Dehydration resistance and tolerance in the brush-legged wolf spider (Schizocosa ocreata): a comparison of survivorship, critical body water content, and water-loss rates between sexes

Abstract

Small-bodied terrestrial animals like spiders face challenges maintaining water reserves essential for homeostasis. They may experience dry microclimates and (or) seasonal variation in water availability, so dehydration is a common stressor that may help explain movement, foraging, and other behaviors. This study examines aspects of dehydration resistance and tolerance in the brush-legged wolf spider, Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae), commonly found in the leaf litter of eastern deciduous forests of North America. Sexes differ in morphology, physiology, reproductive strategy, and life history, likely resulting in divergent abilities to resist and tolerate dehydration. We used humidity-controlled chambers to examine relative survivorship by sex under varying humidity regimes, water-loss rates, body water content, and critical water mass. Spiders survived significantly longer in higher humidity regimes (≥50% RH). Females had significantly better survivorship overall, lower body-loss rates, and lower critical mass, though males had greater percent body water content, indicating that females have greater dehydration resistance and tolerance than males. Although sex-based differences in survival time and water-loss rates are likely an effect of relative body mass, females should be more successful than males during periods of episodic drought and are likely selected to survive later in the season while caring for offspring.