Micro-organisms and metal retention in the woodlouse Oniscus asellus

Abstract Claims by other authors as to the importance of coprophagy and micro-organisms in copper uptake by terrestrial isopods are largely unsubstantiated. This paper describes an expriment which shows that, at least in Oniscus asellus , Cu and Zn and rapidly assimilated irrespective of coprophagy. In contrast, Cd and Pb were not rapidly assimilated although Cd was more readily retained by animals not able to resort to coprophagy. Numbers of bacteria and fungi in the food supply and in both guts and faeces of O. asellus are related to animal activity and corophagy. Numbers of bacteria in faeces are higher than in original litter suggesting a stimulation during passage through the gut, in comparison numbers of fungi show the reverse. In the absence of corophagy numbers of micro-organisms are reduced in the litter, presumably by increased grazing. he ratio of actinomycetes: bacteria in the animal gut ranges from 0.024 to 0.247 and this ratio is affected by both corophagy and the food supply. The metal tolerance of the gut microflora increases as result of feeding on litter contaminated with metals, but is also affected by coprophagy. Although the association of micro-organisms in the feeding strategy of terrestrial isopods still requires a great deal of research it is suggested that actinomycetes could be of importance in the nutrition, and ultimately metal concentration, of O. asellus .