Influence of Temperature on the Tensile Strength of Spider Silk (Araneus gemmoides)
- Laurieanne Dent, Visiting Professor of Biology, Pepperdine University
- Stephen Davis, Distinguished Professor of Biology, Pepperdine University
Differences in day and night temperatures in Southern California can be >30°C and may influence the functioning of ectothermic organisms. Arachnids produce silks from a pair of spinnerets in their abdomen and rely on variance in protein composition to make different types of silks. The rate at which this silk is produced as a function of temperature may influence tensile strength of filaments. We tested the effects of temperature on tensile strength of dragline silk of five specimens of Araneus gemmoides (orb-weaver) which were collected from Malibu Creek State Park in the Santa Monica Mountains of southern California, under five temperature conditions. Each specimen was placed in a 0.0283 m3 mesh enclosure and allowed 24-hours to acclimate to a temperature increase of 5°C. Photoperiods were set at 12-hour intervals for light and dark to simulate the average sunrise at 7:00 and sunset at 19:00 in Malibu. We then removed a single thread of dragline silk and measured tensile strength using an mechanical testing device (Instron 5544-A). We found that dragline silk is typically composed of two monofilaments wrapped together at points and thus quantified transverse area of both the monofilament and the (typically) two monofilament silk strand as a method of trying to understand the atypical stress-strain curves that were obtained. After running a one way ANOVA statistical analysis for repeated measures, we found that at 10°C both the Young’s Modulus and stress at break were significantly greater (P<0.05) than values obtained at 15°C. Additionally, higher masses of spiders seem to correlate with greater tensile strength (R2=0.52). Currently, biomaterial engineers are attempting to exploit the incredible properties of silk for production of fiber materials. Therefore, understanding how Araneus gemmoides silk is influenced by temperature offers insight into the optimal temperature for harvesting silk.