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27 August 2024 Cold tolerance strategy, supercooling, and cold hardening in three populations of the jumping spider Phidippus audax (Araneae: Salticidae)
Michael T. Henshaw, Ethan C. Book, Madison M. Skinner, Emily E. Kowal, Skye E. Johnson, Natalie A. Longo, Abbey Kern, Chloe W. Smith, Sophia Hamilton, Alex Kayfish
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Abstract

Cold temperatures can cause injury and death, and thermal tolerance influences organismal abundance, distribution, and physiology. We characterized cold tolerance and supercooling point (SCP) in the broadly distributed jumping spider Phidippus audax (Hentz, 1845). We found that P. audax is freeze-avoidant, surviving chilling but not freezing. Freeze-avoidant organisms can reduce harm by lowering their supercooling point (SCP), the temperature at which they freeze. We assayed fall/winter SCP in field-acclimated spiders from Michigan and compared lab-acclimated spiders from Texas, Oklahoma, and Michigan. Field-acclimated Michigan spiders decreased their SCP from –4.7 °C in September to –12.9 °C in November. In the lab, Michigan spiders had the lowest SCP (–7.65 °C) followed by Oklahoma (–6.21 °C) and Texas (–5.50 °C). In December and January, nearly all the spiders from Texas and Oklahoma died in the simulated freezing conditions while the Michigan spiders survived at high rates, further suggesting that the Michigan spiders were hardiest followed by Oklahoma and Texas. The lab-acclimated spiders did not consistently reduce their SCP from October to December. Smaller spiders had lower SCPs than larger spiders, and the Michigan spiders were significantly smaller than those from Texas or Oklahoma, suggesting that smaller overwintering size or delayed molting to mature size/sexual maturity may be favored by selection in colder climates. This could help explain differences in size and life cycle between northern and southern P. audax, as well as a previously described trend for smaller spiders to be more common in colder areas or Europe.

Michael T. Henshaw, Ethan C. Book, Madison M. Skinner, Emily E. Kowal, Skye E. Johnson, Natalie A. Longo, Abbey Kern, Chloe W. Smith, Sophia Hamilton, and Alex Kayfish "Cold tolerance strategy, supercooling, and cold hardening in three populations of the jumping spider Phidippus audax (Araneae: Salticidae)," The Journal of Arachnology 52(2), 143-150, (27 August 2024). https://doi.org/10.1636/JoA-S-23-006
Received: 2 February 2023; Accepted: 16 July 2023; Published: 27 August 2024
KEYWORDS
freeze-susceptibility
Freezing
overwintering
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