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We studied the effects of chronic exposure to metals on energy reserves and reproduction in the clam Megapitaria squalida in two nearby populations exposed to different levels of pollution from mining operations in the Gulf of California, Mexico. Female M. squalida from San Lucas beach had good reproductive health status, whereas Santa Rosalia specimens consistently showed low energy reserves, massive oocyte resorption throughout the year, high frequencies of undifferentiated individuals, low proportions of ripe and spawning organisms, smaller and fewer oocytes per follicle, and significantly lower follicular areas. Ovarian levels of Co, Cu, Pb, Mn, and Zn were consistently higher in clams from Santa Rosalia. The poor reproductive health of clams inhabiting this site may be attributed to their long-term exposure to high Co, Cu, and Pb concentrations, as these have been shown to cause toxicity and reproductive impairments in other marine organisms. Unlabelled Image • Female M. squalida from two nearby, metal-polluted sites showed contrasting reproductive health status. • Clams from San Lucas beach showed a good reproductive health status. • Clams from Santa Rosalia had lower energy reserves and impaired reproduction. • These negative effects may be attributed to long-term exposure to Co, Cu, and Pb. [ABSTRACT FROM AUTHOR]