Effects of methyltestosterone, tamoxifen, genistein and Basella alba extract on masculinization of guppy (Poecilia reticulata)

The effects of different anti-estrogenic chemicals were evaluated in guppy, Poecilia reticulata on sex differentiation and survival. New-born fry of the fish were fed diets containing genistein (1 gm kg-1), tamoxifen (100 mg kg-1), methanol extract of Basella alba (1 gm kg-1) and 17α-methyltestosterone (60 mg kg-1) for 30 days. The treated groups showed no significant difference (P>0.05) in survival percentage while a significant increase (P<0.05) in percentage of males were observed in all the treatment groups compared to that in control. Control fish showed the lowest percentage (44.49%) of males while 17α-methyltestosterone treatment provided maximum (81.90%) males, followed by tamoxifen (80.09%), genistein (70.59%) and B. alba (63.55%). Intersex fish with male like colouration and gonopodium development, but female gonad structure was observed in all the treated groups. The nonsteroidal compounds evaluated in this study showed potential for affecting sex ratios although their potency was lower compared to 17α-methyltestosterone. Further studies are needed to determine an optimum treatment regime with these agents for induction of 100% sex reversal in guppy.