Isolation impairs cognition in a social fish

Abstract

In variable environments, animals can learn to alter their behavior to adjust to changes. Sometimes, however, this learning ability can be impaired. For example, challenges in the social or physical environment can trigger physiological responses that compromise an individual's capacity to learn and these can prevent the animal from modifying its behavior to cope with the altered environment. One such disruption that might affect learning ability is the isolation of an individual that would normally live in a social group. To investigate the effects of isolation on cognition, we tested whether social isolation impairs learning skills in a cichlid fish, Cichlasoma paranaense. Two treatments were compared, one with isolated individuals and another with fish housed as part of a social group. Cognition was assessed in terms of the fish learning to associate a visual landmark with an accessible food reward. Fish searched for a food reward in a T-maze: a green or a yellow visual landmark signaled which chamber contained accessible food. Learning was assumed when a fish was able to find the food in nine out of ten trials. All fish, regardless of treatment, found it challenging to reach the learning criterion, but fewer isolated fish (3 out of 15 fish) were likely to learn the task compared to fish housed socially (7 out of 14 fish) (Bayesian logistic regression with 95% of chance that the two treatments differ). The results therefore suggest that social isolation for a normally social species of fish can impair learning. Furthermore, given that fish sometimes need to be isolated to treat them in a specific way, or to monitor an individual's response during a test, our results suggest that there may be some welfare implications for the way we treat and use social species of fish in empirical studies.

Water temperature affects aggressive interactions in a Neotropical cichlid fish

“…C. paranaense inhabits the Paraná basin, whose temperature varies depending on the region and period of the year. Because there is no information regarding the ideal temperature for C. paranaense, we used the mean temperature considered for other cichlid species, which is 27° C (e.g., Figler, Einhorn, 1983;Schofield et al, 2010;Brandão et al, 2015).…”

“…Thus, our aim was to test the effect of water temperature on aggressive interactions in a social Neotropical fish, Cichlasoma paranaense Kullander, 1983, to better understand how individuals cope with changes in the abiotic and social environment. We chose a fish from the Cichlidae family, comprised by social species which are socially ranked through aggressive interactions (Barlow, 2002;Shumway, 2010;Brandão et al, 2015); and also because C. paranaense inhabits Brazilian streams which are at deforestation risk and, consequently, undergo fast temperature variations. Therefore, we designed two studies; the first one aimed to test the critical thermal maximum (CTMax) tolerated by C. paranaense, under isolated and grouped conditions.…”

“…Thus, such mirror test is an efficient way to control for individual responses to variables such as the opponent's sex, size and previous social ranks (Balzarini et al, 2014), which could bias the focal fish's aggressive responses. The aggressive interactions observed here were based on an ethogram developed for C. paranaense (Brandão et al, 2015) and adjusted for mirror interactions, as described for the cichlid Astronotus ocellatus (Agassiz, 1831) by Gonçalves- de-Freitas, Mariguela (2006). Four types of aggressive behaviors were observed: frontal exhibition, lateral exhibition, butting and undulation.…”

Unusual effect of chemical communication on social aggression in juvenile cichlid fish Cichlasoma paranaense (Cichliformes: Cichlidae)

“…Juvenile fish were used to avoid the effect of sex on aggressive interactions, since cichlid males appear to show higher androgen levels than females in adult life (Oliveira, Almada, 1998;Oliveira, 2004). In addition, juveniles C. paranaense are known for their aggressive interactions and establish social hierarchy (see Brandão et al, 2015Brandão et al, , 2018. Thirty-one individuals of similar size (mean ± S.E.…”

Equal performance but distinct behaviors:Astatotilapia burtonisex differences in a novel object recognition task and spatial maze

“…This is not unexpected, given that our experimental paradigm has few trials and a strict learning criterion ("learners" had to learn after only one training trial and not make a mistake in the following three trials). A similar design has been used in another cichlid species, the Nile tilapia Oreochromis niloticus (Lombardi Brandão et al 2015). This study also used a T-shaped barrier in which a focal individual had to navigate around by making either a left turn or right turn to reach a reward and after 30 trials (2x/day) with a criterion of 9/10 correct trials in a row 50% of their focal individual successfully learned the task.…”