Elucidation of malachite green induced behavioural, biochemical, and histo-architectural defects in Cyprinus carpio, as piscine model

Abstract

Colours are an indispensable portion of human survival. Malachite green (MG) is a dye with a bright hue of green, used in textile, paint, and confectionery industry. For the present study, healthy fingerlings of Cyprinus carpio were exposed to sub-lethal concentration (0.087 ​mg/L) of malachite green for 15, 30, and 60 days. Assessment of chronic toxicity was made through varied organs (cornea, erythrocytes, and liver) and analytical methods, comprising behavioural, histopathological, ultra-structural (transmission electron microscopy), biochemical (antioxidant and marker enzymes) and bioaccumulation studies. Behavioural aspects, comprised of opercular and fin (dorsal and caudal) movements, presented an inverse relation with MG treatment, and displayed escaping behaviour from the experimental tank. Scanning electron microscopy (SEM) of MG exposed fish peripheral erythrocytes demonstrated morphological anomalies in form of clubbing, budding, and appearance of the varied shaped cells as stomatocytes, acanthocytes, dacrocytes and fusiform cells in the exposure dependent manner, instead of regular elliptical erythrocytes in control. Corneal epithelium study conducted through SEM in MG treated fish reported damaged pavements cells, microridges, and microplicae, and increased intra-microplicae distance compared to control fish. Elevated levels of serum marker enzymes and disturbed levels of antioxidant enzymes were also evident; accompanied by abundance of MDA-TBARs level suggestive of oxidative stress in MG treated fish. Bioaccumulation studies conducted revealed up to 3.06 fold dye deposition, conferring the enhanced and prolonged toxicity of the dye in the fish. Consequently, MG can be inferred as a strong cellular toxicant even at sub-lethal concentration.