Physiological and behavioural responses to seasonal changes in environmental temperature in the Australian spiny crayfish Euastacus sulcatus

Abstract

The strategies used by ectotherms to minimise the detrimental effects of suboptimal thermal environments on physiological performance are often related to whether they inhabit a terrestrial or aquatic environment. Most terrestrial ectotherms use thermoregulatory strategies to maintain body temperature within an optimal range, while many aquatic ectotherms utilise thermal acclimation to maintain performance over varying seasonal temperatures. This study aimed to elucidate the relative contributions of acclimation and behavioural thermoregulation to maintaining whole-animal performance over varying seasonal temperatures in the semi-terrestrial Lamington spiny crayfish (Euastacus sulcatus). Crayfish activity and surface temperatures were determined by means of radio tracking and behavioural observations. Field studies demonstrated that E. sulcatus is exposed to stable daily temperatures, varying only between seasons from 10 degrees C in late winter to over 20 degrees C in summer. Also, terrestrial behaviour corresponded to a small portion of crayfish time (1.13%), much lower than predicted, indicating that E. sulcatus has limited opportunity for behavioural thermoregulation. We also tested the effect of acclimation to either 10 or 20 degrees C on chela strength and stamina. We found acclimation had a more marked effect on chela stamina than maximum strength measures; however, overall acclimatory capacity was limited in E. sulcatus. Thus, we found that the semi-terrestrial crayfish E. sulcatus used neither thermoregulatory behaviours nor physiological strategies to deal with seasonal changes in environmental temperature.

Global correlates of extinction risk in freshwater crayfish

“…amphibians; Cooper et al, 2008;Sodhi et al, 2008). Many species have no or little capacity to thermoregulate physiologically, so adaptation to warming waters will require shifting to higher altitudes and use of burrows and cool microhabitats (Lowe et al, 2010). Crayfish are susceptible to elevated temperatures, with breakdown of behavioural and physiological responses occurring at only 2°C above current ambient maxima in Euastacus sulcatus (Bone, Wild & Furse, 2014).…”

“…Crayfish are susceptible to elevated temperatures, with breakdown of behavioural and physiological responses occurring at only 2°C above current ambient maxima in Euastacus sulcatus (Bone, Wild & Furse, 2014). Many species have no or little capacity to thermoregulate physiologically, so adaptation to warming waters will require shifting to higher altitudes and use of burrows and cool microhabitats (Lowe et al, 2010). Opportunities for dispersal and use of cool water refuges are limited, and will depend on the condition of the landscape and the spread of invasive The contributions to total variation in range size, other variables and shared variation between range size and other variables add up to one for each model.…”

Thermal acclimation, heat shock and photoperiod: Do these factors interplay in the adaptive responses of crab neuromuscular systems to temperature?

“…It is therefore likely that stress response mechanisms are involved in such environmentally variability. However, Lowe et al (2010) report that a semi-terrestrial Australian crayfish displayed neither behavioural nor acclimation strategies to deal with seasonal changes in temperature. The ability of an organism to survive a normally lethal heat stress can be induced by prior exposure to a sublethal heat stress, the thermotolerance induced is now accepted to be the result of the production of heat shock proteins, (hsps) (Hightower, 1983(Hightower, , 1993Feder et al, 1994;Feder and Hofmann, 1999;Hofmann, 1999;Stillman and Somero, 1996).…”

Negative impacts of elevated nitrate on physiological performance are not exacerbated by low pH

“…Maximum chelae strength was not influenced by nitrate treatment. However, the rate of chelae fatigue and recovery of chelae strength, which are better indicators of aerobic metabolism (Lowe et al, 2010), were affected by nitrate.…”

“…At least three force measurements were taken per individual, and the maximum force (in N) recorded. Muscle fatigue caused by repeated clamping on the force sensor was measured as described by Lowe et al (2010). Briefly, crayfish were allowed to repeatedly clamp down on the force sensor for 5 min.…”