nematocyst

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nematocyst In Cnidaria, part of a cnidoblast; it is a pear-shaped sac with a lid (operculum), the outer end of the sac being extended to form a long, hollow thread which is stored coiled within the sac, immersed in a fluid. On stimulation of a sensory bristle (a cnidocil) the thread is expelled, as a weapon or to capture or hold prey, depending on the type of nematocyst. Some nematocysts are barbed and some inject venom.

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nematocyst In Cnidaria (sea anemones, jellyfish, and corals), part of an epidermal cell (cnidoblast), comprising a sac with a lid, the open end of the sac being extended into a long, hollow thread. The thread is stored inside the sac, coiled and immersed in a fluid. When a sensory bristle (cnidocil) is stimulated, the thread is expelled to capture or hold prey or as a weapon, depending on the type of nematocyst. Some nematocysts are barbed and some inject venom.

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nematocyst See thread cell.