Contribution of the submentalis muscle to feeding mechanics in the leopard frog, Rana pipiens.
This study investigated the functional contributions of the submentalis muscle to the coordination of feeding behavior in the leopard frog, Rana pipiens. Additionally, the anatomical origins of the motor neurons innervating this muscle are identified and described. The m. submentalis is a small muscle connecting the distal mandibular tips. Depending upon the anuran species studied, this muscle contributes to mandibular bending and the degree to which the tongue is protracted, or has little or no role in feeding biomechanics. High-speed videography was used to quantify feeding attempts before versus after bilateral denervation of the m. submentalis. Additionally, the terminal branch of the trigeminal nerve prior to innervating the m. submentalis was retrogradely labeled to identify the origins of motor neurons innervating the muscle. For the kinematic analyses, denervation of the submentalis resulted in significant increases in the time to maximum tongue protrusion, and the duration of tongue protrusion. Neither mandibular bending, nor tongue length variables differed significantly between normal conditions and deafferented conditions. However, when unsuccessful feeding attempts were quantified following the denervation, failed attempts were nearly always due to the tongue not reaching the prey. None of the unsuccessful feedings prior to denervation were due to inadequate tongue protrusion. Anatomical data show a much larger rostral-caudal distribution of the trigeminal motor neurons than previously described for anurans. These data suggest a larger role for the submentalis muscle in Rana than in previously studied anurans with long protrusible tongues, and suggests a feedback mechanism from the trigeminal nerve to the nerves coordinating tongue protraction and retraction.
Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209, USA.
J Brock
JB
Wolff
Martin J
MJ
Lee
Curtis W
CW
Anderson
D000818:Animals; D001696:Biomechanical Phenomena; D005247:Feeding Behavior / Q000502:physiology*; D005453:Fluorescence; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D011894:Rana pipiens / Q000502:physiology*; D013997:Time Factors; D014059:Tongue / Q000502:physiology; D014276:Trigeminal Nerve / Q000502:physiology; D014741:Video Recording