Revisiting the universality of direct pectoral fin development in catfishes: Evidence from the Asian red‐tail catfish Hemibagrus wyckioides

BACKGROUND: Catfishes (Siluriformes) are among the most diverse and evolutionarily successful, yet developmentally understudied, lineages of teleosts. A recent hypothesis, derived from ontogenetic data on clariids and ictalurids, proposes that the direct development of the pectoral fin, characterized by the absence of a distinct larval stage, represents a synapomorphy of Siluriformes. RESULTS: To test this hypothesis, we examined the ontogeny of the pectoral fin skeleton and associated soft tissue in the Asian red-tail catfish Hemibagrus wyckioides (Bagridae). Using immunochemical and whole-mount staining techniques, we demonstrated the presence of a distinct larval stage in the pectoral fin development. In addition, we identified an alternative sequence of endoskeletal disk subdivision that differs from the stereotypical teleost pattern. CONCLUSION: Our results challenge the assumed universality of direct pectoral fin development in Siluriformes; suggest the role of heterochronies in shaping their pectoral fin evolution; and highlight previously unrecognized diversity in developmental patterns of the pectoral fins. This study expands the current understanding of teleost pectoral fin ontogeny and underscores the importance of broader taxonomic sampling for evaluating evolutionary hypotheses in developmental biology.