Accepted 13th March, 2014
The green swordtail, Xiphophorus hellerii, is a commercially important ornamental species. Since phenotypic male with the sword extension of the caudal fin has more commercial value than female, masculinization by means of 17-α-methyltestosterone (MT) was tested. female brood stocks of swordtail were fed different dose rates of synthetic androgen MT( i.e. 25, 50 and 75 mg MT kg-1) of feed and MT 25, 50 and 75 mg kg-1 plus 30 mg kg-1 Vitamin E. MT and vitamin (E+MT) were administrated orally by using pellet dry starter and ethanol alcohol investigated for 30 days. The fry also kept two weeks after feeding to maturation, at the end of experiment. Survival and mortality rate were determined. At the end of the experiment the sex ratio was determined by secondary sex characteristics and macroscopic examination of the gonads after dissection. The results of the present study showed that all MT receiving treatment showed a significantly higher male proportion than control (p<0.05). Univariate Analysis of Variance (ANOVA) of survival rate showed that there is no significantly different among all experimental groups (P> 0.05). However, the survival rate of fries fed MT+vitamin E were higher in comparing with groups fed just MT. Results showed that dose rate of 75 mg MT kg-1 of feed and Vitamin caused in maximum male population (98%) with 16.0% and 8.0% mortality, respectively.
Keywords: Swordtail, Xiphophorus hellerii, sex reversal, masculinization, vitamin E, survival.