The heart of the crustaceans has its own pacemaker neurons inside the heart, which are composed of 9 neurons. The neurons receive innervations of only three kinds of axons originated from the central nervous system; one pair of inhibitory and two pairs of acceleratory axons. Thus, in terms of the neural cardiac control from higher center, this system may have much more simplistic operation comparing to our hearts, because those vertebrate hearts receive hundreds of central nerve fibers so called the autonomic nervous system; sympathetic and parasympathetic nerves. This simplicity of the crustacean hearts may have a great advantage for physiological and physical understanding for the essential mechanism of the heartbeat control. Thus, we performed time series analysis of ECG data of Japanese spiny lobster, Panulirus japonicus. The ECGs were recorded in three conditions of the heart. The isolated hearts, which are obviously disconnected from the center but are well maintained at a steady condition, and the intact hearts, heartbeats of which were recorded at either a freely moving condition or a stressful condition receiving severe immobilizing stress. DFA (Detrended Fluctuation Analysis) revealed a difference of operation of the CNS. The three conditions of the hearts were found to have different scaling properties. Focusing on the difference between the scaling exponents of the isolated heart and the stressful heart, both of which had, intriguingly, almost identical power spectra, we will discuss the possibility to index the CNS operation by means of the scaling exponents.