Effect of dietary administration of methyltestosterone and vitamin C on the sex reversal and survival of Xiphophorus maculatus (Cyprinodontiformes: Poeciliidae)

The common platy, Xiphophorus maculatus, is a commercially important ornamental species. Since phenotypic male has more commercial value than female, masculinization by means of 17-αmethyltestosterone (MT) was tested. Three-five (3-5) day post-hatch larvae were fed by 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 100 mg kg-1 Vitamin C (Vit C). MT and vitamin were administrated orally by using pellet dry starter and ethanol alcohol investigated for 45 days. 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. Univariate Analysis of Variance (ANOVA) of masculinization was significant (p < 0.05) however results of Duncan test showed that there is no significant difference among all experimental groups, in addition with intensification in MT dose, the masculinization was increased. Results of addition Vit C to treatments was significant (p < 0.05) and results of Duncan test showed that there is significant difference among all experimental groups however in higher dose of MT survival was lower than low dose of MT. Vit C increased survival rate in groups 25 and 50 mg MT kg-1. Nevertheless the group 75 mg MT kg-1+Vit C had lower survival rate that this group without Vit C. The obtained results showed that dose rate of 75 mg MT kg-1+Vit C caused maximum male population (55.96%) with 17.81% mortality, and dose rate of 25 mg MT kg-1 without Vit C caused minimum male population (49.47%) with 12.62% mortality. In conclusion results showed the doses of MT used in this study were not effective to masculinize the common platy fishes and Vit C was not able to increase survival in high dose of hormone.