Segmental control of midbody peristalsis during the consummatory phase of feeding in the medicinal leech, Hirudo medicinalis.

Abstract

The ingestive behavior of the medicinal leech includes peristalsis-like movements of the midbody that are organized into both rostral-to-caudal and caudal-to-rostral waves (C. M. Lent, K. H. Fliegner, E. Freedman, & M. H. Dickenson, 1988). The neuronal control of this behavior is unknown. Using surgical manipulations and electromyograms, the authors show that (a) the head and tail ganglia are not necessary for this behavior; (b) the circuit is distributed, with components reiterated along the length of the leech; (c) excitatory signals transmitted from rostral segments via the nerve cord can initiate peristalsis in "empty" caudal segments; (d) inhibitory signals from caudal segments limit the frequency of peristalsis; and (e) stretch of the gut and/or body wall is sufficient to produce peristalsis in the absence of heat or chemical cues. These results are compared with peristalsis in the digestive tract of mammals. The leech may be a good model for studying peristalsis-like behaviors at the cellular level.