Differential Modulation of Cadmium and Cobalt on Conspecific Alarm and Predator-Induced Neophobic Responses in Zebrafish (Danio rerio).

The olfactory system is pivotal in mediating conspecific alarm responses and predator avoidance behaviors in zebrafish (Danio rerio), with its impairment posing significant survival risks. This study examined the differential impacts of two environmentally relevant heavy metals, cadmium (Cd) and cobalt (Co), on olfactory function and predator-induced behavioral responses. Adult zebrafish were exposed to sublethal concentrations of Cd (4 days) and Co (4 h), followed by behavioral assays involving exposure to conspecific alarm substance (CAS) and predator-derived chemical cues. Cd exposure significantly rescued olfactory-mediated responses, as indicated by reduced freezing, erratic swimming, and bottom-dwelling behaviors following CAS exposure, whereas responses to predator odor remained unaffected. In contrast, Co exposure selectively attenuated predator-induced neophobic behaviors without altering CAS-mediated responses. These findings suggest that conspecific alarm responses and predator-induced neophobia are mediated by distinct sensory pathways. This study highlights the utility of zebrafish as a sensitive model for neurobehavioral ecotoxicology and provides critical insights into how specific environmental contaminants can differentially disrupt sensory modalities and threat responses in aquatic vertebrates.