ABSTRACT
Due to drastic increase in industrial activities, heavy metal pollution has become a source of grave concern. Heavy metals not only have hostile effects on living organisms, but they also disturb the delicate balance of the ecosystem. Aquatic ecosystems are particularly affected by heavy metal pollution since most of the industrial wastes are ultimately drained into the water bodies. Fish being at the top of the aquatic food chain accumulates all these toxic heavy metals. In this book chapter, we have tried to go into the mechanistic depths of neurotoxicity caused by heavy metals in fishes. Trace amounts of some heavy metals like iron, copper, zinc, and cobalt are essential to maintain the physiological and biochemical functions in living organisms; however, beyond a certain threshold level, they become toxic. Other heavy metals like lead (Pb), mercury (Hg), and cadmium (Cd) have no known essential role in living organisms. These essential and non-essential heavy metals together constitute an important group of neurotoxicants. Toxic effects of heavy metals come into play when detoxification, metabolic, storage, and excretory mechanisms in fish are not able to counter uptake. Most of the heavy metals disturb the delicate balance between reactive oxygen species (ROS) and antioxidant defense mechanisms in cells, resulting in an increase in the concentration of ROS. This creates oxidative stress in the cells leading to apoptosis (Mieiro et al., 2009).
