Heavy metal contamination of aquatic environments threatens fish health and ecosystems. This review examines the bioaccumulation patterns, toxicity mechanisms, effects of oxidative stress, and histopathological changes induced by heavy metals in various fish species across different habitats. Important heavy metals, including mercury, cadmium, lead, arsenic, chromium, copper, and iron, are discussed. These metals can bioaccumulate in fish tissues via waterborne and dietary exposure, and bioaccumulation depends on several factors such as metal type, fish species, and exposure conditions. The generation of reactive oxygen species is one of the main reasons why heavy metals exert their toxic effects; depletion of antioxidants and damage to cellular components lead to oxidative stress. Oxidative stress is induced by alterations in antioxidant enzymes and increases in lipid peroxidation levels. Histopathological changes were recorded in target organs, such as the gills, liver, and kidneys. We emphasize the existing knowledge gap, which requires further research to provide full insights into fish heavy metal toxicity, with potential implications for human consumers. Understanding the toxicity mechanisms of heavy metals in fish is the key to developing biomarkers and mitigation strategies to protect aquatic ecosystems.

Shrimps are involved in diverse inherent defense reactions involving humoral and cellular immunity to recognize and eliminate viral invaders. Outbreaks provoked by the white spot syndrome virus (WSSV) have caused lethal devastation to penaeid shrimp aquaculture, with notable economic losses worldwide in the last 15 years. Despite intensive studies on WSSV characterization and infection mechanisms, information regarding WSSV-shrimp interactions must be explored to maintain the balance between immune-mediated protection and pathogenesis during viral infection. In-depth studies on cellular and humoral-mediated immune responses against WSSV have also been reported to assist in designing effective control strategies for WSSV, owing to their extensive emergence in large-scale shrimp production profits. This review discusses recent findings on the interaction of WSSV proteins recognized by shrimp receptors regulated by innate signaling immunological pathways, providing more ideas for effective prevention of viral infection. In addition, the molecular modifications exploited by WSSV evade shrimp immune responses for survival and replication. Additionally, summarizing viral reprogramming of host metabolic pathways provides basic knowledge for discovering new approaches to intensify the immune resistance of cultured shrimp against WSSV infections.

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