CAS BB 191 Lecture Notes - Lecture 4: Scleractinia, Gastrovascular Cavity, Coelenterata

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Hydroids, sea anemones, jellyfishes, hard and soft corals. ** nematocysts: stinging organelle contained in special cells called cnidocytes. Used to paralyze prey and for defense, secretes toxins. Tiny capsule made of material similar to chitin. Contains coiled tubular filament inside connected to a toxin vesicle. Operculum: small lid covering end of capsule. Cnidocil: ciliate like trigger mechanism for some nematocysts. Four classes of cnidarians recognized: hydrozoa: includes hydroids, fire corals, portuguese man-o-war, scyphozoa: the true jellyfishes, cubozoa: the box jellyfishes, anthozoa: sea anemones, stony corals and soft corals, class hydrozoa. Margin of bell or umbrella typically ringed with eight notches that are provided with sensory organs (eye spots, light receptors, statocysts) Enteron (lower gastrovascular cavity) subdivided by at least eight septa bearing nematocysts. Divided into three subclasses: zoantharia: sea anemones and stony corals. Body plan multiples of 6 (hexamerous: alcyonaria: sea fans, pens, sea pansies (soft corals) Eight tentacles, pinnate branched: ceriantipatharia: tube anemones and black corals.

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