Convenient method for sex reversal in a freshwater teleost, the medaka

Isobe, Takashi

doi:10.1002/(sici)1097-010x(19990201)283:2<210::aid-jez12>3.0.co;2-f

Cited by 45 publications

(5 citation statements)

References 23 publications

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“…The XX males were sex-reversed F1 offspring that were obtained from crossing an HNI female with an Hd-rR male. Sex reversal was induced by a hormone treatment developed by Iwamatsu (1999). In this method, fertilized eggs were soaked in water containing sex hormone (0n08 µg\ml 17-methyltestosterone) until hatching.…”

Section: (Iii) Mating Experimentssupporting

confidence: 85%

Male-specific restriction of recombination frequency in the sex chromosomes of the medaka, Oryzias latipes

et al. 1999

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In the medaka, Oryzias latipes, the mechanism of sex determination (XX\XY) can be revealed by genetic crosses using a body-colour gene, though it does not have cytologically recognizable sex chromosomes. The recombination restriction of sex chromosomes in heterogametic (XY) males has been demonstrated. To elucidate whether the recombination is prevented by the heterogamety of the sex chromosomes or by maleness, we examined the recombination frequencies among three loci located on the sex chromosomes (r, SL1 and SL2) in heterogametic males (XY), homogametic males (XX and YY), homogametic females (XX) and heterogametic females (XY). The recombination frequencies between r-SL1 and SL1-SL2 were as follows : 0, 0 (XY males) ; 0, 1n5 (XX males) ; 1n6 % (YY males ; 1n2%, 14n4 % (XY females) ; 0n8%, 21n8 % (XX females). These results indicate that the recombination restriction of the sex chromosomes in heterogametic males does not result from heterogametic sex chromosomes, but from maleness. Such sex-chromosomespecific recombination restriction in heterogametic sex may have triggered the differentiation of sex chromosomes in vertebrates.

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Section: (Iii) Mating Experimentssupporting

confidence: 85%

Male-specific restriction of recombination frequency in the sex chromosomes of the medaka, Oryzias latipes

et al. 1999

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“…In the 5 ng/L EE 2 treatment group, we found no phenotypic males, as discerned by the absence of any secondary sex characteristics, such as slightly yellow/bronze coloration and bright anal fin markings. This gave the initial impression that sex reversal had been induced, as occurs in some fish species after exposure to steroidal estrogens (Iwamatsu 1999; Lange et al 2001; Scholz and Gutzeit 2000). Further studies on these F 1 fish found that no fish contained expressible sperm.…”

Section: Resultsmentioning

confidence: 99%

Long-Term Exposure to Environmental Concentrations of the Pharmaceutical Ethynylestradiol Causes Reproductive Failure in Fish

Nash

Kime

Ven³

et al. 2004

Environ Health Perspect

559

341

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Heightened concern over endocrine-disrupting chemicals is driven by the hypothesis that they could reduce reproductive success and affect wildlife populations, but there is little evidence for this expectation. The pharmaceutical ethynylestradiol (EE2) is a potent endocrine modulator and is present in the aquatic environment at biologically active concentrations. To investigate impacts on reproductive success and mechanisms of disruption, we exposed breeding populations (n = 12) of zebrafish (Danio rerio) over multiple generations to environmentally relevant concentrations of EE2. Life-long exposure to 5 ng/L EE2 in the F1 generation caused a 56% reduction in fecundity and complete population failure with no fertilization. Conversely, the same level of exposure for up to 40 days in mature adults in the parental F0 generation had no impact on reproductive success. Infertility in the F1 generation after life-long exposure to 5 ng/L EE2 was due to disturbed sexual differentiation, with males having no functional testes and either undifferentiated or inter-sex gonads. These F1 males also showed a reduced vitellogenic response when compared with F0 males, indicating an acclimation to EE2 exposure. Depuration studies found only a partial recovery in reproductive capacity after 5 months. Significantly, even though the F1 males lacked functional testes, they showed male-pattern reproductive behavior, inducing the spawning act and competing with healthy males to disrupt fertilization. Endocrine disruption is therefore likely to affect breeding dynamics and reproductive success in group-spawning fish. Our findings raise major concerns about the population-level impacts for wildlife of long-term exposure to low concentrations of estrogenic endocrine disruptors.

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“…For this purpose, two methods were applied as follows: (1) the 10-hpf embryos were immersed in Yamamoto's solution containing 0.2 or 2.0 µ g/l of E2, which is 50 or 5 times lower concentration than the lowest effective (Iwamatsu, 1999), and fed to adult with normal diet after hatching; and (2) the newly hatched fry in the absence of E2 were fed to adult with diet containing 5, 10, or 20 µ g of E2 per gram of diet. The E2 dosage of 20 µ g/g of diet is sufficient for complete sex-reversal, and the dosages of 5 and 10 are less effective or result in no sex-reversal depending on each experiment (Yamamoto, 1969;.…”

Section: Resultsmentioning

confidence: 99%

No Effects of Estrogen Receptor Overexpression on Gonadal Sex Differentiation and Reversal in Medaka Fish

et al. 2003

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In order to elucidate a possible role of estrogen receptor in the gonadal sex differentiation and the sex reversal with sex steroids, we examined for the formation of testis or ovary in transgenic medaka fish overexpressing the medaka estrogen receptor under the constitutive medaka beta-actin promoter. The transgenic fish underwent the genetically determined gonadal differentiation and showed the same sex-reversal rates as those of wild-type non-transgenic fish after treatments with estrogen and androgen. These results present invaluable data to reconsider the role of estrogen receptor in the gonadal sex determination.

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Convenient method for sex reversal in a freshwater teleost, the medaka

Cited by 45 publications

References 23 publications

Male-specific restriction of recombination frequency in the sex chromosomes of the medaka, Oryzias latipes

Male-specific restriction of recombination frequency in the sex chromosomes of the medaka, Oryzias latipes

Long-Term Exposure to Environmental Concentrations of the Pharmaceutical Ethynylestradiol Causes Reproductive Failure in Fish

No Effects of Estrogen Receptor Overexpression on Gonadal Sex Differentiation and Reversal in Medaka Fish

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