Chemoreception in the salmon louse Lepeophtheirus salmonis: an electrophysiology approach

Abstract

The search for effective and long-term solutions to the problems caused by salmon lice Lepeophtheirus salmonis (Krøyer, 1837) has increasingly included biological/ecological mechanisms to combat infestation. One aspect of this work focuses on the host-associated stimuli that parasites use to locate and discriminate a compatible host. In this study we used electrophysiological recordings made directly from the antennule of adult lice to investigate the chemosensitivity of L salmonis to putative chemical attractants from fish flesh, prepared by soaking whole fish tissue in seawater. There was a clear physiological response to whole fish extract (WFX) with threshold sensitivity at a dilution of 10 -4. When WFX was size fractionated, L. salmonis showed the greatest responses to the water-soluble fractions containing compounds between 1 and 10 kDa. The results suggest that the low molecular weight, water-soluble compounds found in salmon flesh may be important in salmon lice host choice.

A review of host finding behaviour in the parasitic sea louse, Lepeophtheirus salmonis (Caligidae: Copepoda)

“…Their axons form the antennal nerve which runs back through the antennule and into the large compound thoracic ganglion where integration of signals and output to motor nerves and muscle occurs. Electrophysiological recordings have been made from the antennal nerve of adult male L. salmonis which have shown responses from the first antennae to fish conditioned water and non‐polar low molecular weight compounds derived from the water (Ingvarsdóttir, Birkett, Duce, Genna, Mordue, Pickett, Wadhams & Mordue (Luntz) 2002b) and to low molecular weight water soluble compounds found in salmon flesh (Fields, Weissburg & Browman 2007).…”

“…Electrophysiological recording techniques from the sensory antennal nerve were developed by Ingvarsdóttir et al. (2002b) and Fields et al. (2007) by restraining adult sea lice in a dish of Sylguard within a flow of clean sea water.…”

“…Compounds were identified by coupled gas chromatography -mass spectrometry (GC-MS). Electrophysiological recording techniques from the sensory antennal nerve were developed by Ingvarsdóttir et al (2002b) and Fields et al (2007) by restraining adult sea lice in a dish of Sylguard within a flow of clean sea water. Odour plumes were introduced within the bathing medium using a fine filament and electrodes (glass micropipette or fine tungsten wire) were introduced into the proximal article of the antennule (see Fig.…”

Lepeophtheirus salmonis (Krøyer, 1837): second nauplius and copepodid locomotor appendages, surface areas and possible appendage functions

“…Yolk not only helps with buoyancy but also reduces or eliminates the necessity of searching for food as long as a host is found in time by the copepodid. The copepodid, with its apparent ability to sense potential hosts (e.g.. Fields et al, 2007;Heuch et al, 2007) and its prehensile appendages, appears specialized for responding to a host and attaching to it (Bron et al, 1991). However, mobility and maintaining suitable depth during the planktonic phase are important not only for dispersal but also maintaining suitable position, escaping from predators, and locating a host (e.g., Heuch & Karlsen, 1997).…”

The chemical cues of male sea liceLepeophtheirus salmonisencourage others to move between host Atlantic salmonSalmo salar

“…In addition, L . salmonis are sensitive to the odour of potential host fish at a concentration of 10 −4 , tested electrophysiologically (Fields et al , 2007). Louse behavioural responses suggest that males at least are similarly sensitive to conspecific odours, although this has not been tested electrophysiologically (Ingvarsdóttir et al , 2002).…”