Comparative anatomy of the caudal fin (pinna caudalis) Tor douronensis (Valenciennes, 1842) and Tor soro (Valenciennes, 1842)

Abstract

Tor douronensis and Tor soro were two of the four species of the Tor genus that live in Indonesian waters. However, studies related to the skeleton of these two fish are still rarely disclosed. The aim of this study compared the morphology of the caudal-fin (pinna caudalis) T. douronensis and T. soro. The research stages include sample preparation, making skeleton preparations, image analysis, and identification of skeleton terminology. T. douronensis fish were collected from the waters of the Pagar Alam area, Lahat Regency, South Sumatra, while T. soro was collected from the waters of Bukit Lawang, Bohorok District, Langkat Regency, North Sumatra Province. The caudal-fin (pinna caudalis) is part of the ossa urostylus which produces optimal hydrodynamic propulsion. The caudal-fin (pinna caudalis) Genus Tor is part of the ossa urostylus which is composed of 31 caudal-fin rays (pinnae), six hypural bones, parhypural, pleurostylus, epural, and uroneuralis. The ventral part of T. douronensis and T. soro is composed of the parhypural, and the 1st and 2nd hypural bones. T. douronensis had a parhypural bone that was more prominent and separates from the spina hemalis compared to T. soro. The dorsal part was composed of the 3rd hypural bones to 6th hypural, in T. soro the hypural bone was fused with cartilage. Os pleurostylus T. douronensis had a more prominent shape than T. soro and there was enlargement in the posterior part. The 3rd and 4th hypural bones on T. soro had the largest size. The T. soro had three spina neuralis and three spina hemalis to support the rays of the tail. The bones that composed the caudal-fin of T. douronensis and T. soro were relatively similar to those of some fish from the family Cyprinidae. The results of this study could be used as an alternative to identify T. douronensis and T. soro from the skeleton.