Visual Information Alone Changes Behavior and Physiology during Social Interactions in a Cichlid Fish (Astatotilapia burtoni)

Abstract

Social behavior can influence physiological systems dramatically yet the sensory cues responsible are not well understood. Behavior of male African cichlid fish, Astatotilapia burtoni, in their natural habitat suggests that visual cues from conspecifics contribute significantly to regulation of social behavior. Using a novel paradigm, we asked whether visual cues alone from a larger conspecific male could influence behavior, reproductive physiology and the physiological stress response of a smaller male. Here we show that just seeing a larger, threatening male through a clear barrier can suppress dominant behavior of a smaller male for up to 7 days. Smaller dominant males being “attacked” visually by larger dominant males through a clear barrier also showed physiological changes for up to 3 days, including up-regulation of reproductive- and stress-related gene expression levels and lowered plasma 11-ketotestesterone concentrations as compared to control animals. The smaller males modified their appearance to match that of non-dominant males when exposed to a larger male but they maintained a physiological phenotype similar to that of a dominant male. After 7 days, reproductive- and stress- related gene expression, circulating hormone levels, and gonad size in the smaller males showed no difference from the control group suggesting that the smaller male habituated to the visual intruder. However, the smaller male continued to display subordinate behaviors and assumed the appearance of a subordinate male for a full week despite his dominant male physiology. These data suggest that seeing a larger male alone can regulate the behavior of a smaller male but that ongoing reproductive inhibition depends on additional sensory cues. Perhaps, while experiencing visual social stressors, the smaller male uses an opportunistic strategy, acting like a subordinate male while maintaining the physiology of a dominant male.

Mechanosensory signaling as a potential mode of communication during social interactions in fishes

“…To make this decision, a fish needs as much information about the opponent as possible. Although the roles of visual and chemosensory signals in animal assessment are well documented (Arnott and Elwood, 2009;Bleckmann and Mogdans, 2014;Chen and Fernald, 2011;Ratterman et al, 2009), only one study has examined the role of the lateral line system in mediating mutual assessment (Butler and Maruska, 2015). In that study, we found that lateral-line-ablated male cichlids were less likely to initiate and engage in a territorial encounter compared with lateral-line-intact males ( Fig.…”

“…In teleost fishes, the use of visual, chemosensory and acoustic communication is relatively well studied in different behavioral contexts such as territoriality, reproduction and parental care (Almeida et al, 2005;Amorim et al, 2003Amorim et al, , 2004Barata et al, 2007;Chen and Fernald, 2011;Grosenick et al, 2007;Keller-Costa et al, 2015;Korzan and Fernald, 2007;Korzan et al, 2008;Lobel, 1998;MartinovicWeigelt et al, 2012;Rosenthal and Ryan, 2000;Simoes et al, 2008). However, all fishes also possess another sensory system, the mechanosensory lateral line (Fig.…”

Cognitive skills and the evolution of social systems

“…The behavior of the smaller male was typical of an animal losing his territorial status, leaving the shelter and excavating a new pit at the opposite corner of the tank. The changes in the smaller male resulted entirely from visual information, which also produced a reduction in androgen hormone expression for the first 3 days after removal of the black barrier (Chen and Fernald, 2011). Seven days after the visual exposure began, the smaller male had normal hormone levels but retained the coloration of a ND male.…”

“…Clearly, this kind of ability, when used to gain advantage over competitors, could potentially be very useful. To determine whether A. burtoni males deceive each other with regard to their social status, Chen and Fernald (2011) placed a large male and a small male fish with an appropriately sized female in an aquarium with a 'shared' terracotta pot shelter, divided into halves by a removable opaque and watertight transparent partition (Fig. 5).…”

“…Once the two males had established their territories on the opposite sides of the barrier, the black divider was removed. Modified from Chen and Fernald (2011). were arranged in visually, chemically and physically isolated compartments around a central bystander unit.…”