Abstract:
The present study was carried out to investigate sub-acute effect of water accommodated fraction (WAF) of crude oil by using experimental exposure. Oysters were collected, acclimated and exposed to WAF at concentrations of 0, 6.25, 12.5, 25, 50 and 100%, respectively. Mortality and histopathological effect were examined. Mortality rate has shown that none of mortality was found in control. Mortality rates in all WAF treatments. However mortality rates were relatively low in all treatments and were not different (p>0.05). The highest mortality rate was 10% which found in 100% WAF treatment at 96 hours of exposure. The histopathological results in 5 organs including stomach, intestine, digestive gland, mantle and gill has revealed that crude oil WAF had effects on oyster tissues. Besides, resulthas indicated that WAF caused abnormalities in many systems. Severities of the effects were increased by dose- and time-dependent manner of WAFexposure. The results also indicated that WAF induced cellular protective responsesof oyster such as mucous cell production and mucous secretion, hemolytic aggregation which indicates inflammation of tissues. In addition, abnormality was found in digestive gland have been observed in the lumen is widened. The results also indicated stress response of oyster to the WAF exposure. Although the results from present study has been shown that mortalities of oyster in WAF was not high, exposure to high concentration of WAF affecting oyster tissues and could consequently affect on function of important tissues. Altogether, these results also indicated that WAF may cause long-term effect to wild population which possibly reduces fitness of the next generation.