Potential application of an in vitro gonadal culture assay to determine fish reproductive response to environmental temperature

YAMAMOTO YOJI; ELISIO MARIANO; MIRANDA LENADRO A; ZHANG YAN; STRÜSSMANN CARLOS A

Austin

Congreso; Joint Meeting of Ichthyologists and Herpetologists; 2017

Temperature is a key environmental cue controlling gonadal development and spawning in fish. This control appears to be associated with the influence that this physical variable exerts on gonadal steroidogenesis. This study assessed if profiling of steroid synthesis on in vitro gonadal cultures at different temperatures accurately reflects the fish reproductive response to environmental temperature. The pejerrey Odontesthes bonariensis was selected as model because of its well characterized in vivo reproductive response to temperature changes. Ovarian in vitro cultures of three females were performed at 6 different temperatures between 12 and 27 °C, using Leivovitz L-15 medium containing 17-hydroxy-progesterone (100 ng/ml). Testosterone (T), estradiol (E2), and relative gene expression of gonadal aromatase (cyp19a1a) were measured after 12 hours culture. Cyp19a1a relative expression showed an almost linear decrease with temperature increase, while both T and E2 levels in culture medium showed a Gaussian relationship with temperature. On average, the highest level of E2 was obtained between 19 and 20 °C, while for T it was between 20.5 and 21.5 °C. The optimal temperature range estimated in this study for production of E2 (hormone promoting ovarian development) coincided with the optimal temperaturepreviously reported for ovarian maturation in this species (19-20 °C). The optimal temperature estimated for T production, which was approximately 1.5 °C higher than for E2, could indicate the best temperature for inducing spawning. In conclusion, this study provides promising evidences for the development of a relatively easy in vitro assay to determine fish reproductive response to environmental temperature.