This species is among the most frequently-misidentified in the hobby, almost always being traded as P. kuhlii.
However the latter is currently considered endemic to Java, from where commercial collections are almost unheard of, and has possibly never been seen in aquaria.
In fact the relationship between these two has long been confused and remains so to a certain extent. For example, P. semicincta was regarded valid from 1940 until 1992 when it was placed in synonomy with P. kuhlii by Burridge.
Later Kottelat and Lim (1993) pointed out a lack of adequate evidence in Burridge's work but conditionally agreed with her in considering the two synonymous since they could detect no significant differences between her Javanese neotype, Malaysian specimens and their series from southern Sumatra.
They concluded by suggesting that more work be done to ascertain if the pair, along with the nominal subspecies P. k. sumatrana, represent the same species or not.
In a 1995 article published in German aquarist magazine Datz, Kottelat reported he had received fresh P. kuhlii material from Java and confirmed P. semicincta to be a separate taxa. Kottelat & Widjanarti (2005) stated that 'recent material obtained from Java has shown that the two species are distinct'.
In 2009 Tan and Kottelat confirmed that 'Fresh material from Java shows that the two species have very distinctive colour patterns'.
They also examined specimens collected from the Musi river drainage in southern Sumatra, close to the type locality of P. sumatrana, and found no discernible differences between them and other Sumatran populations of P. semicincta.
P. sumatrana was thus adjudged to be synonymous with P. semicincta rather than P. kuhlii, with the former occurring in Peninsular Malaysia, Sumatra and Borneo and latter endemic to Java.
As far as aquarists are concerned the situation is still confused, since fresh Javanese material has not been described in detail anywhere we know of, meaning we don't know what characters diagnose P. kuhlii sensu stricto. A single colour image appears in Kottelat (2012).
It also seems likely that a number of unidentified, similar-looking populations exist, particularly on Borneo, of which some have undoubtedly appeared in the aquarium trade.
However even if further study reveals P. kuhlii to occur outside Java it appears probable that it is not the common aquarium 'Kuhli/coolie' loach which is more likely to be P. semicincta, one or more unidentified species, or a combination of these.
P. semicincta is included in the P. kuhlii-oblonga group of closely-related species within the genus as per Bohlen et al. (2011).
Unfortunately a contemporary diagnosis of its distinguishing characters is lacking due to the issues surrounding its validity discussed above, and the following are therefore selected from Fraser-Brunner (1940): depth of body contained about 8 times and length of head 6½ times in standard length; 3 pairs of barbels of which the rostral pair are longest; dorsal fin II, 6; anal fin II, 6; pectoral-fin I, 10; colour yellowish with a series of broad transverse bands mostly confined to upper half of body and usually wider above than below; basal half of caudal-fin with asymmetrical black patch.
Its colopur pattern is highly irregular with innumerable variations, both within and between populations, though most specimens exhibit the same basic pattern of dark saddle-like markings, usually wider at the dorsal surface, over a yellow/orange base colour.
Although Fraser-Brunner states the 'saddles' are usually restricted to the upper half of the body there exist many forms in which they extend well below the lateral line. The saddles also break up to a certain extent in some older individuals which can result in some peculiar patterning.
Kottelat and Lim (1993) suggested that the P. kuhlii and P. oblonga species groups represent two of four such assemblages within the genus alongside the P. anguillaris and P. shelfordii groups.
Members were separated from those of the P. kuhlii, P. shelfordii and P. anguillaris groups by their plain body patterning, 8-9 pectoral-fin rays, 45-51 vertebrae and development of adipose keels on both ventral and dorsal extremes of the caudal peduncle.
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.
Within this third lineage are three sublineages formed by P. filinaris, an apparently undescribed fish from the Temburong River in Brunei referred to as P. cf. oblonga IV, and all other species in the group, respectively.
Species in the P. khulii and P. oblonga groups had previously been separated largely on the basis of colour pattern, i.e., barred vs. plain brown, but in the molecular analysis the barred species grouped within the brown. They also display a high degree of morphological affinity with simlarities in body shape and the number of vertebrae.
One brown specimen even grouped together with the barred P. malayana collected from the same locality rather than any of the other plain fish, suggesting a degree of phenotypic variability within species may also be involved.
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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