Pharmacokinetics and metabolism of triclopyr in the crayfish (Procambarus clarki).

Crayfish (Procambarus clarki) were exposed to [14C]triclopyr at concentrations of 1 and 2.5 mg/liter, similar to potential field applications. Following 11 days of exposure, the elimination of accumulated residues was followed for 36 days. The majority of the residue in whole crayfish was present in the carcass (shell, hemolymph). HPLC of hepatopancreas showed the residues were primarily parent triclopyr (greater than 80%). The principle metabolite in the hepatopancreas was confirmed by mass spectrometry as the taurine conjugate of triclopyr. Several minor metabolites also were present at very low levels (less than 0.1 ppm) and were not identified. Residues were eliminated with half-lives of 7 to 17 days, depending on the tissue and exposure concentration. Bioconcentration factors, estimated from uptake and elimination rate constants determined using a compartmental model, were about 1 in whole crayfish and hepatopancreas and about 0.2 in muscle. The results of this study indicate that there is a low potential for accumulation of triclopyr and its metabolites in the crayfish.