Fast regeneration of the olfactory nerve in goldfish: fine structure and behaviour.

Normal olfaction-guided behaviour in goldfish returns surprisingly fast after bilateral transection of the olfactory nerve (ON). In order to find correlation between morphological changes and behaviour we performed parallel studies on the behaviour of the fish and the ultrastructure of the olfactory bulb in axotomised fish. Signs of degeneration were most prominent between the 4th and 6th day post-operatively. First appearance of regenerated ON fibres and terminals was noted on the 10th post-operative day. ON terminals became frequent again two weeks after the operation. This supports earlier suppositions that morphological regeneration plays a crucial role in the fast and complete restoration of olfaction-guided behaviour.