Abstract

lntermolt, adult male and female noble crayfish were collected from two ponds and one lake with relatively low, moderate, and high sedimentary and dissolved calcium levels. There were direct correlations between lateral branchial carapace exoskeleton calcium concentrations, carapace densities and environmental calcium. The highest concentrations were present in crayfish from a eutrophic pond within the City of Kuopio. The lowest concentrations were present in crayfish from an oligotrophic lake in the countryside. Calcium concentrations ranged from 224,300 to 279,900 mg kg^-1 with no significant differences between sexes. The densities of exoskeleton ranged between 34 and 49 mg cm^-2. Differences between sites were significant and were directly related to environmental calcium but differences between sexes were not significant. Magnesium and manganese were minor components of the branchial exoskeleton, 1,300-2,600 mg kg^-1 and 70-175 mg kg^-1, respectively. There were no correlations between environmental magnesium and manganese and their concentrations in crayfish exoskeletons. Females generally had higher concentrations than males. The intensity of infestation of crayfish by the unicellular organism Psorospermium haeckeli Hilgendorf increased as environmental calcium increased.

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