Skeletal ontogeny of the caudal complex in Caspian kutum, Rutilus kutum (Kamensky, 1901) (Teleostei: Cyprinidae) during early development

Study of skeletal ontogeny during early development is crucial in a successful larviculture. In this study, ontogeny of the caudal complex skeleton in Caspian kutum, Rutilus kutum, was studied from hatching up to 50-day post hatching (dph). A total of 520 larvae and fry were randomly sampled, cleared and stained for osteological examinations. The results showed that development of caudal skeleton is started with appearing hypurals 1 and 2 on 4 dph and inflexion occurred on 7 dph with formation of eight cartilaginous plates, including two haemal spines, parhypural and five hypurals, below the notochord. The results also revealed that during post flexion from 13 to 50 dph other structures e.g. rudimentary neural arch, second ural and anterior half of the neural arch of PU3 were appeared. The inflexion point of tail growth pattern in R. kutum is in accordance with inflexion caudal complex, showing ontogeny of the caudal complex skeleton in agreements with its function demands during early development.