Meeting Abstract

P2-100   -   Do glucocorticoid hormones mediate sex reversal in frogs? Ujhegyi, N*; Kalina, C; Mikó, Z; Bókony, V; Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Budapest, Hungary; Department of Ecology, Institute for Biology, University of Veterinary Medicine Budapest, Budapest, Hungary; Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Budapest, Hungary; Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Budapest, Hungary; Department of Ecology, Institute for Biology, University of Veterinary Medicine Budapest, Budapest, Hungary ujhegyi.nikolett@atk.hu http://evolecol.hu/

In ectotherm vertebrates (fishes, amphibians and reptiles) environmental temperature or chemical impacts can influence sex determination during larval or embryonic development. This can result in intersex gonads or in complete sex reversal, a mismatch between phenotypic and genetic sex. This process may have significant consequences for individual fitness and population dynamics, so it is important to understand the mechanisms of sex reversal. In most amphibians and fishes, environmental stressors usually cause female to male sex reversal, and a few laboratory experiments with fish suggest that this may be due to glucocorticoid (GC) hormones inhibiting aromatase and thereby the transformation of male sex hormones into female sex hormones. However, research with reptiles did not support this idea, and amphibians have not been studied in this regard. Our aim was to test whether the elevation of GCs induces sex reversal in agile frogs (Rana dalmatina). In our experiment, we added 5 different concentrations (0, 0.01, 10, 100, or 1000 nM) of corticosterone (the main GC of amphibians) into the tadpoles' rearing water for 6 days during the sensitive period of gonad development. After complete differentiation of the gonads (ca. 2 months after metamorphosis), we dissected the animals and identified phenotypic sex by gonad morphology. We found no statistically significant difference in phenotypic sex ratio between treatment groups, although our sample size was limited by unexpectedly high mortality regardless of treatment. However, the proportion of males increased from 44% in the control group to 53-61% in the groups treated with 0.01 or 10 nM corticosterone, and these two groups had significantly higher frequency of testes with abnormal morphology suggesting intersex. We will complement our results with histological and genetic sexing to better understand how GCs affect sex development in frogs.