Phylum Cnidaria stinging-celled animals

2. Phylum Cnidariastinging-celled animals • Jellyfishes, corals, anemones • Radial symmetry • Two tissue layers with inner mesoglea • Primitive nerve net but no brain • 2-way digestive tract • Stinging cells for capturing food.

3. Introduction to Cnidaria • There are four major groups of cnidarians:1 Anthozoa2 Cubozoa3 Hydrozoa 4 Scyphozoa

4. Body Plans of Cnidarians • Cnidarians have two basic body forms • medusa • polyp

5. Medusa • adult jellyfish • free-swimming or floating • usually have umbrella-shaped bodies four-part symmetry. • The mouth is usually on the concave side, and the tentacles originate on the rim of the umbrella.

6. Medusae

7. Polyps • usually sessile. • have tubular bodies; one end is attached to the substrate. • The mouth (usually surrounded by tentacles) is found at the other end. • Polyps may occur alone or in groups of individuals; different individuals sometimes specialize for different functions, such as reproduction, feeding or defense.

8. Polyp

9. Cnidarians are the simplest organisms that have attained a tissue level of organization.

10. Body Plan

11. Reproduction • Reproduction in polyps is by asexual budding (polyps) or sexual formation of gametes (medusa). • The result of sexual reproduction is a planula larva, which is ciliated and free-swimming.

12. Characteristics of Cnidaria • Radially Symmetrical • Body multicellular, few tissues, some organelles. • Body contains an internal cavity and a mouth. • Two different forms exist, medusa and polyp • Reproduction is asexual or sexual.

13. Characteristics continued • Has a simple net like nervous system • Has a distinct larval stage which is planktonic • Lives in aquatic environments, mostly marine • Mostly carnivorous otherwise filter feeders • May have a minimal skeleton of chiton or calcium carbonate

14. Polyp life cycle

15. Medusa life cycle

16. Class Anthozoa • The true corals • anemones, and sea pens • Anthozoans do not have a medusa stage

17. Anthozoa Sea Pen

18. Anthozoa Sea anemone

19. Anemone

20. Sea anemone and clown fish

21. Sea anemone

22. Aggregating anemones

25. Brain coral

27. Zooxanthellae and coral • All cnidarian species can feed by catching prey with nematocysts • Some of the species have a symbiotic relationship with a dinoflagellate called zooxanthellae. • The zooxanthellae benefit by using nitrogenous waste and carbon dioxide produced by the host, and the cnidarian (coral) benefits from the photosynthesis and increased calcium carbonate production.

28. Class Cubozoa • Box jellyfish belong to the class Cubozoa, named for their cube-shaped medusa • The name sea wasp is applied to some species of cubozoans • Box jellies can be found in many tropical areas • Box Jellyfish are best known for the extremely powerful venom possessed by some of their species • Stings from these species are painful, and are often fatal • The Chironexfleckeri and the Carukiabarnesi species are among the most venomous creatures in the world.

30. Chironex fleckeri

31. Class Hydrozoa • the most diverse group with siphonophores, hydroids, and fire corals • Hydrozoa are predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater. • Some examples of hydrozoans are: Hydra, Obelia, and Portuguese Man o' War (Physalia).

32. Hydra Hydras are very small and must be seen with a microscope

34. Class Scyphozoa • the true jellyfish • include most of the familiar jellyfish • Their stings may cause skin rashes, muscle cramps, or even death. • They can be found in every ocean in the world and in some fresh waters.

35. Moon Jelly

37. Fried egg jelly

38. Ctenophores • Comb jellies • Bioluminescent • Do not have stinging cells

39. Ctenophore Not a true jellyfish