Thermal tolerance and preferred temperature of the Andean Chilean tarantula Euathlus walteri (Araneae: Theraphosidae)

Abstract

Mygalomorph spiders are ectothermic organisms reliant on temperature for movement, prey capture, and reproductive success. The species Euathlus walteri, is endemic to northern Chile and inhabits cold and high-altitude regions. This study investigates the preferred body temperature and the parameters of the locomotor thermal performance curve in females and large juveniles of E. walteri in a controlled laboratory setting. We identified their preferred temperature ranges and examined the correlation between laboratory temperatures and burrow temperatures. The results indicate a preference for warmer temperatures (around 34°C) than the environment temperatures where this species live, actively avoiding colder temperatures. No significant differences in thermal preference were observed between morning and evening periods. We found an optimum temperature of 22 ± 2.0°C, lower thermal limit (LTL) of -1.11 ± 0.76°C and upper thermal limit (UTL) of 44.94 ± 1.79°C. Our preliminary results suggest that individuals that live in this cold environment seek warmer temperatures to compensate for the reduced opportunity to find favorable temperatures in their habitat. Furthermore, our results suggest that locomotor performance is significantly affected by low temperatures and that spiders might select shelters with temperatures that allow them to approach their physiological optimal temperature.