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COMPARATIVE SENSITIVITY OF DIFFERENT LIFE-STAGES OF MEDAKA (ORYZIAS LATIPES) AND BROOK TROUT (SALVELINUS FONTINALIS) TO 2,3,7,8-TCDD
Citation:
Tietge, J E., R. D. Johnson, P. K. Schmieder, AND K M. Jensen. COMPARATIVE SENSITIVITY OF DIFFERENT LIFE-STAGES OF MEDAKA (ORYZIAS LATIPES) AND BROOK TROUT (SALVELINUS FONTINALIS) TO 2,3,7,8-TCDD. Presented at International Symposium on Endocrine Disrupting Substance Testing in Medaka, Nagoya, JAPAN, March 17 - 20, 2000.
Description:
The early life stages of fish are known to be more sensitive than the adults to the toxicological effects of 2,3,7,8-tetrachlorodibenzo(p)dioxide (TCDD). TCDD concentrations in surface waters are sufficiently low that direct exposure of the developing embryo is unlikely to be of consequence. Instead, the most significant route of exposure for fish early life stages is via maternal transfer. This is based on the observation that route of TCDD exposure to adult fish is predominantly dietary (Cook et al, 1990). The extent to which eggs are exposed via maternal transfer is determined primarily by passive partitioning to hydrophobic compartments. Thus, the TCDD concentrations in the adult female, and relative lipid concentrations in the adult female and the eggs are key determinants in estimating early life stage exposure. The toxicity of TCDD to medaka (Oryzias latipes) eggs, based on concentrations in the egg (LC egg 50), was recently reported to be 1,110 pg TCDD/g egg. In this study medaka eggs (< 24 hours post fertilization) were exposed to TCDD via aqueous exposure with toxicity determined over a 32-d period. The measureg lipid content of the eggs was 2.9% (Elonen et al., 1998). While TCDD was known to be toxic to medaka adults, the existing data did not provide ECDD tissue residue nor tissue lipid values to serve as a basis for comparison of life stage sensitivities. Therefore, a study was conducted to determine the median lethal concentration based on whole body TCDD concentrations (LC wb 50). Using a 4 week aqueous exposure to [1,6-3H]-TCDD concentrations ranging from 0.01 to 0.72 ng/L, the adult LCwb50 was determined to be 2400 pg TCDD/g tissue. The lipid concentration in adult medaka was determined to be 9.6%, under the conditions of the study...