Copper and the role of isopods in degradation of organic matter.

On an artificial substrate of filter paper, Porcellio scaber cannot extract copper from leaf litter. If one increases the copper content of the food by soaking the leaves in solutions of CuSO(4) or in organic extracts, assimilation of copper becomes possible, but only at concentrations higher than 1 microgram of copper per milligram of ash. This is too high a level for primary vegetable matter to be considered a plausible source of copper for isopods. I present evidence that in fecal material the critical level at which assimilation of copper becomes feasible is lower than in primary organic material by nearly an order of magnitude, and that isopods are obliged to switch to coprophagy in order to allow accumulation of copper in their bodies.