Reduction in reproductive activity from degeneration of testicular follicles in Megapitaria squalida (Mollusca: Bivalvia) exposed to metal pollution in the Gulf of California.

Over a reproductive cycle, the prevalence and intensity of degeneration of testicular follicles in Megapitaria squalida collected from the mining port of Santa Rosalia (a highly metal-polluted area), and San Lucas (a less polluted site), Gulf of California, Mexico, were evaluated. At San Lucas, most individuals had a typical testicular structure, and degeneration of testicular follicles was present in 9.5 % of spawning organisms. In contrast, at Santa Rosalia, 68 % of males, mainly in the ripe stage, had testicular degeneration (72 % severe intensity, mostly in medium and large-sized). Degeneration was characterized by intense hemocyte infiltration, identified as dense masses with numerous melanized cells in the follicle lumen. In both sites, males with testicular follicles degeneration had a lower condition index compared to males without degeneration. Degeneration of testicular follicles before spawning compromises and decreases the reproductive activity of M. squalida males at Santa Rosalia, which may ultimately affect the population sustainability.