The intestinal parasite Pomphorhynchus laevis (Acanthocephala) interferes with the uptake and accumulation of lead (210Pb) in its fish host chub (Leuciscus cephalus).

Uninfected chub as well as fish experimentally infected with the acanthocephalan parasite Pomphorhynchus laevis were exposed to (210)Pb(2+) for up to 38 days and the uptake and distribution of lead within different fish organs and the parasites was determined at various time points. Highest metal concentrations were detected in the acanthocephalans, followed by intestine, bile, liver, gill and muscle of the fish host. Infected chub had significantly lower (210)Pb levels in the gills on day 17 (P< or =0.01), in the bile on day 24 (P< or =0.05) and in the gills as well as in the intestine on day 38 compared with uninfected fish. A subsequent polynomial regression revealed that lead levels for the infected fish ranged below the levels determined for uninfected fish during most of the exposure period. This is the first proof that P. laevis reduces lead levels in the bile thereby diminishing or even impeding the hepatic intestinal cycling of lead, which may reduce the amount of metals available for the fish organs. This is especially important for ecotoxicological research. For example, organisms used as accumulation indicators may erroneously indicate low levels of pollution if they are infected with parasites which alter their pollutant uptake mechanisms. Additionally, the results gave further experimental evidence for acanthocephalans as accumulation indicators for metals.