The Anatomy and Physiology of the Stomatogastric Nervous System of Squilla : II. The Cardiac System : Physiology

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A subsystem of the stomatogastric ganglion (STG) of the mantis shrimp, Squilla oratoria, which controls movements of the cardiac stomach was studied. Muscles of the cardiac stomach and their motor nerves leaving the STG are described. The paired anterior ventricular nerves and paired lateral ventricular nerves (lvn), which exit the STG, contain the motor axons that control muscular contractions of the cardiac stomach. One pair of superior oesophageal nerves (son) also carry motor axons. The lvn and son give rise to several peripheral nerves which innervate 8 identified muscles. Spontaneous motor activity recorded from the lvn and son (termed the cardiac cycle) has a long cycle period (ca. 10sec) and consists of alternate firing of bursts by two motor neuron groups. Cardiac cycles similar to spontaneous ones are triggered by stimulation of afferent fibers entering the commissural ganglia. Four constrictor and 3 dilator motor neurons in the STG are identified. They are involved in sequential movements of the dorsal and lateral gastric walls of the cardiac stomach. The function of the cardiac cycle is described with reference to the maceration and transfer of food. It is compared to that of the posterior cardiac plate and pyloric cycle (pcp-pyloric cycle) which has been described previously. Comparisons are made of the cardiac systems in STG of stomatopods and decapods.
1988-04-15