関: collar cell

WordNet

any of the flagellated cells in sponges having a collar of cytoplasm around the flagellum; they maintain a flow of water through the body (同)collar_cell

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/07 22:21:55」(JST)

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Choanocytes (also known as "collar cells") are cells that line the interior of Asconoid, syconoid and leuconoid body type sponges that contain a central flagellum, or undulipodia,^[1] surrounded by a collar of microvilli which are connected by a thin membrane. It^{[clarification needed]} is the closest family member to the free-living ancestor called choanoflagellate. The flagellae beat regularly, creating a water flow across the microvilli which can then filter nutrients and other food from the water taken from the collar of the sponge. Food particles are then phagocytosed by the cell. ^[2]

Location[edit source | edit]

Choanocytes are found dotting the surface of the spongocoel in asconoid sponges and the radial canals in syconoid sponges, but they comprise entirely the chambers in leuconoid sponges.

Function[edit source | edit]

By cooperatively moving their flagella, choanocytes generate a flow of water through the sponges pores, into the spongocoel, and out through the osculum. This improves both respiratory and digestive functions for the sponge, pulling in oxygen and nutrients and allowing a rapid expulsion of carbon dioxide and other waste products. Although all cells in a sponge are capable of living on their own, choanocytes carry out most of the sponge's ingestion, passing digested materials to the amoebocytes for delivery to other cells.

Choanocytes can also turn into spermatocytes when needed for sexual reproduction, due to the lack of reproductive organs in sponges (amoebocytes become the oocytes).

Evolutionary Significance[edit source | edit]

Choanocytes bear more than a passing resemblance to Choanoflagellates, and demonstrate key steps in the evolution of animals. Scientist Nicole King helped to establish the distinction.^[3] DNA sequencing indicates that multicellular choanoflagellates and poriferans are sister groups, both descended from the same eukaryotic clade. One can see modern choanoflagellates living in small colonies, illustrating the evolution of sponges by analogy. More complex animals, notably the cnidarians, possess cells whose structures are clearly derived from choanocytes, demonstrating their historical ties to phylum porifera.

References[edit source | edit]

^ A Dictionary of Biology , 2004, accessed 2010-04-06.
^ Anderson, D. (2001) Invertebrate Zoology Oxford University Press
^ Shubin, Neil "Your Inner Fish"

English Journal

The ontogeny of choanocyte chambers during metamorphosis in the demosponge Amphimedon queenslandica.

Sogabe S1, Nakanishi N1, Degnan BM1.
EvoDevo.Evodevo.2016 Mar 8;7:6. doi: 10.1186/s13227-016-0042-x. eCollection 2016.
BACKGROUND: The aquiferous body plan of poriferans revolves around internal chambers comprised of choanocytes, a cell type structurally similar to choanoflagellates. These choanocyte chambers perform a range of physiological and developmental functions, including the capture of food and the generati
PMID 26958337

Biofouling of inlet pipes affects water quality in running seawater aquaria and compromises sponge cell proliferation.

Alexander BE1, Mueller B2, Vermeij MJ3, van der Geest HH1, de Goeij JM4.
PeerJ.PeerJ.2015 Dec 7;3:e1430. doi: 10.7717/peerj.1430. eCollection 2015.
Marine organism are often kept, cultured, and experimented on in running seawater aquaria. However, surprisingly little attention is given to the nutrient composition of the water flowing through these systems, which is generally assumed to equal in situ conditions, but may change due to the presenc
PMID 26664799

Transdifferentiation is a driving force of regeneration in Halisarca dujardini (Demospongiae, Porifera).

Borisenko IE1, Adamska M2, Tokina DB3, Ereskovsky AV4.
PeerJ.PeerJ.2015 Aug 25;3:e1211. doi: 10.7717/peerj.1211. eCollection 2015.
The ability to regenerate is widespread in the animal kingdom, but the regenerative capacities and mechanisms vary widely. To understand the evolutionary history of the diverse regeneration mechanisms, the regeneration processes must be studied in early-evolved metazoans in addition to the tradition
PMID 26336645

Japanese Journal

The stem cell system in demosponges : Insights into the origin of somatic stem cells

Funayama Noriko
Development, growth & differentiation 52(1), 1-14, 2010-01-01
NAID 10027562681

Isolation of the choanocyte in the fresh water sponge, Ephydatia fluviatilis and its lineage marker, Ef annexin

Funayama Noriko,Nakatsukasa Mikiko,Hayashi Tetsutaro [他],AGATA Kiyokazu
Development, growth & differentiation 47(4), 243-253, 2005-06-01
NAID 10016455606

Choanocyte Differentiation in the Fresh-Water Sponge(Organogenesis and Evolution,Symposium,PROCEEDING OF THE 75^<TH> ANNUAL MEETING OF THE ZOOLOGICAL SOCIETY OF JAPAN)