Effect of chemical pollutants on F-actin cytoskeleton in earthworm coelomocytes

Earthworms are very important organisms for soil formation and organic matter breakdown in most terrestrial environments. Because of their strong interaction with soil, they are profoundly affected by soil pollution. The coelomic fluid is one of the first targets of toxicants in earthworms because it can receive and vehicle pollutants to the all animal tissues. The aim of the present work was to investigate possible pollutant-induced alterations in earthworms coelomocytes cytoskeleton in view of future application as sensitive biomarker for soil monitoring and assessment applications. The study was carried out on the earthworm Eisenia foetida. The animals were exposed in controlled laboratory conditions either to the heavy metal based fungicide copper sulphate or to the PAH fluorantene. Coelomocytes were labelled with rhodamine-phalloidine for F-actin visualization by confocal laser scanning microscopy. The attention was focussed on granulocytes which are the cell type major involved in humoral immune response. Results showed a significant (P<0.01) increase in the F-actin content in granulocytes from treated animals with respect to control groups either in copper or fluorantene exposed animals. While in copper exposed animals the increase was markedly limited to the cortical region of the cells, in fluorantene exposed animals a general increase of F-actin polimeryzation was observed in the whole cell. In conclusion the present study demonstrated that F-actin cytoskeleton of earthworm coelomocytes represents an important cellular target of the effect of organic or inorganic chemical pollutants in these bioindicator organisms and give useful information for a potential use of this response as exposure/effect biomarker in soil risk assessment.