NEURAL AND MUSCULAR CONTROL FUNCTIONS OF THE GUT IN ODONTOCETES - MORPHOLOGIC EVIDENCE IN BEAKED-WHALES AND BELUGA WHALES

The present data provide some new and unique. gastrointestinal morphol ogic findings in two species of toothed whales. the Cuvier's beaked wh ale (Ziphius cavirostris) and the beluga or white whale (Delphinapteru s leucas). which are discussed relative to their atypical feeding beha vior and alimentary tract functions. Specifically, the findings show m yenteric neural modifications and muscularis externa structural specia lizations which may support voluntary and involuntary fore- and hindgu t behavior. Histologic evidence of intercalation-like striations in th e gastric and colonic musculature was discovered. as well as an unusua l massive size of the colonic myenteric plexuses. These observations. which are not evident in terrestrial mammalian gastrointestinal tracts . may help explain the unusual upper gastrointestinal tract motility s uch as ingestion-by-sucking in the absence of prehensile teeth and pro cessing of ingesta in a multi-compartmentalized pyloric stomach. Furth er. the hindgut modifications may help explain the animal's acute. rec tal discharge escape mechanism. likened to squid inking. which seems t o be an evolved function of some cetaceans.