Choanoflagellate: Difference between revisions
Josh Grosse (talk | contribs) Classification following Cavalier-Smith |
Added spacing; I'm a bot, sorry if I messed anything up |
||
Line 1: | Line 1: | ||
<table border=1 cellspacing=0 align=right> |
<table border=1 cellspacing=0 align=right style="margin-left: 1em; margin-bottom: 0.5em;"> |
||
<tr><th bgcolor=khaki>'''Choanoflagellates'''</th></tr> |
<tr><th bgcolor=khaki>'''Choanoflagellates'''</th></tr> |
||
<tr><th bgcolor=khaki>'''[[Scientific classification]]'''</th></tr> |
<tr><th bgcolor=khaki>'''[[Scientific classification]]'''</th></tr> |
Revision as of 23:23, 31 March 2004
Choanoflagellates | ||||||
---|---|---|---|---|---|---|
Scientific classification | ||||||
|
The choanoflagellates are a group of flagellate protozoa. They are considered to be the closest relatives of the animals, and in particular may be the direct ancestors of sponges.
Each choanoflagellate has a single flagellum, surrounded by a ring of hairlike protrusions called microvilli, forming a cylindrical or conical collar (choanos in Greek). The flagellum pulls water through the collar, and small food particles are captured by the microvilli and ingested. It also pushes free-swimming cells along, as in animal sperm, whereas most other flagellates are pulled by their flagella.
Most choanoflagellates are sessile, with a stalk opposite the flagellum. A number of species are colonial, usually taking the form of a cluster of cells on a single stalk. Of special note is Proterospongia, which takes the form of a glob of cells, of which the external cells are typical flagellates with collars, but the internal cells are non-motile.
The choanocytes of sponges have the same basic structure as choanoflagellates. Collared cells are occasionally found in a few other animal groups, such as flatworms.