Volume 16, Issue 5
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



The toxicity of DDT for Southeast Asian buffalo leeches, , was tested with a modification of the standard WHO procedures for determining susceptibility-resistance of mosquito larvae to insecticides. Specimens of from Bangkok, Thailand, and Kuala Lumpur, Malaysia, showed a high degree of tolerance. LC values after 120 hours' continuous exposure were 100 ppm for leeches from Kuala Lumpur and 60 ppm for specimens from Bangkok.

The absorption of DDT by specimens of from Japan and of from Malaysia was determined by radioactive assessment of chloroform extracts of leeches that had been exposed for 24 hours in aqueous solution containing 7.1 ppm of ringlabeled C DDT. Results showed that 16% of exposed DDT was recovered from , and 17.4% from .

After assessment of absorption of DDT by the leeches, the chloroform extracts were evaporated to dryness, taken up in acetone, and chromatographed. The chromatogram of extract showed that 49% of the absorbed DDT had been converted to the nontoxic DDE. Chromatograms of extracts by showed neither production of DDE nor other metabolites of DDT analogues. This, as far as could be determined, was the first demonstration of dehydrochlorination of DDT by an annelid.


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