Relationship between reproductive success and male plasma vitellogenin concentrations in cunner, Tautogolabrus adspersus

The gene for vitellogenin, an egg yolk protein precursor, is usually silent in male fish but can be induced by estrogen exposure. For this reason, vitellogenin production in male fish has become a widely used indicator of exposure to exogenous estrogens or estrogen mimics in the aquatic environment. The utility of this indicator to predict impacts on fish reproductive success is unclear because information on the relationship between male plasma vitellogenin and reproductive end points in male and female fish is limited. In the research reported in this article, we investigated whether the presence of male plasma vitellogenin is a reliable indicator of decreased reproductive success in mature fish. Adult and sexually mature male and female cunner (Tautogolabrus adspersus) were exposed to 17β-estradiol, ethynylestradiol, or estrone, three steroidal estrogens that elicit the vitellogenic response. Data were gathered and pooled on egg production, egg viability, egg fertility, sperm motility, and male plasma vitellogenin concentrations. All males, including two with plasma vitellogenin 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 plasma vitellogenin concentrations. Male gonadosomatic index and average daily egg production by females showed significant, but weak, negative correlation with male plasma vitellogenin concentrations. Results suggest that male plasma vitellogenin expression is not a reliable indicator of male reproductive dysfunction in adult cunner exposed to estrogens for 2-8 weeks during their reproductive season, at least in relation to capacity to produce motile sperm or fertilize eggs. Male plasma vitellogenin expression may serve as an indicator of reduced female reproductive function caused by estrogen exposure

An injectable, slow-release implantation method for exposing fish to chemicals over a period of weeks

A slow-release, injectable implant method was developed for administering test chemicals to cunners Tautogolabrus adspersus.The implant is composed of amatrix of a test chemical homogenized in a mixture of Ethocel (Dow Chemical) and coconut oil. The effectiveness of a subcutaneous implant of this matrix in vivo was determined by tracing plasma concentrations of three separate chemicals (estradiol, ethynylestradiol, and atrazine) over time in treated male cunners. Release from the implant was determined based on the percentage of the implanted concentration of test chemical (plus metabolites) that was detected in fish plasma over a 1-2-week period after implantation. Circulating estrogen concentrations measured in plasma from two different cunners that received the estradiol implant were almost identical, indicating that there is a reasonably even distribution of test chemical within the Ethocel-coconut oil preparation and that individual variability may be minimal for release of test chemical from the implant. Metabolites of estradiol and atrazine were a major portion of the circulating concentration of these chemicals. Estradiol and atrazine demonstrated metabolic and clearance profiles that were very different from those of the xenoestrogen ethynylestradiol. A follow-up in vitro study was conducted to further characterize the release of estradiol from the implant matrix. Results showed a rapid release of estradiol from the matrix bolus during the first 24 h, followed by a more gradual release over subsequent days. The in vitro tests indicated that measuring in vivo plasma concentrations may not accurately reflect the release rate of a chemical from the implant matrix, in part because metabolism and clearance affect the circulating concentrations in vivo. © American Fisheries Society 2012