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Arch Environ Contam Toxicol (2012) 63:230240 DOI 10.1007/s00244-012-9760-9
Assimilation of Elements and Digestion in Grass Shrimp Pre-Exposed to Dietary Mercury
David R. Seebaugh William G. Wallace
William J. LAmoreaux Gillian M. Stewart
Received: 6 December 2011 / Accepted: 27 February 2012 / Published online: 30 March 2012 Springer Science+Business Media, LLC 2012
Abstract Grass shrimp Palaemonetes pugio were fed mercury (Hg)-contaminated oligochaetes for 15 days and analyzed for Hg, cadmium (Cd), and carbon assimilation efciencies (AE) as well as toxicological end points related to digestion. Disproportionate increases in stable Hg concentrations in shrimp did not appear to be related to partitioning to trophically available Hg in worms. Hg AE by pre-exposed shrimp reached a plateau (approximately 53 %), whereas Cd AE varied (approximately 4060 %) in a manner that was not dose-dependent. Carbon AE did not differ among treatments (approximately 69 %). Gut residence time was not impacted signicantly by Hg pre-exposure (grand median approximately 465 min), however, there was a trend between curves showing percentages of individuals with markers in feces over time versus treatment. Feces-elimination rate did not vary with dietary pre-exposure. Extracellular protease activity varied approximately1.9-fold but did not exhibit dose-dependency. pH increased over the range of Hg pre-exposures within the anterior (pH approximately 5.336.51) and posterior (pH approximately 5.296.25) regions of the cardiac
proventriculus and Hg assimilation exhibited a negative relationship to hydrogen ion concentrations. The results of this study indicate that previous Hg ingestion can elicit post-assimilatory impacts on grass shrimp digestive physiology, which may, in turn, inuence Hg assimilation during subsequent digestive cycles.
Patterns of pollutant accumulation and toxicity in aquatic fauna can depend on the exposure pathway (e.g., dissolved vs. dietary), making it necessary to elucidate the independent effects of routes for specic pollutants before determining whether or not interactive pathway effects are important in the eld (Hook and Fisher 2001; Griscom et al. 2002). Assimilation of pollutants can be inuenced by partitioning in food as well as consumer digestive physiology (Goto and Wallace 2009; Dang and Wang 2010). The effects of ingested pollutants on digestion may be related to mode of internal exposure. Pre-assimilatory digestive toxicity results from solubilization and bioavail-ability of a pollutant in gut uid and could potentially impact hydrolysis and absorption during a digestive...