Developmental divergence among hatchery strains of rainbow trout (Salmo gairdneri). II. Hybrids

Abstract

The developmental rates of first generation hybrids between six closely related hatchery strains of rainbow trout are compared using hatching time, morphology, and the pattern of ontogenetic change of four enzymes. Hybrid developmental rates can not be explained by additive genetic effects. Nine of 14 hybrid types developed slower than their maternal parent. These results are consistent with a hypothesis of regulatory divergence between the hybridizing strains. Heterotic effects were observed in five hybrid groups in that hybrids developed faster than their maternal parent. A strong dominance component was observed in the reciprocal hybrids of one strain. There was no association between the degree of perturbation of hybrid developmental rates and the genetic distance between hybridizing strains. Hybrids between more distantly related strains were no more delayed in their development than those from closely related strains.Key words: developmental rate, rainbow trout, hybrids, gene regulation.