Pomphorhynchus laevis: the intestinal acanthocephalan as a lead sink for its fish host, chub (Leuciscus cephalus).

Aqueous lead exposure of chub (Leuciscus cephalus) experimentally infected with the parasite Pomphorhynchus laevis resulted in a rapid accumulation of this metal in the intestinal acanthocephalans, reaching concentrations which were significantly greater than in the host muscle, liver, and intestine and approximately 1000 times higher than the exposure con centration. Parasitized chub accumulated significantly less lead in their intestinal wall than their uninfected conspecifics (Mann-Whitney U test, P </= 0.05). From in vitro studies it was shown that lead uptake of P. laevis cystacanths clearly increases by adding 1% eel bile to a commercial RMPI-1640 medium containing 0.1 microg ml(-1) Pb(2+) compared to the controls, which were maintained in RMPI-1640 medium containing lead at the same concentration but without bile. It is therefore most likely that P. laevis in chub absorb bile-bound lead from the host intestine and thus reduce its reabsorption by the intestinal wall, thereby interrupting the hepatic-intestinal cycling of the metal. This is the first example of a beneficial impact of a parasite on its host.