Choanocyte

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Choanocytes make up the choanoderm.

Choanocytes (also choanocytes, collar whip cells) are a cell type that occurs in sponges ( Porifera ). The choanocytes form a covering cell layer in the sponges called the choanoderm. The choanoderm lines the interior of the sponges ( spongocoel , gastric space , scourge chamber ). The collar flagellum cell consists of a rounded cell body ( soma ). On a cell pole sits a long flagellum ( flagellum ). There is a ring of stereovilli around the scourge . This is the eponymous collar. Mucus sits between the individual stereovilli. This creates a mucous line ( plasma collar ). The scourge blow creates a stream of water that feeds water from the sides. The water passes through the mucus border. Food particles floating in the water get caught in the mucus. They are then captured by pseudopodia and taken up by the collar scourge cell by means of endocytosis .

In sponges, the common scourge strike of all choanocytes of the choanoderm creates a collective flow of water. The water flows from the sides (through porocytes ) into the spongocoel, past the collagen flagellum cells of the choanoderm and back out through the outflow opening ( osculum ). The choanocytes remove many particles from the water. Particle-rich water flows into the sponge and particle-poor water flows out. On the one hand, the endocytic choanocytes themselves digest the ingested material. On the other hand, however, they also pass on phagosomes to amoebocytes . The choanocytes also help with reproduction . Their flow of water ensures that sperm are pushed out through the outflow opening. At the same time, the current ensures that foreign sperm are sucked in through the porocytes in order to fertilize the egg cells of the inner mesohyl .

Collar flagella cells are not only found in sponges. Their occurrence in the frilled flagellates ( Choanoflagellata ) is particularly striking . These are microorganisms that either live as individual collagen scourge cells or form small cell colonies from collagen scourge cells. The similarity between the cells of the choanoflagellata and the sponge choanocytes is striking. It extends into fine structural correspondences.

Occurrence

Typical and clearly recognizable collar whip flagellates (Choanoflagellata) and sponges (Porifera) occur. In addition, certain cell types are found in many other animals that are also more similar to collar whip cells. However, they are less similar to the collared flagella cells of adult sponges, but rather their incomplete cell development stages, as found in sponge embryos. Such mono ciliary epithelial cells often fulfill receptor functions.

The disc animals ( Placozoa ) living today do not have any cells that look like collar whip cells at first glance. Instead, they have barrel-shaped cylindrical cells in the highly prismatic epithelium on the ventral side of the body. Similar to the collar flagella cells, these cylinder cells have a central flagella. In the histological thin-section specimen, it can also be seen that the cell membrane protrudes microvilli around the flagella . The cylindrical cells ingest food particles through endocytosis. There are also monociliary cells on the dorsal side of the animal's body. However, they are flatter and without microvilli.

Cells similar to collar whip cells have been found in various cnidarians ( Cnidaria ) belonging to the group of flower animals ( Anthozoa ). There are also cells in the integument of flatworms ( platelets ) that resemble collar-whip cells. They are unicellular mechanoreceptors. Collar flagellar cell-like cells with up to 12 flagella were identified in a free-swimming cordworm larva ( Nemertea ). Furthermore, mechanoreceptors, which are strongly reminiscent of collar flagellate cells, were found in annelids ( Annelida ) from the group of little bristles ( Oligochaeta ). In the digestive tract of a Stachelhäuters ( Echinodermata ) from the group of sea stars ( Asteroidea ) two different cell types were determined, similar to the collar ciliated cells. In echinoderms, monociliary cells serve as receptor and supporting cells .

evolution

Collared flagellates of the species Monosiga brevicollis consist of a single collar flagellate cell.

The collar flagellate cells of the collar flagellates (Choanoflagellata) and sponges (Porifera) can hardly be distinguished from one another. It is therefore assumed that the sponges were the first multicellular animals to evolve from unicellular or colony-forming flagellates. These animals ( Metazoa ) originated in the Proterozoic and were therefore living beings that were very similar to today's sponges and therefore had the typical collar scourge cells. Biomarkers from the cryogenium indicate the presence of sponges at least 635 million years ago. The disc animals (Placozoa) and the tissue animals ( Eumetazoa ) developed from the sponges . The earliest tissue animal fossils resemble today's anthozoa and are around 590 million years old. In such animals, cells similar to those of the collar scourge still occur today. The oldest fossils of bilateral animals ( Bilateria ) come from the upper Ediacarian and are between 542 and 560 million years old.

Many animals living today have cells similar to cervical flagellum cells. Only in the comb jellyfish ( Ctenophora ) and in a branch of the molting animals ( Ecdysozoa ) have they been re-developed beyond recognition. Taken together, it seems very likely that the last common ancestor of all animals belonged to the sponges and possessed choanocytes as a legacy of his collar-flagellate ancestors. Such choanocytes are preserved in adult sponges today. The last common ancestor of all epitheliozoa , i.e. all disc animals and tissue animals, had choanocytes that resembled certain cell development stages in today's sponge embryos. After disc animals and tissue animals had separated from each other, the disc animals changed the cell type further, so that in the only disc animal living today ( Trichoplax adhaerens ) no more cells similar to collar whip cells are found. However, the last common ancestor of all tissue animals still possessed the cells similar to those of the collar whip cells. This animal could have resembled one of today's flower animals. The last common ancestor of all bilateral animals also had cells similar to collar whip cells. The cells evolved in different strains of tissue animals in different directions and changed their shape to a greater or lesser extent. Twice they seem to have been completely lost.

