In goldfish the discriminative ability for odours persists after reduction of the olfactory epithelium, and rapidly returns after olfactory nerve axotomy and crossing bulbs

Abstract

Gold¢sh are ideal vertebrates for the study of regeneration within the peripheral and the central olfactory system. The present behavioural investigations studied the e¡ects of bilateral lesions on the animals' ability to qualitatively discriminate two amino acids (10 7 6 M) and their performance in two more di¤cult tasks: (i) rewarded amino acid applied in a lower concentration, and (ii) rewarded stimulus contaminated. A 50 and 85% reduction of the olfactory epithelium resulted in no recordable behavioural de¢cit. After axotomy of olfactory nerves and lateral olfactory tractotomy, ¢shes were anosmic for seven to ten days. Following replacement of sensory cells in the epithelium, and after regeneration of olfactory tract ¢bres a full functional recovery, i.e. a highly speci¢c regeneration, was recorded. After three surgical modi¢cations of the olfactory bulbs' position, (i) crossing olfactory tracts and bulbs, (ii) crossing tracts and turning bulbs, and (iii) turning bulbs upside down, a full functional recovery was recorded for amino-acid discrimination in a similar concentration. A permanent, and similar slight de¢cit was, however, found during application of di¡erent concentrations, and of contaminated stimuli when medial lateral halves of the bulb were in`incorrect' position (i) and (iii), or olfactory bulbs were positioned in the vicinity of the contralateral epithelium (i) and (ii).

Alteration of the chemical environment disrupts communication in a freshwater fish

“…Chemoreceptor regeneration time is unknown in Xiphophorus, but full regeneration may not even be necessary for certain olfactory discrimination tasks. In goldfish, behavioural responses and amino-acid discrimination ability persisted even after the surface of olfactory epithelium was reduced by 85% (Zippel 2000). Control females that were tested in water without supplemental HA throughout the series of trials consistently showed a strong significant preference for conspecific male odour, suggesting that the response profile of experimental females was due to the effects of HA rather than to habituation to the stimuli.…”

Aggregation of F-Actin in Olfactory Glomeruli: a Common Feature of Glomeruli Across Phyla

“…Despite these obvious differences in glomerular organization, the olfactory system of lower vertebrates, e.g. fish, was shown to perform with high sensitivity in olfactory discrimination tasks and expresses a remarkable regenerative capacity (Zippel, 2000).…”

Network formation and reorganization of the olfactory system of Xenopus laevis

“…This rewiring timeframe is in line with our results in Xenopus larvae (Hawkins et al, 2017). The same authors report that within the same timeframe after ON axotomy also odor-guided behaviour returns (von rekowski and Zippel, 1993;Zippel, 2000). This suggests that in goldfish the regeneration of the whole olfactory system and the sense of smell may be faster than in Xenopus larvae.…”

“…A fast return of olfactory-guided behavior after ON transection has also been observed in goldfish (Hoyk et al, 1993;Zippel, 2000). These researchers showed that after bilateral ON axotomy, regenerated ON fibres and terminals became again visible in the OB about 10 days and two weeks post transection.…”