A possible advantage of displaying the tail: a comparison between the tail and body integument structure in Amphisbaena alba and Leposternon microcephalum (Squamata, Amphisbaenia)

Amphisbaena alba when in a defensive position adopts a horseshoe posture, raises its head and tail and opens its mouth. The tail is rigid; the dorsal surface often has non-pigmented areas which resemble scars. Leposternon microcephalum lives sympatrically with A. alba; it has a soft tail which does not appear to be involved in defensive display. Both species have been observed in captivity. The height to which A. alba raises head and tail during defensive display was measured. Morphometrics and morphology of the integument structure in both species were studied in the body and in the tail from the collagen bundles organization viewpoint. The results reveal a mechanical resistance of the tail in A. alba, but not in L. microcephalum. It is possible that this structure, formed of a dense piece of collagen, serves as a ‘biting block’ ; lesions caused by potential predators could cause no great harm. The skin of the remainder of the body in A. alba (but not in L. microcephalum) is also very resistant; the animal is practically covered by a flexible armour.