Natural environment imposes many challenges to animals, which have to use cognitive abilities to cope with and exploit it to enhance their fitness. Since zebrafish is a well-established model for cognitive studies and high-throughput screening for drugs and diseases that affect cognition, we tested their ability for ambient color preference and 3D objects discrimination to establish a protocol for memory evaluation. For the color preference test, zebrafish were observed in a multiple-chamber tank with different environmental color options. Zebrafish showed preference for blue and green, and avoided yellow and red. For the 3D objects discrimination, zebrafish were allowed to explore two equal objects and then observed in a one-trial test in which a new color, size, or shape of the object was presented. Zebrafish showed discrimination for color, shape, and color+shape combined, but not size. These results imply that zebrafish seem to use some categorical system to discriminate items, and distracters affect their ability for discrimination. The type of variables available (color and shape) may favor zebrafish objects perception and facilitate discrimination processing. We suggest that this easy and simple memory test could serve as a useful screening tool for cognitive dysfunction and neurotoxicological studies.

Many studies regarding the effects of drugs investigate the acute and chronic use of alcohol, but only a few address the effects of caffeine and alcohol combined to the performance of the zebrafish in cognitive tasks. The zebrafish is an important model for studying the effects of drugs on learning, because it has large genetic similarities to humans and the non-invasive administration of the substances favors translational bias of research. In this study, we observed the effects of alcohol and caffeine on zebrafish cognition through an object discrimination test. We noticed that animals subjected to acute alcohol dose and those under alcohol or caffeine withdrawal did not show discrimination. When fish were treated with associated alcohol and caffeine, those chronically treated with alcohol and subjected to moderate acute dose of caffeine showed learning of the task. Our results reinforce the harmful effects of the alcohol use on cognitive tasks, and suggest that continued use of high doses of caffeine cause cognitive impairment during withdrawal of the substance. However, the acute use of caffeine appears to reverse the harmful effects of alcohol withdrawal, allowing discriminative performance equivalent to control fish. Finally, we reiterate the use of zebrafish as a model for drug effects screening and search for active compounds that modulate the alcohol and caffeine effects.

This study investigated the ability of the dusky damselfish Stegastes fuscus to associate conditioned and unconditioned stimuli (single CS-US) and to find a specific place in a clueless ambiece (spatial learning). After tested for colour preference and showing no specific colour attractively, the fish were trained to associate a colour cue with a stimulus fish (conspecific). Fish were then challenged to locate the exact place where the stimulus fish was presented. Stegastes fuscus spent most time close to the zone where stimulus was presented, even without obvious marks for orientation. The results confirm that S. fuscus show single CS-US learning and suggest the fish ability for spatial orientation. Stegastes fuscus appears to use multiple senses (sight and lateral line) for cues association and recall, and appear to perform relational learning similar to mammals. These data suggest the importance of cognitive skill for reef fishes that may have contributed to their establishment and evolutionary success in such complex environment.

Individual differences in behavior are observed in the variety of ways animals respond to environmental challenges, interact in a social group, take risks to access a resource, and so forth. In the present study, we investigated the behavioral reactions of male and female Siamese fighting fish (Betta splendens) in different contexts and how they affect female mate choice. A total of 100 females and 50 males were classified according to boldness, sociability, and aggression, and then female mate choice was observed based on male profile and body color. Our results showed sex-related differences in Siamese fighting fish behavioral profiles: Males exhibited a higher correlation with aggression and females with boldness. Both male and female behavioral profile affected female mate choice. Females preferred bold red and nonaggressive red males. Sex-related differences in behavioral profiles may reflect ecological differences between male and female Siamese fighting fish. Female mate choice could be related to behavioral profiles that indicate better parental care, as male features may influence parental care decisions and the development of offspring behavioral profiles.

Nile tilapia were raised from eggs to 2 months of age under a coloured light regime (violet, blue, green, yellow, and red) and then tested for colour preference in a multiple chamber maze with different colour options. Fish were observed individually during three days at 8, 11, 14, and 17 h, every 2 min for 20 min and the visit frequency in each compartment was analyzed. Young Nile tilapia kept under yellow and red light showed preference for yellow and red, respectively. Fish held under violet, blue, and green light did not show any colour preference or avoidance. These results imply that environmental colour affects colour preference of Nile tilapia, possibly due to lightdependent shift of visual pigments in the retina, indicating that colour preference is not an innate response. This conclusion reinforces the idea that environmental colour modulates fish physiological and behavioural processes.