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

The musculature and innervation of the oesophagus of Homarus gammarus are described as a prerequisite to studies on the mechanisms and control of food ingestion. Of particular interest are two paired sensors (the anterior and posterior oesophageal sensors) which are bilaterally situated at the oesophageal-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. Oesophageal peristalsis is effected by the coordinated contraction of the Oesophageal 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 oesophageal nerve is used as an indication of oesophageal dilatation during peristalsis for studies on the feedback effects of the oesophageal sensors. Electrical and chemical stimulation of the posterior oesophageal sensors can initiate and increase the frequency of oesophageal peristalsis, while stimulation of the anterior oesophageal sensors can slow and terminate oesophageal peristalsis. The results are discussed and a model presented of the role of the oesophageal sensors in feeding.