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

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.