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Sensivity of Adult Reproduction and Reproductive Development in Japanese Medaka Exposed to 4-Tert-octylphenol
Citation:
HAASCH, M. L., D. B. LOTHENBACH, K. M. FLYNN, F. W. WHITEMAN, D. E. HAMMERMEISTER, J. NAGEL, W. BACKE, D. SHADWICK, AND R. D. JOHNSON. Sensivity of Adult Reproduction and Reproductive Development in Japanese Medaka Exposed to 4-Tert-octylphenol. Presented at SETAC Annual Meeting, Milwaukee, WI, November 11 - 15, 2007.
Impact/Purpose:
As part of an ongoing effort to develop methods to assess the reproductive toxicity of chemicals, this investigation relates the population-level assessments of fecundity and fertility to effects on the development of reproductive system of fish in the next generation.
Description:
In response to legislation, the USEPA is developing assessment tools for identifying chemicals likely to cause sublethal effects on reproduction and reproductive development with ultimate adverse impacts on fish populations. While fecundity and fertility data from short-term adult reproduction assays are directly applicable to population-level assessments, effects on reproductive development appear to be more sensitive but are less directly applicable to population assessments. The protocol in this study incorporated both adult and developmental stages thus providing data for comparisons and development of relationships among endpoints and life-stages. In this study 6 replicate breeding pairs of medaka (Oryzias latipes) were exposed to 4-tert-octylphenol (0, 2, 8, 27, 90 and 300 μg/L). Fecundity and fertility were assessed for 5 weeks (4 days/week). Effects on hatch and subsequent reproductive development were assessed by continuing the exposure of the F1 embryos until 43 days post-fertilization. Hatching success was negligible at 300 μg/L. No treatment effects on body weight were observed in either the F0 or F1 populations. Adult fecundity was more sensitive than fertility (LOECs of 8 and 300 μg/L, respectively). In both F0 and F1 generations, the individual genotypic sex (DMY-gene) was compared with several gender-specific endpoints (phenotypes); anal fin papillae, hepatic vitellogenin (VTG) mRNA levels, and gonadal sex. The genotypic F0 male LOEC for increased liver weight, hepatosomatic index and induction of VTG mRNA was 90 μg/L. The genotypic F1 male LOECs for reduced papillae, increased VTG mRNA, intersex, and gonadal sex reversal were 27, 27, 2, and 27 μg/L respectively. These data support previous studies regarding the estrogenicity of 4-tert-octylphenol and indicate the efficacy and sensitivity of assessing alterations of gonadal phenotype through the determination of genetic sex. Relationships among endpoints and life stages will inform further development of protocols optimized for sensitivity, time, reduced animal use, and extrapolation across levels of organization.