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Kirby, Sarah., Sharon Wise, and Adam Pack. 2006

Neuroanatomy of tail autotomy in Redback Salamanders (Plethodon cinereus): neuronal source of muscular control



Sarah Kirby sectioning salamander tailSalamander Tail Cross Section
Tail autotomy (loss of the tail) is a common antipredator tactic for lizards and salamanders. Redback salamanders (Plethodon cinereus) are able to autotomize, and motor neurons are responsible for this autotomy, their tail at any point along the tail by contracting their muscles between vertebrae. The source of the signal to the lower motor for tail autotomy is unknown; the pathway may be a reflexive arc or a descending tract from the brain. Previous research supports the hypothesis that the neuronal signal does not come from the brain but is localized in the spinal cord. To determine the pathway we collected 25 individuals of P. cinereus from Frankfurt, New York. We mechanically pinched the tail to induce tail autotomy in some salamanders and induced just muscle constriction and not tail autotomy in others. A third group of salamanders were left untreated as a control. We fixed all three groups of salamanders and embedded them in araldite plastic for serial sectioning. Histologically, we can then identify the muscles used by the salamanders for tail autotomy. Using a computer program NIH image, we will create a 3D image based on serial sections of tails stained with hemotoxylin and eosin. Once the muscles responsible for tail autotomy have been identified, we will identify the nerves innervating the muscles using silver nitrate. We will then, by using the same computer program, be able to trace the nerves that innervate the constricting muscles to the spinal cord where we believe the signal originates. These two observations will allow us to properly identify the muscles and nerves involved in tail autotomy. We will then be able to determine if the neuronal signal for tail autotomy originates in the brain or spinal cord.