Thermal physiology and metabolic adaptability: the key responses of the invasive crayfish <i>Procambarus clarkii</i> (Girard, 1852) (Decapoda: Astacidea: Cambaridae)

Abstract Understanding the physiological mechanisms that facilitate invasion success is critical for predicting the persistence and spread of non-native species under increasing thermal variability. We examined thermal tolerance, acclimation capacity, and metabolic performance in juveniles of the invasive red swamp crayfish Procambarus clarkii (Girard, 1852) under controlled laboratory conditions. Juveniles were acclimated for 30 days to four ecologically relevant temperatures (20, 24, 28, and 32°C), and upper and lower critical thermal limits (CTmax and CTmin), thermal tolerance breadth (thermal polygon area), acclimation response ratios (ARR), and thermal metabolic scope (TMS) were quantified. Both CTmax and CTmin increased significantly with acclimation temperature, indicating pronounced thermal plasticity. CTmax rose from 37.4 to 40.1°C, whereas CTmin increased from 8.5 to 16.4°C across the acclimation range. The resulting thermal polygon area (286.0°C2) revealed a broad thermal tolerance consistent with a eurythermal strategy. ARR analysis showed asymmetric acclimation capacity, with greater plasticity at lower than at upper thermal limits. Aerobic metabolic performance, expressed as TMS, exhibited a unimodal response across acclimation temperatures, peaking at 28°C and declining at the thermal extremes, yet remaining consistently high and far from physiological collapse across all treatments. Together, these results demonstrate that juvenile P. clarkii combines broad thermal tolerance, asymmetric acclimation capacity, and sustained aerobic performance across a wide thermal range. This suite of ecophysiological traits likely enhances survival, establishment, and spread in thermally heterogeneous freshwater environments, providing mechanistic insight into the invasion success of this globally invasive crayfish under current and future climate variability.