Degeneration of sensory and motor axons in transplanted segments of a crustacean peripheral nerve.

Segments of sensory and motor axons 0.3-0.5 mm in length were taken from crayfish peripheral limb nerves and transplanted into the abdominal cavity of the same animal. Transplanted sensory axons showed relatively few ultra-structural changes after one week, many had undergone complete lysis within two weeks, and almost all degenerated within three weeks. Transplanted motor axons appeared normal after one week, except for some hypertrophy of their surrounding glial sheaths. After two weeks, glial sheaths were grossly hypertrophied around motor axons; axonal mitochondria had increased in number and many had migrated from the periphery to the centre of the axon. The axonal membranes of all motor axons were still intact after three weeks, although most were no longer continuous after four weeks. By five weeks, all axonal material had completely disintegrated. These data suggest that axonal synthetic processes in crayfish sensory (and presumably motor) axons can maintain the axons relatively intact for 7-14 days and that transfer of substances form hypertrophied glial cells to motor axons may account for the longer survival times of transplanted motor axons.