Relationship to animalia
Domain: Eukarya
Clade: Opisthokonta Class: Choanoflagellatea Order: Choanoflagellida Family: Codosigidae Genus: Monosiga Species: M. brevicollis |
M. brevicollis is a member of the choanoflagellates, the sister clade to the animal kingdom. The common ancestor of choanos and animals is estimated to have diverged from the ancestor of fungi about a billion years ago, and the common ancestor ofa nimals is suspected to have diverged from choanoflagellatea between 675 and 875 Mya[1]. Morphologically, they are practically indistinguishable from collar cells found in sponges[1], and share resemblance to some cells found in cnidarians[8].
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Anatomy, Feeding, Ecology, Reproduction
Choanos are unicellular, heterotrophic[4] (they eat bacteria[7]), and form colonies in various configurations[4][6]. A resting choano is roughly spherical, but while swimming they become more elongate. The collars, which help in trapping food while the choano swims[2], are about half as long as the cell, and the flagella about 4.5 times the cell length[3]. Like amoebas, some choanoflagellates can encyst, which involves retracting the flagellum and collar[2]. Little is known about choanoflagellate reproductive cycles, including whether or not there is even a sexual phase[2].
M. brevicollis is a marine choano[4], and choanos form a critical link in the carbon cycle by consuming photosynthetic nanoplankton that larger, choano-eating, predators can't catch[1, p1232][2][4]. At least 405 M. brevicollis genes are suspected to be the result of horizontal gene transfer from algae or prokaryotes[5]. |
References
[1]Campbell & Reece, Biology, 8th Edition
[2]http://www.choano.org/wiki/Choanoflagellates
[3]http://choanoflagellates.lifedesks.org/pages/492
[4]http://genome.jgi-psf.org/Monbr1/Monbr1.home.html
[5]Jipei, Y., Guiling, S., Xiangyang, H., & Jinling, H. (2013). The scale and evolutionary significance of horizontal gene transfer in the choanoflagellate Monosiga brevicollis. BMC Genomics, 14(1), 1-22. doi:10.1186/1471-2164-14-729
[6]http://kinglab.berkeley.edu/research/
[7]http://microbewiki.kenyon.edu/index.php/Choanoflagellata
[8]http://en.wikipedia.org/wiki/Choanocyte
[2]http://www.choano.org/wiki/Choanoflagellates
[3]http://choanoflagellates.lifedesks.org/pages/492
[4]http://genome.jgi-psf.org/Monbr1/Monbr1.home.html
[5]Jipei, Y., Guiling, S., Xiangyang, H., & Jinling, H. (2013). The scale and evolutionary significance of horizontal gene transfer in the choanoflagellate Monosiga brevicollis. BMC Genomics, 14(1), 1-22. doi:10.1186/1471-2164-14-729
[6]http://kinglab.berkeley.edu/research/
[7]http://microbewiki.kenyon.edu/index.php/Choanoflagellata
[8]http://en.wikipedia.org/wiki/Choanocyte