Morphology and odor sensitivity of regenerated snail tentacles.

This study examined certain structural and functional aspects of the olfactory system in regenerated posterior tentacles of the terrestrial snail Achatina fulica. Regeneration of the epithelial sensory pad occurs with accurate size regulation. All five neuronal cell types which are normally revealed by horseradish peroxidase backfilling are also regenerated. The sensory cells attain normal numbers at about 20 weeks postlesion. The organization of neuronal elements within the tentacle is chaotic, however, at early stages of regeneration. Even later, the digitlike extensions of the ganglion, which are characteristic of intact tentacles, fail to appear. The recovery of odor sensitivity was evaluated using a tentacular olfactormeter and a behavioral assay that involved locomotor orientation towards the odor stimulus. Thresholds and concentration-dependent response rates were equivalent for regenerated and intact tentacles, tested in the same animals, at 10 weeks post-lesion.