MARTINEZ, V.G.; ZORAN, M.J.; Texas A&M University; Texas A&M University: Giant Axon Morphallaxis During Segmental Regeneration Of Lumbriculus variegatus

Lumbriculus variegatus, a freshwater oligochaete worm, demonstrates patterned regeneration of lost body parts and morphallaxis of original body parts (neural reflexes and behavior) following segmental amputation. Axial gradients in neurophysiological function of medial and lateral giant fibers provide a model system for the study of the neural plasticity underlying morphallaxis of synaptic function, axonal morphology, and reflexive behavior. Following isolation of anterior and posterior segments, giant fiber sensory fields and conduction velocities are modified during regeneration to reflect new segmental positions (Dev.Bio. 138:94-103). Fluorescence imaging following neurobiotin injections demonstrates strong dye-coupling between segmentally-arranged giant axons in both control and regenerating fragments. Dye-coupling coefficients, based on fluorescence intensity, range from 0.55 to 0.25 depending on segmental level. Dye-coupling between medial axons is increased and the size of lateral axons is decreased during morphallactic plasticity of posterior fragments to more anterior segmental positions. Thus, axonal size and segmental coupling are important loci of changes in giant fiber pathways during neural morphallaxis. VGM is supported by T32MH18882