Observations on mating and reproductive behaviour of Lepeophtheirus salmonis, Krøyer (Copepoda: Caligidae)

Abstract

Mating in Lepeophtheirus salmonis was similar to that reported for L. pectoralis in both the procedure and positions attained by both sexes but the timescales were different. Adult males took up precopulatory positions with, predominantly, pre-adult II females. Males held their respective partners around the 4th pedigerous segment using the second antennae. Females approaching the final moult produced temporary frontal filaments that served to anchor the pair as ecdysis proceeded. Males remained attached to the cephalothorax of the female during her final ecdysis before reattaching around the genital complex. After transferring to the ventral surface of the female, copulation occurred between the adult male and recently moulted adult female. The maxillipeds were used to manipulate and raise the genital complex of the female and a pair of spermatophores was transferred by the swimming legs. Following copulation the male returned to the dorsal surface of the female and held the spermatophores on the female for some time, before leaving her. Several specific behavioral patterns were observed during precopula, at the final moult of the female and during copulation. These involved considerable movement of the genital complexes and precise movements of the appendages by the male. Mate searching and testing behaviours were performed by adult males in the presence of pre-adult and adult females. These behaviours provided evidence that mate recognition by short range chemical, or contact stimuli may have occurred in L. salmonis. In addition, males clustered around moulting females which showed the attractiveness of the female at this stage. Postcopula, allometric growth of the female genital complex was observed and quantified from the time of insemination to the production of the first batch of eggs.