10.18710/8EE2JSHamre, Lars AreLars AreHamre0000-0002-9546-921XUniversity of BergenOldham, TinaTinaOldham0000-0002-8994-0052Institute of Marine Research, NorwayNilsen, FrankFrankNilsen0000-0003-4792-7172University of BergenGlover, KevinKevinGloverInstitute of Marine Research, NorwayReplication Data for: The potential for cleaner fish driven evolution in the salmon louse Lepeophtheirus salmonis: genetic or environmental control of pigmentation?DataverseNO2021Medicine, Health and Life SciencesOtherPigmentationLepeophtheirus salmonisSalmon louseFish parasitesLepeophtheirusBiological CoevolutionAdaptation, PhysiologicalPhenotypic PlasticityPest Control, BiologicalHamre, Lars AreLars AreHamreUniversity of BergenSea Lice Research CentreUniversity of BergenUniversity of BergenUniversity of Bergen2021-04-132021-04-132023-09-28visual data quantification10.1002/ece3.761865281952117671text/plaintext/plaintext/plain1.1CC0 1.0The datasets consist of two files with data from two different experiments. Experiment 1: compares pigmentation of lice cultivated indoor and outdoors in two experiments, one in June and one in September 2008. Photos are taken using translucent light and pigmentation is measured as the mean grey value in 50 pixel wide area on the louse cephalothorax using ImageJ. An equivalent area in the background just outside each louse is also measured and subtracted from the area covered by the louse to give a measure on how much light that is blocked by each louse. Each louse was also given a subjective pigment score: 1= little pigmentation, 2=medium pigmentation, 3= heavily pigmented. Experiment 2: Salmon lice with little pigmentation from Trøndelag was cultivated in an outdoor tank to see whether they developed dark pigmentation when exposed to daylight and sunshine. An old laboratory strain (LsOslofjord) was cultivated in a neighboring tank to compare pigmentation between the two strains. Pigmentation was measured as in experiment 1Abstract: The parasitic salmon louse represents one of the biggest challenges to environmentally sustainable salmonid aquaculture across the globe. This species also displays a high evolutionary potential, as demonstrated by its rapid development of resistance to delousing chemicals. In response, farms now use a range of non-chemical delousing methods, including cleaner fish that eat lice from salmon. Anecdotal reports suggest that in regions where cleaner fish are extensively used on farms, lice have begun to appear less pigmented and therefore putatively less visible to cleaner fish. However, it remains an open question whether these observations reflect a plastic (environmental) or adaptive (genetic) response. To investigate this, we developed a pigment scoring system and conducted complimentary experiments which collectively demonstrate that, a) louse pigmentation is strongly influenced by environmental conditions, most likely light, and b) the presence of modest but significant differences in pigmentation between two strains of lice reared under identical conditions. Based on these data, we conclude that pigmentation in the salmon louse is strongly influenced by environmental conditions, yet there are also indications of underlying genetic control. Therefore, lice could display both plastic and adaptive responses to extensive cleaner fish usage where visual appearance is likely to influence survival of lice.Bergen, Norway