Assessment of the cytotoxic impact of heavy metals on soil invertebrates using a protocol integrating qualitative and quantitative components

Abstract

Slugs (Deroceras reticulatum), isopods (Porcellio scaber), diplopods (J ulus scandinavius), and collembola (Tetrodontophora bielanensis) were exposed to cadmium, lead or zinc at differing concentrations under constant laboratory conditions. Ultrastructural alterations of monitored tissues (for diplopods and collembola, midgut epithelium; for slugs and isopods, midgut gland epithelium) were recorded qualitatively and quantitatively by transmission electron microscopy. In order to combine both qualitative and quantitative aspects of the observed responses into a proposed easy-to-handle ‘impact index’, we developed a protocol according to the physiological basis for the ultrastructural responses. Using this protocol, the data clearly showed the different susceptibilities (1) of organelles to the respective metal, (2) of the investigated species to particular metals, and (3) of the monitored tissue to increasing metal concentration. Moreover, the construction of matrices of impact indices for single symptoms allows the description and analysis of complex syndromes in a mathematical way. Cluster analysis of the present data on controlled laboratory experiments utilizing single contaminants revealed similar patterns of cellular responses to the tested metals in the investigated tissues of P. scaber and J. scandinavius and species-specificity for T. bielanensis and D. reticulatum monitored tissues. Some of the highest metal concentrations seemed to affect the homogeneity of these specific reponse patterns, and did not fit the respective clusters.