Phylogenetic analysis and osteological comparison of the cave-dwelling spined loach, Bibarba parvoculus (Cypriniformes: Cobitidae), and its surface congener

Bibarba parvoculus, a depigmented and small-eyed, spined loach, is endemic to a karst cave in southern China. Both mitochondrial Cytb and nuclear RAG1 gene analyses indicate that B. parvoculus and its only surface congener, B. bibarba, form the basal-most lineage in the so-called Northern Clade of Cobitidae. Genetic divergence for Cytb is 10.3 % between B. parvoculus and B. bibarba. A duplication of the lamina circularis on the second and third pectoral rays occurs in male Bibarba species. The osteology of the two species is illustrated and compared using X-ray microtomography. Bibarba parvoculus has higher vertebral counts, a broader anterior part of the frontal bone at the orbital region and decreased sexual dimorphism when compared with B. bibarba. The coracoid, mesocoracoid and scapula are stouter in males of both species, but the three bones are autogenous in B. parvoculus, while fused with the cleithrum in B. bibarba. Specific differentiation of B. parvoculus is corroborated by both molecular and morphological evidence. The split between the two species is estimated to have occurred in the Early Miocene.

Cobitis xui, a new species of spined loach (Teleostei: Cobitidae) from the Pearl River drainage in southern China

A new spined loach of the genus Cobitis Linnaeus is described from the Buquan River, located in Guangxi Zhuang Autonomous Region, China. The species differs from other members of Cobitis in China by a combination of morphological characters, none of them unique: body depth 14.3‒18.4% SL; lamina circularis long and knife-shaped; Gambetta zones present on the dorsolateral sides of the body (L1‒L5); 8‒11 large transverse elongated blotches on L5; 9‒12 large transverse elongated blotches on L1; maxillary barbels longer than eye diameter; 4‒5 narrow rows of dark spots on the caudal fin; caudal fin with 14 branched rays; a rectangular spot slightly smaller than eye diameter on the upper side of caudal fin base; and caudal-peduncle depth 79.5‒93.1% its length.