Any marine gastropod in the order Nudibranchia. Most nudibranchs lack a shell, mantle cavity (see mollusk), and gills, and breathe through the body surface. The delicately colored body, up to 16 in. (43 cm) long, has bizarre defensive outgrowths, called cerata, that discharge nematocysts ingested from cnidarian prey. Antennalike organs arise from the head. Nudibranchs occur in shallow waters of all oceans, where they feed chiefly on other invertebrates, particularly sea anemones. Some species can swim; others are bottom creepers. The term sea slug sometimes refers to all members of the subclass Opisthobranchia.
Variants of NUDIBRANCH
nudibranch or sea slug
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