Pangio myersi (HARRY, 1949)

Giant Kuhli Loach

SynonymsTop ↑

Acanthophthalmus myersi Harry, 1949

Etymology

myersi: named for Dr. George Sprague Myers of Stanford University ‘in appreciation of his interest and research on Indo-Malayan fishes’.

Classification

Order: Cypriniformes Family: Cobitidae

Distribution

Native to the lower Mekong basin in Laos, Cambodia, Vietnam and Thailand with type locality ‘Nong Khor, southeastern Thailand’.

Habitat

Most commonly found in shallow, slow-moving sections of forest streams or other calm habitats such as swamps, oxbows, and backwaters.

Many such environments are associated with ancient peat swamps and contain black water although it’s also found in clear waters which may or may not be tannin-stained to some extent.

Such habitats are typically shaded from the sun by marginal vegetation and the tree canopy above.

The water has a negligible dissolved mineral content, is poorly-buffered and pH can be as low as 3.0 or 4.0 due to release of tannins and organic acids from decaying organic material.

Depending on locality the substrate may be composed of peat, mud or sand with the fish typically abundant in piles of leaf litter.

Maximum Standard Length

90 – 100 mm.

Aquarium SizeTop ↑

An aquarium with base measurements of at least 60 ∗ 30 cm or equivalent is recommended.

Maintenance

Use a soft, sandy substrate since this species likes to dig and tends to spend some of its time completely buried. When coarser gravel is used it may become stressed or damage itself, and feeding behaviour can be inhibited.

A few driftwood roots and branches, placed in such a way that plenty of shady spots are formed, can be used to add structure to the display and addition of dried leaf litter would provide additional cover and aid in simulating natural conditions.

Fairly dim lighting is also preferable with aquatic plants from genera such as Microsorum, Taxiphyllum, and Cryptocoryne suitable.

Gentle filtration providing a little surface agitation is adequate and high flow rates best avoided. Ensure that small specimens are unable to enter filter intakes and cover the tank well as most loaches do jump at times, especially when introduced to a new environment.

Water Conditions

Temperature: 21 – 26 °C

pH: 3.5 – 7.0

Hardness: 0 – 143 ppm

Diet

Chiefly a micropredator sifting mouthfuls of substrate through the mouth and gills from which insect larvae, small crustaceans and suchlike are extracted with a proportion of the natural diet also likely to comprise organic detritus and plant material from the gut contents of prey.

In the aquarium it will accept sinking dried foods but should also be offered regular meals of live and frozen Daphnia, Artemia, bloodworm, micro worm, grindal worm, etc.

Behaviour and CompatibilityTop ↑

Pangio spp. are peaceful both with one another and other fishes and there exist no reports of them harming tankmates though they may prey on eggs or fry.

In nature they’re often found in large aggregations and in captivity will often pack themselves into a single nook, cranny or cave when at rest, so a group of at least 5-6 specimens should be the minimum purchased.

Small, peaceful species from similar environments such as Boraras, Sundadanio, smaller Rasbora, Trichopsis, Sphaerichthys, Kottelatlimia, etc., constitute the best tankmates.

Some sand-dwelling loaches from the family Nemacheilidae are also suitable but proper research is essential as some can be excessively competitive, territorial or otherwise aggressive.

Sexual Dimorphism

Adult females are typically heavier-bodied and a little larger then males, while in mature males the first pectoral-fin ray is branched and thickened.

Reproduction

Unrecorded.

NotesTop ↑

This species is traded on a regular basis and is also known as ‘Myer’s loach’. In recent years albino and leucistic forms have become available although it’s unclear if these are naturally-occurring or not.

It’s included in the P. kuhlii group of closely-related species within the genus as per Bohlen et al. (2011),  and can be distinguished from other members by the following combination of characters: 8-11 very broad, quadrangular, regular dark body bars; orange base body colour; caudal-fin either entirely black or with a large black blotch at the base and a submarginal dark bar or row of spots.

The latter feature can be useful in identifying young or newly-imported, undernourished specimens which can superficially resemble P. kuhlii or P. semicincta because those two species possess only a dark blotch on the caudal-fin base.

Kottelat and Lim (1993) suggested that the P. kuhlii and P. oblonga groups represent two of four such assemblages within the genus alongside the P. anguillaris and P. shelfordii groups. P. myersi was included in the P. khulii group based on its barred colour pattern and lack of labial barbels.

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.

References

1. Harry, R. R., 1949 - Proceedings of the Biological Society of Washington v. 62: 69-72
   A new loach of the genus Acanthophthalmus from Siam.
2. Bohlen, J., V, Šlechtová, H. H. Tan and R. Britz, 2011 - Molecular Phylogenetics and Evolution 61(3): 854-865
   Phylogeny of the Southeast Asian freshwater fish genus Pangio (Cypriniformes; Cobitidae).
3. Britz, R. and J. Maclaine, 2007 - Ichthyological Exploration of Freshwaters 18(1): 17-30
   A review of the eel-loaches, genus Pangio, from Myanmar (Teleostei: Cypriniformes: Cobitidae).
4. Britz, R. and M. Kottelat, 2010 - Ichthyological Exploration of Freshwaters 20(4): 317-376
   Pangio longimanus, a miniature species of eel-loach from central Laos (Teleostei: Cypriniformes: Cobitidae).
5. Burridge, M. E., 1992 - Copeia 1992(1): 172-186
   Systematics of the Acanthophthalmus kuhlii complex (Teleostei: Cobitidae), with the description of a new species from Sarawak and Brunei.
6. Hadiaty, R. K. and M. Kottelat, 2009 - Zootaxa 2171: 65-68
   Pangio lidi, a new species of loach from eastern Borneo, Indonesia.
7. Kottelat, M., 2001 - WHT Publications Ltd., Colombo , Sri Lanka: 1-198
   Fishes of Laos.
8. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
9. Kottelat, M. and K. K. P. Lim, 1993 - Raffles Bulletin of Zoology 41(2): 203-249
   A review of the eel-loaches of the genus Pangio (Teleostei: Cobitidae) from the Malay Peninsula, with descriptions of six new species.
10. Tan, H. H. and M. Kottelat, 2009 - Ichthyological Exploration of Freshwaters 20(1): 13-69
    The fishes of the Batang Hari drainage, Sumatra, with description of six new species.
11. Tang, Q., H. Liu, R. Mayden and B. Xiong, 2006 - Molecular Phylogenetics and Evolution 39(2): 347-357
    Comparison of evolutionary rates in the mitochondrial DNA cytochrome b gene and control region and their implications for phylogeny of the Cobitoidea (Teleostei: Cypriniformes).
12. Šlechtová, V., J. Bohlen and A. Perdices, 2008 - Molecular Phylogenetics and Evolution 47(2): 812-831
    Molecular phylogeny of the freshwater fish family Cobitidae (Cypriniformes: Teleostei): delimitation of genera, mitochondrial introgression and evolution of sexual dimorphism.
13. Šlechtová, V., J. Bohlen and H. H. Tan, 2007 - Molecular Phylogenetics and Evolution 44(3): 1358-1365
    Families of Cobitoidea (Teleostei; Cypriniformes) as revealed from nuclear genetic data and the position of the mysterious genera Barbucca, Psilorhynchus, Serpenticobitis and Vaillantella.