Morphological analysis of Homaloptera gymnogaster Bleeker, 1853 (Family: Balitoridae) from different elevations in Central Sumatra, Indonesia

Homaloptera gymnogaster (Family: Balitoridae) is an endemic freshwater fish in Sumatra, Indonesia that can be found up until a high elevational aquatic body. There is no previous report about a thorough study on its morphological variations from its various populations. In this study, 47 individuals H. gymnogaster were collected using random sampling from five different elevations (Sikai River at 1996, 1552, 1420, Batang Gumanti on 1531, and Matur River on 1097 m asl), on which 53 morphological characters measured. The result indicated that 41 characters significantly varied with the Kruskal-Wallis test ( P <0.05%), which consist of 29 morphometric and 12 meristic characters. The Mann-Whitney U test (with <0.05% standard confidence) confirmed the high differentiation on morphometric and meristic characters among the study sites. The Principal Component Analysis (PCA) plot hinted that albeit populations in Sikai River divided come from different elevations, were still categorized as the same group. On the contrary, Batang Gumanti and Matur River site separated into different groups. This study concluded that differentiation of morphological characters on H. gymnogaster was influenced by current velocity and river size.