Sex-Related Parental Influences on Early Development of Pacific Salmon

Abstract

Among the fertilized eggs arising from a series of intraspecific and interspecific crosses involving sockeye, pink, and chum salmon, time from fertilization to hatching was longest for crosses involving sockeye males, less for those involving pink males, and least for those involving chum males. For crosses of females of the three species with males of a single species, eggs from pink females took longest to hatch, those from sockeye females took less time, and those of chums took the least. Larva size at hatching was greatest for larvae emerging from chum eggs, irrespective of male parent, less for those emerging from sockeye eggs, and least for those from pink eggs. There were only small differences in the size of larvae at hatching from the eggs of females of one species that had been fertilized by males of each of the three species. Among the pre-hatched embryos developing in eggs of a single species, those with a sockeye male parent grew slowest, those with a pink male parent grew faster, and those involving a chum male parent fastest. In eggs from females of the three species fertilized by the males of one species, embryos in eggs of chum females grew fastest, those in eggs of sockeye females slower, and those in eggs of pink females slowest. Gross malformation among hybrid offspring was not pronounced — only chum male × sockeye female and chum male × pink female hybrids displayed markedly greater proportions of malformed individuals than did the combined intraspecific crosses involving the same parents. It is possible that observed differences in time from fertilization to hatching between eggs of different parental origin are brought about by the interaction of growth rates inherited mainly from the male parents and a critical embryo size related to the size of eggs of the female parent. Identification of parental determinants of early development of salmon should make it possible to create salmon forms capable of exploiting new or changed environments.