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Phylum Cnidaria presentation

Explanation of cnidarians....zoology

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Phylum Cnidaria presentation

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  1. Phylum Cnidaria

  2. Includes • Jelly fish • Anemones • Corals • Hydroids • 10,000 species • Diploblastic tissues level organization.

  3. Habitat A. Aquatic 1. Most Marine 2. Few fresh-water

  4. Internal sac for digestion called gastrovascular cavity • One opening which serve as mouth/anus. • Cells of epidermis and gastrodermis differentiated into different cell types for: • Movement • Protection • Food gathering • Digestion

  5. Characteristic feature of cnidarians is Cnidocytes • Contain Cnidea (commonly known as Nematocyst) • Nematocyst is a capsule enclosing coiled thread with barbs and spines. • Operculum caps the capsule. • Modified cilium called Cnidocil

  6. Cnidocil receive stimulus from prey/enemy. • Nematocyst discharge initiated by opening of operculum. • Thread comes out in twisting motion with enormous speed and penetrate the prey body. • Spines/barbs help to anchor into the prey.

  7. Cnidarian have two body form in their life cycle Polyp: Medusa: Medusa: Free-swimming stage Mouth pointed downward Sexual stage Body is like inverted bowl Usually dioecious • Polyp: • Sessile stage • Attach at aboral end • Asexual stage • Cylindrical body • Mouth pointed upward

  8. Gametes produced by medusa After fertilization zygote formed Zygote transformed to planula larva Larva will form polyp Polyp reproduced by budding Bud may detach or remain attach to parent, forming colony Reproduction gametes zygote Planula larva polyp bud

  9. Maintenance of Function • Gastrovascular cavity carry out theses functions: • Digestion • Exchange of gases • Removal of waste material • Discharge of gametes

  10. Feeds on crustaceans • On contact to prey, nematocyst discharged and paralyze the prey • Tentacles draw the food into mouth and then to gastrovascular cavity • Gastrodermal enzymes help in digestion • Indigested material ejected through the opening • Gas exchange and excretion takes place by diffusion process

  11. Cnidarians have hydrostatic skeleton • Hydrostatic skeleton is water or fluid filled cavity, against which the contractile elements of the body wall acts • It give support to cnidarians body • Gastrovascular cavity act as a hydrostatic skeleton • Epitheliomuscular cellsare contractile cells, help in movement of polyp and medusa

  12. Cnidarians have nerve cells. • Sensory structure distributed throughout the body. • It has receptors for touch. • Epidermis and gastrodermis both possess nerve cells. • These nerve cells interconnected to form network called as Nerve Net. • Some species have Nerve Ring.

  13. Classification Phylum Cnidaria is divided into four major classes. • Class Hydrozoa. • Class Scyphozoa. • Class Cubozoa. • Class Anthozoa.

  14. Class Hydrozoa • Mostly marine, some fresh-water. • Some hydroid lost medusa stage. • Gametes released outside the body. • Mesoglea is acellular. • Colonial formation. • Entire colony has continuous gastrovascular cavity. • Feeding polypcalled Gastrozoids. • Reproductive polyps called Gonozoids.

  15. Hydra • Typical cnidarian body. • Cnidocytes present in epidermis. • One opening surrounded by tentacles. • Attached aborally by pedal disc. • Lacks medusa stage. • Reproduced by budding of polyps. • Sexual reproduction occurs also in polyps. • Epidermal cells will form ovaries and testes that release eggs and sperms. • After fertilization, zygote develop into adult hydra.

  16. Class Scyphozoa • Exclusively marine true-jelly fish. • Medusa is dominant stage. • Mesoglea contain mesenchyme cells. • Cnidocytes present in epidermis and gastrodermis. • Gametes released in gastovascular cavity. • Dioecious. • Common example is Aurelia.

  17. Class Cubozoa • Marine box-jelly fish. • Similar to scyphozoan. • Square-shaped or cuboidal-shaped. • Four tentacles hang from each corner. • Active swimmer. • Polyps and medusa both present in life cycle.

  18. Class Anthozoa • Marine, colonial or solitary. • Lack medusa stage. • Mouth lead to pharynx. • Gastrovascular cavity divided into mesentaries containing cnidocytes and gonads. • Mouth surrounded by tentacles. • Tentacles function to protect and catch food.

  19. Common anthozoans sea anemones. • Monoecious/dioecious. • Fertilization may be external/gastrovascular cavity. • Zygote develop into planula larva • Larva develop into adult animal.

  20. Another common anthozoans are coral. • Similar to anemones. • Secrete cup-shaped exoskeleton. • Made of calciumcarbonate. • Sexual reproduction similar to anemones. • Asexually by budding, live in colony. • Common examples seafans, redcorals.

  21. Brain Corals

  22. Phylum Ctenophora • Commonly known as comb-jellies/sea walnuts. • ~ 90 species. • Diploblastic. • Gelatinous layer between epidermis and gastrodermis. • Gastrovascular cavity present. • Nerve net present.

  23. 8 rows of comb-like paddles • Paddles contain thousands of cilia for swimming. • Adhesive cells colloblastfor protection and feeding. • Ctenophores have two openings. • Regenerate their lost parts. • Monoecious. • Fertilization external. • Larva develops into adult.

  24. Classification • Class Tentaculata: • Have two tentacles. • Large mouth parts. • Class Nuda: • Lacks tentacles. • Swim with plankton.

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