Arshan Halkor, Colton A Howell, Brandon C Vera, Jason A Kaufman
Emotional contagion, the social transmission of affective state between individuals, is widely observed across vertebrates. In zebrafish, behavioral and endocrine stress contagion has been demonstrated when observers view conspecifics expressing species-typical defensive responses. However, it remains unclear whether such transmission reflects generalized sensitivity to conspecific disturbance or depends on the structure and biological relevance of social cues. We tested whether visual exposure to a pronounced non-ethological motor disturbance is sufficient to elicit stress contagion. Demonstrator zebrafish were administered pentylenetetrazole (PTZ), a convulsant that induces seizure-like behavior, while naïve observers viewed them from an adjacent tank. Freezing, darting, bottom dwelling, locomotor activity, social positioning, and trunk cortisol were quantified. PTZ produced a robust seizure-like phenotype and elevated cortisol in demonstrators. Observers of PTZ-treated conspecifics, however, showed no corresponding increases in canonical stress-related behavior or cortisol relative to controls. Social positioning nevertheless differed: both PTZ-treated demonstrators and their observers spent less time in the portion of their respective tanks adjacent to the social partner, indicating altered dyadic spatial organization while leaving the direction of this effect unresolved. Thus, visual exposure to a conspicuous, physiologically stressful, non-ethological conspecific disturbance was insufficient to produce the canonical behavioral and endocrine pattern of stress contagion measured here. The dissociation between altered social-spatial organization and canonical stress responses identifies a boundary condition for affective-state transmission and is consistent with the hypothesis that zebrafish stress contagion depends on the structure, modality, and biological relevance of social cues.