Radiata

1. Radiata By Sarah, Rory, Aimee and Joshua

2. Groups of Cnidarians There are four major groups of cnidarians: • Anthozoa, which includes true corals, anemones, and sea pens; they don't have a medusae stage in their development • Cubozoa, the amazing box jellies with complex eyes and potent toxins; • Hydrozoa, the most diverse group with siphonophores, hydroids, fire corals, and many medusae • Scyphozoa, the true jellyfish.

3. Symbiotic Relationships Corals that make up the shallow water coral reefs have symbiotic zooxanthellae (unicellular algae) within their tissues; the algae receive protection and housing from the polyps, and enable them to produce their calcareous exoskeleton. In turn the algae photosynthesize and produce higher oxygen and healthy water. There are sea anemones that attach to the dorsum of crabs, marine snails, etc. Thus the anemone "travels free" with little competition for food and space, and the symbiote is protected. Many species of small fishes and crustaceans shelter beneath the umbrella of some jellyfish. Anemones and Clownfish use each other for protection as the anenome serves as shelter for the clownfish and in turn, the clownfish scares of other possible anemone predators such as the Parrotfish and some gastropods.

4. Diet • All eat small prey, planktonic organisms (carnivores) • Jellyfish • use nematocysts • Anemones • use nematocysts • Ctenophores • don’t use nematocysts but colloblasts (adhesive cells) which catch small prey either with tentacles or cilia • small organisms, crustaceans and larvae • Corals • use nematocysts

5. Predators • Sea slugs • Sea stars- crown of thorns destroy coral reefs • Nudibranchs- utilize nematocysts • Some fish • Turtles- often confuse plastic bags for jellyfish • Ctenophores • many times do not have natural predators so can be devastating when introduced to non-native ecosystems • often eaten by medusae, sea turtles, fish

6. Jellyfish blooms • Jellyfish blooms are the swarms that some species of jellyfish gather in. • The occurrence of these blooms is dependent on several factors including ocean currents, season, sunlight, water temperature, nutrients, and availabilty of prey • Increased nutrients, ascribed to agricultural runoff, have been cited as contributing to jellyfish proliferation. Ecosystems in which there are high levels of nutrients provide nourishment for the small organisms on which jellyfish feed. • In waters where there is eutrophication, low oxygen levels often result, favoring jellyfish as they thrive in less oxygen-rich water than fish can tolerate.

7. Other Ecological Impacts • In the late 1980s the Western Atlantic ctenophoreMnemiopsis leidyi was accidentally introduced into the Black Sea and Sea of Azov via the ballast tanks of ships, and has been blamed for causing sharp drops in fish catches by eating both fish larvae and small crustaceans that would otherwise feed the adult fish. • In the late 1990s Mnemiopsis appeared in the Caspian Sea . Beroe ovata arrived shortly after, and is expected to reduce but not eliminate the impact of Mnemiopsis there. Mnemiopsis also reached the eastern Mediterranean in the late 1990s and now appears to be thriving in the North Sea and Baltic Sea.[5] • Jellyfish population has been on the rise because of overfishing of jellyfish predators and the increase of nutrition from run-off in the water. • Fish have trouble re-establishing themselves after jellyfish move in because jellyfish eat plankton, which includes eggs and larvae. • Coral reefs provide homes for 25% of all marine species.

8. References • Animal Diversity, Hickman et. al. • http://www.exploringnature.org/db/detail.php?dbID=119&detID=2813 • Britannica, Online Dictionary, Academic edition. http://www.britannica.com/EBchecked/topic/122750/cnidarian/31897/Ecology-and-habitats • http://faculty.washington.edu/cemills/Ctenophores.html • http://www.ucmp.berkeley.edu/cnidaria/cnidaria.html • http://www.mesa.edu.au/cnidaria/