Which temperature matters? Effects of origin, rearing and test conditions on the chemical sensitivity of Pardosa amentata

Abstract

Spiders may be adversely affected by pesticides, yet they are not included in regulatory risk assessment and a related standard guideline to test their sensitivity to chemicals is lacking. Different laboratory setups, including test temperature and relative humidity, have been shown to influence the sensitivity of spiders. The climate from which spiders originate and the rearing conditions in the laboratory prior to ecotoxicological testing may also alter their sensitivity to chemicals, potentially in interaction with test conditions. We investigated the influence of population origin, rearing and test temperature on the chemical sensitivity of the spider Pardosa amentata towards lambda‐cyhalothrin. We collected female P. amentata carrying egg sacs from two climates, i.e., boreal and cool temperate. Spiders were kept in the laboratory and their offspring were reared and tested at 15, 20 and 25°C. Hatching of egg sacs largely failed at 15°C, while a moderate spiderling mortality (40%) was recorded at 20°C. At 25°C, mortality increased (63%) and a faster developmental rate was observed. Rearing and test temperature had no significant effects on spider chemical sensitivity. However, spider chemical sensitivity differed between populations, with spiders from boreal climate being 38% more sensitive than spiders from cool temperate climate. A higher sensitivity towards lambda‐cyhalothrin increases the risk of population reduction in treated areas, with potential alterations of ecosystem functions such as biological control. Our results suggest that the climatic origin of test organisms deserves stronger attention in ecotoxicological research.