Embryo Temperature Has Knock-on Effects on Later Traits in Salmonid Fishes

Through a phenotypic plastic response, early temperatures have knock-on effects on later appearing traits of organisms such as stream-spawning salmonids. Moderately warmer water during embryonic development has carry-over effects to later developing life history characters such as body shape, metabolic rate, growth rate, egg and gonad sizes. Also, adult size and time of the spawning migration may be affected by temperatures experienced at the embryo stage. These responses to early temperature may be regulated by epigenetic mechanisms, such as DNA methylation. The plasticity may be favourable for invasive organisms and for those living in changing habitats and climates. It has been hypothesized that over time, this plasticity may lead to speciation. Research on these early knock-on effects of early temperature is still in its youth, but is rapidly growing, and at the end of the review, issues for future research are suggested.