Effect of heavy metals on four different earthworm’s species specific autofluorescing eleocytes

Abstract

Earthworm is key bio-indicator of soil milieu to assess heavy metal contaminations. The celomic fluid of earthworm plays a significant role in the storage of riboflavin within the celomic cavity thereby maintaining its homeostasis. So the measurement of these autofluorescent ‘self-marking’ eleocytes will give more information about chloragocyte derived cells and species. The present study is to investigate the percentage of autofluorescing cells, riboflavin content, elemental and heavy analysis of immunologically significant eleocytes. The present study is focused on four different earthworms namely Lampito mauritii, Octochaetona serrata, Eudrilus eugeniae and Eisenia fetida, to characterize immune factors such as cellular and riboflavin content exposed to various heavy metal concentrations under laboratory conditions. Four different earthworms were exposed to three different concentrations (63.5, 112.4 and 207.2 μg/mL) of heavy metals (Cu, Cd, and Pb) over 96 h. The celomic fluid were subjected for FACS analysis to find out the percentage difference of autofluorescent eleocytes cells between control and exposed species. The discrepancies between riboflavin content of control and heavy metal exposed worms were analyzed by spectrofluorescence. The low and negligible percentage of autofluorescent cells were recorded in E. eugeniae and L. mauritii but large numbers of autofluorescent cells were recorded in E. fetida and O. serrata. The experimental results show that riboflavin content and autofluroscence cells of the heavy metal exposed worms displays significant decrease in the celomic fluid. The present study clearly demonstrated that investigated species possess the significant population of celomocytes, but they differ considerably in the number of cells per body mass and by species. This non-invasive technique proves stable cellular biomarkers in earthworm for toxicological and biological soil monitoring studies.