Despite the fact that abdominal muscle receptor organ crayfish is one of the most thoroughly studied objects in neurobiology, the ultrastructural mechanisms that make up its two different operating systems are disclosed insufficiently as the focus of these papers was paid to the area of representation of dendrites of sensory neurons in the receptor muscles. Detailed comparative analysis of the fine structure of the soma sensory cells was not conducted. In the present study, we have investigated the ultrastructure of soma of slow- and fast-adapting sensory neurons of abdominal muscle receptor organ Astacus leptodactylus with special attention to the differences between the two systems. Differences in the fine structure of the main cell organelles have been identified and quantified. We have discovered a relatively high concentration of mitochondria in sensitive cells of slow type receptor as well as a large total area of tanks of the endoplasmic reticulum cells in neurons of faster system. We have assumed that the differences revealed in the fine structure of organelles in soma of sensory neurons between the two types of receptors might be partially responsible for the speed of adaptation and for sensitivity thresholds observed in the physiological experiments.