Projections of the olfactory tract fibers in the nurse shark (Ginglymostoma cirratum)

Summary Five nurse sharks were killed between 6 and 43 days after the olfactory tract had been cut unilaterally. Whereas the axon degeneration was demonstrated best with the Nauta-Laidlaw technique after 3–4 weeks survival time, the terminal degeneration, as identified in Fink-Heimer preparations, was best seen in a 13-day specimen. The distribution of olfactory tract fibers is entirely ipsilateral to the lesion, the majority terminating near the attachment of the olfactory peduncle to the hemisphere. Terminal degeneration is restricted caudally to a tongue-like extension of the lateral olfactory area on the ventral surface of the hemisphere with a spill-over into the area superficialis basalis of Johnston. The results indicate that the distribution of olfactory bulb fibers in the shark is much more restricted than had been suggested by most earlier descriptions based on studies of normal material.