Effect of thiourea on the testicular steroidogenesis and secondary sexual characters of a tropical freshwater fish, Mystus (M) vittatus (Bloch).

300 ppm of thiourea solution was found to produce significant decline in the interstitial cells of the testes of Mystus (M) vittatus. The regressive changes have been observed both in the number and the size (diameter) of these cells. The thiourea though could not bring about appreciable changes up to the second week, but during third and fourth week marked cellular regression in the interstitial cells has been recorded. Such cellular changes appear to influence the development of the genital papilla and caudal thickening (the secondary sexual characters - SSC) in the male specimens. Changes in the interstitial cells indicative of gonadal steroidogenesis correlated with the SSC is for the first time reported in a tropical fish. Interesting findings have been described and discussed.