Phenotypic plasticity and epigenetics of fish: embryo temperature affects later-developing traits

Abstract

Temperature during embryonic development affects ecological traits and influences the ability to rapidly adapt to the prevailing conditions in changing environments. Here, we review examples of how these developmental effects are manifested in life-history traits from studies of various fish species, with examples of impacts on somatic growth, age at migration and maturation, gonad allocation and egg size. Temperature during embryogenesis appears important for some behavioural decisions, such as when maturing Atlantic salmon Salmo salar return home from the ocean for spawning in distant rivers during summer. In some species, early temperature influences sex determination. The temperature level during embryogenesis may preadapt the fish to maximize offspring production under the thermal conditions encountered at the embryo stage. This thermal influence is a phenotypically plastic response that triggers polyphenism in salmonids and may be a first step in speciation of North American darters (Percidae). The responses to early temperature appear to be regulated by epigenetic mechanisms, such as DNA methylation, histone modification and micro RNAs.