Inter- and Intraspecific Variation in Sex Hormone-Induced Sex-Reversal in Medaka, Oryzias latipes and Oryzias sakaizumii

Inter- and Intraspecific Variation in Sex Hormone-Induced Sex-Reversal in Medaka, Oryzias latipes and Oryzias sakaizumii

We compared sex-reversal ratios induced by 17α-methyltestosterone (MT) and 17β-estradiol (E2) exposure in two inbred medaka strains: Hd-rR derived from and HNI-II from . All MT exposures (0.2-25 ng mL ) induced complete XX sex-reversal in HNI-II. Although MT exposure at 0.2 ng mL induced XX sex-reve...

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Bibliographic Details
Published in:Zoological science Vol. 36; no. 5; p. 425
Main Authors: Myosho, Taijun, Sato, Tadashi, Nishiyama, Hiroka, Watanabe, Akiho, Yamamoto, Jun, Okamura, Tetsuro, Onishi, Yuta, Fujimaki, Rei, Hamaguchi, Satoshi, Sakaizumi, Mitsuru, Kobayashi, Tohru
Format: Journal Article
Language:English
Published: Japan 01-10-2019
Subjects:
Animals
Estradiol - administration & dosage
Estradiol - genetics
Estradiol - pharmacology
Female
Gonads - drug effects
Male
Methyltestosterone - administration & dosage
Methyltestosterone - pharmacology
Oryzias - metabolism
Phenotype
Sex Determination Processes - drug effects
Sex Differentiation - drug effects
Species Specificity
sex steroid
sexual phenotype
feminization
17α-methyltestosterone
medaka
masculinization
17β-estradiol
sex ratio
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Summary:We compared sex-reversal ratios induced by 17α-methyltestosterone (MT) and 17β-estradiol (E2) exposure in two inbred medaka strains: Hd-rR derived from and HNI-II from . All MT exposures (0.2-25 ng mL ) induced complete XX sex-reversal in HNI-II. Although MT exposure at 0.2 ng mL induced XX sex-reversal at > 95% in Hd-rR, other concentrations tested caused XX sex-reversal at lower frequencies (<50%). MT exposure at 1, 5, and 25 ng mL induced XY sex-reversal in Hd-rR, but not in HNI-II. In Hd-rR, E2 exposure induced XY sex-reversal at > 10 ng mL , and in all fish feminization occurred 500 ng mL . In HNI-II, E2 induced XY sex-reversal at 50 and 250 ng mL , but only at rates below 20%. To clarify whether the strain differences in sex hormone-induced sex-reversal are characteristic of each species, we examined the effects of MT and E2 exposure on sex differentiation in five and two additional strains or wild stocks/populations of and , respectively. MT exposure induced low XX and high XY sex-reversal rates in , except in the Shizuoka population, but the trend was reversed in . Furthermore, E2-induced XY sex-reversal rates varied intraspecifically in . Our results demonstrated that sensitivity to MT and E2 varied within species. To evaluate the ecological impacts of environmental chemicals using medaka, it is important to define not only the species, but the strains, stocks, and populations to obtain accurate results.
ISSN:0289-0003
DOI:10.2108/zs180194