IMPACT OF CADMIUM ON DANIO RERIO’S SENSE OF SMELL

Anthropic activities have significantly increased cadmium availability, which has become a significant stressor in aquatic ecosystems1. Present at high concentrations in a variety of water bodies, it is bioaccumulated and biomagnified in the food chain. Multiple toxic effects have been reported on different organs and tissues2 while information on interferences on sensory systems is relatively scanty3 though the senses are essential for survival. This study investigated the effects of a short exposure (96 h) to 50 μM cadmium chloride on the olfactory organ of adult zebrafish. Cytoanatomy of lamellae was assessed by light microscopy and immunocytochemistry techniques. At the same time, functionality was tested by behavioral odour recognition test4 that was carried out in a labyrinth glass tank in which food was added at the end of a mandatory path. Investigations were extended to animals exposed to cadmium but let recover for six days in clean water. Results demonstrated that the lamellar epithelium is profoundly affected by the metal: the lamina propria becomes oedematous and the epithelium thickens, showing increased numbers of crypt and rodlet cells. Apoptotic cells became numerous, and the cilia of non-sensory cells appeared collapsed. The animals showed reduced performance in behavioral tests being unable to reach the food in five successive trials. After recovery, lamellar damage was reduced and performance in behavioral tests improved. Our data demonstrate that cadmium impairs the sense of smell, and that recovery can occur if the insult ends. Ongoing studies will explore the role played in the observed response by visual information gathered in the labyrinth and memory. Data highlight the significant impact that cadmium pollution can exert on so far neglected aspects of animal survival.