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    Toxicity and Metabolism of Mexacarbate in Freshwater Crayfish Under Laboratory Conditions

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    Adult crayfish (Orconetes limosus) were exposed to 0.1, 1.0, 2.5, 4.0, 7.5, 8.0, 8.5, 9.5, 15.0, 20.0, and 25.0 μg/mL of mexacarbate [4-dimethylamino-3,5-xylyl N-methylcarbamate (Zectran)] in water at 15°C under laboratory conditions. Behavioral abnormalities were noted at levels ⩾ 1.0 μg/mL, but as the duration of exposure increased the animals recovered and behaved similarly to the control group. Signs of acute toxicity and mortality were observed at concentration levels ⩾2.5 μg/mL. The 96-h LC50 value was 8.8 μg/mL. Body weight depression was significant only in the three high dose groups (at 15, 20, and 25 μg/mL). The study was terminated 144 h after treatment. The parent compound (M) and seven metabolites, namely, 4-methylformamido mexacarbate (MFM), 4-formamido mexacarbate (FAM), 4-methylamino mexacarbate (MAM), 4-amino mexacarbate (AM), 4-dimethylamino-3,5-xylenol (DMAX), 4-methylamino-3,5-xylenol (MAX), and 4-amino-3,5-xylenol (AX) were detected in crayfish 144 h after exposure. The primary metabolites detected were MFM and FAM, which accounted for 30 and 20%, respectively, of the body residue. Other metabolites detected accounted for about 9% of the body residue altogether. About 41% of the body residue was contributed by the parent material M. The bioconcentration factor of mexacarbate in crayfish was very low, about 0.58, compared to 2000 to 3000 reported in the literature for fenvalerate and permethrin in fathead minnows.


    mexacarbate, crayfish, 96-h LC, 50, metabolic products, bioconcentration, LT, 50, body weight depression, acute toxicity, behavioral abnormalities, rate of uptake

    Author Information:

    Sundaram, KMS
    Research scientist and project leader, Government of Canada, Canadian Forestry Service, Forest Pest Management Institute, Sault Ste. Marie, Ontario

    Committee/Subcommittee: E47.12

    DOI: 10.1520/STP16806S