BIO 2135 Chapter DigiDiv: Animalia - Radiata/Coelenterata - Cnidaria/Ctenophora
8 Feb 2017
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Document Summary
Carnivores that sting, entangle, or poison potential prey. Use cnidae (nematocysts), an organelle followed from cnidocyte cells, triggered by cnidocil. Dimorphic life cycle polyp + medusa. Nervous system consists of diffuse nerve net, concentration of nerves around the mouth and the edge of the medusa where rhopalia detect gravity, eye cup. Diploblastic epidermis (ectoderm) and gastrodermis (endoderm), mesoglea between the layers. Hydrostatic skeleton fluid filled gut, longitudinal and circular myonemes swims by increasing and decreasing diameter of the medusa. Cnidocyte covered tentacles capture prey, pass through mouth to the coelenteron (gastrovascular cavity), digestion enzymes, phagocytosis. In a polyp, cilia line coelenteron and mix the gut contents. In a medusa, gastrovascular cavity forms a series of canals inside the bell, gut contents act as circulatory fluid. Dioecious; gonads form in epidermis/gastrodermis, release gametes into water. Gonozooids: reproductive polyps, gastrozooids: feeding structures, dactylozooids: protect. = the branch of the colony, connected to hydrorhiza. Surrounds polyps with protective cup/theca living tissue inside.
