A new SNP-based vision of the genetics of sex determination in European sea bass (Dicentrarchus labrax)

Background: European sea bass (Dicentrarchus labrax) is one of the most important farmed species in Mediterranean aquaculture. The observed sexual growth and maturity dimorphism in favour of females adds value towards deciphering the sex determination system of this species. Current knowledge indicates the existence of a polygenic sex determining determination system that interacts with temperature. This was explored by restriction-site associated DNA (RAD) marker analysis in a test panel of 175 offspring that originated from a factorial cross between two dams and four sires from a single full-sib family. Results: The first high-density single nucleotide polymorphism (SNP) based linkage map for sea bass was constructed, consisting of 6706 SNPs on 24 linkage groups. Indications for putative sex-determining QTL (quantitative trait loci) that were significant at the genome-wide threshold were detected on linkage groups 6, 11 and 18 to 21, although a genome-wide association study (GWAS) did not identify individual significant SNPs at a genome-wide threshold. A preliminary genomic prediction approach that tested the efficiency of SNP-based selection for female sea bass showed a slight advantage compared to traditional pedigree-based selection. However, when the same models were tested on the same animals for selection for greater length, a clear advantage of the SNP-based selection was observed. Conclusions: Overall, the results of this study provide additional support to the polygenic sex determination hypothesis in sea bass. In addition, identification of sex-ratio QTL may provide new opportunities for sex-ratio control in sea bass

Fiche Action : CREation CHeptels Experimentaux (CRECHE2016)

Deux objectifs sont visés dans cette partie piscicole qui consistent en la création et la caractérisation de lignées expérimentales, un matériel biologique spécifique développé et entretenu comme support de recherche pour l’ensemble de la communauté scientifique

The shy prefer familiar congeners

The shy–bold continuum is both a fundamental aspect of human behavior and a relatively stable behavioral trait for many other species. Here we assessed whether shy individuals prefer familiar congeners, taking the European sea bass, a recently domesticated fish showing similar behavioral responses to wild fish, as a model to better understand the inter-individual variability in social behavior previously observed in this species. In the wild, the link between familiarity i.e. the preference of fish for familiar congeners and boldness could be part of the mechanism underlying shoaling formation in fish. Thirty fish were individually tested in a device designed to assess the preference for a familiar vs. an unfamiliar congener on the basis of visual cues only. An open field test (OFT) with shelter was performed on the same fish 32 days later to assess the boldness of each individual. Variables of interest included the proportion of time spent in the shelter, border and center zone of the arena and variables of activity. Variables measured in OFT were collapsed into first principal component scores using Principal Components Analysis (PCA) which allowed characterizing a shy-bold continuum. Time spent near the familiar congener was negatively correlated with boldness i.e. shy individuals spent most of the time near the familiar congener. We discuss the relevance of these findings to the understanding of the behavior of European sea bass and suggest that the link between familiarity and shyness is a general aspect of both animal and human behavior

Combining vitassign and colony: an efficient practical procedure for parental assignment with missing parents

Combining VITASSIGN and COLONY : an efficient practical procedure for parental assignment with missing parents. ISGA XI

Combining Vitassign and Colony for pedigree reconstruction in a case of factorial mating with missing parental genotypes

Combining VITASSIGN and COLONY for pedigree reconstruction in a case of factorial mating with missing parental genotypes. Aquaculture Europe 201

Genetic differences for behaviour in juveniles from two strains of brown trout suggest an effect of domestication history

Because captivity constitutes a drastic environmental change, domestication is expected to induce a rapid genetic selection for behavioural traits. In this study, we searched for genetic differences in behaviour among brown trout juveniles from two strains differing for their domestication history, i.e. an almost pure native wild Mediterranean population (W) and an Atlantic domesticated strain (D). In order to assess pure genetic differences among strains, males from the two origins were mated with Mediterranean females to produce two experimental crosses (WW and WD). The swimming activity characteristics of individual WW and WD juveniles were compared before and after the application of a stress (light switched off suddenly, followed by a 5-min period of darkness). For each of the fish observed, mating type origin (WW or WD) was unambiguously reassigned by genotyping. Behavioural responses differed between WD and WW fish. Angular velocity and the time spent immobile were greater for WW fish both before and after the short period of darkness, indicating higher reactivity. Once the light had been turned on again, mean velocity and total distance travelled were higher in WD than in WW fish. WD fish tended to recover levels of swimming activity higher than those before the dark period. This study therefore demonstrates an impact of genetic origin and domestication on swimming activity repertoire (higher reactivity in WW fish), a behavioural trait of particular importance for individual ecological performance. Owing to the contrasted domestication history of the two strains used in the comparison, we assume that the domestication level largely contributes to the behavioural changes observed