Effect of different temperatures on GH-transgenesis, testosterone levels and spermatozoa density of G5 transgenic mutiara catfish (Clarias gariepinus)

Unstable changes in environmental temperature (during the dry season there are several times of rain) can damage the fish reproductive cycle, leading to inhibition of spawning activity. Low temperatures cause slow fish gonad maturation, while high temperatures cause delays in the spermatogenesis process of male fish. The ideal temperature range can increase fish testosterone (T) levels needed to maintain spermatogenesis and GH expression levels during sperm cell proliferation. The effect of temperature on the presence of exogenous GH (CgGH) in G5 transgenic mutiara catfish formed through broodstock breeding GH-transgenesis technology in previous research needs to be evaluated for testicular fertility, especially T levels and spermatozoa (Spz) density during fish gonad maturation. The results showed that the ideal temperature that increases T levels, Spz density and CgGH expression levels in G5 transgenic mutiara catfish is 24°C. Temperatures of 28°C and 32°C tended to reduce T levels and Spz density in both transgenic and nontransgenic catfish. Besides that, the sperm maturation stage (formation of Spz) was more dominantly induced by 24°C compared to other temperature treatments. This indication shows that the maximum enzyme activity involved in T production to drive the spermatogenesis process is regulated at 24°C. As a consequence, the use of transgenic male fish broodstock (transgenesis-GH) and temperature regulation for male fish gonad maturation is more profitable in the range of 24°C–28°C.