SEASONAL, BEHAVIORAL AND GROWTH CHANGES OF JUVENILE CORBICULA-FLUMINEA EXPOSED TO CHRYSOTILE ASBESTOS

Juvenile C. fluminea (5.2-8.6 mm shell length) were collected in winter (8-12.degree. C) and summer (17-23.degree. C) conditions and tested for responses to chrysotile asbestos at concentrations of 0-108 fibers l-1 for 30 days. Growth, siphoning activity, fiber uptake and gill tissue ultrastructure were evaluated. Siphoning activity was significantly reduced by 30 days of exposure at 102-108 fibers l-1 in summer and winter compared to controls and was paralleled by significant reductions in shell growth at 104-108 fibers l-1 in summer and 105-108 fibers l-1 in winter. Differences in shell: tissue growth were apparent with lower values in all groups in the winter compared to their counterparts in the summer due to energy allocations to tissue growth in the winter. Therefore, Corbicula were more susceptible to asbestos in winter conditions due to differences between robust, summer vs inherently weakened winter collected clams. Clams exposed to 108 fibers l-1 accumulated .apprx. 150 fibers mg-1 in gill and 110 fibers mg-1 in viscera after 30 days in both seasons. The presence of asbestos in tissue was consistent with significantly greater water content and total gill locule surface area in 108 fibers l-1 exposed clams relative to controls. Small asbestos fibers were preferentially accumulated in gill and visceral tissues. Corbicula may become a useful biomonitor for asbestos contamination in the USA and abroad due to its ability to accumulate asbestos fibers efficiently.