Keywords: 
• crude oil /
• dispersant /
• zebrafish embryo /
• morphological development /
• toxicity assessment

Abstract: To determine the morphological and developmental toxicity of Oman crude oil dispersed by GM-2 dispersant to the teleost, zebrafish (Danio rerio) embryo was chosen to be semi-statically exposed to water-accommodated fractions (WAF) of Oman crude oil, GM-2 dispersant and chemically enhanced water-accommodated fractions (CEWAF) of Oman crude oil (dispersed by GM-2) at 0-120 hpf (hour post-fertilization) with observing the lethality, hatching and malformation rates. And the general morphology score (GMS) system was used to assess the morphological and developmental toxicity induced by crude oil. Results indicated that compared to that of WAF (with a maximum concentration of 5.233 mg·L^-1±0.213 mg·L^-1), total petroleum hydrocarbons (TPH) concentrations of CEWAF apparently increased to 292.989 mg·L^-1±11.905 mg·L^-1. Lethality induced by WAF and CEWAF also increased with a varying extent, which was only 30.2%±2.8% at 100% WAF, but was more than the median lethal rate at ≥ 40% CEWAF with the LC₅₀ of 153.318 mg·L^-1. By GMS analysis, WAF and CEWAF could significantly delay the development of zebrafish embryos to some extent, especially inducing swim bladder absence, heart rate abnormality, circulation stagnation and sluggish movement (pectoral fins, tail, etc.). Meanwhile, WAF and CEWAF also delayed embryo hatching notably, and even caused embryo unhatching. Results also revealed that Oman crude oil is highly teratogenic, especially in term of pericardial edema, deformed body shape and malformation of the tail. This study indicated that CEWAF of Oman crude oil (dispersed by GM-2) is more toxic than WAF to zebrafish embryo.