Transsexual limb transplants in fiddler crabs and expression of novel sensory capabilities.

We used transsexual limb transplants in fiddler crabs to examine how peripheral sensory structures interact with the central nervous system (CNS) to produce a sexually dimorphic behavior. Female and male chemosensory feeding claws were transplanted onto male hosts in place of nonfeeding, nonchemosensory claws. Successfully transplanted claws retain donor morphologies and contain chemosensory neurons. Neurons in successfully transplanted female feeding claws express the enhanced sensitivity to chemical cues seen in female, but not male, neurons in claws of normal animals. When chemically stimulated, the transplanted claws evoke feeding behavior not observed in normal males, even though the sensory neurons in the transplanted limb project to the host's sexually dimorphic neuropil not known to receive chemosensory input. Behavioral sensitivity is directly related to the sensitivity of peripheral neurons in the transplanted feeding claw. Thus, the interactions between peripheral neurons and their targets may restructure the CNS so that novel sensory capabilities are expressed, and this can produce sexually dimorphic behaviors.