Ultrastructure of the olfactory epithelium in intact, axotomized, and bulbectomized goldfish, Carassius auratus

The ultrastructure of the olfactory epithelium in intact, axotomized, and b ulbectomized goldfish was studied by scanning and transmission electron mic roscopy. A total of 58 adult goldfish of various survival times were examin ed to determine whether the different types of surgery-either olfactory ner ve transection or bulbectomy-yielded differences in the extent or time cour se of cellular degeneration and renewal. Control animals were also examined in detail to elucidate previous controversial findings concerning the type s of olfactory receptor neurons present in goldfish. We found that the inta ct olfactory epithelium of unoperated control goldfish contains the previou sly observed ciliated and microvillous receptor neurons, and the crypt cell , a cell type not yet seen in the goldfish but recently reported in other s pecies of teleosts. Following either olfactory nerve transection or bulbect omy, the olfactory receptor neurons showed similar signs of degeneration an d subsequent cell death, but, surprisingly, the thickness of the olfactory epithelium did not change significantly with either treatment. The time cou rse of receptor cell renewal was different in axotomized and bulbectomized goldfish. In axotomized goldfish, the amount of receptor cells decreased co ntinuously until 8-13 days after surgery, followed by rapid cell renewal. F or bulbectomized goldfish, cell replacement began almost immediately after surgery, with degeneration and cell renewal occurring simultaneously. Six w eeks after bulbectomy, cell death and cell proliferation reached a "steady state," and the epithelia did not further improve. Microsc. Res. Tech. 45:3 25-338, 1999. (C) 1999 Wiley-Liss, Inc.