Metabolic responses to crude oil during early life stages reveal critical developmental windows in the zebrafish (Danio rerio).

Morphological effects of crude oil exposure on early development in fishes have been well documented, but crude oil's metabolic effects and when in early development these effects might be most prominent remains unclear. We hypothesized that zebrafish (Danio rerio) exposed to crude oil as a high energy water accommodated fraction (HEWAF) would show increased routine oxygen consumption (ṀO) and critical oxygen tension (P) and this effect would be dependent upon day of HEWAF exposure, revealing critical windows of development for exposure effects. Zebrafish were exposed to 0%, 10%, 25%, 50% or 100% HEWAF for 24 h during one of the first six days post-fertilization (dpf). Survival rate, body mass, routine ṀO, and P were then measured at 7 dpf. Survival rate and especially body mass were both decreased based on both exposure concentration and day of crude oil exposure, with the largest decrease when HEWAF exposure occurred at 3 dpf. HEWAF effects on routine ṀO also differed depending upon exposure day. The largest effect occurred at 3 dpf, when ṀO increased significantly by ~60% from 10.1 ± 0.8 μmol O/g/h compared to control group value of 6.3 ± 0.4 μmol O/g/h. No significant effects of HEWAF exposure on any day were evident for P (85 ± 4 mmHg in the control population). Overall, the main effects on body mass and ṀO measured at 7 dpf occurred when HEWAF exposures occurred at ~3 dpf. This critical window for metabolism in zebrafish larvae coincides with time of hatching, which may represent an especially vulnerable period in development.