Anatomy posht pashneh pa
As a result, hybridogenous individuals in the complex are difficult to distinguish from the bisexual parent species on external characters.
An unbalanced sex ratio in a population with more females than males is usually evidence that hybridogenous lineages are present (Kottelat and Freyhof, 2007).
The body form is fusiform to rounded or elongate; the mouth is subterminal and has 3-6 pairs of barbels; the mental lobes of the lower lip have two parts: the anterior which is usually short and sometimes divided into lobules, and the posterior which is flap-like and longer and sometimes divided into 2 or more barbel-like extensions; there is 1 row of pharyngeal teeth; and there is an erectile spine in a groove below the eye (anterior in a non-Iranian genus).
Iranian species have one pair of rostral barbels and a rounded or slightly emarginate caudal fin and belong to the subfamily Cobitinae.
The usual population fecundity of clonal forms being twice that of a bisexual species does not apply here because of the larger eggs.
Movement is by undulations of the body, particularly marked in the more elongate species.
A consequence of this form of movement is a reduction in fin size and variation.
Reproduction involves the male chasing the female, entering vegetation and wrapping around the female as eggs are released and fertilised.
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).
Polyploid unisexual, bisexual-unisexual complexes and gynogenetic forms of Cobitis exist in the basins of the Baltic, Black, Caspian and Mediterranean seas (Vasil'ev and Vasil'eva, 1996; Kottelat, 1997; Vasil'eva and Vasil'ev, 1998; Vasil'ev et al., 1999; Bohlen, 2001; Vasil'ev et al., 2011).