Thermal Tolerance of Cyclops bohater (Crustacea: Copepoda: Selection of Optimal and Avoided Conditions in Experimental Conditions

Temperature adaptations of ectothermic species as well as the plasticity of their thermal strategies are important for survival during temperature fluctuations, in particular, caused by global warming. The critical thermal maximum (CTM)—the values of the water temperature at which heat shock was noted (loss of motor activity in case of copepods) was determined under laboratory conditions. The “chronic” method was used to identify the temperature preferences of the copepods in which a group of test organisms are placed into a thermogradient apparatus. The main result is that in the experiment for individuals of the summer generation C. bohater, the optimal thermal conditions (FTP) were within 6–11 °C. Summer generation of this copepod in natural water bodies develops at a temperature of 5–12 °C, which is close to FTP in the experiment. At the same time, the thermal resistance of C. bohater (CTM 31.5 °C) was found to be the lowest among the species of the genus Cyclops. The differences between the thermal preferences of the winter and summer generations expand the temperature of normal performance (TNP) range and indicate a high physiological plasticity of the C. bohater population. This property is likely to allow C. bohater to survive as the climate continues to warm.