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Phyla Cnidaria and Ctenophora

Phyla Cnidaria and Ctenophora. Lee-Mervin Mentoor, Department of biodiversity and conservation biology University of the Western Cape. Introduction. Fossils of these phyla date back to Upper Paleozoic They were then classified under one phylum (coelenterata)

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Phyla Cnidaria and Ctenophora

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  1. Phyla Cnidaria and Ctenophora Lee-Mervin Mentoor, Department of biodiversity and conservation biology University of the Western Cape

  2. Introduction • Fossils of these phyla date back to Upper Paleozoic • They were then classified under one phylum (coelenterata) • Have may features that they share, but some important once that separate them • Seperated on basis of symmetry from other metazoan organisms • Because of there radial symmetry refferrd to as radiata

  3. Organization in Radiates Share developmental and morphological features Better organized organisms in the metazoan Possesses a mouth and coelentera which sponges do not have Allow larger food particle digestion Outer epidermis, inner gastrodermis and mesoglea distinct

  4. Also have epidermal and gastrodermal tissue It’s movement allow food capturing and locomotion No specific tissue for circulatory,respiratory or excretory purposes Organization (cont.)

  5. Reproductivity in Radiates • Utilize both sexual and asexual reproductive modes • When gametes form, its left for fertilization • Fertilized egg develop into solid ball of cells called planula. • Its development varies in different organisms

  6. Morphological features of radiata • Both radially organized and soft-bodied • Uses flexible tentacles to bring food to oral cavity • Body structure allow shape variation • Lack of had part slow movement • Mesogleal tissue increase with growth and they are unable to use gastric cavity for hydrostatic purposes

  7. Phylum Cnidaria • Most common of the two and very diverse • About 10,000 spp. Is known • Simplest metazoans and possesses only mouth and stomach • Specialized cells(cnidocytes) contain nematocysts which they use to immobilize prey • Nematocyst have poisonous fluid and are used in defense and offense

  8. Two body types are present 1)polyp: sessile form without tubular body,polyoid mouth surronded by tentaclesand attached to subtsratum 2)medusa:inverted shape of polyp, and free-swimming form,mouth is situated centrally in concave body. Medusa turn to polyp form when attache to solid substrates Development in cnidaria

  9. 4 classes 1)hydroza-called hydroids;very small;have medusa and polyps phase;2700 spp. 2)Scyphozoa-jellyfishes;dormant medusa;in coastal; 200 spp. 3)cubozoa-box jellies;smaller then jellyfishes;have squere-shaped bell;well developed eyes;15 spp. Different classes in cnidaria

  10. 4)Anthozoa(corals and anenomes) solitery or colonial with no medusa, stinging cells divide digestive cavity of polyp Hard skeleton with carbonate protect coral polyp Form corals About 6500 spp. Classes in Cnidaria(cont)

  11. Smallest of the two and exclusively marine invertebrates Specimens not easily collected(delicate) Tentacles and mouth absent One species have nematocysts for defense Use colooblast for prey capturing Two classes that is hermaphordidic About 100 spp. Phylum Ctenophora

  12. No tentacles Genus boroë are example Prey on jelly and other Ctenophores Classes in CtenophoraClass Nuda

  13. Two tentacles which develop into specialized sheats 1°,2° tentacles present in reduced forms Exaple are gooseberries-Atl. And Pac. Coast Other genuses include maemiopsis, cestum present in upper atl and tropical water Class Tentacula

  14. Simple life cycle carried out in plankton Most are hemaphordidid(one carry both egg and sperm) Egg left to be fertilized and then delop into larval stage Hatches and mature Life Cycle of Ctenophores

  15. 1)Stricberger, MW.1990. Evolution.Jones and artlettpublishers Inc.Bostos 2)Martindale MQ,Finnerty J and Henry JQ.The radiata and the evolutionary origin of bilateria body plan.Unpublished. 20 November 2001. USA 3)www.en.wikipedia.com 4)www.fossilmuseum.net/tree_of _life/PhylumCnidaria 5)www.fossilmuseum.net/GeologicalHistory.htm 6)www.nearctic.com/nathist/miscanim/cnidaria.htm 7)www.palaeos.com/invertebrates/Cinadaria/Cnidaria.htm 8)www.sos.bang.ac.uk/modules References

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