Spatial distribution of juvenile masu salmon (Oncorhynchus masou) with incongruent genotypic and phenotypic sex in Hokkaido, Japan

Toshiaki Yamamoto,Nobuaki Suzuki,Tsuyoshi Tamate,Shigeru Kitanishi

doi:10.1007/s10641-012-0013-6

Toshiaki Yamamoto, Nobuaki Suzuki + Show 2 more

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https://doi.org/10.1007/s10641-012-0013-6

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Abstract

To clarify the spatial distribution of masu salmon Oncorhynchus masou with incongruent genotypic and phenotypic sex, we compared the phenotypic sex determined by gonad analysis with the genotypic sex identified by a male-specific genetic marker, Growth hormone pseudogene (GHp), in 584 individuals inhabiting 23 rivers in Hokkaido, Japan. We found that the genotypic sex is different from the phenotypic sex for 39 individuals in 10 rivers. Among them, 35 individuals (89.7 %) were GHp + females phenotypically. The opposite feature was noted in the remaining four individuals (10.3 %). This study also revealed that GHp + phenotypic females are distributed mainly in the Sea of Japan, whereas GHp- phenotypic male tend to appear in the Sea of Okhotsk. In addition, there was a significant negative correlation between the distance from the Bishabetsu River, where frequency of GHp + phenotypic females was the highest, and the frequency of those individuals in each river. These results suggest that the distribution of masu salmon with incongruent genotypic and phenotypic sex would be related to the movement of individuals among the populations and regions.

Highlights

Sex is determined genetically by a combination of sex chromosomes in all eukaryotes
There was a significant negative correlation between the distance from the Bishabetsu River, where frequency of growth hormone pseudogene (GHp)+phenotypic females was the highest, and the frequency of those individuals in each river. These results suggest that the distribution of masu salmon with incongruent genotypic and phenotypic sex would be related to the movement of individuals among the populations and regions
Phillips et al (2005) clarified that GHp is located at the short arm of Y chromosome in Chinook salmon and coho salmon by means of fluorescence in situ hybridization (FISH) assay, indicating that this marker is effective for identifying sex

Summary

Introduction

Genetic sex determination is thought to follow a XX-XY system or a male heterogamety (Thorgaard 1977). A few genetic markers linked to the Y chromosome in salmonid fish have been developed, enabling identification of sex by genetic analysis (Oty1, Devlin et al 1991; Oty2, Brunelli and Thorgaard 2004; GHp, Du et al 1993). One of the major genetic markers for the sex identification of salmonid fish is the growth hormone pseudogene (GHp). It has been reported that this marker can identify the sex of many salmonid fish species (Chinook salmon Oncorhynchus tshawytscha, Du et al 1993; chum salmon Oncorhynchus keta, Devlin et al 2001; and masu salmon Oncorhynchus masou, Nakayama et al 1999, Zhang et al 2001). It has been reported that this marker can identify the sex of many salmonid fish species (Chinook salmon Oncorhynchus tshawytscha, Du et al 1993; chum salmon Oncorhynchus keta, Devlin et al 2001; and masu salmon Oncorhynchus masou, Nakayama et al 1999, Zhang et al 2001). Phillips et al (2005) clarified that GHp is located at the short arm of Y chromosome in Chinook salmon and coho salmon by means of fluorescence in situ hybridization (FISH) assay, indicating that this marker is effective for identifying sex

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