Genetic variation of resistance to mercury poisoning in steelhead (Oncorhynchus mykiss) alevins

Abstract

Newly hatched steelhead alevins were obtained from the factorial breeding of 24 male and 10 female steelhead trout, Oncorhynchus mykiss. Each set of offspring were in a separate cell. They were tested for resistance to intoxication by methylmercuric chloride (CH 3 HgCl) in water at a nearly constant mercury concentration of 8 mg l À1 . High mortality (81% of the tested alevins) occurred within 2 weeks. Resistance to intoxication, as measured by the time to death, as well as by the survival rate, shared high paternal and maternal variation with negligible interaction. Heritability of time to death was 0.5970.17; heritability of survival (all-ornone trait) was lower (0.2670.09). Mercury in dead alevins increased with time to death, exhibiting a large environmental variation and (comparatively) negligible genetic influence. At the end of the bioassay, the mercury content in survivors varied widely (3-21 mg g À1 wet weight). The content was greater than, but correlated with that of dead alevins from the same cells, and it showed little relation with survival rate. Thus, it seems that resistance to poisoning implies a tolerance to high levels of mercury rather than a limitation of its accumulation.

Blood Mercury Levels of Zebra Finches Are Heritable: Implications for the Evolution of Mercury Resistance

“…Mercury tolerance has been evaluated in few vertebrates. To our knowledge it has only been described in fish [ 37 , 38 ] and in a previous study where we demonstrated reproductive differences among families of zebra finches exposed to mercury [ 22 ]. We are not aware of any published studies of the heritability of traits related to mercury accumulation or tolerance in a terrestrial vertebrate species.…”

Association between Chromosome 4 and mercury accumulation in muscle of the three‐spined stickleback (Gasterosteus aculeatus)

“…Thus, there is empirical evidence that pollutants may act as one of the selective forces in the environment and that genetic adaptation to pollutants is both possible and can occur naturally. Empirical results from family based experiments also show that accumulation of mercury in the body is highly heritable in steelheads (Blanc et al, 2003 ) and zebra finches (Buck et al, 2016 ). The fact that a strong genetic component is observed in such disparate taxa strengthens the assumption that genetic differences generally affect mercury accumulations in vertebrates.…”

Historical Perspective of Transgenerational Epigenetics

“…[65][66][67][68][69][70] Importantly, maternal effects have been shown to account for variation in performance, stress resistance, and life history traits in cases where the embryo heavily relies on large maternally produced yolk and albumen reserves for growth and development. [71][72][73][74] Synthesis of these studies strongly suggested that maternal effects during early development can have a long-lasting impact on the adult phenotype by changing developmental trajectories, as well as having an acute impact on embryonic development and function.…”