Effect of Dimethoate on Body Growth of Representatives of the Soil Living Mesofauna

For the elucidation of effects of a pesticide on life-cycle parameters of arthropods, applicable in the development of ecotoxicological test procedures with soil living animals, attention was drawn to body growth, which has previously been described as a sensitive parameter in Collembola. Body growth of the following three soil-dwelling arthropods was studied under the influence of dimethoate:Folsomia fimetaria(L.),Hypogastrura assimilisKrausbauer, andHypoaspis aculeiferCanestrini. The effect of this insecticide and acaricide proved to be sex and species specific. Two models were compared for modeling individual body length. The logistic growth model fitted data for all species, whereas the growth model of von Bertalanffy was less applicable forF. fimetariaandH. aculeifer.The growth rate coefficient of the logistic model proved to be a robust parameter useful for predicting effects of dimethoate on juvenile growth ofF. fimetariaandH. aculeifer.Adverse effect concentrations on growth for these species were the following: EC10= 0.11 mg dimethoate/kg dry soil forF. fimetariaand EC10= 0.59 mg dimethoate/kg dry soil forH. aculeifer.ForH. assimilis,no adverse effects on growth were observed at the tested concentrations. The results are compared to other life-cycle parameters (endpoints).