The use of two species of crayfish as environmental quality sentinels: the relationship between heavy metal content, cell and tissue biomarkers and physico-chemical characteristics of the environment.

In systems as heavily disturbed as rivers, the use of biological sentinels is a most interesting way of obtaining continuous assessment of environmental quality. This study seeks to establish the value of such sentinels of two species of crayfish: the native crayfish (Austropotamobius pallipes, Lereboullet 1858) and an introduced species, signal crayfish (Pacifastacus leniusculus, Dana 1852), by comparing the habitat quality (water and sediments) and heavy metal contents in crayfish with the degree of stress manifested by the animals, measured by cell and tissue biomarkers. For this purpose a histological study of the digestive gland was carried out together with measurements of heavy metal contents in samples from various points of the river network of Bizkaia (Spain), selected on the basis of their degree of disturbance. The results establish a positive correlation between these environmental conditions, the cell and tissue biomarkers of the digestive gland (thinning of the digestive epithelium, enlargement of digestive lysosomes) and the heavy metal contents of the animals (converted to an index of pollutant load).