Ohio State and UJAT/Mexico: Evaluating the Potency of Phytochemicals to Sex-Reverse Tilapia
by Konrad Dabrowski, Mary Ann G. Abiado, Gustavo Rodriguez Montes de Oca, The Ohio State University, and Wilfrido Contreras Sánchez, Universidad Juárez Autónoma de Tabasco, Mexico
uly 1, 2001, marked the beginning of a new CRSP project on Studies on Fate of Methyltestosterone and its Metabolites in Tilapia and on the Use of Phytochemicals as an Alternative Method to Produce a Monosex Population of Tilapia.
Collaborators are Konrad Dabrowski and Mary Ann G. Abiado of The Ohio State University (OhSU), Columbus, Ohio, and Wilfrido Contreras-Sánchez and Gabriel Márquez-Couturier of Universidad Juárez Autónoma de Tabasco (UJAT), Tabasco, Mexico. The research aims to determine the concentration of methyltestosterone (MT) derivatives in tilapia and in water using radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) and to evaluate the potential action of phytochemicals on sex differentiation in tilapia.Three students from Mexico are working on the projectGustavo Rodriguez Montes de Oca, a Ph.D. student at Ohio State, and Maria de Jesus Contreras Garcia and Guadalupe Morales Lara, undergraduate students in biology at UJAT.
Results from both locations showed that the incorporation of 1% quercetin in the diet does not affect sex determination in tilapia. However, the addition of 1% quercetin and 1000 ppm vitamin C in the diet shows potential for promoting growth in tilapia. Further studies are recommended to evaluate higher percentage of quercetin in the diet.
This study demonstrated that the phytochemical quercetin has no feminizing effect on tilapia. The next step is to evaluate its masculinizing effect in a separate study using either all-female populations from FishGen Ltd, based at Swansea University, United Kingdom, or from mixed-sex populations available from fish vendors in the United States. Contreras-Sánchez will be visiting OhSU during the course of the investigation to train Rodriguez in analyzing concentrations of MT in the water and diet by RIA and HPLC. Contreras-Sánchez Ph.D. research at Oregon State University involved the use of these techniques for analyzing levels of MT in water and pond sediments.