They take in air at the surface, and pass it through the intestine where the mucosa absorbs the oxygen and carbon dioxide waste is released through the vent.
Menon (1992) considers that structural details of the bony covering of the swimbladder and the nature of the scales are only of use at the generic level.
Lip structures, fin positions relative to one another and secondary sexual characteristics in males are important characters in differentiating species in India.
This name is not repeated under each Species Account. This genus is characterised by an elongate and compressed body, a usually bifid, erectile spine below the eye (sometimes hidden under the skin), 3 pairs of short barbels (4 at the snout tip and 2 at the mouth corners), minute scales cover the body (as many as 200 but they are seldom counted accurately), lateral line faint or indistinct, dorsal and anal fins small, caudal fin rounded or truncate, and swimbladder in a bony capsule with a free portion visible.
Males have bony extensions of their pectoral fin rays, known as lamina circularis or scale of Canestrini, and no swellings of their body sides.
Males of bisexual lineages are sperm donors but the sperm only induces egg development and contributes no genetic material.
The all-female lineages are therefore sperm parasites and have to occur in sympatry with one of the parental species in a hybrid complex.Maximum size is about 40 cm but most are much smaller.The origins of this group of loaches may well lie at the end of the Eocene or in the early Oligocene in South China, spreading along a northern route through Europe and Siberia during the Oligocene-Miocene-Pliocene period and then later southwards into Southwest Asia (Sawada, 1982; Menon, 1987; 1992; Bănărescu and Nalbant, 1998; Šlechtov et al., 2008; Tang et al., 2008).This family of loaches, sometimes called sting-loaches, is found in Eurasia and Morocco and has about 28 genera with about 236 species (Berra, 2001; Nelson, 2006; Eschmeyer and Fong, 2011).Berra (2001) does not indicate the more southern distribution of this genus in Khuzestan and Fars provinces of Iran. Anonymous (1988a) places Cobitidae on the Official List of Family-Group Names in Zoology (rather than the grammatically correct but unused Cobitididae) and Cobitis taenia is designated as the type species for the genus Cobitis (see also Kottelat (1986) for further information).Economidis and Nalbant (1996) discuss characters used in the study of these fishes and consider scales to be characteristic of each species along with colour pattern, sexual dimorphism, suborbital spine morphology, barbel and mental lobe morphology, and others.