Characterization of the thermal micro-environment ofParaphysa parvulaPocock 1903 (Araneae: Theraphosidae), a spider from the Chilean Andes

Abstract

We characterize, in both the laboratory and the field, the preferential thermal microenvironments of Paraphysa parvuia (Pocock 1903) (Araneae: Theraphosidae), a mygalomorph spider that successfully inhabits the high elevation environments of the Chilean Andes. We studied 1 16 spiders. Their average body temperature in the field was 31.02 ± 2.74°C , similar to the laboratory preferred temperature of 31.7 ± 2.31° C, and higher than the ideal temperature of reproductive females, 29.34 ± 2.81° C. In non-reproductive spiders, we found significant associations between body temperature and the temperatures of the air, substrate and rocks; however, the strongest association was between body and rock temperatures. Similar results were obtained in reproductive females, but there the best predictor of the body temperature was air temperature in the shelter. In both cases, the air temperature remained below body temperature and well below the temperature of the rocks and stones. Both situations show the importance of behavioral thermoregulation and the mechanisms of heat transfer into the microenvironment in the body temperature regulation of spiders. Conduction from the environment, heat transfer by small convection currents, and radiation from the hot stones constitute small environmental cues that allow these spiders to maintain an optimal temperature. The selection of shelters meeting specific temperature regimes appears to be a key condition for the optimization of female reproductive success and survival of females and juveniles in a high elevation environment.

Effect of thermal acclimation on preferred temperatures in two mygalomorph spiders inhabiting contrasting habitats

“…Conduction from the environment, heat transfer by small convection currents and radiation from hot stones all allow spiders to maintain a physiologically appropriate temperature. In this context, the selection of shelters that meet specific temperature conditions appears to be a key condition for the optimization of female reproductive success and the survival of females and juveniles (Schmalhofer, 1999; Canals et al ., 2007; Figueroa et al ., 2010; Veloso et al ., 2012). The species in the present study show preferred temperatures in the range of those reported for other mygalomorph spiders.…”

“…Mygalomorph spiders are ectotherm predators that depend upon thermal micro‐environments for energy saving, reproduction and capture of their prey (Greenstone & Bennett, 1980; Humphreys, 1987; Schmalhofer, 1999; Canals et al , 2007; Figueroa et al , 2010; Veloso et al , 2012). However, thermoregulatory behaviour, thermal tolerance and preferred temperatures are only studied in less than 1% of the species of spiders (Humphreys, 1987), and the species that inhabit temperate environments are less well known (Schmalhofer, 1999).…”

“…In particular, in mygalomorph spiders, only the preferred temperatures of Aphonopelma sp. and Paraphysa parvula are reported (Seymour & Vinegar, 1973; Shillington, 2002; Veloso et al , 2012).…”

“…Some spiders have also been shown to select retreat sites in accordance with the thermal properties of the environment (Hammerstein & Riechert, 1988). Species from different environments typically also have different thermal preferences (Pulz, 1987; Schmalhofer, 1999) and these may vary seasonally (Schmalhofer, 1999), with the breeding season (Hanna & Cobb, 2007; Veloso et al ., 2012) or during the day, as in other ectotherms (Canals et al ., 1997). However, acclimation temperatures are reported to have no affect on the thermal preferences of araneomorph and mygalomorph spiders (Sevacherian & Lowrie, 1972; Seymour & Vinegar, 1973).…”

Thermal preference ofDysdera crocataC. L. Koch 1838 (Araneae: Dysderidae)

“…Species from different environments typically also have different thermal preferences (Pulz 1987;Schmalhofer 1999) and these may vary seasonally (Schmalhofer 1999), with the breeding season (Hanna & Cobb 2007;Veloso et al 2012) or during the day, as in other ectotherms (Canals et al 1997;Alfaro et al 2013). The election of low temperatures and a relatively narrow range may be explained by phenotypic plasticity as an adaptation to the particular environmental conditions present in Chile.…”