Persistent effects on adult swim performance and energetics in zebrafish developmentally exposed to 2,3,7,8-tetrachlorodibenzo- p-dioxin

Abstract

TCDD (2,3,7,8-tetrachlorodibenzo- p-dioxin) remains a potent and persistent toxicant in aquatic environments, causing lethal developmental deformities in fish. However, few studies have examined sublethal or persistent effects of developmental TCDD exposure and none have examined its effects on swimming capabilities in sub-adult fish. The objective of the current study was to examine whether effects of TCDD exposure during the critical period of cardiovascular development (2–4 days post fertilization) on swim performance, triglyceride stores and cardiovascular deformities would persist until adulthood in zebrafish. Zebrafish larvae were exposed between 48 and 96 h post fertilization to 1, 0.1, 0.01 ng/L TCDD or DMSO control (0.005%), then raised in clean water for 90 days. Despite having equal survivability, no significant increase in gross deformities and no change in cytochrome P450 1A (CYP1A) activity was observed, while critical swimming speed and dorsal aorta diameter were significantly decreased in TCDD-exposed fish at 90 days. Furthermore, whole body triglycerides were significantly elevated in TCDD-exposed fish both before and after swim testing. Therefore sublethal TCDD exposure during zebrafish development caused a persistent decrease in swim endurance. The cause of this persistent decrease in swim endurance is not known, but may be related to behavioral adaptations limiting swimming capabilities, failure to mobilize triglyceride stores, vascular deformities limiting blood flow to the periphery, or a combination of these factors.