The present study includes toxicity experiments carried out under laboratory conditions for 24 - and 48 - hours periods by using renewal toxicity test system to determine the comparative toxicities of crude oil ( Basrah regular crude oil ) and refined oil products ( diesel oil , gas oil , gasoline , grease oil , kerosene , motor oil , paraffin wax and automatic transmission oil ) to several species of molluscs collected from Shatt Al – Arab river
. These species of molluscs are snails , Lymnaea auricularia , Theodoxus jordani , Physa acuta , Melanopsis nodosa , and Melanoides tuberculata , and bivalves , Corbicula fluminea and Corbicula fluminalis . The toxicity experiments showed that the different types of oils vary widely in their toxicities to the species tested . The gasoline is clearly the most toxic fraction , while Kerosene is the next most toxic fraction , and is slightly less toxic than Basrah regular crude oil .The remaining fractions diesel oil and gas oil are relatively less toxic to the species tested , while the grease oil is almost non – toxic . Paraffin wax is non – toxic to all species , while the motor oil and automatic transmission oil are toxic to different species in varying degrees . There are some variation in the pattern of recovery rates of each species of snails from exposure to the oils .
The order of sensitivity of molluscs species tested were : L . auricularia > P . acuta > M . nodosa > T . jordani > M . tuberculata > C . fluminalis > C . fluminea . The overall acute effects of hydrocarbons on the species of molluscs tested are abnormal activities , narcosis and anesthesia , the loss of ability to react to the external cue , rapture the tissues and die . |