In tilapia, being a gonochoristic species, differentiation of gonads takes place early in life and remains unchanged henceforth. Because gonads possess bipotential character, phenotypic sex can be affected by environmental cues. The present study addresses the feasibility of reversing sex in female Nile tilapia by exposing fry to thermal treatment. Eggs stripped from ripe females were artificially inseminated and incubated at 28°C. Beginning 10 days post fertilization (dpf), part of the fry was exposed to 36°C for 10 days before being returned to 28°C, whereas the remaining fry was kept at a constant 28°C. From 90 to 240 dpf every 30 days 24 fish were sacrificed to study the macro- and micro-morphologic structures of the gonads.  It turned out that 37% of the thermally treated genetic females had undergone sex reversal to become phenotypic males. No such cases were observed in the control group. The testes of the sex-reversed genetic females were structurally normal; immunohistochemical studies revealed the normal proliferative activity of spermatogonia. The gonads of the non-responding females were found to have all features of functionally normal ovaries.

Aulidya Nurul Habibah