Meeting Abstract

P3.143  Wednesday, Jan. 6  Pouch morphology and function in brown pelicans, Pelecanus occidentalis YANEGA, G.M.*; MEYERS, R.A.; National Evolutionary Synthesis Center (NESCent), Durham; Weber State University, Ogden gregor.yanega@nescent.org

The pouch of brown pelicans (Pelecanus occidentalis) is a highly derived and specialized structure, which expands to hold a volume of about 11 liters during diving. Previous work has shown that the mandibular rami bow due to a rostral bending zone that is only about 20% mineralized, and a lateral syndesmosis that is about 50% mineralized. Our current work examines the musculature of the pouch in order to determine (1) its homologies with the lingual and sublingual muscles of other birds (e.g., chicken, pigeon, egret), and (2) the function of these muscles in pouch opening and closing (water removal). We document the presence of large amounts of loose connective tissue in the pouch and tongue area, along with pleating/folding of the intraoral epithelium and external pouch skin, facilitating pouch expansion during feeding. Although the pouch is thin, and the tongue highly reduced, we found muscles throughout that we were able to homologize with those of other birds. Further, we found an elaborate network of elastin fibers within the floor of the mouth that we believe is important in passive pouch emptying. However, the Mm. serpihyoideus, mylohyoideus, and constrictor colli intermandibularis were all candidates for raising the floor of the mouth and evacuating water. We believe that rorqual whales are an appropriate model and may use analogous feeding and emptying mechanisms. In addition to feeding, the pouch is well-vascularized, and plays an important role in thermoregulation via gular fluttering; the pouch musculature must also be able to function in that role.