Phylum Cnidaria A. 2 body forms 1. Medusa: jellyfish a. motile b. umbrella shaped c. tentacles and mouth underneath 2. Polyp: corals a. sessile b. tubelike c. Tentacles and mouth on top

Some cnidarians exist as either a medusa or polyp but many will alternate between the two during their life cycle. Radial symmetry The unique feature of the Cnidaria is that they have stinging cells, called nematocysts. Each of these cells contains a thread-like sting that is discharged in attack or defense. Carnivores

Class Hydrozoa: Hydra Classs Scyphozoa: Jellyfish Class Anthozoa: Corals

Class Hydrozoa Hydra, Portuguese man-of-war No Medusa Stage Most are found in lakes, rivers, ponds Some are Marine; ex: Portuguese man-of-war Attach to rocks or other plants through their basal disk Brown or white Move by a tumbling or somersaulting action. (pg 642) Reproduce: 1. Asexually: budding; Polyps produce buds, they will grow into a new polyp, then they will eventually separate from the old polyps body and attach themselves to rocks or plants and live independently. Parent Bud

2. Sexually Reproduction: Mostly marine hydrozoas. a. The medusas release sperm or eggs into the water. The gametes fuse and produce zygotes that develop into free-swimming larvae (planulae). The planulae will settle and attach to the bottom of the ocean floor and develop into a polyp. Each polyp will produce multiple buds (called a colony). These buds do not separate from the body (as it does in asexually reproduction). They will stay attached and eventually turn into male and female medusas. These medusas will leave the polyps to grow and mature.

Feeding When feeding, hydras extend their body to maximum length and then slowly extend their tentacles. Despite their simple construction, the tentacles can extend four to five times the length of the body. Once fully extended, the tentacles are slowly maneuvered around waiting for a suitable prey animal to touch a tentacle. Once contact has been made, nematocysts on the tentacle fire into the prey and the tentacle itself coils around the prey. Within 30 seconds, most of the remaining tentacles have already joined in the attack to control the struggling prey. Within two minutes, the tentacles will surround the prey and move it into the mouth. Within ten minutes, the prey will be enclosed within the gastrovascular cavity and digestion will have started. The hydra is able to stretch its body wall considerably in order to digest prey more than twice its size. After two or three days, the undigestible remains of the prey will be discharged by muscular contraction through the mouth.

Hydra Structure A: Tentacle B. Budd/new hydra forming C. Mesoglea D. Basal Disk E. Cnidocyte (stinging cells) F. Nematocyst (used for defense) G. Gastrovascular cavity (Help Digest) H. Endoderm (inner cell layer) I. Ectoderm (outer cell layer) J. Sperm sac K. Mouth

Class Scyphozoa Jellyfish Can range from a thimble to as large as a queen-size mattress. Feeding: predators; use their tentacles to capture and sting their prey. Their nematocysts can be extremely toxic. Reproduction: sexually. Alternation of polyps and medusas (as discussed in Hydrozoa) Dominant form is the Medusa Moon Jellyfish

Class Anthozoa Largest class Consists of only polyp form Ex: sea anemones, coral Reproduce: asexually: budding. Sexually be releasing eggs and sperm into the ocean where fertilization will occur. Most species live in warm water and they are brightly colored. Feeding: They feed on fishes, which are caught by means of the numerous nematocysts in their tentacles. These animals are known for their symbionts. These include species of fish that actually live among the tentacles of large anemones, somehow avoiding lethal contact with the nematocysts. Other anemones have unicellular algae living within their tissues, from which they probably derive some nutrition. Yet others have a symbiotic relationship with hermit crabs, which gather up the anemones and place them on the snail shells that the crabs occupy. The anemones benefit from food particles dropped by the crab, and the crab gains protection from predators due to the presence of the nematocyst-laden anemones. Anemonaes

CORAL GRIEF: Global warming isn't just affecting cold areas CORAL GRIEF: Global warming isn't just affecting cold areas. Coral reefs are found mainly in warm waters. Tiny animals called coral polyps build the reefs. But if the water gets too warm, the polyps can die. That's already starting to happen at the Great Barrier Reef, Earth's largest coral reef.