Acclimation to moderate temperatures can have strong negative impacts on heat tolerance of arctic arthropods

The Arctic is impacted by some of the fastest temperature changes observed on Earth, but the impact on terrestrial arthropod fauna is unclear. Acute physiological thermal limits of terrestrial ectotherms from high latitudes often exceed the local air temperatures, suggesting that they may be able to cope with increasing temperatures. However, knowledge of how arctic terrestrial arthropods cope with elevated temperatures for longer periods is lacking. Here we investigate how acclimation temperature and exposure time affect the acute physiological heat tolerance of five terrestrial arthropod species (Neomolgus littoralis, Megaphorura arctica, Nysius groenlandicus, Psammotettix lividellus, and Nabis flavomarginatus) immediately after collection in arctic and sub-arctic habitats. We show that although acute heat tolerances are relatively high, even exposure to moderate (temperature span assessed ca. 3-29°C) acclimation temperatures for 24 hours have strong negative effects on heat tolerance..., Microhabitat temperatures
Temperature loggers were placed at the sites where the animals were collected. At Ny Ålesund, two SmartButton loggers (SmartButton, ACR System Inc.) were placed in and on gravel at the beach to record the thermal environment (every 5 minutes) where individuals of N. littoralis were caught, and at a protected and an exposed tundra area, representative. At Narsarsuaq, air temperature and ground-level temperature at the collection site were continuously recorded (every 15 minutes) using TMS-4 dataloggers (TMS-4, TOMST, Czech Republic) to record the thermal environment in which the individuals were caught.
Thermal tolerance
Two assays were used to measure heat tolerance in the present study: 1) critical thermal maximum temperature (CTmax), where the specimens were exposed to gradually increasing temperatures and the temperature at which they entered heat coma was recorded, and 2) heat knockdown time (HKDT), where the specimens were exposed to a constant, stressful ..., , # Acclimation to moderate temperatures can have strong negative impacts on heat tolerance of arctic arthropods

[https://doi.org/10.5061/dryad.m63xsj49q](https://doi.org/10.5061/dryad.m63xsj49q)

## Description of the data and file structure

The data consists of an Excel file with the following sheets:

1\) Readme (sheet 1).

2\) Heat tolerance data (sheet 2; Svalbard CTmax): Critical thermal maximum temperature (CTmax; °C), where the specimens were exposed to gradually increasing temperatures, and the temperature at which they entered heat coma was recorded. Two species from Svalbard (*Neomolgus littoralis, Megaphorura arctica).*

3\) Heat tolerance data (sheet 3-4; Acclimation Svalbard and Greenland): The effect of moderate acclimation temperatures (°C) and exposure times on upper thermal limits (HKDT: heat knockdown time; minutes) of five arctic arthropods: *Neomolgus littoralis, Megaphorura arctica, Nysius groenlandicus*, *Psammotettix lividellus*, and *Nabis flavomarginatus* immed...