%0 Journal Article
%T Toxicity of Commercial Neem Extract to Earthworms (Pheretima peguana)
%A Ptumporn Muangphra
%A Ravi Gooneratne
%J Applied and Environmental Soil Science
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/925950
%X The LC50 of commercial neem extract (Sadao Thai III containing azadirachtin; NEEM) on filter paper in the earthworm Pheretima peguana at 48£¿h and 72£¿h was 3.79 and 3.33£¿ g£¿ , respectively. In earthworms exposed to five NEEM concentrations from 0.39 (~10% of 48-h LC50) to 3.13 (~80% of 48-h LC50) g£¿ , the radial thickness of the epidermis and body wall significantly ( ) decreased, and thickness of intestinal epithelium increased but only at high doses, approximately 25-fold above the concentration permitted for use as an insecticide in field applications (0.09£¿ g£¿ ). NEEM significantly ( ) increased the number of binucleated coelomocytes in the micronucleus test (detects chromosomal aberrations) at 3.13£¿ g£¿ , approximately 35-fold higher than the recommended dose, but it did not cause coelomocyte DNA single-strand breaks in the comet assay. Thus, NEEM is cytotoxic (increase in binucleates through the inhibition of cytokinesis) but not genotoxic to earthworm coelomocytes. This study demonstrates that the recommended dosage of commercial neem extract as an insecticide in agricultural practices is safe for earthworms. 1. Introduction The most active chemical of neem extract (Sadao Thai III; NEEM) is azadirachtin (Aza), which belongs to the tetranortriterpenoid group of organic compounds. It functions as an ecdysone blocker and a feeding deterrent for some insect pests. There is a perception that NEEM is an environmentally friendly insecticide, so it is often used in high concentrations, and this can lead to a heavy load of NEEM in soil. High NEEM soil concentrations can cause chronic toxicity to nontarget organisms such as crustaceans (Daphnia magna and Hyalella azteca) [1] through leaching from soil into waterways. NEEM has also been shown to induce genotoxicity in rodents [2, 3] and fish [4]. These effects raise concern over the safe use of NEEM as a pesticide in agricultural practices. Although earthworms are often used in terrestrial ecotoxicity evaluation [5], there is little information available on the effects of NEEM on earthworm immune competent cells and histology of the epidermis, skin, body wall, and intestinal lining. In earthworms, coelomocytes are the circulating leukocytes present in the coelomic cavity and play an important role in immune defense. They have been used to study the effect of genotoxicants such as nickel (Ni) and cadmium (Cd) [6, 7] on earthworms. The genotoxicity of NEEM to earthworm coelomocytes has not been reported. DNA damage induced in mammalian and aquatic species by chemical and physical agents can lead to the
%U http://www.hindawi.com/journals/aess/2011/925950/