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Lecture

Cnidaria

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Department
Biology
Course
BIOL 2030
Professor
Scott Kelly
Semester
Fall

Description
Cnidaria – Jellyfish & cousins Cnidaria Phylum of simple, aquatic, mostly marine, invertebrate animals containing corals, sea fans, and sea anemones (class Anthozoa), the hydroids and milleporine corals (Hydrozoa), the jelly-fishes (Scyphozoa) and the box-jellies (Cubozoa). They include both colonial and solitary forms. Individuals are generally radially symmetrical, with only one opening (mouth) to the gut and a simple two-layered body with a primitive nerve net between the two layers. Cnidaria have hydroid (polyp) and/or medusa forms, and bear stinging cells (cnidoblasts) on the tentacles fringing the mouth. With the phylum Ctenophora, the Cnidaria form the largest grouping known as the coelenterates Cnidocil Minute process projecting from a cnidoblast (stining cell), whose stimulation causes Cnidocyte discharege of a nematocyst Colloblast Stinging cell of sea anemone, jellyfish, and other coelenterates, containing a coiled thread which is dischared on contact with prey Comb Plates A locomotor organ consisting of a row of strong cilia whose bases are fused Dactylozooid Palpon:an individual hydroid modified for catching prey and for defence, being long and slender usually with tentacles and usually without a mouth Diploblastic Having only two germ layers, endoderm and ectoderm, as in coelenterates & sponges Gastrozooid Individual specialized for feeding in a siphonophore colony Gonozooid Reproductive individual of a hydrozoan colony Manumbrium Tube bearing the mouth hanging down from the undersurface of a medusa Mesenchyme [Mesoglea] Gelatinous, non-cellular layer between the inner and outer body wall in sponges and coelenterates Myofibrils Individual contractile thread in the cytoplasm of a muscle cell, each myofibril being composed of many actin and myosin filaments Nematocyst Stinging cell of sea anemones, jellyfishes, and other coelenterates, containing a long coiled thread which is dischared on contact and pierces prey. (this is a reference to content of the cell itself) Ocelli Simple eye or eye spot found in many invertebrates; in cnidarians, in rhopalium Operculum Lid/covering flap of a cnidocyte Pedalium Base of each tentacle differentiated into a blade-like structure Pneumatophore The air sac/float of siphonophores (ex. Portugese man of War) Radial Canal Rhopalium Marginal sense-like organ in some jellyfish Ring Canal Sensory Lappets Touch &| chemical receptors in rhopalium Spirocysts/Ptychocysts Content of cnidocyte which enables adhesion to the surface Stratocysts Sensory structure in rhopalium Velarium Like velum, only contains endodermic canals Velum The ring of tissue projecting inwards from margin of a bell *Phylum Table* Body Forms 2 body shapes: Polyp & Medusae  Gastrovasular Cavi
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