A screening of medicinal compounds for their effect on egg strings and nauplii of the salmon louse Lepeophtheirus salmonis (Krøyer)

Abstract

Egg strings and nauplii of the salmon louse Lepeophtheirus salmonis were exposed to a variety of medicinal compounds at 50 mg L(-1) for 30 min in two experiment series. This medicine concentration was selected as a starting point for a screening series. Hatching of egg strings and development to copepodid larvae were monitored in one experiment, and the survival and development of nauplii were monitored in the other. Two compounds, emamectin benzoate and cypermethrin, inhibited hatching effectively. Several compounds affected nauplii, either directly or through inhibiting development to the infective stage. A total of 50 mg L(-1) of azamethiphos, cypermethrin, emamectin benzoate and propoxur was lethal to >70% of the larvae. Diflubenzuron, fenoxycarb, pymetrozine, pyriprole and tebufenozide diminished the ability of nauplii developing to copepodids.

A screening of multiple classes of pharmaceutical compounds for effect on preadult salmon lice Lepeophtheirus salmonis

“…; Aaen et al . ) proved to be a suitable way of overcoming this problem, offering low toxicity to the parasite and sufficiently dissolving most of the compounds. In a pilot study, a 50/50 mixture of the emulsion and DMSO was the most gentle to preadult sea lice.…”

“…However, high solubility in such solvents does not necessarily mean that the compound is soluble in seawater. A mix of DMSO and an emulsion (Muan et al 1985;Aaen et al 2016) proved to be a suitable way of overcoming this problem, offering low toxicity to the parasite and sufficiently dissolving most of the compounds. In a pilot study, a 50/50 mixture of the emulsion and DMSO was the most gentle to preadult sea lice.…”

“…; Aaen et al . ). Every test tube was vortexed vigorously until the test substance was sufficiently dispersed.…”

“…Test substance dilution: 30-min exposure Every group of parasites was exposed to 50 mg L À1 of the test substance for 30 min. The correct concentration of the medicinal compound was obtained by weighing 12.5 mg of each substance in glass test tubes, dissolving it in 125 lL room-tempered dimethylsulphoxide (DMSO, Sigma-Aldrich) and 125 lL heated (40°C) emulsion (Muan et al 1985;Aaen et al 2016). Every test tube was vortexed vigorously until the test substance was sufficiently dispersed.…”

“…The aim of this study was to screen a wide range of substances for their in vitro effect on preadult L. salmonis using the IRAC classification scheme of insecticides as a basis for the selection of compounds (http://www.irac-online.org/modes-of-action/ [accessed on 17 September] (Aaen, Hamre & Horsberg ). Furthermore, the aim was to identify sensitive physiological and biochemical pathways in the salmon lice, with which medicinal compounds were able to interfere.…”