Scanning Electron Microscopy (SEM)-based Analysis of Fish Scales in the Genus <i>Schizothorax</i> (Teleostei: Cyprinidae) From Kashmir Himalayas

In this study, scanning electron microscopy (SEM) was used to investigate the microstructural scale morphology of five Schizothorax species (S. curvifrons, S. esocinus, S. labiatus, S. niger, and S. plagiostomus) from Kashmiri waters. The research aimed to improve taxonomic clarity and facilitate species differentiation within this genus. Species-specific variations in scale features revealed by SEM included length, width and shape of scales; focus area sculpture; number and width of radii; circuli number and intercircular space; length of lateral line canal and size of anterior opening of canal. Notable findings include polygonal-shaped scales in S. niger and S. plagiostomus, while circular scales were noted in S. curvifrons, S. esocinus, and S. labiatus. S. curvifrons had the largest scales, while S. plagiostomus had the smallest. The maximum number of radii was observed in S. plagiostomus, and the minimum in S. niger. Circuli were most numerous in S. esocinus and S. plagiostomus, and minimum in S. niger. Moreover, lepidonts on circuli and chromatophores on the posterior margin were absent across all species. Lateral line canal length was similar in S. esocinus, S. labiatus, and S. plagiostomus, with significant variation in S. niger and S. curvifrons. These morphological traits provide valuable insights into the differentiation of Schizothorax species and serve as a foundation for resolving taxonomic complexities within this genus. Such findings are crucial for accurate species identification, a key step in developing effective conservation strategies for these endemic fishes of the Kashmir Valley.