Thermal stress responses of two sympatric crayfishes in Louisiana, Procambarus clarkii Girard, 1852 and Procambarus zonangulus Hobbs & Hobbs, 1990 (Decapoda: Astacoidea: Cambaridae)

Abstract

Abstract Water temperature is an important abiotic component in farmed and wild crayfish habitats as it influences individual and population characteristics including growth, metabolic activity, and overall population vigor. Thermal limits, however, have not been established for the two commercially important crayfishes in Louisiana, the red swamp crayfish Procambarus clarkii (Girard, 1852) and the southern white river crayfish P. zonangulus (Hobbs & Hobbs, 1990). We aimed to determine the thermal stress responses for the two species. Thermal stress was examined by the critical thermal maxima (CTmax) for crayfish acclimated to 24, 27, or 30 °C for two weeks prior to experimentation. Water temperature in all acclimation trials was increased 1 °C h–1 and the end-point temperature for an individual was determined by the failure of righting response within 30 seconds. CTmax values (±SD) for P. clarkii acclimated at 24, 27, and 30 °C were 39.5 ± 0.5, 39.1 ± 0.3, and 39.4 ± 0.7 °C respectively, and 39.8 ± 0.8, 38.8 ± 0.8, and 39.0 ± 0.6 °C for P. zonangulus. CTmax did not differ significantly between species in any of the acclimation treatments. Thermal stress was also examined by measuring P. clarkii and P. zonangulus hemolymph glucose concentration every two hours for crayfish acclimated at 26 °C for two weeks and water temperature increased 1 °C h–1. Hemolymph glucose concentration began to increase at 36 °C in P. zonangulus and 38 °C in P. clarkii. Large increases in mean hemolymph glucose concentration (±SE) were observed in both P. clarkii (67.19 mg–dl ± 24.55) and P. zonangulus (74.11 mg–dl ± 18.04) at 40 °C.