Jenna Monroy

Microhylid and hemisomatid frogs have the unique ability to aim their tongues in three dimensions during protraction. Many of these frogs are fossorial, specializing on termites or other small insects for food. Aiming their tongues enables the frogs to re main in one place while feeding. Both families use a hydrostatic mechanism for elongation in which the protractor muscle, the m. genioglossus, contracts to decrease the height thereby increasing the length of the tongue. This mechanism permits a large var iability in the velocity and acceleration of protraction. Hemisus marmoratum, the pig-nosed frog protracts its tongue at a relatively low velocity and acceleration compared to other frogs. The neural control of the m. genioglossus has changed to increase precision and accuracy by increasing the number of motor units. These smaller motor units have lower conduction velocities which slows the velocity at which the tongue is protracted. My goals are to investigate the aiming ability of other hydrostatic elongators that protract the tongue at higher velocities and accelerations. Faster protractors may have less control over the tongue in three dimensions because they have larger, faster contracting motor units. I plan to describe the pattern of activation of the tongue muscles, the nervous innervation, and aiming ability of several hydrostatic elongators.

Publications:

Brainerd, E. L. and Monroy, J. A. (1998) Mechanics of lung ventilation in a large aquatic salamander, Siren lacertina. J. Exp. Biol. 201: 673-682.full text (PDF)

Meyers, J.J., O'Reilly, J.C., Monroy, J.A. and K.C. Nishikawa 2004. Mechanism of tongue protraction in microhylid frogs. J. Exp. Biol. 207, 21-31. full text (PDF)