Tests on the locomotion of the elongate and limbless reptile Ophisaurus apodus (Sauna: Anguidae)

A series of Ophisaurus apodus was filmed while traversing plane surfaces, fields of nails and pins at different spacings, and channels of different diameter. Small individuals can practise slow lateral undulation on very rough surfaces, but with increased speed, all shift to slide-pushing, using either constrained bends of the body or very wide swings of the tail. In fields ofclosely-spaced pins, they travel by undulation, often pushing at a limited number of sites and pulling and pushing the trunk among these. Amid pins of wider spacing, the undulation involves some repositioning of curves. In channels, they utilize continuous bend concertina movement with the initial bend formed anteriorly and subsequent ones added, either to the level of the cloaca or on to the tail as well. The cloaca1 region cannot be established on the basis of locomotor pattern, as the propulsive waves pass smoothly from head to tail. Maximum voluntary velocities (of the centre of gravity) were 13 cm/s for slide-pushing, 55 cm/s for lateral undulation, and 3 cm/s for concertina movement. Propulsion is entirely effected by bending of the trunk; tests gave no evidence that the dorsal and ventral portions of the integumentary armour show significant anteroposterior displacement relative to each other.