Ontogenetic Development of Hyperostosis in the Crevalle Jack Caranx hippos (Linnaeus, 1766) and New Records of...

Hyperostosis is a non-pathological condition widely reported in marine teleosts, yet its developmental dynamics and underlying drivers remain poorly understood. This study investigates the ontogenetic progression and anatomical distribution of hyperostosis in Caranx hippos based on a growth series of 39 specimens collected along the Brazilian coast. Individuals were categorised into two size classes (class 1 < 400 mm and class 2 ≥ 400 mm), and skeletal alterations were assessed through radiographic imaging, morphometric analyses and histology. Hyperostosis was detected in 87.2% of specimens and affected nine skeletal regions, including dorsal and anal pterygiophores, cleithrum, ribs, pelvic bones, neural and hemal spines and for the first dorsal fin pterygiophore, preopercle and opercle. The dorsal pterygiophores were the earliest and most consistently affected elements, with detectable changes in individuals as small as 184 mm TL, suggesting an early onset of the condition. Other regions exhibited a size-dependent pattern, with hyperostosis appearing sequentially and increasing in frequency and extent with growth. Morphological variation among skeletal elements indicates region-specific expression, with pronounced differences in thickness, width and mass between hyperostotic and non-hyperostotic bones. Comparisons with previous studies confirm a species-specific pattern of hyperostotic distribution in C. hippos, with minor variation in the onset and extent of affected regions. The observed ontogenetic progression supports the hypothesis that hyperostosis develops sequentially across skeletal elements rather than simultaneously. These findings, combined with ecological and biomechanical considerations, suggest that hyperostosis results from multiple interacting factors, including growth-related mechanical loading and environmental variability. Overall, this study provides a comprehensive characterisation of hyperostotic development in C. hippos, highlighting the importance of ontogenetic approaches for understanding the biological and functional significance of this condition in marine fishes.