Social isolation and aggressiveness in the Amazonian juvenile fish Astronotus ocellatus

Abstract

We tested the effect of social isolation on the aggressiveness of an Amazonian fish: Astronotus ocellatus. Ten juvenile fishes were transferred from a group aquarium (60 x 60 x 40 cm) containing 15 individuals (without distinguishing sex) to an isolation aquarium (50 x 40 x 40 cm). Aggressiveness was tested by means of attacks on and displays toward the mirror image. The behavior was video-recorded for 10 min at a time on 4 occasions: at 30 min, 1 day, 5 days and 15 days after isolation. The aggressive drive was analyzed in three ways: latency to display agonistic behavior, frequency of attacks and specific attacks toward the mirror image. The latency to attack decreased during isolation, but the frequency of mouth fighting (a high aggressive attack) tended to increase, indicating an augmented aggressive drive. Our findings are congruent with the behavior of the juvenile cichlid, Haplochromis burtoni but differ from the behavior observed in another cichlid, Pterophylum scalare. Increased aggressiveness in A. ocellatus may be mediated by means of the primer effect, the effect of prior residence or processes involving recognition of a conspecific.

Water temperature affects aggressive interactions in a Neotropical cichlid fish

“…This was not expected for CT, at which we had anticipated a stable frequency of restrained aggression between the initial and final observations, due to the absence of temperature manipulation. In fact, an additional effect of social isolation seems to have affected individual aggressive performance, as it is already known for other teleost fish species (Gómez-Laplaza, Morgan, 2000;Gonçalves-de-Freitas, Mariguela, 2006). This increased aggressive behavior after isolation may be also linked to the previously described emergency life-history stages (Wingfield, 2003), indicating that the individuals are under social stress, which could explain the rise in aggressive interactions seen for C. paranaense at CT similarly to IT.…”

“…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.…”

Glomerular nucleus of the weakly electric fish, Gymnotus sp.: Cytoarchitecture, histochemistry, and fiber connections—Insights from neuroanatomy to evolution and behavior

“…The involvement of the pretectum in communication signals is documented in other vertebrate groups (frog: Fuzessery and Feng,1983; bats: Behrend and Schuller,2000; squirrels: Dujardin and Jürgens,2005). This involvement is also consistent with the complexity of the glomerular nucleus in cichlids (percomorphs), a taxa that exhibits a distinguishable array of visual displays during intraspecific interactions (Muske and Fernald,1987; Gonçalves‐de‐Freitas and Mariguela,2006; Korzan et al,2008). We therefore hypothesize that the hypertrophied and highly differentiated glomerular nucleus of cichlids is related to their complex visual social signaling.…”

Bayesian analysis improves experimental studies about temporal patterning of aggression in fish

“…This pattern is also described for other species such as juvenile Oreochromis niloticus (Alvarenga and Volpato, 1995), Tilapia zilli (Neat et al, 1998) and Oreochromis massambicus (Ros et al, 2006). Although, this pattern is not clear for all species, as in hatchery-reared steelhead (Oncorhynchus mykiss) (Berejikian et al, 2001) and oscar (Astronotus ocellatus) (Gonçalves- de-Freitas and Mariguela, 2006). In this sense, whether or not using total attacks may be species-specific and should be previously investigated.…”

“…Usually, when this happens, researchers state that the aggressive behavior is the same between the non-statistically significant days even when there is an increase/decrease pattern (e.g. Gómez-Laplaza and Morgan, 1993;Adams et al, 2000;Terleph, 2004;Gonçalves de Freitas and Mariguela, 2006). Indeed when considering p-values we might misinterpret non-significant results (Gelman, 2013;Ludwig, 2005;Pitak-Arnnop et al, 2010).…”