The Kinematics of Prey Capture and the Mechanism of Tongue Protraction in the Green Tree Frog Hyla Cinerea

Abstract

Prey capture was studied in the green tree frog (Hyla cinerea) before and after denervation of either the m. genioglossus or m. submentalis using high-speed videography and kinematic analysis. The prey capture behavior and extent of tongue protraction of several members of the subfamilies Hylinae, Pelodryadinae and Phyllomedusinae were also studied. Results show that the m. genioglossus is necessary to produce complete tongue protraction and that the m. submentalis is necessary for mandibular bending, but not necessary for complete tongue protraction in Hyla cinerea. The tongue of Hyla cinerea resembles the weakly protrusible tongues of the archaeobatrachian frogs Ascaphus and Discoglossus more than the highly protrusible tongues of other neobatrachians, such as Rana or Bufo. A weakly protrusible tongue is present in the subfamilies Hylinae and Pelodryadinae, and a highly protrusible tongue is present in the subfamily Phyllomedusinae. These results suggest that hyline and pelodryadine hylids have retained the ancestral anuran tongue morphology and that highly protrusible tongues have evolved once within the family Hylidae, in the subfamily Phyllomedusinae.