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An in vivo model fish system to test chemical effects on sexual differentiation and development: exposure to ethinyl estradiol

Aquatic Toxicology

By:
, , and
DOI: 10.1016/S0166-445X(99)00026-0

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Abstract

A model system was characterized which may be used as an in vivo screen for effects of chemicals or environmental mixtures on sexual differentiation and development of reproductive organs and gametes. We evaluated the effects of a model environmental estrogen, ethinyl estradiol (EE2), on the d-rR strain of medaka, Oryzias latipes, using a nano-injection exposure. Gonad histopathology indicated that a single injection of 0.5-2.5 ng EE2/egg can cause phenotypic sex-reversal of genetic males to females. Sex-reversals could be detected as early as 7 days post-hatch. Sex-reversed males had female-typical duct development and the secondary sex characteristics we measured were generally consistent with phenotype, with the exception of a few EE2-exposed XX and XY females which possessed ambiguous anal fins. Using discriminant analysis, we determined that the presence or absence of the secondary sex characteristic, a dorsal fin notch, was a very reliable indicator of gonadal sex. No instances of gonadal intersexes were observed. Ethinyl estradiol also appeared to reduce growth but not condition (weight-at-length) and exposed XX females appeared to have a higher incidence of atretic follicles relative to controls. Our results suggest that estrogenic chemicals may influence sexual differentiation and development and that the medaka model is well suited to assessing these effects. Copyright (C) 2000 Elsevier Science B.V.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
An in vivo model fish system to test chemical effects on sexual differentiation and development: exposure to ethinyl estradiol
Series title:
Aquatic Toxicology
DOI:
10.1016/S0166-445X(99)00026-0
Volume
48
Issue:
1
Year Published:
2000
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Aquatic Toxicology
First page:
37
Last page:
50
Number of Pages:
14