Characterization of the thermal death time landscape for Enchytraeus albidus

Abstract

The influence of non-stressing temperatures on life-history traits of enchytraeids (e.g. growth and reproduction) is well described in the literature, but less is known about the influence of stressful temperatures, especially at the high end of the scale. In light of predicted climate changes, where the frequency and intensity of extreme weather events are increasing, it is important to provide detailed knowledge of the thermal limits of species. Experiments leading to a comprehensive understanding of species´ Thermal Death Time (TDT) landscape are particularly valuable because this allows modelling and predicting mortality under dynamic thermal scenarios. In static assays, we determined TDT₅₀ of adult worms at a range of temperatures showing that 50% mortality (TDT₅₀) was reached by exposure to 35.5 °C for only 6 min, whereas TDT₅₀ at 31 °C was 257 min. By fitting the TDT curve to the measurements, we described the influence of temperature on the rate of injury accumulation leading to 50% mortality. Based on injury accumulation rates derived from static assays, we predicted the TDT₅₀ in dynamic assays of various temperature ramping rates with high precision. Additional experiments showed that eggs and juveniles had the same sensitivity to high temperature as adult worms. Combined with previous research, our results show that E. albidus has a wide thermal niche in which survival is possible, from ca. − 25 to + 35 °C. However, exposure time is of the essence for surviving stressful temperatures in the high and low temperature ranges. We discuss that the wide thermal niche of E. albidus may partly explain how this species has become so widely distributed, from the temperate coastal climate in northern Spain to the high Arctic in Svalbard.