Links Between Paternal Life History And Offspring Metabolic Rate And Body Size During Early Life In Masu Salmon Oncorhynchus Masou

Offspring growth is greatly influenced by both the maternal and paternal genotypes. However, although the effects of maternal genotype on offspring growth are recognised widely, ecological studies of the paternal genotype have not focused on the links with physiological traits, especially at the embryo stage. In this study, we conducted three experiments to determine the effects of two contrasting paternal life history traits (anadromous males, which return to their natal rivers for spawning after migrating to the sea, and resident males, which mature in rivers without migrating to the sea) on offspring growth during early life based on the metabolic rate in masu salmon Oncorhynchus masou. In the first experiment, metabolic rates of fertilised eggs were compared between 24 half-sibships. Results suggested that the metabolic rate of embryos was higher for the offspring of resident males than of anadromous males. In the second experiment, the body sizes of 133 half-sibships at the yolk-sac absorption stage were compared. The offspring from the resident males were larger, which could be related to metabolic rate differences at the embryo stage associated with paternal life history. In the third experiment, the differences in body size observed at the yolk-sac absorption stage were positively correlated with growth after 60 days of fry rearing. Our findings, taken together with previous demonstrations that faster-growing males tend to become younger resident males, are thus consistent with early growth and associated traits, such as metabolic rate, being heritable from the male parent to the offspring.