The effects of silver nanoparticles on oyster embryos

Nanoparticles may be introduced into aquatic environments during production processes and also as a result of release following their use in various commercial formulations and biologic applications. Filter-feeding bivalve mollusks such as oysters are valuable model species for characterizing nanoparticle bioavailability and interactions with basic cellular processes. The adults release their gametes into the environment, so their embryos and larvae are also likely targets of nanoparticles. The purpose of these studies was to characterize the toxicity of metal nanoparticles on embryonic development of oysters, Crassostrea virginica and to compare the relative sensitivity of embryos to adults. Newly-fertilized oyster embryos were exposed to silver nanoparticles (AgNP) and then the percent normal development after 48 h was assessed. Studies were conducted with adult oysters in which they were also exposed to AgNP for 48 h, and the effects on lysosomal destabilization were determined. The expression of metallothionein (MT) gene expression was also assessed in both embryos and adults. Adverse effects on embryonic development were observed at concentrations similar to those that caused both statistically and biologically significant effects on lysosomal destabilization of adults. Significant increases in MT mRNA levels were observed in both embryos and adult oysters, and MT levels were highly induced in embryos. While we do not know whether the toxicity and gene expression responses observed in this study were due to the nanoparticles themselves or the Ag ions that dissociated from the nanoparticles, these kinds of basic studies are essential for addressing the potential impacts of nanoengineered particles on fundamental cellular processes as well as aquatic organisms.