The gonadal health status of the chocolate clam Megapitaria squalida collected from the Santa Rosalía mining port and San Lucas beach (reference site), Gulf of California, Mexico, was assessed through histological analysis of the reproductive tissue, from which the histopathological alteration index (HAI) was determined. In addition, copper and iron accumulation in tissue was revealed using histochemical techniques. Our results showed a large presence of copper (30%) and iron (45%) only in the gonad tissue of clams from Santa Rosalía, in which histopathological alterations observed were inflammatory responses, degenerative-progressive processes, cell death, and response to infectious agents. The HAI was significantly higher in Santa Rosalía specimens (mean ± SE, 72.18 ± 6.12) than in San Lucas clams (4.60 ± 1.07). At San Lucas beach, a higher prevalence of histopathological alterations occurred in clams in the spent stage (43.2%) and in autumn (18.4%) and winter (17.8%) in concordance with the normal reproductive rest period, whereas at Santa Rosalía a higher prevalence occurred in clams at the ripe stage (76.9%) and in spring (83.7%). In conclusion, our results showed the deteriorated health condition of gonads in M. squalida from the Santa Rosalía mining port, which suggests there is a relationship with chronic exposure to local high levels of heavy metals. The high prevalence and intensity of histopathological alterations in the gonad suggest a strong adverse effect on gametogenesis, gamete quality, and, ultimately, in the reproductive potential of M. squalida at this site.

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Background. It is known that organisms inhabiting polluted marine habitats may experience adverse physiological effects. The port of Santa Rosalía, Gulf of California, is characterized by high concentrations of heavy metals in sediments, particularly Cu, Zn, Co, Mn, Pb, and U, which are potentially toxic to the marine biota. In addition, this port receives urban wastewater that contributes mostly organic pollutants to the coastal zone. Goals. The main objective of this work was to determine whether clams in the mining region showed adverse effects because of the contamination. Methods. Through the analysis of biometric parameters, condition index, and weight-length relationship, the overall health of the chocolate clam Megapitaria squalida was evaluated in the coastal zone of the Santa Rosalía port and compared with data for clams from four mining-free areas. Results. Our findings revealed that clams from Santa Rosalía showed poor health, evidenced by their smaller size, inferior condition, and negative allometric growth compared to clams from all other sites, including San Lucas, a site located a few kilometers away from the pollution hot-spot and where the conditions of temperature and food availability are similar to those in the port area. Conclusions. All of the above suggests negative physiological effects in this species possibly caused by contamination from metals and/or organic pollutants from urban discharges. Particularly, it is likely that M. squalida at the mining site allocates more energy towards depurating or storing metals, in turn leading to poorer condition and deficient growth.

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De enero a diciembre de 2006 se analizó la variación en los valores de los índices gonadosomático (IGS), de músculo (IM), de glándula digestiva (IGD) y del manto (IMA) de Nodipecten subnodosus en Bahía de los Ángeles, B.C., México. Se analizaron un total de 334 organismos dentro de un intervalo de tallas de 48 a 172 mm de altura de concha. El IGS mostró un patrón estacional, indicando que la madurez gonádica se presentó de abril a junio. Tanto el IGD como el IMA presentaron correlación significativa con el IGS (P< 0.05). El IM no presentó correlación significativa con el IGS (P > 0.05). El análisis de la variación de los índices morfofisiológicos indica que es posible que en Bahía de los Ángeles, B.C., N. subnodosus presente un ciclo de almacenamiento y transferencia de energía desde tejidos somáticos hacia la gónada, para soportar la gametogénesis. N. subnodosus se reproduce en un rango de temperatura bien definido (inicia su gametogénesis entre los 17 °C y 18 °C de temperatura superficial del mar y alcanza su máxima madurez entre los 23.5 °C y 26.8 °C). Variation in the morphophysiological indices of the lion paw scallop Nodipecten subnodosus (Sowerby, 1835) in Bahía de los Ángeles, B.C., Gulf of California From January to December, 2006 the variation of the gonadosomatic (IGS), muscle (IM), digestive gland (IGD) and mantle indices (IMA) of Nodipecten subnodosus in Bahía de Los Angeles, B.C., Mexico were analyzed. A total of 334 organisms were examined, all within an interval of 48 to 172 mm of shell height. The IGS showed a seasonal pattern indicating that the gonadic ripeness appeared from April to June. Both, the IGD and the IMA had a significant correlation with the IGS (P < 0.05). The IM did not show a significant correlation with the IGS (P > 0.05). The analysis of the variation of the morphophysiological indices indicates that it is possible that in the Bahía de Los Angeles, B.C., N. subnodosus presents a cycle of storage and transference of energy from somatic tissues to the gonad to support gametogenesis. N. subnodosus reproduces in a defined rank of temperature, it begins its gametogenesis between 17 °C and 18°C of temperature of the water and reaches its maximum ripeness between 23.5 °C and 26.8 °C.