Caligus elongatus Nordmann genotypes on wild and farmed fish

Abstract

Two mitochondrial genotypes have been described for Caligus elongatus Nordmann in Norway. This article reports on the distribution of C. elongatus mitochondrial cytochrome C oxidase 1 genotypes from wild fish hosts from the SE Norwegian coast. For comparison, lice from areas with fish farming were included in the study. The genotype distribution of 841 lice from wild coastal (n = 535), wild North Sea pelagic (n = 26), farmed (n = 160) and wild hosts in areas of fish farming (n = 89) is presented. The genotype frequencies of C. elongatus on wild coastal hosts varied significantly between spring and autumn. Lice from these fish show a large proportion of genotype 1 lice in March-June every year. Genotype 2 lice were found more frequently in autumn. Genotype 1 was clearly associated with the lumpfish, Cyclopterus lumpus L. The genotype frequency appeared to be different in areas with aquaculture. Caligus elongatus from farmed fish and wild fish caught close to Atlantic salmon fish farms in Norway were predominantly genotype 1 in autumn. Genotypes of C. elongatus on the SE coast of Norway vary according to season and fish species. Factors involved in the encounter between fish and lice are important for the establishment of lice on their hosts.

How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere

“…Genetic analyses indicate that L. salmonis is one well-mixed population across the North Atlantic, but that there has been some genetic drift from the North Pacific population; thus genetics are unlikely to distinguish farm and wild host populations (Costello 2006;Todd 2006). While Caligus elongatus von Nordmann has two genotypes in the North Atlantic, whether they have diverged based on seasonal reproductive cycles, host selection or other environmental factors remains to be determined (Øines & Heuch 2007). However, indirect support from spatial transmission models indicates that farms can be significant sources of lice on wild fishes (Krkošek et al , 2006bFrazer 2008Frazer , 2009 Mordue & Birkett 2009).…”

Infection of wild fishes by the parasitic copepod Caligus elongatus on the south east coast of Norway

“…The recent discovery of the 2 distinct genotypes of Caligus elongatus (Genotypes 1 and 2; Øines & Heuch 2005Øines & Heuch , 2007 has now made possible a more detailed study of the infection routes of the parasite. Conveniently, lumpfish had > 98% Genotype 1 lice (Øines & Heuch 2007).…”

Intra- or inter-specific difference in genotypes of Caligus elongatus Nordmann 1832?

“…A study using mitochondrial cytochrome C oxidase subunit 1 DNA sequences (mtCO1), identified two genetically distinct groups of C. elongatus, presented as genotype 1 and 2 (qines and Heuch 2005Heuch , 2007qines et al 2006). Furthermore the two genotypes varied in frequency on wild fishes at different times of the year, occurring sympatrically both on individual fish and in the same coastal area, although at different intensities in autumn and spring qines andHeuch 2005, 2007).…”

“…Furthermore the two genotypes varied in frequency on wild fishes at different times of the year, occurring sympatrically both on individual fish and in the same coastal area, although at different intensities in autumn and spring qines andHeuch 2005, 2007). The present study investigates if these two groups have morphological characters and additional molecular data that may shed more light on the species status of these two genotypes.…”