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RELATIONSHIP BETWEEN REPRODUCTIVE OUTPUT AND MALE PLASMA VITELLOGENIN LEVELS IN CUNNER, TAUTOGOLABRUS ADSPERSUS
Citation:
Mills, L J., R GutjahrGobell, D B. Horowitz, N D. Denslow, M. Chow, AND G Zaroogian. RELATIONSHIP BETWEEN REPRODUCTIVE OUTPUT AND MALE PLASMA VITELLOGENIN LEVELS IN CUNNER, TAUTOGOLABRUS ADSPERSUS. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Baltimore, MD, November 11-15, 2001.
Description:
The egg yolk protein precursor vitellogenin (VtG) is normally produced in the liver of female oviparous fish in response to an estrogen signal from the developing ovary. The VtG gene in male fish, usually silent, can be induced by estrogen exposure. As a result, VtG production in male fish has become a widely used indicator of exposure to exogenous estrogens or estrogen mimics in the aquatic environment. The relevance of this indicator to effects on fish reproductive success is unclear, because information on the relationship between male plasma VtG and reproductive endpoints, such as egg production, egg viability or egg fertility, is limited. During a series of laboratory experiments exposing the temperate reef fish cunner to 17 -estradiol and ethinyl estradiol, we have gathered data on egg production, egg viability, egg fertility, sperm motility, and plasma VtG concentrations in males. In our experiments, all males, even those with plasma VtG levels approaching 400 mg/ml, still produced motile sperm. Neither the percent fertile eggs nor the percent viable eggs produced by reproductively active fish demonstrated a significant correlation with male plasma VtG concentrations. Average egg production per female per day did show a significant inverse correlation with male plasma VtG concentrations. Our results indicate that the widely-used indicator of estrogen exposure, male plasma VtG expression, is not a good indicator of male reproductive function, but may serve as an indicator of reduced egg production in female cunner.