestive system of amphioxus (Branchiostoma lanceolatum)",
    year = "1975",
    booktitle = "Symposium of the Zoological Society, London, v. 36, p. 17-41",
    note = "talkorigins\_source = {true}; raw\_reference = {Welsch, U., 1975, The fine structure of the pharynx, cryptopodocytes and digestive system of amphioxus (Branchiostoma lanceolatum): Symposium of the Zoological Society, London, v. 36, p. 17-41.}"
}

@article{rähr1979the,
    author = "Rähr, H.",
    title = "The Circulatory System of Amphioxus (Branchiostoma lanceolatum (Pallas))",
    year = "1979",
    journal = "Acta Zoologica",
    url = "https://doi.org/10.1111/j.1463-6395.1979.tb00594.x",
    doi = "10.1111/j.1463-6395.1979.tb00594.x",
    number = "1",
    openalex = "W1990682207",
    pages = "1-18",
    volume = "60",
    references = "doi101002jmor1051390403, doi1010079783642651045, doi10100797836429105483, doi101007bf02933895, doi101016s0022532071900207, doi1023073225209, doi105962bhltitle159385, doi105962bhltitle6408, moller1973the, openalexw2321178397"
}

@incollection{zou1991contractile,
    author = "Zou, Yong-shui",
    title = "CONTRACTILE SYSTEM OF AMPHIOXUS (BRANCHIOSTOMA BELCHERI)",
    year = "1991",
    booktitle = "Retrospect and Prospect of Protein Research",
    url = "https://doi.org/10.1142/9789814360425\_0013",
    doi = "10.1142/9789814360425\_0013",
    openalex = "W2483228165",
    pages = "52-55"
}

@article{fagotti1998actin,
    author = "Fagotti, Anna and Di Rosa, Ines and Simoncelli, Francesca and Chaponnier, Christine and Gabbiani, Giulio and Pascolini, R.",
    title = "Actin isoforms in amphioxus Branchiostoma lanceolatum",
    year = "1998",
    journal = "Cell and Tissue Research",
    url = "https://doi.org/10.1007/s004410051047",
    doi = "10.1007/s004410051047",
    number = "1",
    openalex = "W2050707594",
    pages = "173-176",
    volume = "292"
}

Amphioxus neuroanatomy is important not just in its own right but also for the insights it provides regarding the evolutionary origin and basic organization of the vertebrate nervous system. This review summarizes the overall layout of the central nervous system (CNS), peripheral nerves, and nerve plexuses in amphioxus, and what is currently known of their histology and cell types, with special attention to new information on the anterior nerve cord. The intercalated region (IR) is of special functional and evolutionary interest. It extends caudally to the end of somite 4, traditionally considered the limit of the brain-like region of the amphioxus CNS, and is notable for the presence of a number of migrated cell groups. Unlike most other neurons in the cord, these migrated cells detach from the ventricular lumen and move into the adjacent neuropile, much as developing neurons do in vertebrates. The larval nervous system is also considered, as there is a wealth of new data on the organization and cell types of the anterior nerve cord in young larvae, based on detailed electron microscopical analyses and nerve tracing studies, and an emerging consensus regarding how this region relates to the vertebrate brain. Much less is known about the intervening period of the life history, i.e., the period between the young larva and the adult, but a great deal of neural development must occur during this time to generate a fully mature nervous system. It is especially interesting that the vertebrate counterparts of at least some postembryonic events of amphioxus neurogenesis occur, in vertebrates, in the embryo. The implication is that the whole of the postembryonic phase of neural development in amphioxus needs to be considered when making phylogenetic comparisons. Yet this is a period about which almost nothing is known. Considering this, plus the number of new molecular and immunocytochemical techniques now available to researchers, there is no shortage of worthwhile research topics using amphioxus, of whatever stage, as a subject.

