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<p>Heavy metal contamination threatens freshwater biodiversity by affecting genetic diversity, protein function, and physiology. Zinc (Zn), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni), and copper (Cu) induce stress in fish, making it crucial to understand <i>Dawkinsia</i> species’ adaptations to assess pollution’s ecological impact. In January 2025, eight individuals of <i>Dawkinsia filamentosa</i> and twelve surrounding water samples were collected from a single site in the Sita River, Karnataka, India. All samples were obtained in triplicate to ensure analytical precision and reproducibility. This study examines genetic variability, metal-binding potential, and histopathological effects of heavy metal exposure in <i>Dawkinsia</i> species, focusing on <i>Dawkinsia filamentosa</i> from the Sita River, Karnataka, India. Phylogenetic results revealed substantial genetic divergence among <i>Dawkinsia</i> species, with <i>D. arulius</i> and <i>D. rubrotincta</i> forming a closely related clade. Significant genetic variations were observed in <i>D. arulius</i>,<i> D. austellus</i>, and <i>D. filamentosa</i> (lineages 2, 10, and 11), suggesting potential adaptive responses to heavy metal stress. Molecular docking analysis revealed that <i>D. filamentosa</i> from the Edathua-Pamba and Manimala Rivers exhibited the highest binding affinity for Cd (− 8.4 to − 10.1&#xa0;kcal/mol) and Zn (− 7.1 to − 9.3&#xa0;kcal/mol). Additionally, <i>D. filamentosa</i> lineage 11 from the Sita River demonstrated a strong binding affinity for Zn (− 8 to − 12&#xa0;kcal/mol). The inductively coupled plasma mass spectrometry analysis confirmed high concentrations of Zn in the Sita River, suggesting prolonged exposure to metal contamination. The high Zn-binding affinity observed in <i>D. filamentosa</i> lineage 11 from the Sita River suggests a potential evolutionary response to metal exposure, supporting the hypothesis that metal contamination drives genetic adaptation. The genetic divergence between <i>D. filamentosa</i> lineage 11 and the present study species, despite their co-occurrence in the Sita River, further indicates selective pressure from metal toxicity. Histopathological analysis revealed significant kidney, gill, and liver damage associated with zinc exposure, indicating physiological stress and potential organ dysfunction. This study highlights the role of heavy metal–induced selection in shaping genetic diversity and molecular adaptations in <i>Dawkinsia</i> species. The observed species-specific variations in metal-binding residues suggest distinct tolerance mechanisms influenced by pollution levels. These findings emphasize the necessity of continuous monitoring and pollution mitigation efforts to protect freshwater biodiversity from heavy metal contamination.</p>

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Genetic adaptation and metal-binding affinity in Dawkinsia species (Cypriniforms: Cyprinidae): assessing the impact of heavy metal contamination in freshwater ecosystems

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Atchuthan Purushothaman,
  • Thirugnanasambandam Rajendran,
  • Inbakandan Dhinakarasamy

摘要

Heavy metal contamination threatens freshwater biodiversity by affecting genetic diversity, protein function, and physiology. Zinc (Zn), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni), and copper (Cu) induce stress in fish, making it crucial to understand Dawkinsia species’ adaptations to assess pollution’s ecological impact. In January 2025, eight individuals of Dawkinsia filamentosa and twelve surrounding water samples were collected from a single site in the Sita River, Karnataka, India. All samples were obtained in triplicate to ensure analytical precision and reproducibility. This study examines genetic variability, metal-binding potential, and histopathological effects of heavy metal exposure in Dawkinsia species, focusing on Dawkinsia filamentosa from the Sita River, Karnataka, India. Phylogenetic results revealed substantial genetic divergence among Dawkinsia species, with D. arulius and D. rubrotincta forming a closely related clade. Significant genetic variations were observed in D. arulius, D. austellus, and D. filamentosa (lineages 2, 10, and 11), suggesting potential adaptive responses to heavy metal stress. Molecular docking analysis revealed that D. filamentosa from the Edathua-Pamba and Manimala Rivers exhibited the highest binding affinity for Cd (− 8.4 to − 10.1 kcal/mol) and Zn (− 7.1 to − 9.3 kcal/mol). Additionally, D. filamentosa lineage 11 from the Sita River demonstrated a strong binding affinity for Zn (− 8 to − 12 kcal/mol). The inductively coupled plasma mass spectrometry analysis confirmed high concentrations of Zn in the Sita River, suggesting prolonged exposure to metal contamination. The high Zn-binding affinity observed in D. filamentosa lineage 11 from the Sita River suggests a potential evolutionary response to metal exposure, supporting the hypothesis that metal contamination drives genetic adaptation. The genetic divergence between D. filamentosa lineage 11 and the present study species, despite their co-occurrence in the Sita River, further indicates selective pressure from metal toxicity. Histopathological analysis revealed significant kidney, gill, and liver damage associated with zinc exposure, indicating physiological stress and potential organ dysfunction. This study highlights the role of heavy metal–induced selection in shaping genetic diversity and molecular adaptations in Dawkinsia species. The observed species-specific variations in metal-binding residues suggest distinct tolerance mechanisms influenced by pollution levels. These findings emphasize the necessity of continuous monitoring and pollution mitigation efforts to protect freshwater biodiversity from heavy metal contamination.