Background. Hyperostosis is a productive change characterized by an increase of the periosteal ossification combined to resorption of the bony tissue. It is common in several fish species. Its presence has been reported in the silver scabbardfish, Lepidopus caudatus (Euphrasen, 1788). The aim of the presently reported study is to improve the knowledge on the presence of hyperostotic pterygiophores in L. caudatus. Materials and methods. In total, 50 specimens of Lepidopus caudatus, captured off the coast of Messina (Sicily, Italy) were examined by radiography. Deformed pterygiophores were decalcified and processed for histopathological examination, and the sections obtained were stained with haematoxylin and eosin. Results. Forty (80%) of the 50 specimens examined showed skeletal deformities exclusively on the pterygiophores of the dorsal fin. In total, 433 deformities were observed. Histological examination showed slight expansion of the bone tissue, which was poor in cells and characterised by thin layers of compact bone tissue. Macroscopic, radiographic, and histological findings were consistent with diagnosis of hyperostosis. Conclusion. Hyperostosis of L. caudatus does not affect its consumption. However, it may be a complication for filleting techniques as the presence of hyperostosis along the longitudinal axis of teleosts does not allow a complete and repeatable filleting technique. This could increase the possibility of bacterial contamination, loss of muscle tissue, and imperfections in cutting and trimming.

fish osteology, histology, pterygiophore, hyperostosis, periosteal ossification, resorption of bony tissue