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Marine Ecology Progress Series

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MEPS 659:175-184 (2021)  -  DOI:

Effectiveness and potential application of sex-identification DNA markers in tunas

Satoru N. Chiba1,5,*, Shinpei Ohashi1, Fumiya Tanaka1, Ayako Suda2, Atushi Fujiwara2, Derke Snodgrass3, Hidetada Kiyofuji1, Keisuke Satoh1, Nobuaki Suzuki1,4

1National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, 5-7-1 Orido, Shimizu, Shizuoka 424-8633, Japan
2Research Center for Bioinformatics and Biosciences, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama 236-8648, Japan
3Sustainable Fisheries Division, NOAA Fisheries, 75 Virginia Beach Drive, Miami, FL 33149, USA
4Fisheries Agency, Ministry of Agriculture, Forestry and Fisheries, 1-2-1 Kasumigaseki, Chiyoda, Tokyo 100-8907, Japan
5Present address: Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, 116 Katsurakoi, Kushiro, Hokkaido 085-0802, Japan
*Corresponding author:

ABSTRACT: Sex-identification DNA markers are useful tools for sexing organisms that lack externally visible sexual dimorphism, and thus, they provide biological information for ecological and evolutionary studies. Tunas of the genus Thunnus (Scombridae), which comprises 8 species, lack sexual dimorphism of external morphology or coloration. In this study, we applied recently developed genotypic sex-identification markers for Pacific bluefin tuna to other tuna species to evaluate their effectiveness in sex identification. A sex-identification marker named ‘primer pair II’ demonstrated relatively high effectiveness in all tuna species, except southern bluefin tuna. Primer pair II was further tested in 209 albacore individuals collected during the scientific observer program onboard Japanese commercial long-line vessels, and it demonstrated robust performance for genotypic sex identification. The sex ratio of this albacore sample (1:1.4) significantly deviated from the expected 1:1 with the dominance of males, and the mean body size of males was higher than that of females. As all cross-species amplifications of the male-specific markers, except those for the southern bluefin tuna, were male-heterozygous polymorphisms, it is likely that a male-heterozygous sex-associated region exists in the Thunnus genome. The evolution of sex-determination systems in tunas was analyzed by ancestral state reconstruction, which showed that a common ancestor, before the evolution of the genus, possessed the male-heterozygous sex-associated genome region.

KEY WORDS: Sex-specific PCR · Thunnus · Male heterogametic sex · Sex ratio · Sexual dimorphism · Sex determination

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Cite this article as: Chiba SN, Ohashi S, Tanaka F, Suda A and others (2021) Effectiveness and potential application of sex-identification DNA markers in tunas. Mar Ecol Prog Ser 659:175-184.

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