Toxicological Effect Of DEHP Exposure On Pinctada Martensi

Phthalic acid esters (PAEs) are generally used as a plasticizer to improve the softness of the plastics. Di(2-ethylhexyl) phthalate (DEHP) is a typical PAEs with low prices, stability, liquidity and less prone to volatile. It is commonly found in the aquatic environment and is an environmental endocrine disruptor. Due to their immunotoxicity, reproductive toxicity and indissolubility in the environment, DEHP has been listed as one of priority pollutants. Marine bivalves are commonly used as biomarkers for monitoring marine environment pollution, because of their sessile lifestyle and high capacity to accumulate organic pollutants. So far, the studies of ecotoxicological effect of DEHP exposure on important commercial species of tropical ocean pearl oyster Pinctada martensi have been no published. The cytological, ecotoxicological and biochemical methods were used to examine the effects of DEHP exposure on early embryonic development of Pinctada martensi on the organismal, tissue and cellular levels in this study. DEHP effects on non-specific immune function and oxidative stress in the haemolymph of adult organisms, the DNA damage as well as antioxidant enzyme activity in embryo cells were also examined. Analysis of DEHP dose-response relationships and screening of sensitive biomarkers revealed the mechanisms of DEHP toxicity to marine organisms and provide early warning for chemical pollution in marine environment. Such data could provide scientific basis for conducting ecological risk assessment. Following research conclusions were reached:1. DEHP had a significant impact on the D-shaped veliger larvae. Mortality of the D-shaped larvae positively correlated with length of exposure and LC50decreased, reaching51.15mg·L-1at48h. In the range of concentrations, higher concentrations of pollutant caused significant increase in abnormally shaped veliger larvae with clear dose-response relationship. After48hours of exposure, abnormality rate of D-shaped larvae positively correlated with DEHP concentration, with clear dose-response relationship, and individual deformity appeared. The results showed that DEHP exposure can impact on the development of D-shaped veliger larvae of Pinctada martensi and the population structure of Pinctada martensi.2, DEHP induced obvious DNA damage in embryo cells in Pinctada martensi. Higher concentrations of DEHP increased the average length of DNA migration, exhibiting a significant dose-effect relationship. Longer duration of DEHP exposure also increased the average length of DNA migration from8h to16h exposure time, and then decreased at16h. It indicated that DEHP may damage Pinctada martensi DNA.3. DEHP also had an obvious impact on non-specific immune defense system and Lipid peroxidation levels in Pinctada martensi. After2weeks of exposure, DEHP had a significant impact on the Pinctada martensii immune function. The total number of haemocytes decreased, following a dose-response relationship. Meanwhile cell membrane stability and phagocytosis activity were affected while, showing the trend of the first increased and then decreased. DEHP also caused a significant increase in total glutathione (GSH) and a trend of decreased after an initial increase in lipid peroxidation (MDA), indicating the development of oxidative stress. The total number of haemocytes was the most sensitive biomarker to DEHP concentration of0.5mg·L-1(LOEC<0.5mg·L-1).4. DEHP exposure had some effects on the antioxidant enzyme activity in different organizations of Pinctada martensi. In gill tissues, the activities of GPx, SOD, GST was effect significantly after10days exposure. And the GPx activity was the most sensitive biomarker to DEHP exposure of2mg·L-1, LOEC<2mg·L-1. In hepatopancreas, the activities of SOD, GPx had been inhibited, showing a certain dose-effect relationship, and the impact of GST activity after exposure was not obvious. The most sensitive biomarker was SOD activity, LOEC<0.5mg·L-15. Changes in non-specific immune function and oxidative stress, and the DNA damage in embryo cells of Pinctada martensi could be used as sensitive biomarkers for DEHP pollution of marine environment.