The gastrointestinal tract of Adélie penguins – morphology and function

Abstract

The aim of this study was to provide data on the morphology of the gastrointestinal tract of Adelie penguins (Pygoscelis adeliae). It was found to consist of a long oesophagus, a two-chambered stomach, a small intestine measuring only 5.2×body length, two rudimentary caeca and a short colon, typical of carnivorous birds. The stomach comprised a glandular proventriculus and a muscular gizzard that frequently contained grit. An acidic pH was recorded in both chambers. Ultrastructural studies of the small intestinal mucosal membrane revealed epithelial cells with elongated, irregular microvilli and high affinity for toluidine blue, absorptive intestinal epithelial cells and goblet cells. Numerous large lymphocyte-like cells were observed close to the brush border of the epithelium, and empty spaces on the epithelial surface reflected normal cell loss in the small intestine. The rudimentary caeca and colon provide relatively little volume and time for symbiotic bacteria to aid the digestion of crustacean chitin.