Analysis of Sublethal Toxicity in Developing Zebrafish Embryos Exposed to a Range of Petroleum Substances using BE-SPME and Whole Transcriptome Microarray

The OECD 236 Fish Embryo Acute Toxicity Test guideline relies on four endpoints to describe exposure related effects (coagulation, lack of somite formation, tail-bud detachment from yolk-sac, and presence of heartbeat). Danio rerio (zebrafish) embryos were used to investigate these endpoints along with a number of additional sublethal effects (i.e. cardiac dysfunction, pericardial edema, yolk sac edema, tail curvature, hatch success, pericardial edema area, craniofacial malformation, swim bladder development, fin development, and heart rate) following five day exposures to one of seven petroleum substances. The substances investigated included two crude oils, three gas oils, a diluted bitumen, and a petrochemical containing a mixture of branched alcohols. Biomimetic extraction via solid phase microextraction (BE-SPME) was used to quantify freely dissolved test substances as the exposure metric. The most prevalent effects observed were pericardial and yolk sac edema, tail curvature, and lack of embryo viability. Whole transcriptome microarray was used to profile gene expression following exposure to two petroleum substances. Meaningful downregulated differential expression was localized to concentrations that already displayed sublethal morphological effects; therefore, whole transcriptome profiling did not provide sufficient data to be able to predict sublethal morphological effects. A BE-SPME threshold was determined to characterize sublethal morphological alterations that preceded embryo mortality. Overall, this work aids in the understanding of aquatic hazards of petroleum substances to developing zebrafish beyond traditional OECD 236 test endpoints and shows applicability of BE-SPME as an analytical tool to predict sublethal embryotoxicity