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PRELIMINARY OBSERVATIONS OF ATRAZINE-INDUCED EFFECTS UPON GONADAL DIFFERENTIATION IN RIVULUS MARMORATUS, A NATURALLY HERMAPHRODITIC FISH
Citation:
Davis, W P., G M. Cripe, A. Thiyagarajah, E. F. Orlando, B. Doheny, AND K. J. Bogel. PRELIMINARY OBSERVATIONS OF ATRAZINE-INDUCED EFFECTS UPON GONADAL DIFFERENTIATION IN RIVULUS MARMORATUS, A NATURALLY HERMAPHRODITIC FISH. Presented at e-Hormone, Tulane University, New Orleans, LA, 10/16-18/2003.
Description:
The commonly used agricultural herbicide atrazine has been recognized as an endocrine disrupting chemical. In amphibians and reptiles, atrazine has been reported to alter sexual differentiation and induce secondary sexual characteristics that have been attributed to enhanced aromatase activity. The mangrove rivulus, Rivulus marmoratus, is a naturally self-fertilizing simultaneous hermaphrodite. We studied the effects of atrazine upon the differentiation of the ovotestis, the hermaphroditic rivulus gonad. Newly hatched rivulus were exposed for one month to a series of atrazine concentrations and then maintained atrazine-free to maturity. Fish were euthanized, fixed and evaluated histologically. From previous experience we have observed that some rivulus developed gonads consisting primarily of testicular tissue, at frequencies of 10-15% in laboratory culture, or up to 25% in specific wild populations. Interestingly, occurrence of "female" gonads, i.e., with exclusively ovarian tissue, have never been reported from natural populations. However, a previously reported laboratory exposure study with nonylphenol described rivulus gonads lacking testicular tissue. In the current study, we observed gonads that lacked discernible testicular tissue in atrazine-exposed rivulus (19 of 116 total). We refrain from calling rivulus without testicular tissue "female" until completion of further studies. In the study, an unusually frequent (approximately 50%) of rivulus developed testicular but lacked ovarian tissue. Among the atrazine-exposed cohort, we also observed unique examples (n=7), of gonads with abnormal hyperplastic testicular tissue extension that impinged anteriorly upon the transverse septum and/or surrounded the gallbladder. The mechanisms associated with the hyperplastic testicular tissue growth remain to be determined.