@article{doi101139z04163,
    author = "Wicht, Helmut and Lacalli, Thurston C.",
    title = "The nervous system of amphioxus: structure, development, and evolutionary significance",
    year = "2005",
    journal = "Canadian Journal of Zoology",
    abstract = "Amphioxus neuroanatomy is important not just in its own right but also for the insights it provides regarding the evolutionary origin and basic organization of the vertebrate nervous system. This review summarizes the overall layout of the central nervous system (CNS), peripheral nerves, and nerve plexuses in amphioxus, and what is currently known of their histology and cell types, with special attention to new information on the anterior nerve cord. The intercalated region (IR) is of special functional and evolutionary interest. It extends caudally to the end of somite 4, traditionally considered the limit of the brain-like region of the amphioxus CNS, and is notable for the presence of a number of migrated cell groups. Unlike most other neurons in the cord, these migrated cells detach from the ventricular lumen and move into the adjacent neuropile, much as developing neurons do in vertebrates. The larval nervous system is also considered, as there is a wealth of new data on the organization and cell types of the anterior nerve cord in young larvae, based on detailed electron microscopical analyses and nerve tracing studies, and an emerging consensus regarding how this region relates to the vertebrate brain. Much less is known about the intervening period of the life history, i.e., the period between the young larva and the adult, but a great deal of neural development must occur during this time to generate a fully mature nervous system. It is especially interesting that the vertebrate counterparts of at least some postembryonic events of amphioxus neurogenesis occur, in vertebrates, in the embryo. The implication is that the whole of the postembryonic phase of neural development in amphioxus needs to be considered when making phylogenetic comparisons. Yet this is a period about which almost nothing is known. Considering this, plus the number of new molecular and immunocytochemical techniques now available to researchers, there is no shortage of worthwhile research topics using amphioxus, of whatever stage, as a subject.",
    url = "https://doi.org/10.1139/z04-163",
    doi = "10.1139/z04-163",
    openalex = "W2092757339",
    references = "anadn1998distribution, bone1959the, bone1961the, castro2003distribution, dogiel1903das, doi101002cne901150105, doi101002jmor1050540103, doi1010079783642182624, doi101007bf00348527, doi101007bf02028391, doi101016jydbio200604457, doi101016s0022532062800070, doi101098rstb19940059, doi101098rstb19960022, doi101111j146363951995tb00986x, doi101139z04160, doi101159000079744, doi101159000147530, doi101242dev125142701, doi101242jcss310052509, doi1023071535762, doi103166jds1391111, doi105962bhltitle159385, doi105962bhltitle55924, flood1974histochemistry, holmes1953the, openalexw2394638245, openalexw659399033, ruiz1991the, stokes1995ciliary"
}

Amphioxus (Cephalochordata) belongs to the most basal extant chordates, and knowledge of their brain organization appears to be key to deciphering the early stages of evolution of vertebrate brains. Most comprehensive studies of the organization of the central nervous system of adult amphioxus have investigated the spinal cord. Some brain populations have been characterized via neurochemistry and electron microscopy, and the overall cytoarchitecture of the brain was studied by Ekhart et al. (2003; J. Comp. Neurol. 466:319-330) with general staining methods and retrograde transport from the spinal cord. Here, the cytoarchitecture of the brain of adult amphioxus Branchiostoma lanceolatum was reinvestigated by using acetylated tubulin immunohistochemistry, which specifically stains neurons and fibers, in combination with some ancillary methods. This method allowed reproducible staining and mapping of types of neuron, mostly in brain regions caudal to the entrance level of nerve 2, and its comparison with spinal cord populations. The brain populations studied and discussed in detail were the Retzius bipolar cells, lamellate cells, Joseph cells, various types of translumenal cells, somatic motoneurons, Rohde nucleus cells, small ventral multipolar neurons, and Edinger cells. These observations expand our knowledge of the distribution of cell types and provide additional data on the number of cells and the axonal tracts and commissural regions of the adult amphioxus brain. The results of this comprehensive study provide a framework for comparison of complex adult populations with the early brain neuronal populations revealed in developmental studies of the amphioxus.

