Phylum Cnidaria

1. Phylum Cnidaria Chapter 26.3

2. Vocabulary • Cnidocyte • Nematocyst • Polyp • Medusa • Gastrovascular Cavity • Nerve Net • Hydrostatic Skeleton • External Fertilization

3. Phylum Cnidaria • General Characteristics • All aquatic (mostly marine) • Radial symmetry • Cell organized into tissues – two true tissues, no organs • Diploblastic • Only one opening • Cnidocytes –stinging cells

4. Cnidocyte • Specialized cell for defense and capturing prey • Nematocyst: stinging capsules with thread like projections that stick to or tangle prey

5. More Characteristics • Gastrovascular cavity • Central digestive compartment • Sessile (polyps) or free-floating (medusa) • Planular (free swimming) Larvae • Nerve cells organized into nerve net • Includes: Jellyfish, Hydras, Sea Anemone, and Coral

6. Two Life Stages • Polyp • Vase-shaped • Sessile • Medusa • Bell-shaped • Free swimming • Two Layers: • Epidermis – outer • Gastrodermis – inner

7. Cnidarian Reproduction • Asexual – budding and fragmentation • Sexual – external fertilization in water

8. Jellyfish Life Cycle Fertilization occurs in the open water, producing many diploid zygotes. MEIOSIS Female medusa 2N) FERTILIZATION Sperm (N) Adult medusas reproduce sexually by releasing gametes intothe water. Each zygote grows into a ciliated larva. The larva eventually attaches to a hard surface and develops into a polyp. Male medusa (2N) Youngmedusa Swimming larva Polyp The polypbuds to release young medusas. Buddingpolyp

9. Immortal JellyFish • http://www.youtube.com/watch?v=2kLSiE-eNjw

10. Feeding • Carnivorous • Tentacles filled with nematocysts shoot poison into prey • Pull prey into mouth and into gastrovascular cavity (digestive chamber with opening) • Digestion is extracellular • Partially digested food is absorbed by gastroderm • Digestion completed internally within cells of gastroderm • Undigested material are passed out of body through the mouth

11. Respiration, Excretion, Circulation • Cells respire and eliminate waste through body walls by diffusion • After digestion, nutrients are carried through the body by diffusion

12. Response to Environment • Specialized sensory cells called a nerve net gather information from environment • Allow them to detect stimuli such as touch of a foreign object • Statocystsare groups of sensory cells that help determine direction of gravity • Ocelli are eyespots made of cells that detect light

13. Movement • A hydrostatic skeleton (layer of muscles that work with water allow movement) • Anemone circular muscles contract when mouth is closed and hold in water; allows it to become taller • Medusas and jellyfish move by jet propulsion when muscle contractions close the body and pushes water out of the bell--moving it opposite direction

14. Class Hydrozoa • Most alternate between polyp and medusa form • Examples: • Hydra • Polyp only • Obelia • Physalia (Portuguese man-of war)

15. Class Hydrozoa

16. Portuguese Man Of War • “Anyone unfamiliar with the biology of the venomous Portuguese man-of-war would likely mistake it for a jellyfish. Not only is it not a jellyfish, it's not even an "it," but a "they." The Portuguese man-of-war is a siphonophore, an animal made up of a colony of organisms working together.” –National Geographic

17. Class Scyphozoa • True jellyfish • Have polyps and medusa stage but polyp is reduced • Aurelia (moon jelly)

18. Class Anthozoa • Sea Corals and Sea Anemones • Exist only as polyps • Sometimes solitary but usually colonial • Eat plankton or fish • Metridium - Sea anemone

19. Class Anthozoacon’t • Renillareniformis - Sea Pansy • Sea pen

20. Class Cubazoa • Box Jellyfish • Have what is considered the most potent toxin in the world • Located in waters off Australia and in the Indo-Pacific • Box Jelly Video “You have virtually no chance of surviving the venomous sting, unless treated immediately. The pain is so excruciating and overwhelming that you would most likely go into shock and drown before reaching the shore. So don't go swimming alone! Be sure to know the first aid procedures. “

21. Exit Slip • Comparing characteristics of sponges and cnidarians, how are the two phyla different and how are they similar. • List at least 2 similarities and 2 differences.

22. Cnidaria Importance • Uses • Food • Coral used for decoration and jewelry • Medicinal • Soft corals produce a palytoxin that have anti-tumor properties • Palytoxin also used to elucidate the activity of sodium-potassium pumps • Treatments for hypertension and heart disease

23. Coral Reefs • Richest marine habitats/ecosystems. • 1000’s of species of fish and invertebrates live in association with reefs. • Much interdependence of species.

24. Reefs in Peril • Reefs can handle/recover from short-term stress (i.e. a hurricane). • Long-term stress is hard on the reef and therefore the whole ecosystem. • Pollution and invasive species are examples of long-term stresses.

25. Phylum Ctenophora • Known as the Comb Jellies • 90 spp. • Very similar to Cnidarians • General Characteristics: • All marine • All carnivorous • Swim by means of cilia • Reproduction is mainly hermaphroditic, but some asexual reproduction • Found in temperate or tropical waters close to the coast • Phosphorecence