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EFFECTS OF EXPOSURE TO ENVIRONMENTAL ESTROGENS ON REPRODUCTIVE PARAMETERS IN A MARINE FISH, TAUTOGOLABRUS ADSPERSUS
Citation:
Mills, L J., R GutjahrGobell, D B. Horowitz, AND G Zaroogian. EFFECTS OF EXPOSURE TO ENVIRONMENTAL ESTROGENS ON REPRODUCTIVE PARAMETERS IN A MARINE FISH, TAUTOGOLABRUS ADSPERSUS. Presented at Endocrine Disruptors Workshop: Program Review, Research Triangle Park, NC, October 29-31, 2002.
Description:
Estradiol (E2), ethynylestradiol (EE2) and estrone (E4) are steroidal estrogens that are released into the aquatic environment in sewage treatment effluent. To determine whether these estrogens could impact reproductive parameters in a model fish species, actively spawning male and female cunner (Tautogolabrus adspersus) were exposed in the laboratory by implanting E2, EE2, or E4 subcutaneously in a slow-release matrix. A separate experiment was conducted with each of the three estrogens. An experiment consisted of four treatments: control (implant matrix only) and three concentrations of estrogen (0.05, 0.5 or 2.5 mg/kg). Four replicate tanks, each with 3 females and 1 or 2 males, were used per treatment. Reproductive success of fish before and after implantation was assessed through daily measurements of egg production, number of fertile eggs, and number of viable developing eggs. At the end of a two-week exposure period, blood was drawn from each fish for plasma steroid hormone and vitellogenin analysis. Fish were then dissected, gonads weighed, and select tissues preserved for later histopathological analysis.
Egg production prior to the implantation procedure was not significantly different among the three experiments, averaging about 280 eggs/gram female/day. Egg viability prior to implantation ranged from 17-20%, while mean egg fertility ranged from 25-52%. After implantation, only egg production in the 2.5 mg/kg EE2 treatment was significantly lower than in the controls. Notable, but not statistically significant, decreases in egg production relative to controls were observed in the 2.5 mg/kg E2 treatment, and the 0.5 and 2.5 mg/kg E4 treatments. Neither mean percent viability nor percent fertility was significantly different than controls in any estrogen treatment. All estrogen treatments induced production of the female protein vitellogenin (Vtg) in males, but EE2 more so than the others. In males from the highest concentration of EE2, average plasma concentration of Vtg (480 mg/ml) was approximately forty times (12 mg/ml) that in the high E2 treatment and nine times (53 mg/ml) that in the high E4 treatment. Overall, these results indicate that short-term exposure of mature cunner to estrogens induces Vtg production in males and may decrease egg production in females.
To investigate whether the presence of male Vtg is a reliable indicator of decreased reproductive success in mature fish, data on egg production, egg viability, egg fertility, sperm motility, and male Vtg concentrations from the two-week exposure experiments were combined with results of earlier eight-week exposure experiments. All males, including two with Vtg levels exceeding 300 mg/ml, produced motile sperm. Neither percent fertile eggs nor percent viable eggs produced by reproductively active fish demonstrated a significant correlation with male Vtg concentrations. Male gonadosomatic index and average daily egg production by females showed significant, but weak, negative linear correlation with male Vtg concentrations. Results suggest that male Vtg expression is not a reliable indicator of male reproductive dysfunction in adult cunner exposed to estrogens during their reproductive season, at least in relation to their capacity to produce motile sperm or to fertilize eggs. In some cases, male Vtg expression may serve as an indicator of reduced reproductive function in females exposed to estrogens at the same time.