T7 AM Metals in the Environment: Dietary Concerns in Aquatic Systems
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 327-329

(BUC-1117-833483) Trophic transfer of cadmium from the Oligocheate Lumbriculus variegatus to predatory stoneflies (Perlodidae and Perlidae).

Buchwalter, D^{1, 2}, Cain, D¹, Klaper, R³, Luoma, S¹, ¹ US Geological Survey, Menlo Park, CA, USA² North Carolina State University, Raleigh, NC, USA³ University of Wisconsin - Milwaukee, Milwaukee, WI, USA

ABSTRACT- Aquatic insects play important ecological roles in streams and are widely used to evaluate ecological conditions. In trace metal-contaminated streams, insects accumulate metals from both aqueous and dietary sources. Physiological processes related to metal accumulation, efflux and detoxification ultimately determine inter-specific sensitivity differences. However, risk assessments typically focus on dissolved trace metal exposures, and may underestimate risks to some species if dietary exposures are not considered. To assess inter-specific differences in species ability to detoxify dietary cadmium exposures, we fed stonefly larvae from the families Perlidae and Perlodidae ¹⁰⁹Cd contaminated prey. The freshwater oligochaete Lumbriculus variegatus served as a food source throughout these studies. Cd uptake, efflux and subcellular fractionation studies were conducted in Lumbriculus to characterize their internal Cd distributions. In addition, metallothionein gene expression studies were conducted to validate fractionation studies in Lumbriculus. These studies proved Lumbriculus variegatus to be a suitable and consistent food source for feeding studies. Oligochaetes were fed to four perlid and 2 perlodid stonefly species. Sub-cellular Cd distributions were measured in each of these 6 species, allowing us to make comparisons among families, species and routes of exposure. Metal bioaccumulation patterns showed the following: 1) sub-cellular Cd distributions were consistent among members of the same family. This consistency was observed from both dietary and dissolved sources; 2) dietary exposures resulted in greater proportions of Cd body burdens in potentially toxic sites, suggesting that dietary exposures are potentially more toxic than dissolved exposures to both perlid and perlodid stoneflies; 3) regardless of route of exposure, the perlodids had a greater proportion of the Cd body associated with metallothionein-like proteins than the perlids, suggesting they were better protected against Cd toxicity than the perilids. These results are discussed in relation to phylogeny and bioassessment.

Key words: cadmium, aquatic insects, diet, detoxification