Joint Action Response and Haematological Profile of Macrobrachium vollenhoevenii (Herklots, 1857) Exposed to Binary Mixtures of Spent Lubricant Oil and Dispersant

摘要

The lethal effects of Spent Lubricant Oil (SLO) and dispersant acting singly and jointly as binary mixtures in predetermined (9:1) and equitoxic (3:1) ratios on Macrobrachium vollenhoevenii were evaluated and haematological parameters were used to assess effects of sub lethal exposure. The concentration-addition model (relative toxic units RTU) and Synergistic model (SR) were used to assess their interaction of the tested mixtures meant to simulate environmental control settings in aquatic ecosystems. On the basis of derived toxicity indices, the dispersant (96 h LC_(50) = 0.06 ml L~(-1)) was found to be about 1.33 times more toxic than the SLO (96 h LC_(50) = 0.08 ml L~(-1)) when acting singly against M. vollenhoevenii while the joint action response indicated that the equitoxic ratio (96 h LC_(50) = 0.56 ml L~(-1)) was relatively more toxic. The evaluation of the binary mixtures based on RTU (with reference to SLO) revealed conformity to model of synergism (RTU = 5.66; 1.33) for predetermined and equitoxic ratios while the synergistic evaluation indicated antagonism (SR = 0.44) and synergism (SR = 1.33) for predetermined and equitoxic mixtures, respectively. The haematological parameters of M. vollenhoevenii exposed to sub lethal concentrations (l/10th, l/100th and 1/1000th of 96 h LC_(50) values) of the tested mixtures indicated that the total leucocyte count and differential polymorpho-neutrophils count increased significantly (p>0.05) with exposure period and concentrations while the differential lymphocyte count had an inverse relationship. The differential eosinophils count appeared to have no significant changes (p>0.05). The environmental significance of the results in establishing safe limits for dispersant use in aquatic ecosystems are discussed.