@article{doi101002cne23785,
    author = "Castro, A. and Becerra, Manuela and Manso, Marı́a Jesús and Anadón, Ramón",
    title = "Neuronal organization of the brain in the adult amphioxus (Branchiostoma lanceolatum): A study with acetylated tubulin immunohistochemistry",
    year = "2015",
    journal = "The Journal of Comparative Neurology",
    abstract = "Amphioxus (Cephalochordata) belongs to the most basal extant chordates, and knowledge of their brain organization appears to be key to deciphering the early stages of evolution of vertebrate brains. Most comprehensive studies of the organization of the central nervous system of adult amphioxus have investigated the spinal cord. Some brain populations have been characterized via neurochemistry and electron microscopy, and the overall cytoarchitecture of the brain was studied by Ekhart et al. (2003; J. Comp. Neurol. 466:319-330) with general staining methods and retrograde transport from the spinal cord. Here, the cytoarchitecture of the brain of adult amphioxus Branchiostoma lanceolatum was reinvestigated by using acetylated tubulin immunohistochemistry, which specifically stains neurons and fibers, in combination with some ancillary methods. This method allowed reproducible staining and mapping of types of neuron, mostly in brain regions caudal to the entrance level of nerve 2, and its comparison with spinal cord populations. The brain populations studied and discussed in detail were the Retzius bipolar cells, lamellate cells, Joseph cells, various types of translumenal cells, somatic motoneurons, Rohde nucleus cells, small ventral multipolar neurons, and Edinger cells. These observations expand our knowledge of the distribution of cell types and provide additional data on the number of cells and the axonal tracts and commissural regions of the adult amphioxus brain. The results of this comprehensive study provide a framework for comparison of complex adult populations with the early brain neuronal populations revealed in developmental studies of the amphioxus.",
    url = "https://doi.org/10.1002/cne.23785",
    doi = "10.1002/cne.23785",
    openalex = "W1882862961",
    references = "castro2003distribution, doi101007bf00348527, doi101007bf02028391, doi101007bf02933895, doi101387ijdb072436jg, holmes1953the, openalexw2394638245"
}

@article{he2018correction,
    author = "He, Chunpeng and Han, Tingyu and Liao, Xin and Zhou, Yuxin and Wang, Xiuqiang and Guan, Rui and Tian, Tian and Li, Yixin and Bi, Changwei and Lu, Na and He, Ziyi and Hu, Bing and Zhou, Qiang and Hu, Yue and Chen, J.-Y. and Lu, Zuhong",
    title = "Correction to ‘Phagocytic intracellular digestion in amphioxus (Branchiostoma)’",
    year = "2018",
    journal = "Proceedings of the Royal Society B: Biological Sciences",
    url = "https://doi.org/10.1098/rspb.2018.1277",
    doi = "10.1098/rspb.2018.1277",
    number = "1881",
    openalex = "W2810153670",
    pages = "20181277",
    volume = "285"
}

The digestive methods employed by amphioxus (Branchiostoma)—both intracellular phagocytic digestion and extracellular digestion—have been discussed since 1937. Recent studies also show that epithelial cells lining the Branchiostoma digestive tract can express many immune genes. Here, in Branchiostoma belcheri, using a special tissue fixation method, we show that some epithelial cells, especially those lining the large diverticulum protruding from the gut tube, phagocytize food particles directly, and Branchiostoma can rely on this kind of phagocytic intracellular digestion to obtain energy throughout all stages of its life. Gene expression profiles suggest that diverticulum epithelial cells have functional features of both digestive cells and phagocytes. In starved Branchiostoma, these cells accumulate endogenous digestive and hydrolytic enzymes, whereas, when sated, they express many kinds of immune genes in response to stimulation by phagocytized food particles. We also found that the distal hindgut epithelium can phagocytize food particles, but not as many. These results illustrate phagocytic intercellular digestion in Branchiostoma, explain why Branchiostoma digestive tract epithelial cells express typical immune genes and suggest that the main physiological function of the Branchiostoma diverticulum is different from that of the vertebrate liver.

