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TOXICITY OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN TO EARLY LIFE STAGE BROOK TROUT (SALVELINUS FONTINALIS) FOLLOWING PARENTAL DIETARY EXPOSURE
Citation:
Johnson, R D., J E. Tietge, K M. Jensen, J D. Fernandez, A L. Linnum, D B. Lothenbach, G W. Holcombe, P M. Cook, S A. Christ, D L. Lattier, AND D A. Gordon. TOXICITY OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN TO EARLY LIFE STAGE BROOK TROUT (SALVELINUS FONTINALIS) FOLLOWING PARENTAL DIETARY EXPOSURE. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 17(12):2408-2421, (1998).
Description:
The toxicity of TCDD to early life stages of F1 generation brook trout (Salvelinus fontinalis) was determined when dosed by maternal transfer. Effects were compared across six treatments including a control. The experimental groups based on TCDD concentrations in freshly spawned eggs (control, 41, 84, 156, 285 and 517 pg TCDD per gram egg (wet weight)) were established by period beginning with final gonadal maturation and continuing until just prior to spawning. Meassurement endpoints assessed at various times throughout the study included (1) TCDD and lipid concentrations in ovaries, eggs, alevins, and juvenile fish (2) mortality (3) fertility indices (4) growth (5) juvenile sex ratios (6) pathology and (7) cytochrome CYP1A1 levels in embryos. The cumulative lethality dose response was determined just prior to hatch, at swim-up and at the end of the study. The concentration in eggs causing 50% mortality at swim-up and at the end of the study were 138 and 127 pg TCDD per gram egg, respectively. No treatment effects were observed on fertility, growth, or juvenile sex ratios. Pathologies were observed that have been previously reported in TCDD-exposed salmonid embryos including edema in free embryos from all TCDD-exposed treatment groups at hatch. At the end of the test juvenile fish from all treatments exhibited increased prevalence of exophthalmia compared to controls. The ECegg50 for this effect was 117 pg TCDD per gram egg. Histological analysis of the end-of-test juveniles, in gonad, nerve, vertebrae, neuromasts, liver, kidney, gut, gas bladder, skin, and blood vessels did not indicate any significant pathology below the LCegg50. CYP1A1 levels in whole 91-d postspawn free embryos from the 84 pg TCDD per gram egg treatment were 2.8 times higher compared with control or 41-pg TCDD per gram egg treatments. Results from this study were consistent with other published results of TCDD effects on salmonids in which exposures occurred after fertilization.