This species is exported occasionally, often as bycatch among shipments of congeners.
It's included in the P. shelfordii group of closely-related species and can be distinguished from other members by the following combination of characters: body with a more-or-less conspicuous series of midlateral blotches, sometimes forming a solid lateral stripe; a dark bar-like marking at the base of the caudal-fin; caudal-fin mottled; three dark bars on head (not including snout markings); median lobe of lower lip forming a barbel; 46-51 vertebrae.
Patterning is highly variable depending both within and between populations and as currently understood the species represents an assemblage containing a number of unidentified taxa (Kottelat and Lim, 1993; Tan and Kottelat, 2009; Bohlen et al., 2011; Kottelat, 2012).
For example, those from Singapore and Johor possessing intricate mottling on the dorsal surface while individuals from Terengganu have a series of saddle-like markings either alternating or connecting with the midlateral markings. The former may actually be Pangio muraeniformis (de Beaufort 1933) although we've been unable to confirm this as yet.
Sarawak specimens have a similar pattern to those from Terengganu but the midlateral markings tend to be extended vertically and considerably darker at mid-body, with the dorsal saddles much lighter and tending to adjoin each other leaving only thin pale patches between. The species was described from the Sungai (river) Sarawak close to the city of Kuching.
In fish from Bangka Island the midlateral blotches form a continuous dark stripe with irregular markings with dorsal patterning consisting of either poorly-defined predorsal saddles or fine spots.
In those from the upper Kapuas River, Kalimantan Barat, Borneo, possess irregular midlateral markings which are darker at midbody height and relatively few, irregularly-shaped, diffuse dorsal saddles.
In the lower Kapuas populations have a speckled body patterning with a black midlateral stripe and dorsal saddles in just the occasional specimen.
Some Sumatran and Bornean populations of P. shelfordii superficially resemble P. piperata which can cause issues with identification as the two often occur together.
In general however the body patterning in P. piperata is much plainer than that of P. shelfordii, and they differ in vertebral counts (mode 47 vs. 50, respectively).
The pectoral fins in male P. piperata are also proportionally longer being approximately twice as long as those in females vs. slightly longer in P. shelfordii.
Kottelat and Lim (1993)[5] suggested that the P. shelfordii group represents one of four such assemblages within the genus alongside the P. anguillaris, P. kuhlii and P. oblonga groups.
This unofficial system was followed until Bohlen et al. (2011) published a molecular phylogenetic analysis including 18 recognised species plus a number of undescribed ones.
Their results suggest the existence of three, rather than four, major lineages within the genus; the P. anguillaris and P. shelfordii groups represent two of them with Kottelat and Lim's P. kuhlii and P. oblonga groups together forming the third.
P. shelfordii group members are separated from those of the P. kuhlii-oblonga and P. anguillaris groups by possession of a pair of labial 'barbels' on the lower lip, a dark bar at the base of the caudal-fin, several rows of spots on the caudal-fin and a relatively slim caudal peduncle.
They currently include P. atactos, P. incognito, P. muraeniformis, P. piperata, P. shelfordii and P. superba.
Pangio is among the most speciose cobitid genera and widespread throughout South and Southeast Asia with species diversity thought to be considerably greater than currently recognised.
Pangio species are often generically referred to as 'kuhli' or 'coolie' loaches in the aquarium hobby, the latter a variation of the former which was itself derived from the surname of German naturalist Heinrich Kuhl (1797-1821). Ichthyologists tend to refer to them as 'eel loaches'.
They're distinguished from other cobitids by their long, slender body shape, relatively high number of vertebrae and the position of the dorsal-fin which is situated well behind the origin of the pelvic fins (vs. in front of, above or only slightly behind).
Several described members were previously included in the genus Acanthophthalmus which Kottelat (1987) demonstrated to be a syonym of Cobitis, and he chose the replacement name Pangio in preference to its simultaneous synonym Apua (Blyth, 1860).
Myers (1929) placed P. anguillaris as type species of Cobitophis, a grouping containing the very elongate species, while Perugia (1892) originally described P. doriae in the genus Eucirrhichthys. The former was synonymised with Acanthophthalmus by Nalbant (1963) and the latter by Roberts (1989).
The family Cobitidae, often referred to as 'true' loaches, is widely-distributed across most of Eurasia with the Indian subcontinent, Southeast Asia and China representing particular centres of species diversity.
Phylogenetic analyses by Tang et al. (2006), Šlechtová et al. (2007) and Šlechtová et al. (2008) revealed that the group constitutes a separate genetic lineage to the family Botiidae (the two were previously grouped together under Cobitidae as subfamilies Cobitinae and Botiinae).
In the most recent study Pangio was found to be more closely affiliated with Acantopsis, Acanthopsoides and Kottelatlimia than Lepidocephalichthys as had been previously hypothesised.
All cobitids possess sharp, motile, sub-ocular spines which are normally concealed within a pouch of skin but erected when an individual is stressed, e.g. if removed from the water. Care is therefore necessary as these can become entangled in aquarium nets and with larger species even break human skin.
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