Kingdom Animalia Phylum Cnidaria Characteristics n Radial or

Kingdom Animalia Phylum Cnidaria

Characteristics n Radial or biradial symmetry n Diploblastic organization n Mesoglea between epidermis and gastrodermis n Gastrovascular cavity n Nerve net n Cnidocytes – used in defense and feeding

Reproduction/Life Cycle n Can be monoecious or dioecious n Alternate generations between polyp and medusa form n Polyp – asexual and sessile n Medusa – dioecious and free swimming

Reproduction Cont’d n Planula – Cnidaria larvae n Polyps are produced by budding or planula n Medusae formed by budding from a polyp body wall

Feeding n Use cnidocytes to stun or kill prey n Tentacles contract to bring food to mouth n Food is digested in gastrovascular cavity

Support and Locomotion n Hydrostatic Skeleton n Some classes have longitudinal muscles that aid in movement n Polyps – somersault, inchworm, glide on base, and walk on their tentacles n Medusae – swim and float

Classification n. Class Hydrozoa n. Class Scyphozoa n. Class Cubozoa n. Class Anthozoa

Class Hydrozoa n Mostly marine, but the only class with freshwater members! n Alternate generations n Mostly colonial polyps

Obelia n Gastrozooid – feeding polyp formed from planula larvae n Grows through budding into more gastrozooids n Gonozooid – reproductive polyp that forms medusa by budding n Medusae then reproduce sexually

Gastrozooid Gonozooid

Gonionemus n Medusa predominant n Has a velum (shelf-like lip that projects inward) n Velum creates jet propulsion n Mouth at end of a manubrium n Nerve ring that coordinates swimming movements n Statocyst – responds to gravity

Hydra n Freshwater n Polyps only, no medusae n Testes form sperm by meiosis n Ovaries form one egg each

Physalia n Portuguese man-of- war n Colonial n Cannot swim n Cnidocytes in tentacles are lethal to small vertebrates and dangerous to humans

Class Scyphozoa n All marine n “True Jellyfish” – medusa dominant

Stinging Nettle, Mastigias

Aurelia n Gastrodermal cells have cilia to circulate food n Feeds on plankton n Rhopalia – chemoreceptors n Lappets – touch receptors n Statocysts – gravity sensors n Ocelli - photoreceptors

Class Cubozoa n Medusae are cuboidal n Polyps are reduced or absent n Tentacles hang from corners

Class Anthozoa n Polyps only, no medusae n Mouth has a pharynx n Gastrovascular cavity is divided into sections n Sexual and asexual reproduction

Sea Anemones

Corals