PRELIMINARY-STUDY OF THE LOCOMOTOR ABILITIES OF AMPHIBIA, GYMNOPHIONA

The locomotor kinematics of two morphologically different species of Gymnophonia, a slender (Grandisonia alternans) and a stout-type (Hypogeophis rostratus) were tested when faced to specified kinds of substrates, smooth-walled channels, field of pegs, diversely rough plane surfaces. The animals respond to the diverse situations through different modes of coordination of the musculo-skeletal and musculo-cutaneous systems. In channels, the slender and longer which possesses the smallest number of vertebrae uses concertina, while the stouter which has more vertebrae, uses a rectilinear motion. The comparison between the body velocity and a predicted velocity (wave frequency time the space travelled by one point of the body) yields an efficiency threshold. This optimum is reached for Grandisonia in channels and field of pegs, and for Hypogeophis on gravel. Beyond this threshold, the animals change their mode of coordination suggesting that the size and structural components constitute limiting factors facing to the external constraints.