Do Propagation and Culture Methods for Native Freshwater Mussels Influence Their Chemical Sensitivity?

Assessing freshwater mussel (Unionidae) sensitivity to pollutants is necessary in identifying tolerance thresholds and setting protective water quality criteria for these ecologically important and globally imperiled fauna. Thus, there is a need to transform mussel larvae into juveniles for use in ecotoxicological and other studies. Improving standard host-fish infection techniques have contributed to the success of mussel propagation; recently, in vitro culture methods have increased the efficiency and cost-effectiveness of transforming juvenile mussels in the laboratory. Because the relative chemical sensitivities of juveniles from both methods are not well examined, in vitro cultured juveniles are not currently recommended by the American Society for Testing and Materials for use in toxicity testing. The study objective was to evaluate the relative sensitivity of in vitro and host-fish produced juvenile mussels to chemical toxicants. We conducted standard 96-hour acute toxicity tests with selected species (Lampsilis cardium, L. abrupta, and Utterbackia imbecillis) and six chemicals: chloride, nickel, ammonia, copper, and two aquatic herbicides. We calculated the median lethal concentration (LC50) for each species-chemical combination and compared the LC50s of the two culture methods. Four of the 11 tests produced statistically significant differences in LC50 between culture methods, which has both testing and conservation implications.