Triploidy affects standard and postprandial metabolism in brook charr, Salvelinus fontinalis

The use of sterile triploids in aquaculture is currently limited because of reduced performance in situations of aerobic stress such as high temperature, hypoxia, and exhaustive exercise. Many studies have therefore attempted to find underlying metabolic differences between triploids and their diploid counterparts to improve triploid rearing protocols. This study investigated the effects of triploidy on postprandial metabolism (and therefore also pre-feeding standard metabolic rate; SMR) by measuring oxygen uptake and total ammonia nitrogen (TAN) excretion at 14-15°C of previously fasted (for eight days) diploid and triploid brook charr, Salvelinus fontinalis, from 48h before to 48h after being fed a single ration of 0.4% body mass. Triploids had significantly lower SMRs and higher postprandial metabolic rates (i.e., specific dynamic action) and net TAN excretion than diploids. While this greater cost of processing a meal may not represent a major diversion of metabolic reserves for triploids, it could affect their growth and survival when simultaneously faced with oxygen-limiting conditions.

The role of recombination on genome-wide patterns of local ancestry exemplified by supplemented Brook Charr populations

Assessing the immediate and long-term evolutionary consequences of human-mediated hybridization is of major concern for conservation biology. Several studies have documented how selection in interaction with recombination modulates introgression at a genome-wide scale, but few have considered the dynamics of this process within and between chromosomes. Here, we used an exploited freshwater fish, the Brook Charr (Salvelinus fontinalis) for which decades of stocking practices have resulted in admixture between wild populations and an introduced domestic strain to assess both the temporal dynamics and local chromosomal variation in domestic ancestry. We provide a detailed picture of the domestic ancestry patterns across the genome using about 33,000 mapped SNPs genotyped in 611 individuals from 24 supplemented populations. For each lake, we distinguished early and late-generation hybrids using admixture tracts information. To assess the selective outcomes following admixture we then evaluated the relationship between recombination and admixture proportions at three different scales: the whole genome, chromosomes and within 2Mb windows. This allowed us to detect the signature of varied evolutionary mechanisms, as reflected by the finding of genomic regions where the introgression of domestic haplotypes are favored or disfavored. Among these, the main factor modulating local ancestry was likely the presence of deleterious recessive mutations in the wild populations, which can be efficiently hidden to selection in the presence of long admixture tracts. Overall, our results emphasize the relevance of taking into consideration local ancestry information to assess both the temporal and chromosomal variation in local ancestry toward better understanding post-hybridization evolutionary outcomes.