Platyctenida is the only benthic group of organisms in the phylum Ctenophora. Platyctenida are considered to be a phylogenetically young group along with the orders Lobata and Beroida and are believed to have stemmed from an ancestral version of the order Cydippida, after some kind of bottleneck effect in the phylum. This has been supported by strong morphological and developmental data, specifically the sharing of what has been termed a "Cydippida-like" larva form in all 4 orders. Platyctenida is thought to be a polyphyletic group.[1]
Description
Ranging in size 15 cm and below, they have dorsalventrally flattened, oval bodies and secondarily bilaterally symmetrical, platyctenids look very much like nudibranchs or flatworms and are often confused for them. All but 1 species of platyctenids do not possess the iconic ctene rows (the ciliated comb-rows) that distinguishes the Ctenophores but they still possess the pair of tentilla-bearing tentacles and adhesive collocytes that also characterize the phylum in pores along the dorsal surface.[2] They cling to and creep on surfaces by everting the pharynx and using it as a muscular "foot".
They are usually cryptically-colored, live on rocks, algae, soft coral, or the body surfaces of other invertebrates; primarily certain species of Cnidarians and Echinoderms (primarily the genus Coeloplana sp.). They are often revealed by their long tentacles with many sidebranches, seen streaming off the back of the animal into the current. They tend to be ectosymbiotic with the organisms they live on.[3]
Whereas most Ctenophores are hermaphroditic, certain platyctenids have been found to be asexual, and furthermore, where other Ctenophores have been found to reproduce using external fertilization, certain species of platyctenids have been found to use brood pouches.[4]
References
^Podar, M., Haddock, S., Sogin, M., & Harbison, R. 2001. A Molecular Phylogenetic Framework for the Phylum Ctenophora using 18S rRNA Genes. Molecular Phylogenetics and Evolution. Vol: 21 (2), 218-230
^Rudman, W. B. 1999. Benthic ctenophores. Sea Slug Forum, Australian Museum, Sydney
^Eeckhaut, I., Flammang, P., Lo Bue, C., & Jangoux, M. 1997. Functional morphology of the tentacles and tentilla of Coeloplana bannworthi (ctenophore, platyctenida), an ectosymbiont of Diadema setosum (echinodermata, echinoida). Zoomorphology, 117:165-174.
^Harbison, G. R. 2001. Ctenophora. Encyclopaedia of Life Sciences
Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 176. ISBN978-0-03-056747-6.
1)Rudman, W. B. 1999. Benthic ctenophores. Sea Slug Forum, Australian Museum, Sydney
2)Eeckhaut, I., Flammang, P., Lo Bue, C., & Jangoux, M. 1997. Functional morphology of the tentacles and tentilla of Coeloplana bannworthi (ctenophore, platyctenida), an ectosymbiont of Diadema setosum (echinodermata, echinoida). Zoomorphology, 117:165-174.
3)
4)Podar, M., Haddock, S., Sogin, M., & Harbison, R. 2001. A Molecular Phylogenetic Framework for the Phylum Ctenophora using 18S rRNA Genes. Molecular Phylogenetics and Evolution. Vol: 21 (2), 218-230
January 31, 2023
platyctenida, order, comb, jellies, coeloplana, astericola, surface, seastarscientific, classificationkingdom, animaliaphylum, ctenophoraclass, tentaculataorder, familiescoeloplanidae, willey, 1896, ctenoplanidae, willey, 1896, lyroctenidae, komai, 1942, savan. Platyctenida is an order of comb jellies PlatyctenidaCoeloplana astericola on the surface of a seastarScientific classificationKingdom AnimaliaPhylum CtenophoraClass TentaculataOrder PlatyctenidaFamiliesCoeloplanidae Willey 1896 Ctenoplanidae Willey 1896 Lyroctenidae Komai 1942 Platyctenidae Savangiidae Harbison amp Madin 1982 Tjalfiellidae Komai 1922Taxonomy EditPlatyctenida is the only benthic group of organisms in the phylum Ctenophora Platyctenida are considered to be a phylogenetically young group along with the orders Lobata and Beroida and are believed to have stemmed from an ancestral version of the order Cydippida after some kind of bottleneck effect in the phylum This has been supported by strong morphological and developmental data specifically the sharing of what has been termed a Cydippida like larva form in all 4 orders Platyctenida is thought to be a polyphyletic group 1 Description EditRanging in size 15 cm and below they have dorsalventrally flattened oval bodies and secondarily bilaterally symmetrical platyctenids look very much like nudibranchs or flatworms and are often confused for them All but 1 species of platyctenids do not possess the iconic ctene rows the ciliated comb rows that distinguishes the Ctenophores but they still possess the pair of tentilla bearing tentacles and adhesive collocytes that also characterize the phylum in pores along the dorsal surface 2 They cling to and creep on surfaces by everting the pharynx and using it as a muscular foot They are usually cryptically colored live on rocks algae soft coral or the body surfaces of other invertebrates primarily certain species of Cnidarians and Echinoderms primarily the genus Coeloplana sp They are often revealed by their long tentacles with many sidebranches seen streaming off the back of the animal into the current They tend to be ectosymbiotic with the organisms they live on 3 Whereas most Ctenophores are hermaphroditic certain platyctenids have been found to be asexual and furthermore where other Ctenophores have been found to reproduce using external fertilization certain species of platyctenids have been found to use brood pouches 4 References Edit Podar M Haddock S Sogin M amp Harbison R 2001 A Molecular Phylogenetic Framework for the Phylum Ctenophora using 18S rRNA Genes Molecular Phylogenetics and Evolution Vol 21 2 218 230 Rudman W B 1999 Benthic ctenophores Sea Slug Forum Australian Museum Sydney Eeckhaut I Flammang P Lo Bue C amp Jangoux M 1997 Functional morphology of the tentacles and tentilla of Coeloplana bannworthi ctenophore platyctenida an ectosymbiont of Diadema setosum echinodermata echinoida Zoomorphology 117 165 174 Harbison G R 2001 Ctenophora Encyclopaedia of Life Sciences Barnes Robert D 1982 Invertebrate Zoology Philadelphia PA Holt Saunders International p 176 ISBN 978 0 03 056747 6 1 Rudman W B 1999 Benthic ctenophores Sea Slug Forum Australian Museum Sydney2 Eeckhaut I Flammang P Lo Bue C amp Jangoux M 1997 Functional morphology of the tentacles and tentilla of Coeloplana bannworthi ctenophore platyctenida an ectosymbiont of Diadema setosum echinodermata echinoida Zoomorphology 117 165 174 3 Harbison G R 2001 Ctenophora Encyclopaedia of Life Sciences4 Podar M Haddock S Sogin M amp Harbison R 2001 A Molecular Phylogenetic Framework for the Phylum Ctenophora using 18S rRNA Genes Molecular Phylogenetics and Evolution Vol 21 2 218 230 Retrieved from https en wikipedia org w index php title Platyctenida amp oldid 1125611273, wikipedia, wiki, book, books, library,
