Redescription , new distribution record , DNA sequence and length-weight relationship of the Eel-loach Pangio pangia ( Cypriniformes : Cobitidae ) in the River Ganges Basin , India

The Eel-loach Pangio pangia has never been reported from East India in the River Ganges. In August, 2011, we collected a total of 39 individuals of this species during fish diversity explorations in River Ganges at Narora. This is the first record for Uttar Pradesh (North India). We present additional diagnostic features and description for this species previously known only from very old descriptions generally based on preserved specimens. Additionally, a molecular signature of the internal transcribed spacer 2 (ITS2) region between 5,8S and 28S ribosomal RNA genes was sequenced and submitted to NCBI (Accession No. JQ619873). The length-weight relationship showed allometric growth as b value of overall length-weight relation was 2,71 at p<0,00 which, ranged from 2,65 to 2,76. The substantial threats and issues regarding unawareness of this understudied fish species are highlighted to help sustaining fish biodiversity in India.

In River Ganges in East India, Hamilton (1822) was first to describe Cobitis pangia as a synonym of Pangio pangia, however, the locality of this species was unknown (Froese & Pauly, 2010).Later the species was placed under the genus Pangio and has been redescribed by Britz and Maclaine (2007).The basin of River Ganges, which has very high cultural, heritage and religious values, drains about 1 060 000km 2 and it is the fifth largest in the world (Welcomme, 1985).The River Ganges supports an exceedingly rich diversity of freshwater fishes and nutritional security of local people (Sarkar et al., 2011).Current studies revealed that substantial number of species in this River is being shifted and moving upward in the upper stretches of the River due to change in temperature clime and rainfall patterns (Sarkar et al., 2011).We collected P. pangia from the middle stretch of the River Ganges near Narora, Uttar Pradesh which is a new distribution record of this species in this state and after a very long period in River Ganges.The conservation status of this species listed as least concern (LC) as per the FISHBASE and IUCN (2010).In addition, lack of definite information on the abundance, distribution and biological aspects of this species has hampered the planning and management strategies for their conservation.
As far as we know, there is no previous record of P. pangia in North India, especially in Uttar Pradesh, the present report may be considered as the first evidence of a broader distributional range of P. pangia, indicating that the species may be more widely distributed than previously acknowledged.The length-weight relationship was additionally investigated which could serve as first baseline information for fishery biologists and conservationists.The threats to this species were also discussed.

METHODOLOGY
The specimens were collected from the middle stretch of the River Ganges near Narora (28°11,305 N, 078°23,797E) about 170km from New Delhi, capital of India (Fig. 1).The specimens were collected using a cast net during an experimental shoreline fishing operation in August, 2011.All the samples were transported to the laboratory where they were identified following Talwar and Jhingran (1991) and Jayaram (2010).The specimens were subsequently counted and a total of twelve morphometric and meristic characters were taken with a Mitutoyo digital caliper to the nearest 0,01mm (Table 1).A digital photograph of the specimen was taken, and it was then fixed in 10% formaldehyde for further studies.Physical and chemical parameters of the site were also collected (water temperature, conductivity, pH, total dissolved solids, and dissolved oxygen) using YSI multiparameter sonde.Water velocity was measured by flow meter (JDC Electronics SA, Switzerland).
The statistical relationship between total length (TL) and total body weight (TBW) of the fishes was derived using the formula: Where W= weight of fish in grams, a= intercept (constant), L= length of fish in centimeters and b= regression coefficient (slope).
All data were log-transformed and the ensuing least squares linear regressions (Zar, 1984) performed by GRAPHPAD PRISM 5.0, with the weight as the dependent variable.A linear regression on log-transformed data was highly significant (p<0,00) for P. pangia.
Internal Transcribed Spacer 2 (ITS2) of ribosomal DNA is regarded as one of the candidate DNA barcode because it possesses a number of valuable characteristics, such as the availability of conserved regions for designing universal primers, the ease of its amplification and sufficient variability to distinguish even closely related species.The success rates for using the ITS2 region to identify dicotyledons, monocotyledons, gymnosperms, ferns, mosses and animals were 76,1%, 74,2%, 67,1%, 88,1%, 77,4% and 91,7% respectively at the species level (Yao et al., 2010).

Diagnostic
Morphometric and meristic details of P. pangia (Fig. 2) are presented in Table 2.The average total length of 39 specimens was 50,41mm which ranged between 44,2 to 62,2mm with average body depth 5,64mm.The fin formula comprised: D ii 6 ⁄ A ii 5 ⁄ P i 6 ⁄ V i 4. Head was very short and its length measured 3,34 times in head width.Standard length was 8,16±0,14 times in body depth.Eyes were minute, covered by skin, in middle of head.Head length measured 9,03±0,11 times in eye diameter.Dorsal fin was short inserted in posterior half of body, nearer caudal fin base than tip of snout.Predorsal length was measured 2,78 times in post dorsal length.

Description
Body elongate strongly, compressed and anguilliform.Head deeply compressed.Eyes minute.Mouth small and inferior, lips thick, lower lip with two contiguous prolongations.Three pairs of barbels.Dorsal fin small.Caudal fin truncate.Scales minutely embedded in skin and the fresh specimens were uniformly reddish brown in color.

