MEHTA, Rita/S; MOON, Brad/R; University of Tennessee; University of Louisiana: Muscular Control of Constriction in Loxocemus bicolor

The epaxial muscles of snakes control a diverse set of behavior patterns related to locomotion and feeding. Constriction is a prey-handling behavior in which prey is immobilized by two or more points on a snake’s body. This behavior pattern is a behavioral homology for a large subset of the alethinophidia. Constriction has been lost and gained several times in advanced snakes. In colubroid lineages in which constriction is present, the behavior pattern is kinematically different from those of more basal snakes. Comparisons of epaxial muscle activity during constriction can be used to examine the homology of constriction behavior in basal and advanced snakes. During feeding in Gopher snakes the epaxial muscles fire while the snake begins constricting prey and are intermittently active during sustained constriction. Here we studied the postures and muscular control of constriction in the basal snake Loxocemus bicolor. In 14 feeding events by three individuals, Loxocemus used lateral bends to coil around mammalian prey. This bending pattern is similar to that in colubroids but differs from the ventral bending of boids. The epaxial muscles in Loxocemus fired during the beginning of a constriction event and also intermittently while constricting both live and dead mice. Therefore, lateral bending initiated by the epaxial muscles is homologous for majority of the alethinophidia. Boids appear to have evolved constriction postures and perhaps muscle activation patterns that differ from other lineages.