''Salpingoeca rosetta'' is a species of

Choanoflagellate Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and ...

s in the family Salpingoecidae. It is a rare marine

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

consisting of a number of cells embedded in a jelly-like matrix. This organism demonstrates a very primitive level of

cell differentiation Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular ...

and specialization. This is seen with flagellated cells and their collar structures that move the cell colony through the water. Similar low level

cellular differentiation Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellula ...

and specification can also be seen in sponges. They also have collar cells (also called

choanocytes Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body types of sponges that contain a central flagellum, or ''cilium,'' surrounded by a collar of microvilli which are connected by ...

due to their similarities to choanoflagellates) and amoeboid cells arranged in a gelatinous matrix.
Unlike ''S. rosetta'',

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

s also have other cell-types that can perform different functions. Also, the collar cells of sponges beat within canals in the sponge body, whereas Salpingoeca rosetta's collar cells reside on the inside and it lacks internal canals. Despite these minor differences, there is strong evidence that Proterospongia and Metazoa are highly related. Its genome has been studied as a model for pre-

metazoan Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ho ...

evolution. The genome is 55 megabases in size. Homologs of cell adhesion, neuropeptide and glycosphingolipid metabolism genes are present in the genome. Dayel Protero Colonies inset

Reproduction cycle

''S. rosetta'' has a sexual cycle during which it transitions between haploid and diploid stages. When nutrients become limiting, haploid cultures of ''S. rosetta'' become diploid. This ploidy shift coincides with mating during which small, flagellated cells fuse with larger flagellated cells. Evidence has also been obtained for historical mating and recombination in ''S. rosetta''. ''S. rosetta'' can be induced to undergo sexual reproduction by the marine bacterium '' Vibrio fischeri''. A single protein of ''V. fischeri'', EroS, fully recapitulates the aphrodesiac-like activity of living ''V. fischeri''.

Colonial organization

''S. rosetta'' was named for the rosette-shaped colonies formed by its cells. The colonies are held together by adhesion molecules long thought to be found only in

Metazoan Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ho ...

organisms. Additionally, recent evidence suggests that a bacterial sulfonolipid, called rosette inducing factor (RIF-1) and produced by '' Algoriphagus machipongonensis'', triggers colony formation in ''S. rosetta''. The effect of RIF-1 on colony formation in ''S. rosetta'' has been suggested as an example of how interactions between bacteria and eukaryotes may have led to multicellularity in the latter.

References

External links

* Choanoflagellate species Protists described in 2011 {{Holozoa-stub