Influence of episodic exposures of chlorpyrifos to an estuarine cyprinodontid, Fundulus heteroclitus

Episodic exposure to chlorpyrifos can inhibit AChE and weaken bone strength. The primary objective of this study was to examine the effects of short-term exposures to chlorpyrifos, followed by a recovery period, on Fundulus heteroclitus brain AChE activity, CYP2B induction, and caudal vertebrae strength. All parameters were measured following four 6-h episodic exposures to chlorpyrifos. During the tests, organisms were exposed to 2.5, 5.0 and 10.0 μg l−1 of chlorpyrifos. Positive and negative controls were used to account for osmoregulatory effects. Daily (4 days) and weekly (4 weeks) exposures were conducted with laboratory-reared and wild fish. Our results demonstrated that several 6-h pulsed doses of chlorpyrifos in 5 g kg−1 salinity seawater significantly inhibited brain AChE activity, may have affected CYP2B activity, and significantly weakened caudal vertebrae in test organisms. Some of these effects appear to be confounded with gender, suggesting a potential seasonal or hormonal factor is involved.