Choanoflagellate
Salpingoeca sp.
Collar flagellate ( Choanomonada, also Choanoflagellata ) are a group of single-celled organisms.
Features
Collar flagellates are with sizes of typically up to 10 microns comparatively small protists. Characteristic of it is above all a "collar" from 30 to 40 fine, thread-like cell processes ( microvilli ) that exists in this form with any other Protistengruppe, and a single flagellum at its center that juts out over the collar. A formerly well- known second Scourge went over the development history lost and it can only be preserved at kinetosome prove.
In planktonic species living there are called Loricae, rib-like structures zytoskelettäre. Many sessile species form Thecae from extracellular, goblet - shaped or jug, sometimes stalked cell envelopes.
Way of life
Collar flagellates occur either as stationary or as free-floating individuals or colonies in the sea as in fresh water. They feed on organic particles, especially of bacteria floating in the water, which they catch by this approach swirl with the movement of their scourge to her collar. The particles are then absorbed and digested at the base of the microvilli and the underlying cell by the end of pseudopods.
System
In addition to the mushrooms, the multicellular animals and the Mesomycetozoa the collar flagellates represent one of the four groups of the so-called Opisthokonta dar.
They are traditionally into three further here by Adl et al. ranglos mentioned groups:
Evolution
The collar scourge system of the collar flagellates is very likely homologous to the Choanozyten the sponges ( Porifera ); however, this is disputed by some researchers. Choanoflagellates and sponge isolated from organisms Choanozyten are indistinguishable. Sponges and collar flagellate form, as a bridge between single-and multi -cellular organisms. Earlier considerations, the sponges were emerged independently of the other Metazoa from colony forming choanoflagellates, however, have been refuted by the genomics. Studies of the genome make it appear probable that the collar flagellates represent the sister group of multicellular animals, ie represent among the protozoa their nearest living relatives. Earlier assumptions that choanoflagellates itself could be the root group of the Metazoa have not been confirmed by recent analyzes.
Evidence
- Klaus Hausmann, Norbert Hülsmann, Renate Radek: Protistology, 3rd edition, Schweizerbart, 2003, p 81, ISBN 3-510-65208-8
- Iñaki Ruiz- Trillo, Andrew J. Roger, Gertraud Burger, Michael W. Gray, B. Franz Lang (2008): A phylogenomic investigation into the Origin of Metazoa. Molecular Biology and Evolution 25 ( 4) :664 - 672.
- Barry SC Leadbeater, Qibin Yu, Joyce Kent, Dov J. Stekel (2009): Three-dimensional images of choanoflagellate loricae. Proceedings of the Royal Society B Biological Science 276 (1654): 3-11.