Salmon lice, Lepeophtheirus salmonis, exhibit specific chemotactic responses to semiochemicals originating from the salmonid, Salmo salar

Adult male salmon lice, Lepeophtheirus salmonis, displayed kinetic and rheotactic behavioral responses to seawater conditioned with the Atlantic salmon, Salmo salar. The kinetic response was initiated by a range of skin, mucus, and flesh preparations from salmon and from a nonsalmonid, the turbot Scophthalmus maximus. Kinesis was quantified by digitally recording the movement of individual lice and by measuring both speed and distance traveled. A directional response, measured in Y-tube assays, was seen in the presence of salmon-conditioned water, but not of turbot-conditioned water. Thus, there is strong evidence that chemical signals are used by salmon lice to mediate host-finding behavior. It is hypothesized that, although salmon lice are excited by the presence of fish-derived semiochemicals, there is a salmonid-specific signal that mediates their positive rheotactic response to a host.[PUBLICATION ABSTRACT]