Characterization and Differential Expression of Sex Genes in Adults of Tropical Gar (Atractosteus tropicus)

The tropical gar (Atractosteus tropicus) is a primitive freshwater fish of significant commercial importance in southeastern Mexico. However, its population is in danger due to habitat loss and overexploitation. Cultivation emerges as a viable reproductive management strategy; yet further studies are crucial to understanding molecular markers guiding reproductive management, differentiation, and sexual maturation in this species. We analyzed the expression of five sex-related genes (foxl2, sox9, cyp17a1, dmrt1, and cyp19a1) in the brain, liver, and gonads of adult A. tropicus (four females and five males). Methodologically, we collected samples and conducted RNA extraction, cDNA synthesis, and gene expression analysis using qPCR. The gonadal histology provided morphological context that reveals that the differential expression of genes establishes differences between sexes. The sexual phenotype of females is observed with the high expression of dmrt1, while in males, there is a reduction in the expression of dmrt1 and high levels of sox9, foxl2, and cyp17a1. Our findings establish dmrt1 and cyp19a1 as potential sex biomarkers and provide a molecular basis for developing sexing protocols in A. tropicus.