ZEPNEWSKI, Eric*; NISHIKAWA, Kiisa: Collagen and Anuran tongues

In previous studies, three non-exclusive mechanisms which frogs use to protract their tongues have been identified. These include mechanical pulling (short tongue frogs), inertial elongation (long tongue frogs), and hydrostatic elongation. In an evolutionary context, mechanical pulling is the most basal, while hydrostatic elongation is the most derived. Along with the musculoskeletal differences there may be more subtle morphological differences which can account for behavioral variation among these frogs. In particular, the angle of the collagen fibers surrounding the tongue musculature may affect tongue protraction mechanics. Collagen fibers oriented at an angle greater than 54^� 44^� will facilitate elongation while fibers oriented at an angle less than 54^� 44^� will not. The data show a positive correlation between fiber angle and protraction length of anuran tongues. We hypothesized that the collagen fibers surrounding the tongue protraction musculature has evolved towards higher angles, which will facilitate a longer and more extensible tongue. In this research we compared the collagen fiber angles of a basal mechanical puller to a derived inertial elongator and a hydrostatic elongator. We predict that mechanical pullers will have fiber angles less than 54^� 44^� which will not facilitate elongation. Inertial elongators and hydrostatic elonagtors will have a more derived condition of having fiber angles oriented at angles greater than 54^� 44^�.