Abdul Majeed, N. | bioRxiv Science

bioRxiv2022

Symbolic quantitative cognition in wild zebrafish (Danio rerio)

Zebrafish (Danio rerio) constitute an excellent model system to investigate the neural and genetic basis of quantitative cognition We tested the ability of reward quantity discrimination of wild-type zebrafish in an associative learning task. We used an operant conditioning paradigm in which the number of horizontal lines zebrafish approached in a 2-alternative forced choice task predicted the number of food reward pellets they would receive. Zebrafish did not learn a preference for the 2-line stimulus predictive of receiving 2 food pellets. However, a subset of the fish performed significantly above chance in a discrimination task with the same apparatus, in which the 2-line stimulus was associated with the same reward but the choice of the 1-line stimulus was not rewarded. Zebrafish also showed a population level learning in a simpler spatial association task with the same apparatus. We also explored the explanatory value of alternative spatial learning hypotheses such as a Win-Stay, Lose-Shift (WSLS) strategy at the individual level for fish in navigating these spatially randomised tasks.

animal behavior and cognition↗

bioRxiv2020

To group or not to group: Effect of prolonged exposure to predation and resource availability on the shoaling behaviour of zebrafish (Danio rerio)

Individuals of many species live in groups to obtain anti-predatory advantages, foraging benefits and for social reasons. Living in large groups can reduce predation, but as group size increases, competition for resources also increases. The trade-off between the advantages of group living for an individual and competition caused by it can determine group dynamics, and this trade-off can vary with environmental conditions. Shoaling behaviour, the tendency of fish to form groups, is shown to be affected by factors such as resource availability, presence of predators and conspecifics. Although studies indicate that both predation and starvation pressure in an environment can determine whether fish choose to shoal or not, whether prolonged exposure to such conditions influences shoaling behaviour remains little explored. Here, we test how predation pressure and resource availability may interactively shape the shoaling behaviour of zebrafish (Danio rerio) when exposed to combinations of these pressures over a two-week period. We find that shoal size increases with predation and decreases with starvation, and that greater predation pressure increases shoaling tendencies even under reduced food availability. Overall, we show that prolonged exposure to varying predation pressure and resource availability can together influence shoaling tendencies of fish even when such pressures are relaxed. Significant statementIn group living species, group structure and dynamics depend on various intrinsic factors and environmental stressors. Shoaling behaviour in fish, where individuals aggregate to form groups, is shown to be altered with environmental factors such as predation and resource availability. Although studies have examined the effects of these cues on shoaling behaviour, the ecological circumstances experienced by fish could also influence shoaling tendencies. We here show that shoaling behaviour is also shaped by previous experience of fish to predation and food resource availability. We check how shoaling behaviour varies with differences in predation pressure and resource availability after prolonged exposure to these conditions by measuring the shoal size and shoal cohesion in zebrafish. This study illuminates how shoaling tendencies of individuals shaped by the environmental conditions persist even when these environmental pressures are removed.

animal behavior and cognition↗