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 morphologic findings in two species of toothed whales, the Cuvier's beaked whale (Ziphius cavirostris) and the beluga or white whale (Delphinapterus leucas), which are discussed relative to their atypical feeding behavior and alimentary tract functions. Specifically, the findings show myenteric neural modifications and muscularis externa structural specializations which may support voluntary and involuntary fore- and hindgut behavior. Histologic evidence of intercalation-like striations in the gastric and colonic musculature was discovered, as well as an unusual 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 such as ingestion-by-sucking in the absence of prehensile teeth and processing of ingesta in a multi-compartmentalized pyloric stomach. Further, the hindgut modifications may help explain the animal's acute, rectal discharge escape mechanism, likened to squid inking, which seems to be an evolved function of some cetaceans.
Pfeiffer
C J
CJ
Department of Biomedical Sciences and Aquatic Medicine, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061.
D000818:Animals; D004064:Digestive System / Q000033:anatomy & histology* / Q000294:innervation; D004068:Digestive System Physiological Phenomena; D009132:Muscles / Q000033:anatomy & histology / Q000502:physiology; D014907:Whales / Q000033:anatomy & histology* / Q000502:physiology