PHYLUM CNIDARIA (Sea Anemones, Jellyfish, Coral, Hydras) ~10 000 species FACT: Cnidarians have a single external opening that serves as both the mouth and the anus!

CNIDARIA Cnidae refers to the creatures’ “stinging cells” Are further up the “evolution ladder” meaning they are more complex than Porifera (sponges) Three Classes Class Hydrozoa Class Scyphozoa Class Anthozoa

CNIDARIA MULTICELLULAR cells are specialized and organized into tissues and sometimes even into simple organs all Cnidarian have specialized defense cells that sting = cnidocytes cnidocytes (the cell) contain a unique organelle = called nematocyst = “stinger” GERM LAYERS Only endoderm and ectoderm Endoderm – forms inner gastrodermis Ectoderm – forms outer epidermis

CNIDARIA MOVEMENT medusa form (bell-shaped) is motile (moving) polyp form (vase-shaped) is sessile (non-moving) some cnidarians exist in both forms throughout their life cycle (alteration of generations) medusa polyp (motile) (sessile)

CNIDARIA Two body forms Polyp Medusa Tubular shape Mouth faces upwards Sessile Medusa Mouth faces downwards Motile (drifters)

CNIDARIA REPRODUCTION Asexual – budding Sexual – monoecious, produce both sperm and eggs Sexual – male (produce sperm) - female (produce eggs)

CNIDARIA no body cavity because no true mesoderm radial symmetry non-segmented have tissues gastrodermis (gas exchange and digestion) epidermis (protection) middle layer = mesoglea (jelly-like) have a “nerve net”

CNIDARIA DETAILED STRUCTURE (Example of Hydra)

CNIDARIA BODY SYSTEMS REPRODUCTIVE SYSTEM – a rudimentary system in some organisms Asexual Reproduction budding (no system) Sexual Reproduction Monoecious = individuals produce both sperm (testis) and eggs (ovary) Dioecious = male produce sperm (testis) and females produce eggs (ovary)

CNIDARIA BODY SYSTEMS REPRODUCTIVE SYSTEM and LIFE CYCLES Alternation of generations Aurelia (jelly fish) Obelia (hydra) http://trc.ucdavis.edu/biosci10v/bis10v/week9/moonjellemba.mov

CNIDARIA BODY SYSTEMS DIGESTIVE SYSTEM – not a true system food enters gastrovascular cavity via mouth extracellular digestion (enzymes secreted into cavity) cells lining the cavity absorb digested nutrient and smaller food particles

CNIDARIA BODY SYSTEMS CIRCULATORY SYSTEM – not a true system nutrients and gasses diffuse directly across the thin cell layers RESPIRATORY SYSTEM – not a true system gas exchange directly between cells and water by diffusion (O2 diffuses into and CO2 out of cells) Both across epidermis and gastrovascular tissues

CNIDARIA BODY SYSTEMS EXCRETORY SYSTEM – not a true system waste diffuses from cells into gastrovascular cavity waste is then released through the mouth MUSCULAR SYSTEM – NONE no muscle cells but some cells can contract and relax (e.g. in the tentacles) SKELETAL SYSTEM – NONE

CNIDARIA BODY SYSTEMS Nervous System – a basic system a net of nerve cells react to presence of food and danger for feeding and protection Hydra Feeding

CNIDARIA GENERAL INFORMATION HABITAT mostly marine waters (marine = salt water) some freshwater species SIZE as small as 0.5 cm tall bell of up to 2.4 m diameter and tentacle ranging upwards of 50 meters

CNIDARIA - Class Hydrozoa colonial organisms hydras, Portuguese Man-of-War medusa and polyp forms

CNIDARIA - Class Scyphozoa “Cup Animals” jelly fish predominantly in the medusa form

CNIDARIA - Class Anthozoa “Flowering Animals” sea anemones coral predominantly in the polyp form sea anemone coral and clown fish

http://www.youtube.com/watch?v=pYUZxS1bZR4 = Steve Irwin and Box Jelly