Loaches of the genus Cobitis of the subfamily Cobitinae are small benthic freshwater fishes with a wide distribution area covering large parts of Eurasia and one additional species in north-west Africa. Classification of the genus Cobitis has been studied by many authors in China, and eight species of this genus were described. They are Cobitis macrostigma Dabry, 1872, Cobitz's sinensis Sauvage et Dabry, 1874, Cobitis dolichorhynchus Nichols, 1918, Cobitis melanoleuca Nichols, 1925, Cobitis lutheri Rendahl, 1935, Cobitis granoei Rendal 1935, Cobitis arenae (Lin), 1943 and Cobitis rarus Chen, 1981. But their identification was not explained by the morphological features such as the number and shape of lamina circularis in males, pigmentary zones of Gambetta, and body scales, which was diagnostic characters of genus Cobitis.Loaches. of Cobitis are characterized by the marked sexual dimorphism and pigmentary zones of Gambetta. There is an osseous lamina circularis on the base of the first branched ray of pectoral fin in males and the rays length is longer and thicker than that of females. In fact, males are usually smaller overall than females, having proportionally longer pectoral, dorsal, anal, and pelvic fins. Males also have longer barbels. Dorsal fin is inserted from more posterior part in females. Speckles pattern on the body side presented five pigmentary zone of Gambetta, which is the five lines of dark speckles on the dorsal-lateral side of the trunk of Cobitis, called L-1-L-5.The present work was a taxonomical revision of the Chinese loaches of the genus Cobitis, based on the specimens kept in the Freshwater Fishes Museum, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province. Eight species are valid, including of the species of C. dolichorhynchus, C. melanoleuca and C. rarus Chen, which were not valid by many authors. Those loaches are assigned to the subgenus Cobitis s. str. Bacesu, 1961, which is characterized by one lamina circularis on the first branched ray of pectoral fin of males and small, oval or round scales with large and almost central focus area. In details, male C. arenae has a caeciform lamina circularis at the base of first ray of pectoral fin; male C. granoei, a semilunar lamina circularis; male C. lutheri, a stemlike lamina circularis; male C. sinensis, a cystiform lamina circularis; male C. dolichorhynchus, a semicircular knife-shaped lamina circularis; male C. melanoleuca a kidney-shaped lamina circularis; male C. rarus, a slender fingered lamina circularis, and male C. macrostigma, a dentiform lamina circularis.
Chen Yi-Feng; Chen Yong-Xia.Secondary sexual characters, pigmentary zones of Gambetta and taxonomical revision the genus Cobitis from China (Pisces, Cobitidae, Cobitinae),Acta Zootaxonomica Sinica,2005,30(4):647-658