Physiological and biochemical responses to elevated temperature in a threatened freshwater crayfish, Euastacus sulcatus (Decapoda: Parastacidae)

Abstract

Projected elevations in environmental temperature are expected to have a detrimental effect on organisms with distributions that are already restricted to high-altitude refugia, especially where dispersal is compromised due to population isolation by unsuitable intervening habitats. The present study was carried out on such an organism, namely Euastacus sulcatus, to determine: (1) the temperature at which thermal stress occurs under laboratory conditions; and (2) whether thermal stress is already occurring naturally in contemporary field-acclimatised individuals. The laboratory data provided evidence that biochemical and physiological stress occurred in E. sulcatus at 22.5°C or higher. In the field, oxidative stress was characterised by an increase in the oxidised redox state of glutathione within a low-altitude population accompanied by significantly elevated protein carbonyls and lipid peroxidation. The data confirmed that potential thermal stress was present in E. sulcatus residing at the lower end of its altitudinal distribution, indicating that this threatened species is already challenged within localised populations in their natural environment. Together, these results reveal that future increases in environmental temperature are not only likely to result in increased baseline levels of stress in E. sulcatus, but also forecast further restriction in the altitudinal distribution of the species in a warming climate.