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COMPARATIVE SENSITIVITY OF DIFFERENT LIFE-STAGES OF MEDAKA AND SALMONID FISHES TO 2,3,7,8-TCDD
Citation:
Schmieder, P. K., K M. Jensen, R. D. Johnson, AND J E. Tietge. COMPARATIVE SENSITIVITY OF DIFFERENT LIFE-STAGES OF MEDAKA AND SALMONID FISHES TO 2,3,7,8-TCDD. Presented at International Symposium on Endocrine-Disrupting Substances 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)dioxin (TCDD). Embryo larval stages of medake, for example, experience 50% lethality when TCDD residues in the eggs are 1396 pg/g. By contrast, medaka adults experience 50% lethality when whole body TCDD residues are 2400 pg/g. However, when reproductively active medaka adults are exposed to TCDD, even at lethal levels, no toxicity is observed in the F1 generation. This apparent discrepancy can be explained by the fact that the delivered TCDD dose to the eggs via maternal exposure is well below toxic concentrations. This is apparently due to the relatively low lipid concentration in medaka eggs (approximately 3%) compared to that in the adult. Becuase TCDD is quite lipophilic, the TCDD concentration in medaka eggs is several times lower than the TCDD concentration in the female that spawned them. These data will be compared to data from salmonid species whose F1 generation are adversely affected by maternally derived TCDD residues. This analysis suggests that the sensitivity difference between life-stages of medaka and salmonids should be interpreted in the context of actual egg residues accumulated via maternal exposures when considering the toxicity of highly lilpophilic chemicals.