Muscle activity in autotomized tails of a lizard (Gekko gecko): a naturally occurring spinal preparation

Abstract

We quantified muscle activity in tails of lizards (Gekko gecko) during running and after autotomy of the tail. We chose different animals and varied where we broke the tails in order to obtain three experimental preparations having: no regenerated tissue or prior tail loss (non-regenerated), a large regenerated portion and a few original caudal vertebrae (partially regenerated), and only regenerated tissue (fully regenerated). All observed axial motor patterns were rhythmic. During running of intact animals, muscles in non-regenerated tails were activated in an alternating, unilateral pattern that was propagated posteriorly. After autotomy, non-regenerated tails had unilateral muscle activity that alternated between the left and right sides and propagated anteriorly. Autotomized, partially regenerated tails had unilateral, alternating muscle activity that lacked any longitudinal propagation. Autotomized, fully regenerated tails had periodic muscle activity that occurred simultaneously for both left and right sides and all longitudinal positions. Neither tactile stimulation nor removal of the tail tip prior to autotomizing the tail affected the motor pattern. Several features of the motor pattern of autotomized tails changed significantly with increased time after autotomy. Autotomized tails with one or more spinal segments moved longer and more vigorously than autotomized tails consisting entirely of regenerated (unsegmented) tissue.

Losing stability: tail loss and jumping in the arboreal lizardAnolis carolinensis

“…25% vs 50% of tail) will also be an important step toward a more ecologically relevant understanding of autotomy in relation to jumping behavior. We note that many lizards commonly lose parts of tails naturally (Vitt et al, 1977) and recover them relatively quickly by regeneration (Hughes and New, 1959;Rumping and Jayne, 1996) and therefore such manipulations do not cause longterm damage to the animals.…”

“…This remarkable ability has evolved multiple times within lizards and different species exhibit a range of mechanisms enabling tail loss, such as fracture planes between or within vertebrae, and a host of modifications to other tail tissues, including blood vessels and musculature (Etheridge, 1967). After separation, the muscles of the autotomized tail can continue to contract and these movements act to distract a predator long enough for the lizard to escape (Dial and Fitzpatrick, 1983;Naya et al, 2007;Rumping and Jayne, 1996).…”

Time-varying motor control of autotomized leopard gecko tails: multiple inputs and behavioral modulation

“…In many animals, the autotomized appendage is not notably active after it has been disconnected from the individual that releases it. In some lizards, however, the autotomized tail often moves (sometimes vigorously) for a substantial amount of time following its detachment (Rumping and Jayne, 1996;Higham and Russell, 2010). Although it is understood that tails can move following autotomy, we know little about the time-varying patterns of neuromuscular activity that induce these movements.…”

“…Two studies have examined muscle activity patterns using electromyography (EMG) in the autotomized tails of geckos (Rumping and Jayne, 1996;Higham and Russell, 2010). These studies revealed interesting differences between an arboreal gecko (Rumping and Jayne, 1996) and a desert-dwelling terrestrial gecko (Higham and Russell, 2010).…”

“…These studies revealed interesting differences between an arboreal gecko (Rumping and Jayne, 1996) and a desert-dwelling terrestrial gecko (Higham and Russell, 2010). Unlike the arboreal gecko, the tail of the terrestrial gecko exhibits complex motor patterns that result in diverse and highly variable movements.…”