On the rhythmical coupling of the axial and appendicular systems in small terrestrial lizards (Sauria : Gymnophthalmidae)

No previous study of the relative movements of the limbs and of the vertebr al axis has previously attempted to understand coupling and decoupling acti ons, Micrable-pharus maximiliani and Colobosaura modesta, from open habitat s of Brazil, offer a good opportunity for testing the functionality of the association between the basic locomotor systems. Experimental animals were set in maximally constraining conditions, causing drastic reductions in the potential sites for exchange of forces. Basic kinematic patterns of limbs and axial movements are described and discussed for three different conditi ons of substrate roughness. An axial travelling wave during lateral undulat ion can be associated with a relatively short trunk, interlimb distance cor responding to 50 or 75% of the axial wave length. This is coupled to a trot . Comparison of body speed (U) and wave axial speed (V) allows determinatio n of when limb activity is added to axial propulsion. Competition occurs be tween vertebral axis and limbs which are never in phase relation, even when their frequencies are similar. Axial movements proved to be the main locom otor effector in quadrupedal as well as in limbless Gymnophthalmidae. It is suggested that this predominant role facilitates trends toward limblessnes s.