Does Application of Pyrethroid Insecticides Induce Morphological Variations of Oedothorax apicatus Blackwall, 1850 (Araneae: Linyphiidae)?

Abstract

Pesticides can have a lethal or sublethal effect on spiders and are able to influence their locomotion, activity, web building, reproduction and abundance. Effects of pesticides on spider morphological variations have been poorly investigated. In this study, we explored the influence of pyrethroid insecticides (Fastac®, Talstar® and Trebon®) on variations of linear measurements (body length, carapace and abdomen length, carapace and abdomen width) and carapace shape in Oedothorax apicatus (Blackwall, 1850) from conventional, integrated and organic oilseed rape fields. Multiple applications of various pyrethroid insecticides on the conventional field over a longer period of time influenced significantly the morphological variability in female specimens only. These females had longer bodies with longer and wider carapaces and abdomens in comparison with females from the organic and integrated fields. A wider posterior part of the carapace and less protruded frontal part were detected in female spiders from the integrated and conventional fields. We presumed that these results may be attributed to faster growth, which might be the consequence of a pyrethroid hormetic effect on female individuals. In the case of male spiders, significant morphological differences between the experimental fields were not observed, probably due to their higher mobility.