Effects of 1,2,4-trichlorobenzene on the enzyme activities and ultrastructure of earthworm Eisenia fetida

Adult Eisenia fetida earthworms were exposed to sub-lethal concentrations of 1,2,4-trichlorobenzene to assess the toxicity of contaminated soils. The LC50 of 1,2,4-TCB at 7 and 14 d were 945 +/- 175 and 890 +/- 169 mg kg(-1). A lower dose of 1,2,4-TCB (25 mg g(-1)) had stimulatory effects on SOD and AChE activities, but AChE activities were significantly inhibited at higher treatment levels (100 and 400 mg g(-1)). SOD activities increased after 2, 7, and 14 d of exposure, but AChE activities were significantly inhibited at 400 mg/kg 1,2,4-TCB after 2, 7, and 14 d of exposure, and the inhibition rates were 25.41%, 28.65%, and 25.05%. Ultrastructural observation of the intestinal epithelium at three concentrations (control, 50, and 400 mg g(-1)) revealed that the epicuticle, cuticle layer, and microvilli were damaged with increasing 1,2,4-TCB concentration. At 400 mg kg(-1), mitochondria were seriously injured and the smooth endoplasmic reticulum was seriously dilated. (C) 2011 Published by Elsevier Inc.