Shoaling promotes place over response learning but does not facilitate individual learning of that strategy in zebrafish (Danio rerio)

Mechanisms of collective learning: how can animal groups improve collective performance when repeating a task?

Learning is ubiquitous in animals: individuals can use their experience to fine-tune behaviour and thus to better adapt to the environment during their lifetime. Observations have accumulated that, at the collective level, groups can also use their experience to improve collective performance. Yet, despite apparent simplicity, the links between individual learning capacities and a collective's performance can be extremely complex. Here we propose a centralized and broadly applicable framework to begin classifying this complexity. Focusing principally on groups with stable composition, we first identify three distinct ways through which groups can improve their collective performance when repeating a task: each member learning to better solve the task on its own, members learning about each other to better respond to one another and members learning to improve their complementarity. We show through selected empirical examples, simulations and theoretical treatments that these three categories identify distinct mechanisms with distinct consequences and predictions. These mechanisms extend well beyond current social learning and collective decision-making theories in explaining collective learning. Finally, our approach, definitions and categories help generate new empirical and theoretical research avenues, including charting the expected distribution of collective learning capacities across taxa and its links to social stability and evolution. This article is part of a discussion meeting issue 'Collective behaviour through time'.

Fentanyl Induces Novel Conditioned Place Preference in Adult Zebrafish, Disrupts Neurotransmitter Homeostasis, and Triggers Behavioral Changes

Abuse of new psychoactive substances increases risk of addiction, which can lead to serious brain disorders. Fentanyl is a synthetic opioid commonly used in clinical practice, and behavioral changes resulting from fentanyl addiction have rarely been studied with zebrafish models. In this study, we evaluated the rewarding effects of intraperitoneal injections of fentanyl at concentrations of 10, 100, and 1000 mg/L on the group shoaling behavior in adult zebrafish. Additional behavioral tests on individual zebrafish, including novel tank, novel object exploration, mirror attack, social preference, and T-maze memory, were utilized to evaluate fentanyl-induced neuro-behavioral toxicity. The high doses of 1000 mg/L fentanyl produced significant reward effects in zebrafish and altered the neuro-behavioral profiles: reduced cohesion in shoaling behavior, decreased anxiety levels, reduced exploratory behavior, increased aggression behavior, affected social preference, and suppressed memory in an appetitive associative learning task. Behavioral changes in zebrafish were shown to be associated with altered neurotransmitters, such as elevated glutamine (Gln), gamma-aminobutyric acid (GABA), dopamine hydrochloride (DA), and 5-hydroxytryptamine (5-HT). This study identified potential fentanyl-induced neurotoxicity through multiple neurobehavioral assessments, which provided a method for assessing risk of addiction to new psychoactive substances.

Teleost Fish as an Experimental Model for Vaccine Development

Advances in vaccine development depend on animal models to test innovative therapies. Recent studies have reported the successful introduction of teleost fish as a new vertebrate model in scientific research, with emphasis on the species Danio rerio (zebrafish). This chapter aims to give an overview of important aspects related to the immune system of fish, as well as the current progress of the successful use of these animals in studies for the development of vaccines, assisting in the determination of efficacy and clinical safety. Among the advantages of using fish for the development of vaccines and immunomodulatory drugs, it is worth highlighting the reproductive capacity of these animals resulting in a high number of individuals belonging to the same spawning, transparent embryos, low cost of breeding and high genetic similarity that favor translational responses to vertebrate organisms like humans.

Pigeons retain partial memories of homing paths years after learning them individually, collectively or culturally

Memory of past experience is central to many animal decisions, but how long specific memories can influence behaviour is poorly understood. Few studies have reported memories retrieved after several years in non-human animals, especially for spatial tasks, and whether the social context during learning could affect long-term memory retention. We investigated homing pigeons' spatial memory by GPS-recording their homing paths from a site 9 km from their loft. We compared solo flights of naive pigeons with those of pigeons that had last homed from this site 3-4 years earlier, having learnt a homing route either alone (individual learning), together with a naive partner (collective learning) or within cultural transmission chains (cultural learning). We used as a control a second release site unfamiliar to all pigeons. Pigeons from all learning treatments outperformed naive birds at the familiar (but not the unfamiliar) site, but the idiosyncratic routes they formerly used several years before were now partially forgotten. Our results show that non-human animals can use their memory to solve a spatial task years after they last performed it, irrespective of the social context during learning. They also suggest that without reinforcement, landmarks and culturally acquired 'route traditions' are gradually forgotten.

Fish learn collectively, but groups with differing personalities are slower to decide and more likely to split

We tested zebrafish shoals to examine whether groups exhibit collective spatial learning and whether this relates to the personality of group members. To do this we trained shoals to associate a collective spatial decision with a reward and tested whether shoals could reorient to the learned location from a new starting point. There were strong indications of collective learning and collective reorienting, most likely by memorising distal cues, but these processes were unrelated to personality differences within shoals. However, there was evidence that group decisions require agreement between differing personalities. Notably, shoals with more boldness variation were more likely to split during training trials and took longer to reach a collective decision. Thus cognitive tasks, such as learning and cue memorisation, may be exhibited collectively, but the ability to reach collective decisions is affected by the personality composition of the group. A likely outcome of the splitting of groups with very disparate personalities is the formation of groups with members more similar in their personality.

Summary: Zebrafish groups were trained to make collective decisions and memorised locations by using cues. However, collective decisions were made slower by the splitting of groups comprising individuals of dissimilar personality.