Eggs swell and reach as large as 3.5 mm in diameter and as a result are retained in the vegetation although they are not adhesive.A number of species are popular aquarium fishes, including the coolie or kuhli loaches and the weatherfish.None of the Iranian fishes are used in this fashion but they can be quite colourful. taenia is a potential fishing bait for predatory fishes such as Sander lucioperca and has been examined experimentally for this purpose in Turkey (Kuşat et al., 1995).Genus Cobitis Linnaeus, 1758 These fishes are found in Europe, North Africa and Asia. They are known generally as سگ ماهي (sag mahi meaning dog fish) in Farsi, the equivalent of loach in English.
Movement is by undulations of the body, particularly marked in the more elongate species.
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).
An early Oligocene route also existed between the Anatolian landmass and Central Asia (Tang et al., 2008) and cobitids may have invaded the Euro-Mediterranean zoogeographic subregion at least five times independently based on cytochrome b data.
Some members of this family can live in oxygen-poor waters.
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.