veliger

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veliger In Mollusca, a shelled larva, developed from a trochophore, which possesses two large, semicircular folds bearing cilia, used in swimming and feeding, lost as the veliger develops, and a mantle, foot, shell, and other adult features. It is in the veliger stage of Gastropoda that torsion occurs (some scientists believe torsion developed as a larval defensive mechanism, the twisting through 180° enabling the larva to withdraw its head and velum into the protective shell with the opening guarded by an operculum on the end of the foot).