Factors Affecting the Development of Testis-Ova in Medaka, Oryzias Latipes, Exposed to Octylphenol

Abstract

Abstract-There are many endocrine-disrupting chemicals in the environment that have the potential to alter the development of sexual characteristics in fish and wildlife. Little is known about the factors that influence the development of an intersex condition in fish. Japanese medaka (Oryzias latipes) were exposed to octylphenol (OP), a known estrogen agonist, during various life history stages to determine the factors that control induction of testis-ova, an intersex condition. In male medaka exposed to OP (100 g/L) beginning at 1, 3, 7, 21, and 35 d posthatch, the incidence of testis-ova at 100 d posthatch was highest in the 3-d posthatch treatment (4 of 14 males) and declined when exposures were initiated with older fry. Exposure to OP (100 g/L) from hatch for a period of 1 or 2 months did not induce testis-ova, but exposure for 3 months resulted in 3 of 50 males developing this condition. Exposures of adult male medaka to OP (200 and 300 g/L) for either 18 or 36 d resulted in only one testis-ova in a male fish exposed for 36 d to the highest nominal concentration. In addition to testis-ova, male medaka exposed to OP developed testicular fibrosis. Overall, these data indicate that prolonged exposure of male medaka to an estrogen agonist beginning around the period of gonadal differentiation is optimal for the development of testis-ova, but this intersex condition can be induced when exposure begins at later life stages.

Long-term estrogen exposure of whitefish Coregonus lavaretus induces intersex but not Lake Thun-typical gonad malformations

“…Both field and laboratory studies have shown that exposure of developing fish to estrogenactive compounds can induce alterations in gonad morphology, including the development of hermaphroditic or intersex gonads, i.e. the presence of oocytes in testicular tissue (Gray & Metcalfe 1997, Gray et al 1999, Seki et al 2002, Palace et al 2006.The aim of the present study is to evaluate whether exposure of developing coregonids to estrogen-active compounds would induce the specific Lake Thuntypical gonad malformations, i.e. intersex, gonad compartmentations and adhesions/fusions, and aplasia/ atrophy.…”

Experimental Evaluation of Vitellogenin as a Predictive Biomarker for Reproductive Disruption

“…Environmental contaminants can have organizational effects on sex differentiation and on expression of secondary sex characteristics in a variety of vertebrates (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). In addition, numerous studies have documented the activational effects of exogenous chemicals on levels of sex steroid hormones and on hormone-mediated protein synthesis (12,(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36).…”

“…Alkylphenol exposure caused feminization of the testis in medaka [Oryzias latipes (8,9)] and carp [Cyprinus carpio (7)] and reduced testis and ovary growth in juvenile rainbow trout [Oncorhynchus mykiss (47,48)]. o,p´-DDT also caused feminization in medaka, either by immersion exposure of fry (11) or by injection into fertilized eggs (10).…”

“…We used medaka as a model because they are easily maintained in the laboratory and are known to be sensitive to environmental estrogens (8)(9)(10)(11)53,54). We chose to use o,p´-DDT as a model environmental estrogen for several reasons.…”

Bioconcentration and metabolism of 4-tert-octylphenol in roach (Rutilus rutilus) fry

“…Exposure of sexually undifferentiated male carp (Cyprinus carpio) to the xenoestrogen 4-tert-pentylphenol resulted in formation of an oviduct and ovo-testis [9]. Similarly exposure of male Japanese medaka (Oryzias latipes) to t-OP during gonadal differentiation resulted in the intersex condition [10].…”