Melanophore: A biosensor for water pollution analysis.

Chemical pollutants bioaccumulate in aquatic animals and can reach humans, causing adverse health effects. Pollution of aquatic ecosystems from industrialization and anthropogenic xenobiotics is a global issue. Poikilothermic animals possess pigment cells called integumentary melanophores, derived from neural crest cells, which contain melanin and can detect environmental pollution. These melanophores serve as effective bioassay tools for pharmacological drugs and chemical contaminants. Studies show pollutants like Aroclor 1242 and naphthalene influence crustacean color changes, indicating pollutant impact on chromatophores. Fish melanophores are sensitive to various pollutants and function as sensors of ecological stress, while both melanophores and erythrophores act as bioindicators of water contamination. Exposure to contaminants can cause morphological damage to fish scales, including chromatophore scattering and lepidont disruption. In amphibians, insecticides such as dimethoate lead to melanophore degeneration and bleaching. Melanophore-based toxicity sensors have potential for detecting hazardous substances in drinking water and can also identify bacterial toxins and pathogenic bacteria through cell-based biosensing. Acute pigment dispersion occurs rapidly within minutes to hours, whereas morphological changes appear over days to months. This review explores acute physiological and long-term morphological responses of melanophores in fish, amphibians, and even crustaceans exposed to aquatic pollutants. It distinguishes between short-term pigment translocation as a marker of acute toxicity and longer-term structural changes indicating chronic environmental stress. The review critically evaluates the advantages and limitations of melanophore-based biomonitoring and underscores their potential for in vitro sensing of diverse aquatic contaminants, including bacterial toxins.