Meeting Abstract

49.4  Tuesday, Jan. 5  The ontogeny of feeding systems in caecilians (Lissamphibia: Gymnophiona) – sucking, scraping, and biting KLEINTEICH, T; University of Hamburg thomas.kleinteich@uni-hamburg.de

The caecilian feeding system is unique among vertebrates in that two jaw closing mechanisms are integrated: jaw closure is driven by the ancestral jaw closing muscles (mm. levatores mandibulae) plus a secondarily recruited hyobranchial muscle (m. interhyoideus posterior). The caecilian skull is kinetic due to a movable quadrate-squamosal complex. There is a variety of feeding habits (suction feeding, skin feeding, intrauterine feeding, biting) at different stages of caecilian ontogeny, that relate to different reproductive modes. Here I will compare functional parameters of the caecilian feeding system (i.e. lever arm lengths, muscle physiological cross sectional areas, muscle fiber orientations, effective mechanical advantages, estimated bite forces) over ontogeny in three species with different feeding habits. Suction feeding specimens differ notably in their feeding system morphology from specimens that apply skin or intrauterine feeding. In suction feeding caecilians, the ancestral jaw closing musculature has the largest physiological cross sectional area and is supposed to generate the highest forces within the dual jaw closing system. In skin and intrauterine feeding individuals, the additionally recruited m. interhyoideus posterior is the most powerful muscle. Muscle fiber orientation of the ancestral jaw closing muscles relative to the lower jaw is acute-angled in suction feeders and approximately perpendicular in skin and intrauterine feeding caecilians. Differences in muscle fiber orientation reflect different patterns of optimization for velocity (suction feeding) vs. force (skin and intrauterine feeding). The jaw closing system of suction feeding specimens is limited to gape angles less than 35°; skin and intrauterine feeding caecilians feed with wider gape angles.