@article{he2018phagocytic,
    author = "He, Chunpeng and Han, Tingyu and Liao, Xin and Zhou, Yuxin and Wang, Xiuqiang and Guan, Rui and Tian, Tian and Li, Yixin and Bi, Changwei and Lu, Na and He, Ziyi and Hu, Bing and Zhou, Qiang and Hu, Yue and Lu, Zuhong and Chen, J.-Y.",
    title = "Phagocytic intracellular digestion in amphioxus (Branchiostoma)",
    year = "2018",
    journal = "Proceedings of the Royal Society B: Biological Sciences",
    abstract = "The digestive methods employed by amphioxus (Branchiostoma)—both intracellular phagocytic digestion and extracellular digestion—have been discussed since 1937. Recent studies also show that epithelial cells lining the Branchiostoma digestive tract can express many immune genes. Here, in Branchiostoma belcheri, using a special tissue fixation method, we show that some epithelial cells, especially those lining the large diverticulum protruding from the gut tube, phagocytize food particles directly, and Branchiostoma can rely on this kind of phagocytic intracellular digestion to obtain energy throughout all stages of its life. Gene expression profiles suggest that diverticulum epithelial cells have functional features of both digestive cells and phagocytes. In starved Branchiostoma, these cells accumulate endogenous digestive and hydrolytic enzymes, whereas, when sated, they express many kinds of immune genes in response to stimulation by phagocytized food particles. We also found that the distal hindgut epithelium can phagocytize food particles, but not as many. These results illustrate phagocytic intercellular digestion in Branchiostoma, explain why Branchiostoma digestive tract epithelial cells express typical immune genes and suggest that the main physiological function of the Branchiostoma diverticulum is different from that of the vertebrate liver.",
    url = "https://doi.org/10.1098/rspb.2018.0438",
    doi = "10.1098/rspb.2018.0438",
    number = "1880",
    openalex = "W2807596500",
    pages = "20180438",
    volume = "285",
    references = "doi10103831933, doi101038nature06967, doi101038nature12034, doi101038ni0708705, doi101038nrg2318, doi101038nri3244, doi101038nrm1244, doi101073pnas93126025, doi101159000443526"
}

Digestive systems and extracellular digestion are key animal features, but their emergence during early animal evolution is currently poorly understood. As the last common ancestor of non-bilaterian animal groups (sponges, ctenophores, placozoans and cnidarians) dates back to the beginning of animal life, their study and comparison provides important insights into the early evolution of digestive systems and functions. Here, I have compiled an overview of the development and cell biology of digestive tissues in non-bilaterian animals. I will highlight the fundamental differences between extracellular and intracellular digestive processes, and how these are distributed among animals. Cnidarians (e.g. sea anemones, corals, jellyfish), the phylogenetic outgroup of bilaterians (e.g. vertebrates, flies, annelids), occupy a key position to reconstruct the evolution of bilaterian gut evolution. A major focus will therefore lie on the development and cell biology of digestive tissues in cnidarians, especially sea anemones, and how they compare to bilaterian gut tissues. In that context, I will also review how a recent study on the gastrula fate map of the sea anemone Nematostella vectensis challenges our long-standing conceptions on the evolution of cnidarian and bilaterian germ layers and guts.

