Nemacheilineloaches are small size benthic freshwater fishes inhabiting swift, clear andwell-oxygenated water bodies and belong to the family Nemacheilidae.Nemachelidae fishes are unique for the relatively high species diversity,including more than 651 fish species distributed in India, South China,Southeast Asia, Baluchistan, Western Iran, South Anatolia, and Laka Tsana inNorth East Africa and about 80 species alone are reported in the Indian region.These loaches are preferred locally for food besides their role in thelucrative aquarium trade (Menon et al., 1987).
Apart from this, the cavesdwelling species are of scientific value from an evolutionary viewpoint (Romeroand Green et al., 2005; Kottelat et al., 2007; Juan et al., 2010). Furthermore,from the biodiversity perspective too, this group has immense potential as mostof the ichthyofaunal discoveries during the recent times have been from thissubfamily (Vishwanath and Nebeshwar et al.
, 2004, 2005; Sreekantha Gururaja etal., 2006; Vishwanath and Shanta et al., 2006; Kottelat et al., 2007) and manymore should be expected in India.NemacheilusGenus asdescribedby Kottelat (1990) and Banarescu &Nalbant (1995) is distributed throughout Indochina, Sundaland and with twoisolated species in western India (Kottelat, 1984, 1990; Banarescu &Nalbant et al., 1995). At present, as per current onlinehttp://www.
fishbase.org, version (11/2017), Nemacheilus comprised of 278species out of these about 23 reported in India. The body is not elongate, atleast partly covered with scales although minute, belly straight and horizontal(S. China; India; Pakistan; Afghanistan; W. Iran & N.
E. Africa). Body witha lateral band; a blackish rounded spot at the middle of the base of caudal fin;anal opening placed at a distance about 30 to 43 percent in that between pelvicand anal fins (Western Ghats). Nemacheilus consists of a group ofspecies which are remarkably similar in general morphology. Because they lackthe usual spines, scutes and various other processes and peculiarities ofstructures, the species of Nemacheilus are often the most difficult todistinguish. Environmental conditions tend to produce similar characters and itis probable that the great resemblance between the various species of Nemacheilusis due to a similarity in their environment. The usual environment of rapidrunning water of these loaches is full of stress and the animals that inhibitsuch habitat have to adjust themselves constantly to any fluctuation in themicroclimate or ecological niche.
In these circumstances, the organisms aremodeled and remodeled till ultimately the elucidation of their true systematicposition becomes a matter of great difficulty. This is what has happened in Nemacheilusand consequently, the taxonomy of these fishes has been in great confusion(Menon et al., 1987). These fishes also show high levels of morphological andecological conservatism (Kottelat et al., 1988). In the past, this conservatismallowed several authors to ascribe most loaches to the genus Nemacheilusbased on body coloration (i.e.
number and type of bands), a number of branchedrays in the dorsal fin, and the nature of caudal fin (Menon et al., 1987;Kottelat et al., 1988; Talwar and Jhingran et al., 1991). However, recentcladistics analyses recognized the generic status of the numerous subgenerawithin the subfamily (Jayaram et al., 2010; Eschmeyer et al.
, 2011; Froese andPauly et al., 2011). TheWestern Himalayan region of India particularly Uttarakhand is endowed with vastfreshwater resources and thus known to harbor a rich diversity of freshwater fishes (Hora andMukerji et al.
, 1936; Hora et al.,1937; Menon et al., 1949, 1974; Pant et al., 1970; Singh et al., 1990).Nemacheilidae species from the genera Acanthocobitis, Nemacheilus, andSchistura reported so far in this region of India. (Prokofiev et al.
, 2009;Jayaram et al., 2010; Negi R.K et al., 2010; Lokeshwar et al., 2012).
Despitethe vast biodiversity within Nemacheilidae, the molecular and cytogenetic analysisof this group remain poorly explored. The study also attempted to clarify thesystematic status of these species using molecular and cytogenetic tools andresults could form the taxonomic base for the revision of identity of thesespecies in India subcontinent.