NEUROTOXIC EFFECTS OF THERMAL VARIATION ON THE NERVOUS SYSTEM AND EYE OF ADULT ZEBRAFISH

Neurotoxicity refers to any adverse effect on the chemistry, struc ture, or function of the nervous system, triggered by chemical or physical influences. Environmental changes may induce neurotoxic responses in animals, with aquatic species particularly vulnerable due to the susceptibility of their ecosystems to chemical and physi cal alterations. Our research has shown that adult zebrafish (Danio rerio), a widely used model in neuroscience, respond sensitively to thermal variation. Chronic exposure to low (18°C) or high (34°C) temperatures for 21 days—compared to the control temperature of 26°C—significantly altered brain proteomic profiles, lipid composi tion, and behaviour, both in individual fish and in small shoals. Notably, similar behavioural and molecular effects were also evi dent after shorter (4-day) exposures. Importantly, these effects extended beyond the brain. Proteomic analysis of the eye revealed that high-temperature exposure upregulated the sirtuin signalling pathway and downregulated proteins involved in oxidative phosphorylation, electron transport, and ATP synthesis. In the brain, these changes were accompanied by reduced expression of synaptic and neurotransmitter-related proteins, while in the eye, they corre sponded with decreased phototransduction proteins. These findings demonstrate that thermal stress can have broad neurotoxic conse quences, impairing both central and visual nervous system function. They highlight the zebrafish as a powerful model for studying tem perature-induced neurotoxicity and emphasise the ecological rele vance of environmental temperature stability for aquatic organisms.