Skewed genetic sex ratio in reciprocal hybrids between pink salmon and masu salmon

Abstract

　Skewed sex ratio has often been observed in hybrids, but the sex was always determined by gonadal phenotypes. Here, we artificially induced reciprocal hybrids between pink salmon and masu salmon and then examined the genetic sex ratio in the hybrids based on the presence or absence of the sex-determining gene sdY. As a result, the sex of 8-month-old hybrids between pink salmon female×masu salmon male and masu salmon female×pink salmon male skewed to female, while 12-month-old hybrids between masu salmon female×pink salmon male were exclusively male. Since the sex ratio between the early embryos and hatching alevin was 1:1, it was considered that the skewed sex ratio was due to the difference of survival rate between genetic males and females.