Assessment the impact of 17α-methyltestosterone hormone on growth, hormone concentration, molecular and histopathological changes in muscles and testis of Nile tilapia; Oreochromis niloticus

Abstract: The present study was designed to explain clearly why methyltestosterone is widely used by the Egyptian producers of farmed tilapia and also to investigate its fate in treated fish to guarantee that no hazards on consumers, producers and on the environment. In this study, samples of untreated and treated Nile tilapia were collected at several time intervals. Water quality parameters were within the acceptable range for fish growth. The present analyses showed highly significant increase in body weight, body length, condition factor (K), HSI and GSI, between different time intervals (April -November, 2009) in the untreated control and treated groups. On the other hand, plasma testosterone and residual concentration of testosterone hormone in muscle showed highly significant differences between the studied months in untreated control and treated groups. Molecular biological analyses revealed that methyltestosterone was able to induce DNA fragmentation and molecular genetic variability (using RAPD-PCR fingerprinting pattern) in the testis tissues of the treated Nile tilapia; Oreochromis niloticus, which was higher in the first four studied months than the untreated control tilapia. Additionally, histopathological examination showed no changes and no traces of hormone accumulation in the muscle structure. Testis showed moderate number of spermatozoa followed by increasing in number of spermatozoa at the end of the study