Characteristics of immune-competent amoebocytes non-invasively retrieved from populations of the sentinel earthworm Lumbricus rubellus (Annelida; Oligochaeta; Lumbricidae) inhabiting metal polluted field soils

Lumbricus rubellus is a cosmopolitan earthworm devoid of riboflavin-storing eleocytes; its immune competent coelomocytes are predominantly amoebocytes. Our aim was to determine whether amoebocyte cytometrics in L. rubellus are robust biomarkers for innate immunological responses to environmental pollutants. Investigations were conducted on populations inhabiting three unpolluted and five metalliferous (mainly Pb+Zn+Cd) habitats in the UK and Poland. Inter-population differences in worm mass and amoebocyte numbers did not consistently reflect soil or tissue metal concentrations. Flow cytometry indicated that autofluorescence of the amoebocytes differs between cells from the unpolluted and metal-polluted worms, and pinocytosis of neutral red by amoebocytes was lower (especially at 15 versus 60 min incubation) in worms from the polluted Poland site compared with the reference population. To conclude, amoebocyte cytometrics and functionality are potentially useful for environmental diagnostics; deployment is contingent on better understanding potential confounders.