Fishes 2026, 11(6), 340; https://doi.org/10.3390/fishes11060340 (registering DOI) - 5 Jun 2026
Abstract
Schizothorax macropogon is an endemic fish species of the Tibetan Plateau whose distribution largely overlaps with hydropower facilities. In this study, the fish were exposed to simulated tunnel darkness for 7 days to evaluate microstructural changes in the gills, dorsal muscle, and midgut.
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Schizothorax macropogon is an endemic fish species of the Tibetan Plateau whose distribution largely overlaps with hydropower facilities. In this study, the fish were exposed to simulated tunnel darkness for 7 days to evaluate microstructural changes in the gills, dorsal muscle, and midgut. The results showed that gill lamellae exhibited divergent trends with continued bending and shortening in the dark group, contrasting with rupture in the control group. Moreover, the number of mitochondria-rich cells in the dark group increased initially and then decreased, while remaining stable and evenly distributed in the control group. No significant pathological damage was observed in the skeletal muscles of both groups, and muscle fiber diameters displayed a “V”-shaped trend over time in both groups. However, muscle fiber diameters were significantly smaller in the dark group than in the control group. Furthermore, intestinal villus height decreased continuously over time in both groups, with goblet cell numbers initially rising before falling and consistently remaining lower in the dark group compared to the control group. These findings suggest that short-term exposure to darkness may disrupt circadian rhythms, induce behavioral anomalies and energy metabolism disorders, leading to microstructural alterations in gill, muscle, and intestinal tissues that reflect either adaptation or damage. This study provides histological insights into the physiological effects of tunnel darkness on fish and offers key scientific evidence for optimizing lighting conditions in plateau tunnel fishways.
Full article
(This article belongs to the Special Issue Ecohydrology and River Connectivity: Implications for Fish Conservation)
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