Temperature effects on sex differentiation of the reciprocal hybrids of Odontesthes bonariensis and Odontesthes hatcheri (Atherinopsidae).
The pejerrey Odontesthes bonariensis (Valenciennes 1835) and the Patagonian pejerrey Odontesthes hatcheri (Eigenmann 1909) are Atherinopsid species with commercial importance and potential for aquaculture. The hybrids of the two species are viable but their mode of sex determination is unknown. This study examined the gonadal histology and sex ratios of reciprocal hybrids that were reared at 15, 17, 21, 25 or 29°C during the sex differentiation period. The genetic sex of hybrids from O. hatcheri fathers was inferred from a sex-linked SNP marker. Both hybrids showed female-biased sex ratios at the lowest temperature, female-biased to balanced sex ratios at intermediate temperatures and balanced or male-biased sex ratios at 29°C, but unlike in purebred O. bonariensis, the lowest and highest temperatures did not yield monosex populations. The proportion of females in the offspring was affected more by parental genome than by hybrid combination. Female hybrids bearing the O. hatcheri Y chromosome showed temporary arrest of ovarian development that was rescued in adults. These results reveal strong interactions between genotype and temperature for sex determination and differentiation of the hybrids and provide important clues to understand the mechanisms of sex determination in these species.