Meeting Abstract

S2.7  Tuesday, Jan. 4  The development and evolution of mammalian swallowing CAMPBELL-MALONE, R*; CROMPTON, A W; THEXTON, A J; GERMAN, R Z; Johns Hopkins University; Harvard University; King’s College, London; Johns Hopkins University rzgerman@jhu.edu

Suckling is a synapomorphy that characterizes mammals. It consists of two distinct behaviors: (1) sucking, a cyclic tongue-based behavior, which is periodically interrupted by (2) swallowing, a reflex that empties milk from the pharynx into the esophagus. Infant feeding was recorded in four species, cats, macaques, opossums and pigs using simultaneous EMG and fluorographic/radiographic recording. During sucking, including intraoral transport, there were subtle differences amongst the species in the kinematics of tongue movement, and in the timing of EMG activities of tongue and hyoid muscles. These differences reflected craniofacial anatomy, particularly rostrum length, more than evolutionary relationships. Infant pigs and possums had a continuous flow of milk through the oral cavity, whereas infant cats and macaques used their tongue to interrupt and control the flow of milk. However, the kinematics and EMG patterns of the swallow are consistent across these species. The consistency of the EMG patterns in the infant mammalian swallow suggests a single evolutionary reorganization of the oropharyngeal apparatus. The subsequent diversification of adult mammalian feeding mechanisms was both made possible and limited by this evolutionary innovation. As Smith (1992) concludes, the reorganization of the mammalian oropharynx is as evolutionarily and functionally significant as the changes in the masticatory apparatus.