Remarks
Due to very smooth and soft body the species often become twisted and easily disformed even in best prepared collections.The species are often difficult to measure with accuracy, thus, careful handling of the samples is recommended at the time of collection.Menon, 1999;Kapoor et al., 2002;Talwar & Jhingran,1991;Shaji et al., 2000, Thomas et al., 1999;Dahanukar et al.,2004 3 Pangio longipinnis (Menon, 1992) Manipur, Kharangpat Lake, South of Imphal 3 Menon, 1999

Habitat
The collection site has a moderate flow (0,06ms -1 ) with leteral scour pools and riffles.Substrate was mostly cobbles (80%) and gravels (40%).The stream bank was stable, and its mean width was measured 45m and depth 0,92m.Scattered shrubs and mid-story trees were the canopy cover.Based on the habitat parameters, the site was considered a mid-reach stream.Water was muddy due to heavy rainfall in the monsoons.Dissolved oxygen was measured 7mg/l, temperature, 29,12°C, conductivity 0,087m/mhos and total hardness, 28mg/l.

Length-weight relation
This is the first information on the length weight relationship of P. pangia.The curves obtained by plotting weight against the length for specimens of P. pangia revealed curvilinear nature (Fig. 3).The calculated coefficient of correlation between body length and weight was 0,996 showing a high degree of correlation.In the present study, the estimates of parameter b ranged from 2,65 to 2,76 and b value of overall length-weight relation was 2,71 showing allometric growth.The figure also shows that the weight of fish increased as an exponential function of its length.

DISCUSSION
Inadequate knowledge about abundance and distribution of species confines not only our understanding of the ecological and evaluative processes but also affect our capacity to use this information in conservation management plans (Maitland, 1995).P. pangia Hamilton, described in 1822 in River Ganges has never been reported subsequently (Table 1), though many of the fish diversity studies carried out by several authors in River Ganges and its tributaries (Srivastava, 1980;Ravenga & Mock, 2000;Sinha, 2007;Sarkar & Bain, 2007;Sarkar, Gupta & Lakra, 2010;Lakra, Sarkar, Kumar, Pandey, Dubey & Gusain, 2011;Sarkar et al., 2011).Moreover, various other investigators; Banarescu and Nalbant (1968), Talwar and Jhingran (1991), Menon (1999), Kottelat (1996) and Jayaram (1999) also documented P. pangia, while these information did not provide distributional data, or specimens voucher locations except a recent study by Vishwanath et al. (2007) who reported this species from the drainages of Myanmar.
In view of the above that we reported this species in River Ganges after a very long period therefore, our recent record of this species suggests the population of P. pangia to be in a precarious state which emphasized the first distribution record of this species in North India of the River Ganges.From a taxonomic point of view, the genus Pangio is also important while, only four species were documented in India.It is interesting to know that as the species has never reported at this stretch of River Ganges, thus the current record revealed the possibilities due to climate change since other current studies showed perceptible shifts in many of the freshwater fishes (Sarkar et al., 2011).Additionally, our present findings unwrapped the possibility for new distribution records of P. pangia and other species of this genus.
Growth of fish usually indicated through increase in length and weight (Jobling, 2002) which is the most appropriate characteristic to determine the population analysis at a particular time.So far our knowledge, this is the first report on the length weight relationship of P. pangia.The exponential value of the length-weight relationship 'b' in P. pangia followed the cube law especially the pooled data ('b' = 2,71), indicating thereby an allometric pattern of growth in the fish.According to Hile (1936) and Martin (1949) the value of 'b' usually remains constant at 3,0 for an ideal fish.However, Beverton & Holt (1957) suggested the departure of the 'b' value from 3 is rare in adult fishes.The b values obtained in the present work conform with those of earlier researchers who have estimate the b value in various fish species, e.g.Ahmed and Saha (1996) and Sarkar, Deepak and Negi (2009) in the Ganga basin; Ramakrishniah (1988) in Nagarjunasagar reservoir, India; and Pet, Gevers, van Densen and Vijverberg. (1996) in Sri Lankan reservoirs.Presently, there are no studies done on the freshwater fish P. pangia on the length-weight relationship thus, our findings are advantageous for better understanding on factors influencing fish growth in various habitats in north Indian water bodies.
The exploitation of natural resources threatens P. pangia.The fishermen are not much aware of this species and caught as by-catch when netting for small sized fishes.Because their body is very smooth and easily disformed therefore, it is very difficult to handle and kept as live while netting.Barrages and pollution from industrial sewage from thermal power plant at Narora were the major threat to this species.Cultivation of water chesnut at the sampling site was also observed which destroy the habitat of P. pangia and threatens its survival.There are also problems with catchment mismanagement.Unfortunately, scarce knowledge about this species has mired their conservation and management plans in India.
In conclusion, our first record of this species revealed the uncertainty that whether the population of this species is resident in River Ganges or not.Therefore, more exploration in the streams and Rivers of the Ganges basin at various spatial scales are to be encouraged for the better understanding of their habitat.As there is no study on molecular taxonomy of this species therefore there is also a need to characterize the population, using morphological and molecular tools.Additionally, our study has provided the first basic and baseline information on the length-weight relationships of P. pangia from the Ganges River that would be beneficial for fishery biologists and conservationists to impose adequate regulations for sustainable fishery management of this understudied fish.

FIG. 1 .
FIG. 1. Drainage map of River Ganges with sampling location at Narora.

TABLE 1
Distribution records of the genus Pangio in India.