Nemacheiline
loaches are small size benthic freshwater fishes inhabiting swift, clear and
well-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 in
North East Africa and about 80 species alone are reported in the Indian region.
These loaches are preferred locally for food besides their role in the
lucrative aquarium trade (Menon et al., 1987). Apart from this, the caves
dwelling species are of scientific value from an evolutionary viewpoint (Romero
and Green et al., 2005; Kottelat et al., 2007; Juan et al., 2010). Furthermore,
from the biodiversity perspective too, this group has immense potential as most
of the ichthyofaunal discoveries during the recent times have been from this
subfamily (Vishwanath and Nebeshwar et al., 2004, 2005; Sreekantha Gururaja et
al., 2006; Vishwanath and Shanta et al., 2006; Kottelat et al., 2007) and many
more should be expected in India.

Nemacheilus
Genus as
described
by Kottelat (1990) and Banarescu &
Nalbant (1995) is distributed throughout Indochina, Sundaland and with two
isolated species in western India (Kottelat, 1984, 1990; Banarescu &
Nalbant et al., 1995). At present, as per current online
http://www.fishbase.org, version (11/2017), Nemacheilus comprised of 278
species out of these about 23 reported in India. The body is not elongate, at
least partly covered with scales although minute, belly straight and horizontal
(S. China; India; Pakistan; Afghanistan; W. Iran & N. E. Africa). Body with
a 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 pelvic
and anal fins (Western Ghats). Nemacheilus consists of a group of
species which are remarkably similar in general morphology. Because they lack
the usual spines, scutes and various other processes and peculiarities of
structures, the species of Nemacheilus are often the most difficult to
distinguish. Environmental conditions tend to produce similar characters and it
is probable that the great resemblance between the various species of Nemacheilus
is due to a similarity in their environment. The usual environment of rapid
running water of these loaches is full of stress and the animals that inhibit
such habitat have to adjust themselves constantly to any fluctuation in the
microclimate or ecological niche. In these circumstances, the organisms are
modeled and remodeled till ultimately the elucidation of their true systematic
position becomes a matter of great difficulty. This is what has happened in Nemacheilus
and consequently, the taxonomy of these fishes has been in great confusion
(Menon et al., 1987). These fishes also show high levels of morphological and
ecological conservatism (Kottelat et al., 1988). In the past, this conservatism
allowed several authors to ascribe most loaches to the genus Nemacheilus
based on body coloration (i.e. number and type of bands), a number of branched
rays 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, recent
cladistics analyses recognized the generic status of the numerous subgenera
within the subfamily (Jayaram et al., 2010; Eschmeyer et al., 2011; Froese and
Pauly et al., 2011).

The
Western Himalayan region of India particularly Uttarakhand is endowed with vast
freshwater resources and thus known to harbor a rich diversity of freshwater fishes (Hora and
Mukerji 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, and
Schistura 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). Despite
the vast biodiversity within Nemacheilidae, the molecular and cytogenetic analysis
of this group remain poorly explored. The study also attempted to clarify the
systematic status of these species using molecular and cytogenetic tools and
results could form the taxonomic base for the revision of identity of these
species in India subcontinent.

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