GONADAL DEVELOPMENT AND ENDOCRINE RESPONSES IN JAPANESE MEDAKA (ORYZIAS LATIPES) EXPOSED TO o,p′-DDT IN WATER OR THROUGH MATERNAL TRANSFER

Abstract

Abstract-Various isomers and metabolites of DDT disrupt endocrine systems and gonadal development in fish and wildlife, and o,pЈ-DDT has been shown to be an relatively potent estrogen agonist. In this study, we exposed Japanese medaka (Oryzias latipes) to o,pЈ-DDT using two exposure protocols: direct exposure of early life stages to aqueous solutions from 1 to 100 d posthatch and exposure of female medaka to aqueous solutions, followed by mating with unexposed males to produce offspring that were exposed through mechanisms of maternal transfer. In treatments with direct aqueous exposures, an intersex condition of the gonad (testisova) was observed in male medaka exposed at early life stages to nominal o,pЈ-DDT concentrations of 50, 10, and 5 g/L, indicating that this estrogen agonist can alter gonadal development when exposure occurs continuously over the period of gonadal differentiation. Comparisons with previously published data on the induction of testis-ova by exposure to nonylphenol (NP) and octylphenol (OP) indicated that the relative potencies for induction of intersex in medaka are o,pЈ-DDT Ͼ NP ഠ OP, which is not consistent with the relative estrogenic potencies of OP Ͼ NP Ͼ o,pЈ-DDT observed in the yeast estrogen screening (YES) assay. In the maternal transfer protocol, no testis-ova were observed in the offspring, although there was some delay in time to hatch of the offspring. Medaka exposed by maternal transfer showed no other toxicological responses during early life stages, but when treated fish reached sexual maturity, the females showed more advanced development of oocytes. In addition, when medaka exposed by maternal transfer were subsequently exposed at 10 months of age to 17␤-estradiol (12 mg/L), there was a significantly greater induction of hepatic vitellogenin in DDT-exposed males in comparison to control males, indicating that exposure to estrogenic chemicals during early life stages may potentiate vitellogenin induction following exposure events later in the life of the fish.

In ovo exposure to o,p -DDE affects sexual development but not sexual differentiation in Japanese medaka (Oryzias latipes).

“…Female white croakers (Genyonemus lineatus) collected from San Pedro Bay, California, with body burdens of ≥ 3.8 ppm ΣDDT (total of all isomers of DDT and its breakdown products) could not be induced to spawn and exhibited only earlystage oocytes, of which high numbers were atretic relative to reference fish (Hose et al 1989). In contrast to our results, Metcalfe et al (2000) reported advanced oogenesis in female medaka developed from eggs with o,p´-DDT concentrations of approximately 80-102 ng/egg, although both reference and treated groups began producing viable eggs at the same time. Males in this same study did not display small gonads and associated secondary sexual effects (lack of breeding tubercles) that we observed.…”

“…Males in this same study did not display small gonads and associated secondary sexual effects (lack of breeding tubercles) that we observed. However, when Metcalfe et al (2000) exposed these male progeny to estradiol at 10 months of age, they found that the male offspring showed significantly greater induction of vitellogenin than did controls, suggesting that early DDT exposure may have potentiated vitellogenin induction later in life.…”

“…Metcalfe et al (2000) have reported that maternal exposure to o,p´-DDT (egg concentrations estimated at 80-102 ng/egg) failed to produce intersex progeny. Although the lack of male offspring produced by treated females might have been indicative of complete feminization of genetic males, these authors did not consider this finding definitive evidence of sex reversal because their experiments were not conducted with fish that had a male genetic marker (e.g., d-rR strain).…”

Histopathological changes in the reproductive system (ovaries and testes) of Oreochromis mossambicus following exposure to DDT

“…These nominal concentrations were selected in the context of field measurements from a survey done in an urban reserve in South Africa (Bornman et al, 2007). The concentrations also fall within the sub-lethal range that has been tested by other authors (Benton et al, 1994;Metcalfe et al, 2000;Cheek et al, 2001). The fish were kept under a 12:12 light:dark (LD) cycle regulated by electric timers throughout the exposure period, and the water temperature at 25-28 °C.…”

“…Technical-grade DDT contains 65-80% p,p'-DDT, 15-21% o,p'-DDT and up to 4% p,p'-DDD (bis[4-chlorophenyl]-1,1,-dichloroethane) (ATSDR, 2002). The o,p-isomer constitutes about 15% of technical-grade DDT, and has been reported to be weakly estrogenic (Donohoe and Curtis, 1996;Metcalfe et al, 2000;Papoulias et al, 2003). DDTisomers, including o,p'-DDT have been implicated in reduced development of penises in male alligators from a contaminated Lake Apopka, Florida, USA (Guillete et al, 1994).…”