Individual evidence

  1. ^ Félix Dujardin: Histoire naturelle des zoophytes . Librairie encyclopédique de Roret, Paris, 1841, p. 306.
  2. ^ Sally P. Leys, Dafne I. Eerkes-Medrano: Feeding in a Calcareous Sponge: Particle Uptake by Pseudopodia . In: Biology Bulletin . Volume 211, 2006, p. 157.
  3. ^ Neil A. Campbell, Jane B. Reece: Biology . Heidelberg / Berlin 2006, p. 769.
  4. ^ "> Henry James-Clark: On the Spongiae Ciliatae as Infusoria Flagellata . In: Memoirs read before the Boston Society of Natural History . Volume 1, 1867, pp. 305-340.
  5. Jump up ↑ Barry SC Leadbeater: The Choanoflagellates . Cambridge University Press, 2015, p. 1.
  6. ↑ Manuel Maldonadoa: Choanoflagellates, choanocytes, and animal multicellularity . In: Invertebrate Biology . Volume 123, 2004, p. 1.
  7. ^ W. Westheide, R. Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates . Munich, 2007, pp. 125–126.
  8. ^ V. Storch, U. Welsch: Systematic Zoology. Spektrum Akademischer Verlag, Heidelberg / Berlin 2004, pp. 37–38.
  9. ↑ KM Lyons: Collar cells in planula and adult tentacle ectoderm of the solitary coral Balanophyllia regia (anthozoa eupsammiidae). In: Cell and Tissue Research. 145 (1), 1973, pp. 57-74.
  10. ^ WM Goldberg, GT Taylor: Cellular structure and infrastructure of the black coral Antipathes aperta: 2. The gastrodermis and its collar cells. In: Journal of Morphology . 202 (2), 2005, pp. 255-269.
  11. ↑ U. Ehlers, B. Ehlers: Monociliary receptors in interstitial Proseriata and Neorhabdocoela (Turbellaria Neoophora). In: Zoomorphology. 86 (3), 1977, pp. 197-222.
  12. ↑ C.-E. Cantell, Å. Franzén, T- Sensenbaugh: Ultrastructure of multiciliated collar cells in the pilidium larva of Lineus bilineatus (Nemertini). In: Zoomorphology. 101 (1), 1982, pp. 1-15.
  13. ↑ K. Moritz, V. Storch: Electron microscopic examination of a mechanoreceptor of invertebrates (Priapuliden, Oligochaeten). In: Cell and Tissue Research. 117 (2), 2004, pp. 226-234.
  14. ^ A. Martinez, J. Lopez, AC Villaro, DP Sesma: Choanocyte-like cells in the digestive system of the starfish Marthasterias glacialis (Echinodermata). In: Journal of Morphology. 208 (2), 2005, pp. 215-225.
  15. ^ W. Westheide, R. Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates . Munich 2007, p. 807.
  16. ^ Henry James-Clark: On the Spongiae Ciliatae as Infusoria Flagellata . In: Memoirs read before the Boston Society of Natural History . Volume 1, 1867, pp. 305-340.
  17. ↑ H. Philippe, R. Derelle, P. Lopez, K. Pick, C. Borchiellini, N. Boury-Esnault, J. Vacelet, E. Renard, E. Houliston, E. Quéinnec, C. Da Silva, P. Wincker, H. Le Guyader, S. Leys, DJ Jackson, F. Schreiber, D. Erpenbeck, G. Morgenstern, Wörheide, M. Manuel: Phylogenomics Revives Traditional Views on Deep Animal Relationships. In: Current Biology. Volume 19, 2009, p. 706.
  18. ↑ Martin Dohrmann, Gert Wörheide: Dating early animal evolution using phylogenomic data . In: Scientific Reports . Volume 7, 2017, p. 4.
  19. ↑ J. Alex Zumberge, Gordon D. Love, Paco Cárdenas, Erik A. Sperling, Sunithi Gunasekera, Megan Rohrssen, Emmanuelle Grosjean, John P. Grotzinger, Roger E. Summons: Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals . In: Nature Ecology & Evolution . Volume 2, 2018, p. 1709.
  20. ↑ Martin Dohrmann, Gert Wörheide: Dating early animal evolution using phylogenomic data . In: Scientific Reports . Volume 7, 2017, p. 4.
  21. ↑ S. Xiao, X. Yuan, AH Knoll: Eumetazoan fossils in terminal Proterozoic phosphorites? In: PNAS. 97 (2000), pp. 13684-13689.
  22. ^ GM Narbonne: The Ediacara biota: Neoproterozoic origin of animals and their ecosystems . In: Annual Reviews of Earth and Planetary Sciences. 33 (2005), pp. 421-442.
  23. ↑ Thibaut Brunet, Nicole King: Premetazoan genome evolution and the regulation of cell differentiation in the choanoflagellate Salpingoeca rosetta . In: Developmental Cell . Volume 43, 2017, p. 125.
  24. ↑ Martin Dohrmann, Gert Wörheide: Dating early animal evolution using phylogenomic data . In: Scientific Reports . Volume 7, 2017, p. 4.