Pollutant induced alteration in Eisenia fetida coelomocytes: a novel biomarker in soil monitoring

Aim: Biological responses to pollutant exposure (i.e. biomarkers) are increasingly investigated in sentinel organisms and proposed as sensitive ‘early warning’ tools in environmental quality assessment. Invertebrate haemolymph and coelomic fluid cells have received increasing attention in last years from a toxicological point of view because they are involved in the internal defence system of the organism; therefore any impairment of their functioning can alter health conditions of the entire organism. The aim of the present work was to investigate possible pollutant induced morphometrical alterations in earthworms coelomocytes in view of future application as sensitive, simple and quick biomarker for soil biomonitoring applications. Eisenia foetida exposed to CuSO4 or pesticide methiocarb was utilized as model organism. Methods: Coelomocytes were stained with Diff Quick and observed under optical microscope; the images obtained from video camera were digitalised using the LUCIA images analysis software (NIKON). The coelomocyte alterations were investigates together with previously standardized biomarkers such as tissutal levels of metallothioneins, acetylcholinesterase activity, coelomocyte lysosomal membrane stability. Results: A significant (P<0.001) enlargement of coelomocytes was observed either in CuSO4 or methiocarb exposed animals. These alterations correlate with results obtained with standardised biomarker: a significant increase in metallothioneins was observed in the earthworms treated with copper sulphate with respect to the control group (P<0.001), and an inhibition of acetylcholinesterase was measured in the organisms treated with methiocarb (P<0.0001). Lysosomal membrane stability decreased in both treated groups (P