Dorsal fin morphology and phylogenetic insights in bamboo sharks (Chiloscyllium spp.)

Abstract

Two closely related species, C. hasseltii and C. griseum, showed overlapping shape variations in their first dorsal fins. However, the proportions of the first dorsal fin height/total length and the first dorsal fin inner margin/total length were observed to be significantly different between these two species. This difference can be integrated into the dichotomous key for Chiloscyllium. Phylogenetic analysis based on the cytochrome c oxidase I (COI) gene was consistent with the morphology of the first dorsal fin, indicating that C. punctatum differs from other Chiloscyllium species. However, phylogenetic tree based on the NADH dehydrogenase 2 (ND2) gene fragments grouped the clade of C. punctatum with other clades of Chiloscyllium. Most Chiloscyllium species formed monophyletic groups based on the two gene fragments, except for C. hasseltii and C. griseum, which clustered together. This research provides practical knowledge for field-based species identification and accurate classification within the genus Chiloscyllium, enhances our understanding of its phylogenetic relationships, and supports the future development of a field guide.