Semiochemical strategies for sea louse control: host location cues

Abstract

The development of behavioural bioassays and electrophysiological recording techniques has enabled the role of semiochemicals to be investigated for the first time in Lepeophtheirus salmonis (Krøyer). Adult male sea lice L salmonis were activated by, and attracted to, salmon-conditioned water (SCW) and SCW extract. Non-host fish odours, turbot-conditioned water (TCW) and turbot-conditioned water extract (TCW extract), elicited activation but no attraction in the lice. Solid-phase extraction techniques were developed to extract low molecular weight components of fish odours, and biological activity was shown to be confined to these. Electrophysiological activity from aesthetascs in the first antennae was found and neural responses to odours were recorded from the antennal nerves. Preliminary experiments on individual chemicals (isophorone, 1-octen-3-ol) linked to salmon revealed behavioural activation and electrophysiological responses in adult male L salmonis. Isophorone was shown to be significantly attractive to sea lice when placed in a slow-release system in a perfused tank of seawater in a choice situation. Proof of concept has been established for successfully extracting odour cues from seawater, analysing their biological activity and applying these to slow-release technologies for field trapping of lice. Future work involving linked GC-MS techniques using behaviour, electrophysiological responses, and organolepsis will establish further host location cues specific to Atlantic salmon.

Effect of environmental salinity on sea lice Lepeophtheirus salmonis settlement success

“…Sea lice have been shown to respond both directionally and with increased activity to odour from Salmo salar (Ingvarsdottir et al 2002). Positioning close to a halocline may also increase their host encounter rate (Lyse et al 1998, Finstad et al 2000.…”

Screening of candidate genes encoding proteins expressed in pectoral fins of fugu Takifugu rubripes, in relation to habitat site of parasitic copepod Caligus fugu, using suppression subtractive hybridization

“…Most general cues are smaller molecules, for example, adult male L. salmonis were activated by and attracted to isophorone [13] and infective copepodids were activated and showed directional responses to isophorone and 6-methyl-5-hepten-2-one [8]. However, in the case of monogenean parasites, host glycoproteins, proteins, and carbohydrates can also serve as attractants or modify behavior [25]; for example, the Neobenedenia girellae oncomiracidium may respond to glycoproteins from its host [26,27].…”

“…Fish act mainly as senders of kairomones; in the case of fish-zooplankton interactions, kairomones function primarily as a warning of the presence of a predator [11]. However, kairomones generated by potential hosts can affect the behaviors of both infective copepodid stages and adults of L. salmonis, and provide cues which enable them to distinguish their salmonid hosts from other non-host fish [8,12,13].…”

Arthropod semiochemicals: mosquitoes, midges and sealice

“…In an aquatic situation, crustacean ectoparasites such as salmon lice also use hostspecific cues to switch on orientated behaviours (compound 17 in Figure 1). Such cues can be extracted from the water in which salmon have been swimming [11,12]. The use of more ubiquitous signals of respiration, such as the presence of bicarbonate ions, in locating fish hosts has not yet been investigated.…”