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<p>Ultraviolet-B (UVB) radiation is a critical environmental stressor that affects aquatic organisms, particularly during vulnerable early life stages. This study investigated the effects of low ambient UVB exposure (1.0&#xa0;W/m<sup>2</sup>, corresponding to 6–12% of ambient summer UVB in the low-to-mid altitudes of the Indian Himalayas) on the sac-fry larvae of golden mahseer (<i>Tor putitora</i>) over a 7-day period. Four experimental groups were established: two UVB-exposed groups maintained under dark (UVD) and visible light (UVL) conditions, and two unexposed control groups maintained under dark (CTD) and visible light (CTL) conditions. The light treatments (UVL and CTL) were utilized to determine the potential of visible light to modulate UVB-induced effects and to rule out the light induced changes. UVB exposure significantly increased mortality and induced developmental malformations, however, heart rate remained unaffected across all treatments. Thermal tolerance was significantly impaired; specifically, the lower critical thermal minimum (CTmin) increased in both UVD and UVL treatments, while the upper critical thermal maximum (CTmax) and overall thermal scope decreased significantly in the UVD treatment alone. Gene expression analysis revealed a marked upregulation of key molecular markers involved in DNA repair (<i>p53</i>), apoptosis (<i>bcl2</i>, <i>caspase3a</i>), oxidative stress (<i>nrf2a2</i>), inflammatory response (<i>il</i>-<i>1β</i>), and proteostatic protection (<i>hsp70</i>) in both UV-exposed groups. Our findings demonstrate that direct exposure to even low levels of ambient UVB can induce acute physiological and molecular stress in <i>T. putitora</i> larvae. Given the projected increase in UVB penetration due to climate change and anthropogenic activity, these stressors may overwhelm the adaptive repair mechanisms of early life stages, potentially leading to long-term population-level declines. The study provides a preliminary information on the impact of ambient UVB on the early larval stages of mid-to-hight altitude dwelling fishes of Indian Himalayas.</p> Graphical anstract <p></p>

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Low ambient ultraviolet-B exposure induced phenotypic, ecophysiological, and molecular changes in the early larva of Himalayan golden mahseer, Tor putitora

  • 期刊论文

  • 发表日期：

    2026年7月20日

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  • M. Junaid Sidiq,
  • Alexander Ciji,
  • Narinder Kumar Chadha,
  • Paramita Banerjee Sawant,
  • Lokesh Pawar,
  • Parvaiz Ahmad Ganie,
  • Pramod Kumar Pandey,
  • M. S. Akhtar

摘要

Ultraviolet-B (UVB) radiation is a critical environmental stressor that affects aquatic organisms, particularly during vulnerable early life stages. This study investigated the effects of low ambient UVB exposure (1.0 W/m2, corresponding to 6–12% of ambient summer UVB in the low-to-mid altitudes of the Indian Himalayas) on the sac-fry larvae of golden mahseer (Tor putitora) over a 7-day period. Four experimental groups were established: two UVB-exposed groups maintained under dark (UVD) and visible light (UVL) conditions, and two unexposed control groups maintained under dark (CTD) and visible light (CTL) conditions. The light treatments (UVL and CTL) were utilized to determine the potential of visible light to modulate UVB-induced effects and to rule out the light induced changes. UVB exposure significantly increased mortality and induced developmental malformations, however, heart rate remained unaffected across all treatments. Thermal tolerance was significantly impaired; specifically, the lower critical thermal minimum (CTmin) increased in both UVD and UVL treatments, while the upper critical thermal maximum (CTmax) and overall thermal scope decreased significantly in the UVD treatment alone. Gene expression analysis revealed a marked upregulation of key molecular markers involved in DNA repair (p53), apoptosis (bcl2, caspase3a), oxidative stress (nrf2a2), inflammatory response (il-1β), and proteostatic protection (hsp70) in both UV-exposed groups. Our findings demonstrate that direct exposure to even low levels of ambient UVB can induce acute physiological and molecular stress in T. putitora larvae. Given the projected increase in UVB penetration due to climate change and anthropogenic activity, these stressors may overwhelm the adaptive repair mechanisms of early life stages, potentially leading to long-term population-level declines. The study provides a preliminary information on the impact of ambient UVB on the early larval stages of mid-to-hight altitude dwelling fishes of Indian Himalayas.

Graphical anstract