Proterospongia
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| Genus: | Proterospongia
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Proterospongia is a genus of single-celled aquatic organisms which form colonies. It belongs to the choanoflagellate class. As a colony-forming choanoflagellate, Proterospongia is of interest to scientists studying the mechanisms of intercellular signaling and adhesion present before animals appeared.[1][2]
Physical characteristics[edit]
Members of Proterospongia have the typical choanoflagellate cell structure characterized by a cell body 5-10μm in diameter with a 20-30μm apical flagellum surrounded by a collar of 15-25 actin-filled microvilli.[3][4] The flagellum propels swimming cells through the water column and creates water currents through the microvilli, which trap foodstuff such as bacteria and detritus.[3][4] The arrangement of organelles in Proterospongia appears consistent with other choanoflagellates and is characterized by an anterior dictyosome under the flagellar base, a central nucleus, peripheral mitochondria and a posterior food vacuole.[3][4]
As a member of the Codonosigidae family, Proterospongia have only a fine investment that is indistinct by light microscopy or completely lack an outer-covering.[3][4] Proterospongia species are distinguished by colony morphology, which vary from simple chains of cells to striking astral assemblages.[5] Colonies having extracellular jelly or mucilage have been described by Kent, Lackey, and Leadbeater; however the composition of this substance is unknown.[3][4][5][6] Kent also described a Proterospongia species containing two types of cells embedded in mucilage; however, this is the only account of such a species and it has been suggested that the observed amoeboid cells were actually posterior tentacles that are present on some choanoflagellates.
Life history[edit]
Although several Proterospongia species have been described, only P. choanojuncta has a described life history. Based on this description, Proterospongia alternates between colonial and swimming and adherent solitary states.[3][4] Leadbeater’s 1983 description resulted in the consolidation of Choanocea perplexea and Proterospongia choanojuncta species into Proterospongia choanojuncta. Additional studies of solitary and colonial species may result in further species consolidation.
Classification[edit]
Proterospongia is a taxonomic classification of colonial Codonosigidae choanoflagellates based on the physical appearance of individual cells and the morphology of the colony. First described by Kent in Manual of the Infusoria (1880-1882), there are six described species of Proterospongia and the colony structure varies between species. The members of Proterospongia genus remain to be classified in a phylogenetic framework.
See also[edit]
Citations[edit]
- ^ King, N. The Unicellular Ancestry of Animal Development. Developmental Cell (2004) 7:313-325
- ^ King, N. and S. B. Carroll. 2001. A receptor tyrosine kinase from choanoflagellates: molecular insights into early animal evolution. Proc Natl Acad Sci U S A 98:15032-7.
- ^ a b c d e f Leadbeater, B.S.C.; Thomsen H.A. Order Choanoflagellida. The Illustrated Guide to the Protozoa, second edition, (2000) pp. 14-37.
- ^ a b c d e f Leadbeater, B.S.C. Life-History and Ultrastructure of a New Marine Species of Proterospongia (choanoflagellida). J. mar. biol. Ass. U.K. (1983) 135-160
- ^ a b Kent, W.S. Manual of the Infusoria (1880-1882)
- ^ Lackey, J.B. Morphology and Biology of a Species of Proterospongia. Trans. Amer. Micro. Soc. (1959) pp. 202-206.
Additional references[edit]
- Dawkins, Richard (2005), The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution, Houghton Mifflin Harcourt, ISBN 978-0-618-61916-0
- James, T. Y., F. Kauff, C. L. Schoch, et al. mult. 2006. Reconstructing the early evolution of Fungi using a six-gene phylogeny. Nature 443:818-22.
- Lang, B. F., C. O'Kelly, T. Nerad, M. W. Gray, and G. Burger. 2002. The closest unicellular relatives of animals. Curr Biol 12:1773-8.
- Philippe, H, Snell, EA, Bapteste, E, Lopez, P, Holland, PWH, and D Casane. 2004. Phylogenomics of eukaryotes: the impact of missing data on alignments. Molecular Biology and Evolution. 21(9):123-135.
- Snell, EA, Furlong, RF, and PWH Holland. 2001. Hsp70 sequences indicate that choanoflagellates are closely related to animals. Current Biology. 11:967-970.