Assessment Of Sublethal Endpoints For Crude Oil Toxicity Testing With The Nematode Caenorhabditis Elegans

In recent years, with the oil spill accidents occur frequently, the effect of crude oil on the ecosystem, especially effect on the organism has been widespread concern in the academic circles. However, oil toxicity assessment and evaluation of the repair of spilt more concentrated in acute lethal concentration and teratogenic rate and lack of life cycle and sub lethal levels of study. In addition, overflow effect of oil on the ecosystem is often a multi-level. There are few creatures that can simultaneously evaluate the toxicity of water and sediment in crude oil.Caenorhabditis elegans can not only live in the soil, and in the soil pore water. With a translucent body, it can be observed clear reproductive structure and motion behavior under the microscope. Exposure three days can cover the whole life cycle, because eggs could develop into adults in only three days. And antioxidant system is perfect. Therefore, in order to optimize the current crude oil toxicity evaluation methods, this paper selects Caenorhabditis elegans as a biological evaluation, according to the 24 hour half lethal concentration determine the crude oil water solution of sub lethal exposure concentrations and the nematode uterus pregnant egg number and vulval structure and offspring numbers in 3 days as the reproductive toxicity evaluation index; in locomotion and feeding index for behavior toxicity evaluation index; antioxidant defense system activity as oxidation toxicity evaluation index. Using reproductive index, behavior index and antioxidant defense system index at sublethal levels. we assess the toxicity of crude oil in whole life circle.Here is the main conclusion:(1) The lethality of C. elegans after WAF expose 24h is 6.957g/L.(2) Reproductive test showed that:WAF caused significant toxic effects on C. elegans. After WAF exposing 24h, vulva abnormal rate increased in all treatment groups and eggs in venter decreased in 70 and 700mg/L groups. After exposing 72h, brood size decreased in 70 and 700mg/L groups.(3) Behavior test showed that:WAF caused significant toxic effects on movement and feeding in C. elegans. After WAF exposing 24h, forward thrashes and head thrashes decreased in 700mg/L group, after WAF exposing 2h, feeding in 700mg/L decreased significantly, after exposing 3h. feeding in 70mg/L decreased significantly.(4) Oxidative stress test showed that:WAF increased H2O2 and MDA concentration, and then increased antioxidase activities. After exposing 24h. H2O2 concentration increased in all groups while after pretreating with vitamin E. H2O2 concentration decreased compared with all expose groups. MDA concentration increased in 70 and 700mg/L groups and decreased to normal when pretreat with vitamin E. CAT and SOD activities increased in 70 and 700mg/L groups, and increased higher when pretreat with vitamin E. However, WAF have no effect on GSH-Px activety.In conclusion, reproduction (egg in venter, brood size and vulva abnormal rate), behavior (movement and feeding) and oxidative stress (H2O2 and MDA concentration and CAT and SOD activity) in C. elegans were sensitive to WAF. Compared to other organism, C. elegans has short lifespan, easy to culture and can be used to assess crude oil pollution in soil, fresh water and sediment. This experiment can provide the toxic data for the evaluation and remediation of crude oil pollution, and provide the basis for the emergency plan.