Meeting Abstract
Food processing describes any kind of mechanical reduction or preparation of food items prior to deglutition. The most commonly used processing mechanism in gnathostomes is ‘chewing’. Chewing is defined as any form of intraoral processing by rhythmic jaw movements and represents the most common processing mechanism in tetrapods. Non-mammalian tetrapods typically have a hinge-like jaw joint that only permits simple arcuate (open/close) movements of the mandible during chewing. By contrast, the specialized jaw systems in most mammals permit complex 3-D movements of the mandible involving propalineal (longitudinal) as well as transverse (lateral) movements. However, only limited information is available on intraoral processing mechanisms in reptiles and lissamphibians. In fact, it was generally accepted that many reptiles and most lissamphibians do not process food intraorally but rather swallow it whole and unreduced. Here, we use biplane high-speed fluoroscopy and 3D kinematics analyses to show that the neotenic salamander Siren intermedia not only uses intraoral food processing but also relies on a mandibular motion pattern involving propalineal (11.72 ± 3.49 % of cranial length) as well as transverse (4.95 ± 2.05 ° angular displacement at the mandibular symphysis) movements. The mandibular motion pattern seen in Siren involves a complexity not previously documented for non-mammal tetrapods. Our data on intraoral food processing in lissamphibians also challenge the commonly held view that complex chewing movements are restricted to mammals.
