Feeding Behavior in Fish: Inluence of Long-Term Light Deprivation on Serotonin Effects in the Carp Cyprinus carpio L.

Abstract

The influence of long-term light deprivation (1 and 4 months) on the latency of leaving a start chamber (t₁), feeding latency (t₂), and food intake (or ration, R) was studied in carp Cyprinus carpio juveniles injected with serotonin (5-HT), as observed during 96 h post injection. It was found that 5-HT has no significant effect on t₁ regardless of the illuminance regime (constant dark in experiment vs. alternating light/dark in control) while exerting a maximum effect on t₂. One hour after 5-HT injection, t₂ increases 5 times in fish deprived of light for 1 month and 11.6 times in those deprived of light for 4 months as compared to the control group. A significant 5-HT-induced decrease in R was observed after 1 month both in experimental and control groups and after 4 months in the experimental (light-deprived) group only. Possible mechanisms underlying the effect of 5-HT on the above parameters of fish feeding behavior under conditions of long-term light deprivation are discussed.