@article{doi101007s0044101903075x,
    author = "Steinmetz, Patrick R. H.",
    title = "A non-bilaterian perspective on the development and evolution of animal digestive systems",
    year = "2019",
    journal = "Cell and Tissue Research",
    abstract = "Digestive systems and extracellular digestion are key animal features, but their emergence during early animal evolution is currently poorly understood. As the last common ancestor of non-bilaterian animal groups (sponges, ctenophores, placozoans and cnidarians) dates back to the beginning of animal life, their study and comparison provides important insights into the early evolution of digestive systems and functions. Here, I have compiled an overview of the development and cell biology of digestive tissues in non-bilaterian animals. I will highlight the fundamental differences between extracellular and intracellular digestive processes, and how these are distributed among animals. Cnidarians (e.g. sea anemones, corals, jellyfish), the phylogenetic outgroup of bilaterians (e.g. vertebrates, flies, annelids), occupy a key position to reconstruct the evolution of bilaterian gut evolution. A major focus will therefore lie on the development and cell biology of digestive tissues in cnidarians, especially sea anemones, and how they compare to bilaterian gut tissues. In that context, I will also review how a recent study on the gastrula fate map of the sea anemone Nematostella vectensis challenges our long-standing conceptions on the evolution of cnidarian and bilaterian germ layers and guts.",
    url = "https://doi.org/10.1007/s00441-019-03075-x",
    doi = "10.1007/s00441-019-03075-x",
    openalex = "W2965377678",
    references = "doi101038s4155901806410, doi101093acprofoso97801995494290030004"
}

Despite their pivotal role, the evolutionary origins of vertebrate digestive systems remain enigmatic. We explored the cellular characteristics of the amphioxus (Branchiostoma floridae) digestive tract, a model for the presumed primitive chordate digestive system, using bulk tissue companioned with single-cell RNA sequencing. Our findings reveal segmentation and a rich diversity of cell clusters, and we highlight the presence of epithelial-like, ciliated cells in the amphioxus midgut and describe three types of endocrine-like cells that secrete insulin-like, glucagon-like, and somatostatin-like peptides. Furthermore, Pdx, Ilp1, Ilp2, and Ilpr knockout amphioxus lines revealed that, in amphioxus, Pdx does not influence Ilp expression. We also unravel similarity between amphioxus Ilp1 and vertebrate insulin-like growth factor 1 (Igf1) in terms of predicted structure, effects on body growth and amino acid metabolism, and interactions with Igf-binding proteins. These findings indicate that the evolutionary alterations involving the regulatory influence of Pdx over insulin gene expression could have been instrumental in the development of the vertebrate digestive system.

@article{doi101126sciadvadq0702,
    author = "Dai, Yichen and Pan, Rongrong and Pan, Qi and Wu, Xiaotong and Cai, Zexin and Fu, Yongheng and Shi, Chenggang and Sheng, Yizhe and Li, Jingjing and Lin, Zhe and Liu, Gaoming and Zhu, Pingfen and Li, Meng and Li, Guang and Zhou, Xuming",
    title = "Single-cell profiling of the amphioxus digestive tract reveals conservation of endocrine cells in chordates",
    year = "2024",
    journal = "Science Advances",
    abstract = "Despite their pivotal role, the evolutionary origins of vertebrate digestive systems remain enigmatic. We explored the cellular characteristics of the amphioxus (Branchiostoma floridae) digestive tract, a model for the presumed primitive chordate digestive system, using bulk tissue companioned with single-cell RNA sequencing. Our findings reveal segmentation and a rich diversity of cell clusters, and we highlight the presence of epithelial-like, ciliated cells in the amphioxus midgut and describe three types of endocrine-like cells that secrete insulin-like, glucagon-like, and somatostatin-like peptides. Furthermore, Pdx, Ilp1, Ilp2, and Ilpr knockout amphioxus lines revealed that, in amphioxus, Pdx does not influence Ilp expression. We also unravel similarity between amphioxus Ilp1 and vertebrate insulin-like growth factor 1 (Igf1) in terms of predicted structure, effects on body growth and amino acid metabolism, and interactions with Igf-binding proteins. These findings indicate that the evolutionary alterations involving the regulatory influence of Pdx over insulin gene expression could have been instrumental in the development of the vertebrate digestive system.",
    url = "https://doi.org/10.1126/sciadv.adq0702",
    doi = "10.1126/sciadv.adq0702",
    openalex = "W4405632874",
    references = "doi101007s00441019030355, doi101074jbcm115664003, doi101387ijdb170196nh"
}