Using a non-invasive method of recording of heart activity in crayfish Astacus astacus in early ontogenesis (1-9 months) and analysis of parameters of cycles of laser light cardiogram, it is shown that cardiac contraction rate (CCR) decreases with increases of weight and size of the animals. The range of changes of CCR parameters in air and in water is wider in larger crayfish of the same age, than in crayfish retarding from them in size and weight. This seems to allows the larger crayfish to be better adapt to environmental changes. It is shown that in crayfish, at change of environmental conditions, inotropic parameters of the cardiogram, amplitude of diastole and systole (DA and SA), change more, than chronotropic parameters, duration of diastole and systole (DD and SD). This may indicate that systems of regulation of inotropic parameters of the cardiac activity are the first to become mature in ontogenesis of the crayfish cardiovascular system; later, maturation of system of regulation of chronotropic parameters of the heart activity occurs. This is confirmed by results of experiments on adult crayfish. Analysis of correlations between parameters of cardiogram cycles in crayfish has shown that regardless of crayfish weight, higher correlation coefficient values are revealed between inotropic parameters of the heart activity cycles, than between chronotropic parameters. In larger crayfish, DD values are higher, than SD, whereas in stress, SD is longer than DD. During stress, the highest negative values of the correlation coefficient are revealed between CCR and DA, CCR and SA regardless of in which medium (air, water) the crayfish is placed.