Paraquat terrestrial invertebrates

Adverse effects of paraquat in sensitive species of terrestrial plants and soil microflora have been documented at application rates of 0.28 to 0.6 kg/ha (death, inhibited germination of seeds, reduced growth), at soil concentrations of 10 to 25 mg/kg (growth inhibition), and at soil-water concentrations as low as 1.6 mg/L (reduced growth, inhibited synthesis of protein and RNA). Among terrestrial invertebrates, certain species of mites were sensitive to paraquat at recommended rates of application, and the sensitive honey bee died when its diet contained 100 mg/kg. However, paraquat in soils was not accumulated by earthworms and other species of soil invertebrates after applications up to 112 kg/ha. These points, and others listed in this section, are discussed in greater detail later. 

The utility of antioxidants in terrestrial animals has received relatively little attention so far. In earthworms, inhibition of CAT and glutathione peroxidase but not SOD have been demonstrated in E.fetida exposed to lead and uranium (Labrot et al., 1996). However, SOD and CAT activity were not induced in E. veneta and E.fetida exposed to Zn, Cu and Hg and the herbicide paraquat (Honsi et al., 1999). Antioxidant enzyme measurement therefore cannot be considered a reliable biomarker of exposure in soil invertebrates. 

Terrestrial invertebrates show varying degrees of sensitivity to paraquat. In honeybees (Apis mellifera), 100.0 mg paraquat/kg syrup (diet) produced toxic signs, 4.4 kg/ha applied as a spray killed 90% in 3 days, and... 

---