W7 AM Acclimation / Adaptation of Animals to Metals: Resistance, Tolerance, and Cost
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 327-329

(MCG-1117-861066) The influence of acclimation to Cu or Cd on the toxicity and bioaccumulation of Cu and Cd in rainbow trout and Daphnia magna.

McGeer, J¹, Nadella, S², Wood, C², ¹ Natural Resources Canada, Ottawa² McMaster University, Hamilton

ABSTRACT- The understanding of the potential impacts of chronic metal exposure is complicated by the fact that responses of fish to long term metal exposure can be variable, for example gill metal burden can change considerably, and as well, many metals induce acclimation. This study examines the influence of pre-exposure to chronic sublethal waterborne Cu or Cd on the subsquent uptake and distribution of Cu and Cd in both rainbow trout and Daphnia magna. In the trout experiments fish were exposed to either 3 ug/L Cd or, 75 ug/L Cu for one month with minimal mortality and no effect on growth. Chronic sublethal exposure to metal resulted in acclimation (resistance to acute challenge) to the metal of exposure as well as cross acclimation to the other metal. Exposure also resulted in significant accumulations of metal (either Cd or Cu) in the gill, kidney and liver. Accumulations of Cd were highest in the gill while those of Cu were greatest in the liver. Following a month of exposure to either Cd or Cu, metal uptake into gills, blood, liver, kidney, gastrointestinal tract and whole body was studied over time using radioisotopes (109Cd or 64Cu). Acclimation to Cd resulted in a reduction in the rate of Cd uptake into the gills and whole body compared to uptake rates of naive fish exposed to 3 ug/L Cd. When challenged at the higher level of 10 ug/L Cd, acclimated fish had significantly higher rates of gill Cd uptake and previous exposure to Cu similarly enhanced Cd uptake. In addition, chronic metal exposure resulted in altered routing of new metal through different body compartments. In Daphnia magna experiments whole body metal accumulation and acclimation were assessed. The results illustrate the changes in metal uptake and internal distribution that occur during chronic sublethal exposures and help to build an understanding of the physiology of acclimation responses in rainbow trout and Daphnia magna.

Key words: acclimation, metal, rainbow trout, Daphnia magna