Zepnewski, E.*; Nishikawa, K.: Connective tissue in ballistic tongues

Nerve transection experiments of the main tongue protractor muscle showed differences in feeding behavior between Rana pipiens and Bufo woodhousii. Bufo woodhousii shows a reduction in tongue protraction length without directional deviation. The tongueof R. pipiens, while also showing a reduction in extension, deviates toward the intact side. We hypothesize that the differences in behavioral responses are due to the amount and orientation of epimysial connective tissue surrounding the protractor muscle. Total amounts of collagen and elastin were measured for both species. Polarized light microscopy was used to measure the orientation angle of the collagen fibers surrounding the protractor muscle. Bufo woodhousii showed less connective tissue and fiber angles greater than 54⁰44^‘ which facilitates elongation. The tongue of R. pipiens contains greater amounts of connective tissue and fiber angles less than 54⁰44^‘ which resists elongation. This fact, combined with the loss of angular momentum due to unilateral denervation of the protractor muscle, may account for the deviation seen in R. pipiens. Previous studies have also shown Megophrys montana to be an inertial elongator. Based on normal feeding, we hypothesize collagen fiber angles in this species to also exceed 54⁰ 44^‘ yet be less than B. woodhousii. Megophrys montana may represent an intermediate between R. pipiens and B. woodhousii. Results from this study may have interesting evolutionary and ecological implications perhaps showing convergent evolution between distantly related taxa.