The flow of copper through a terrestrial food chain : II. Factors influencing the copper content of isopods

Abstract

1) In terrestrial isopods total copper concentration increases exponentially with size, the exponentb in the equationy=a·x ^b being larger in populations rich in copper than in populations poor in copper. 2) However, immediately after hatching all species so far tested in Tirol contain the same amount, i.e., approximately 0.13 μg Cu per mg dry weight. 3) A very close correlation (r=0.98) exists between the mean copper concentrations of isopods and litter, from a series of habitats ranging widely in their copper content. The correlation with the copper concentration of the soil is much less clearly expressed. 4) In isopods kept in culture and fed litter from their original habitats the concentration of copper increases. This increase is almost entirely due to an elevation of the copper content of the hepatopancreas. 5) Feeding a low-copper diet to a high-copper population for four weeks did not alter significantly the mean copper concentration of the animals. 6) There is a marked temperature-dependent seasonal fluctuation in the copper content of isopods, with a maximum in winter and a minium in summer. 7) On the basis of dry weight the concentration factor for copper is about six, the same as that for cadmium in another species of isopod studied by Martin et al. (1976) in England, and much higher than the concentration factors for the same metals by pulmonate snails.