Corals, Anemones, Sea Fans, and Jellies

1. Corals, Anemones, Sea Fans, and Jellies Phylum Cnidaria The Stingers

2. Phylum Cnidaria Characteristics • Radially symmetrical: symmetry around a point

3. Characteristics continued • Mesoglea: layer of jelly separating two tissue layers of cup or umbrella-shaped body • Gastrovascular cavity: space in middle of the body for digestion and reproduction, often surrounded by tentacles

4. Characteristics continued • Tentacles usually lined with several different types of nematoblast, which produce structures called nematocysts • May be mucus coated to entrap prey • Some have deadly poisons to stun or kill prey

5. Nematocyst firing

6. Two Body Forms Polyp: organisms that are attached (e.g. corals and sea anemones) Medusa: free-floating, mouth and tentacles typically point downward (e.g. jellies)

7. Class: Anthozoa (Corals and Anemones) • Largest class in the phylum Cnidaria • Includes more than 6,000 species • All are polyps • Some are colonial (corals, soft corals), others are individual (anemones, a few corals) Red Gorgonian, colonial coral, NOAA Close up of a coral colony

8. Life Cycle Coral life cycle

9. Hard corals and dinoflagellates • The color of hard corals comes from the dinoflagellates in the genus Symbiodinium, also called zooxanthellae • These organisms live inside coral, provide food and help eliminate waste through photosynthesis Zooxanthellae living inside coral

10. Coral bleaching • Zooxanthellae live best in well-lit, clear water • Thrive in low-nutrient, less productive waters (with little plankton to block the sunlight) • Runoff of pollution can cause plankton to grow and zooxanthellae to die • Without zooxanthellae, corals lose their colors = coral bleaching

11. Anemone mutualism • Found in the tropical Indo-west Pacific or tropical Pacific, Indian Ocean, and Red Sea • Anemonefish (e.g. clownfish) receive protection by living amongst the stinging tentacles • Fish passes back and forth through the tentacles to pick up anemone cells, the anemone recognizes its own cells on the fish so doesn’t sting it

12. Class: Hydrozoa (Fire Corals and Siphonophores) • Alternate between polyp and medusa forms during their life cycle

13. Fire corals • Fire corals—create a mild burn upon contact • Waxy, tan appearance and grow in small tree-like colonies or as an encrusting colony on an existing reef

14. Siphonophores • One species measured to be a total length of 40 m (131 ft) • Many represent a bridge between colonial animals and complex organisms • Exist as colonies • Within colonies are special polyps adapted to feeding, reproduction, movement, and other functions • Major predators with some consuming significant quantities of krill • Example: Portuguese man-of-war

15. Jellies Class: Scyphozoa (true jellyfish) Class: Cubozoa (box jellyfish) Phylum: Ctenophora (comb jellyfish)—not Cnidaria

16. Class: Scyphozoa (true jellies) • Range in size from smaller than a coin to more than a meter across with tentacles more than 3 m long • Most are large planktonic organisms that swim but also drift with the current • Weak swimmers, move by contracting their rounded body, or bell • Feed on almost anything they catch

17. Scyphozoa life cycle

18. Scyphozoa continued • Efficient predators • Prey for Leatherback turtle and several species of large fish—predators move seasonally with jellies • Plastic bags, balloons, and small trash often are mistaken by turtles as jellies and can harm them by clogging their digestive systems