Low Temperature Acclimation in the Desert Spider, Agelenopsis aperta (Araneae, Agelenidae)

Agelenopsis aperta (Gertsch) inhabits desert grasslands and lava beds in the southwestern U.S.A. The capacity of this species to cold-harden was assessed by exposing second generation laboratoryreared specimens to an artificial low temperature cycle simulating the "summer-autumn-winter" transition. Low temperature acclimation had no effect on whole body supercooling points, freeze tolerance or rates of oxygen consumption. Elevated levels of cryoprotectants were n o t detected using high performance liquid chromatographic techniques. Cold tolerance was similar between males, females and immatures. Exposure to temperatures immediately above the whole body supercooling point caused no apparent injury. It is hypothesized that movement into protected overwintering microhabitats may obviate the necessity for the evolution of seasonal mechanisms of cold-hardening in A. aperta.