PHYLUM CNIDARIA HYDRAS JELLYFISH SEA ANEMONES CORAL BOX

PHYLUM CNIDARIA HYDRAS, JELLYFISH, SEA ANEMONES, CORAL, BOX JELLYFISH

I. General Information 1. “Cnido” means nettle (stinging cell) 2. EX: hydras, jellyfish, sea anemones, coral 3. Found in marine & freshwater 4. Symmetry: Radial • Oral & aboral surface • No cephalization 5. Acoelomates

6. Diploblastic: two tissue layers develop from gastrula stage. a. b. c. Ectoderm- develops into epidermis (skin) – Epitheliomuscular cells- for movement – Cnidocytes- for food capture/defense Mesoglea- gelatinous middle layer containing nerve net. – Polyp- thin – Medusa- thicker Gastroderm-develops into gut cavity – Gland cells- lubricate digestive cavity – Gastroderm- secretes digestive enzymes to digest prey.

General Body Plans: Basal disk Polyp & Medusa

II. Body Forms 1. Polyp a. Cylindrical, column-like body b. Mouth points up, surrounded by tentacles c. Sessile, attached to surface by basal disc d. Ex: hydra, sea anemone

2. Medusa a. Bell or cup shaped body b. Mouth points downward surrounded by tentacles. c. Free swimmingmoves by gently pulsating body d. Ex: jellyfish

III. Skeleton/support 1. Polyp: • have a hydrostatic skeleton- fill GVC w/water. • Gives support • Aids in movementsomersaults, inchworm • Ex: hydra, anemone • Exception- coral is sessile 2. Medusa: • Mostly float w/currents • Can pulse bell

IV. Digestion/Feeding 1. Eat daphnia, protists, larva, etc 2. Use cnidocyte containing nematocyst on tentacles to sting/stun prey 3. Stuff food into mouth using tentacles at oral end. (mouth on hump called hypostome) 4. Food is digested by gastroderm cells that line the gastrovascular cavity (GVC) 5. Solid Wastes leave thru mouth. 6. Incomplete gut b/c only 1 opening

How do cnidocytes work? 1. The cnidocyte contains the nematocyst- fluid filled capsule with coiled, barbed thread. 2. Prey brush against the cnidocil which is like a trigger hair 3. A lid called the operculum flips open & thread containing barbs stabs/entangles prey. 4. Cnidocyte degenerates & a new one takes its place

V. Excretion 1. Liquid wastes: eliminated by diffusion 2. Solid wastes: discharged through the mouth

VI. Respiration 1. DIFFUSION through cell membranes directly exposed to water.

VII. Nervous System 1. Nerve net- layer of nerve cells in mesoglea that react to stimuli. 2. Most primitive form of nervous system in animal kingdom. 3. Jellyfish consist of cells called statocystssenses gravity, coordinates movement

VIII. Reproduction 1. Asexual a. Budding- hydras, coral, sea anemones 2. Sexual a. Monoecious- hermaphrodite • Spermary- makes sperm • Ovary- makes eggs • EX: hydra (polyps) b. Dioecious- sperm & egg are produced in separate sexes. • EX: jellyfish (medusa)

IX. Jellyfish Life Cycle 1. Sperm released by male medusa. Egg released by female. 2. Sperm & egg join to form zygote. 3. Zygote divides & differentiates into a free swimming larva called a planula. 4. Planula lands on a structure & begins to grow into a polyp. 5. Immature jellyfish grow in budding stacks called a strobila 6. When immature jellyfish buds break off they are called ephyra. 7. Ephyra grow into adult medusa jellyfish. Alternation of Generations

X. Classification Craspedacusta sowerbyi (Cobb, Bartow, etc. ) Class Hydrozoa * marine & fresh water * can live as single animal or colony * may be polyp or medusa * gametes made on outside of body * EX: hydra, Portuguese man-o-war

Class Scyphozoa * all marine * predominant medusa stage * gametes made internally in gonads and released through the gastric pouch and finally through the mouth * called “true jellyfish” * EX: Aurelia, Lion’s mane jellyfish

Lions Mane Jelly

Class Anthozoa * all marine * solitary or colonial polyps * budding, monoecious or dioecious * anthozoa means “flower animal” * EX: sea anemones, coral

Class Cubozoa * all marine; found in warm tropical water * medusae are cube shaped; tentacles hang down from each corner * have deadly poison * EX: sea wasp (box jelly)

XI. Economic/Environmental Significance 1. Part of food chain 2. Control animal populations 3. Coral & sea anemone provide habitat for other animals in coral reefs 4. Some corals provide medicines & jewelry EX: Cancer, arthritis, histamines, antibiotics 5. Coral reefs attract not only fish but tourists