Hybrid salmonids: Ploidy effect on skeletal meristic characteristics and sea lice infection susceptibility

This study examined how triploidization and species hybridization affects skeletal related meristic characteristics in salmonids with the goal of understanding the maternal and paternal contribution. The study also investigated the hybrid sea louse infection rate in hybrid salmonids. In order to do so, a number of vertebrae, scales along the lateral line, and dorsal fin rays were measured in diploid and triploid Atlantic salmon, Arctic char, and Atlantic salmon (female) X Arctic char (male) hybrids. The success of triploidization was 100%, and some spontaneous triploid individuals (~15%) were found among the hybrids. In general, hybrids displayed intermediate counts for all three characteristics with salmon displaying the highest number of dorsal fin rays, and char displaying the highest number of scales and vertebrae. The effect of triploidization was always strongest among the hybrids. However, the direction of the effect differed between structures in the hybrid; triploidization increased the number of vertebrae and reduced the number of fin rays towards the level observed in diploid char, and reduced the number of scales towards the level observed in diploid salmon. We conducted a second experiment whereby diploid Atlantic salmon and Atlantic salmon (female) X Arctic char (male) hybrids were exposed to an experimental challenge with the parasitic salmon louse (Lepeophtheirus salmonis). There was no difference in the sea-lice infection level between Atlantic salmon and the hybrids. This study shows that the present model with diploid and triploid Atlantic salmon (female) X Arctic char (male) hybrids may be a useful tool for the study of which traits are maternally and paternally inherited in salmonids. The understanding of morphological development with regard to meristic traits could be advantageous for both hybrid and triploid fish domestication. © 2014 Blackwell Verlag GmbH.