Moulting in the chalimus larva of the salmon louse Lepeophtheirus salmonis (Copepoda, Caligidae)

The ultrastructure of moulting in the chalimus phase of the parasitic caligid copepod Lepeophtheirus salmonis is described for the first time. The major features of the moult sequence correspond to those of other Crustacea, save for the absence of a distinguishable intermoult as defined by reduced epidermal activity and a cessation of cuticle production. This latter may be explained cither in terms of a continuous moulting process related to the constant food supply available to a parasite or in terms of a highly abbreviated intermoult period. The findings are discussed with respect to studies of other Crustacean species.