Lateral movements of a massive tail influence gecko locomotion: an integrative study comparing tail restriction and autotomy

Abstract

Tails are an intricate component of the locomotor system for many vertebrates. Leopard geckos (Eublepharis macularius) possess a large tail that is laterally undulated during steady locomotion. However, the tail is readily shed via autotomy, resulting in the loss of tail function, loss in body mass, and a cranial shift in the center of mass. To elucidate the function of tail undulations, we investigated changes in limb kinematics after manipulating the tail artificially by restricting tail undulations and naturally by removing the tail via autotomy. Restricting tail undulations resulted in kinematic adjustments similar to those that occur following tail autotomy, characterized by more flexed hind limb joints. These data suggest that effects of autotomy on locomotion may be linked to the loss of tail movements rather than the loss of mass or a shift in center of mass. We also provide empirical support for the link between lateral tail undulations and step length through the rotation of the pelvic girdle and retraction of the femur. Restriction and autotomy of the tail limits pelvic rotation, which reduces femur retraction and decreases step length. Our findings demonstrate a functional role for tail undulations in geckos, which likely applies to other terrestrial vertebrates.

The ecology and evolution of autotomy

“…Recent research has built upon these findings by investigating the kinematic and morphological mechanisms that decrease locomotor performance after autotomy. For instance, Jagnandan & Higham () experimentally demonstrated that changes in the locomotion of lizards after tail loss were due to the absence of lateral undulations of the tail, rather than the loss of body mass per se or the anterior shift in the centre of mass. Additionally, in Anolis carolinensis , tail autotomy affected their in‐air stability while jumping (Gillis, Bonvini, & Irschick, ).…”

Patterns of growth in the presacral vertebral column of the leopard gecko (Eublepharis macularius)

“…Eublepharis macularius stores large quantities of fat in its tail (Cheek, 2005;Lynn et al, 2013;Jagnandan, Russell & Higham, 2014;Russell, Lynn, Powell, & Cottle, 2015), a load which must be compensated for in locomotion. The tail is held off the ground as the lizard walks at a normal pace, the standing wave produced by locomotory undulations of the trunk being transmitted as a travelling wave producing undulations in the tail (Jagnandan & Higham, 2017). The tail is autotomic (Cheek, 2005;Jagnandan et al 2014;Lynn et al, 2013;Russell et al, 2015), and loss of the entire tail results in the instantaneous loss of a considerable amount of weight (20-23% of total body mass in juveniles [Lynn et al, 2013]; 25% of total body mass in adults [Jagnandan et al, 2014]), and to the sudden absence of an appendage that plays a significant locomotory role (Gillis & Higham, 2016;Jagnandan & Higham, 2017).…”

“…The tail is held off the ground as the lizard walks at a normal pace, the standing wave produced by locomotory undulations of the trunk being transmitted as a travelling wave producing undulations in the tail (Jagnandan & Higham, 2017). The tail is autotomic (Cheek, 2005;Jagnandan et al 2014;Lynn et al, 2013;Russell et al, 2015), and loss of the entire tail results in the instantaneous loss of a considerable amount of weight (20-23% of total body mass in juveniles [Lynn et al, 2013]; 25% of total body mass in adults [Jagnandan et al, 2014]), and to the sudden absence of an appendage that plays a significant locomotory role (Gillis & Higham, 2016;Jagnandan & Higham, 2017). E. macularius adopts a more sprawling locomotory posture after tail loss, principally through adjustment of the angles adopted by the segments of the hindlimb, and pelvic rotation is reduced (Jagnandan & Higham, 2017;Jagnandan et al, 2014), but walking speed is unaffected (Jagnandan & Higham, 2017).…”

The vertebrate tail: a gene playground for evolution

“…Particularly, animals living in aquatic environments, such as fish or crocodiles, use their tail mainly as a propelling device [2,3]. Land vertebrates also benefit of the tail for locomotive purposes, either as an additional leg for kangaroos, facilitating walking mechanics in lizards, or serving as a counterbalance to help animals like cats or mice move through narrow or unstable surfaces [4][5][6][7]. An interesting variation upon this function was the evolution of prehensile tails, which allow grasping and holding to objects [8,9].…”