Oesophageal sensors and their modulatory influence on oesophageal peristalsis in the lobster, Homarus gammarus

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Abstract
The musculature and innervation of the esophagus of H. gammarus are described as a prerequisite to studies on the mechanisms and control of food ingestion. Paired sensors (the anterior and posterior esophageal sensors) are bilaterally situated at the esophageal-cardiac sac valve. These are similar to contact chemoreceptors previously described in insects and are classified as such on morphological grounds and with indirect electrophysiological evidence. Esophageal peristalsis is effected by the coordinated contraction of the esophageal musculature. This is controlled by rhythmical bursting neuronal activity, which can be recorded from the nerve trunks in the area. A characteristic burst recorded from the superior esophageal nerve is used as an indication of esophageal dilatation during peristalsis for studies on the feedback effects of the esophageal sensors. Electrical and chemical stimulation of the posterior esophageal sensors can initiate and increase the frequency of esophageal peristalsis, while stimulation of the anterior esophageal sensors can slow and terminate esophageal peristalsis. The results are discussed and a model presented of the role of the esophageal sensors in feeding.