Genetic load, the accumulation of deleterious mutations, may threaten population viability by reducing individual fitness. In polyploids, allelic redundancy may mask deleterious alleles, but it can also promote their accumulation. We experimentally tested this relationship in the tetraploid Adriatic sturgeon (Acipenser naccarii).
Twelve captive breeders were sequenced, and ~1,000 SNPs of predicted impact were selected. About 400 offspring from controlled crosses were genotyped and monitored for survival and growth over one year. Load indices were computed and correlated with fitness traits.
Larvae that died before yolk sac absorption carried significantly higher loads at high-impact sites compared to surviving juveniles. Among juveniles, genetic load at high-impact loci showed a strong negative correlation with body size, with individuals carrying higher loads displaying up to 30% reductions in length and weight.
Our study provides the first experimental validation in a polyploid vertebrate linking predicted genetic load to observed fitness. Results demonstrate that tetraploidy does not completely buffer deleterious mutations and that load accumulation can affect both survival and growth. These findings highlight the importance of managing genetic diversity and minimizing inbreeding in ex-situ breeding programs for endangered sturgeons.
 

Adriatic Sturgeon, SNPs, Endemixit