The genus Pangio is one of the most species-rich genera in the loach family Cobitidae and is widespread across South and Southeast Asia. It is the largest genus within the southern lineages of Cobitidae, with nearly three dozen recognized species. Pangio loaches are small (<12 cm total length), elongated freshwater fishes. According to Kottelat and Lim (1993), Pangio loaches are distinguished from members of all other genera of the family Cobitidae by their very slender and compressed bodies, by the position of the dorsal fin (which originates distinctly behind the pelvic origin rather than in front, above, or slightly behind), and by the large number of vertebrae. Mature males of all species can be easily distinguished from females by the presence of a thickened first branched pectoral fin ray. Breeding males can be recognized by the presence of a tuberculate pad on the dorsal surface of the pectoral fin, covering the distal half of the enlarged first branched ray and part of the second branched ray.
The different Pangio species inhabit a variety of habitats ranging from moderately swift to very slow flowing streams and representatives are found from India and southern Vietnam to Java. Pangio loaches live in benthic substrates, typically in submerged leaf litter and dense aquatic vegetation. Several species may occur together at the same locality and up to seven species may be found within a single river basin. They are gregarious when kept in aquaria (and presumably in nature), congregating under rocks or decaying vegetation.
Some Pangio species are collected and exported for the aquarium trade. These banded species are generally known as "kuhli loaches" based on the specific epithet of one species, P. kuhlii (named after an active collector in the Dutch East Indies, Heinrich Kuhl [1797-1821]). They are easily recognized by their bright pink to orange and black barred color pattern. They are sometimes inappropriately called "Coolie Loaches" in the aquarium literature. Partly for this reason, several researchers have begun to use the common name "eel-loaches" to refer generally to all Pangio species.Kottelat and Lim (1993) reviewed the eel-loach species of the Malay Peninsula (Singapore, West Malaysia and Thailand south of the Isthmus of Kra), including comments on the systematics of species from adjacent areas.
As noted above, the Kuhli Loach (Pangio kuhlii) and close relatives are familiar fishes in the aquarium trade. Pangio kuhlii is apparently widely distributed on the Sunda Shelf, except in Sarawak (northwestern Borneo), where it is replaced by P. agma (Burridge, 1992). This distribution pattern is shared with several other pairs of fish species (Kuttelat and Lim 1993). Pangio kuhlii is known from West Java, Sumatra, Kalimantan Timur and Kalimantan Barat (East and West Kalimantan, Borneo), and the Malay Peninsula at least as far north as Phangnga (records from Burridge [1992] from central and southeastern Thailand were considered questionable by Kittelat and Lim [1993], who suggested they may actually refer to P. myersi). Pangio kuhliihas 6 to 10 usually irregular bars along its body with a dark large quadrangular blotch occupying the proximal (i.e., closer to body) half of the caudal (tail) fin; in contrast to some other Pangio species, the median lobe of the lower lip is not produced into a barbel; and the vertebral count is 34 to 37+ 12 to 15 = 47 to 51 vertebrae.
Based on the molecular phylogenetic analysis by Bohlen et al. (2011), there are three main lineages within the genus Pangio, two of which correspond to two of the four groups recognized by Kottelat and Lim (1993), with the third group matching the remaining two groups of these authors combined. The kuhlii-group includes all species with a dark brown or black banding pattern on yellow or red background, including P. kuhlii.
Burridge (1992) provided technical descriptions of the genus and analysis of the P. kuhlii complex.
(Burridge 1992; Kottelat and Lim 1993; Bohlen et al. 2011 and references therein)
The true Kuhli loach (Pangio kuhlii), occasionally referred to as eel loach, is a small eel-like freshwater fish belonging to the loach family (Cobitidae). They originate from the island of Java and Sumatera[2] in Indonesia. This snake-like creature is very slender and nocturnal.
The kuhli loach is an eel-shaped fish with slightly compressed sides, four pairs of barbels around the mouth, and very small fins. The dorsal fin starts behind the middle of the body, and the anal fin well behind this. The eyes are covered with transparent skin. The body has 10 to 15 dark brown to black vertical bars, and the gaps between them are salmon pink to yellow with a light underside. When the fish is not actively breeding, distinctions between males and females are not readily apparent. However, close observation will reveal that males have a more muscular upper/dorsal cross-section and their pectoral fins tend to be larger, more paddle-shaped, and often have some pigment in them. When breeding, the females often become larger than the male and their greenish ovaries can be seen through the skin before spawning. Spawning is not easy, but when it occurs a few hundred greenish eggs are laid among the roots of floating plants. Kuhli loaches reach maturity at 2 3⁄4 inches (7 cm) and have a maximum length of 4 inches (10 cm). This fish can live for up to about 14 years.
The natural habitat of the kuhli loach is the sandy beds of slow-moving rivers and clean mountain streams. They are a social fish and are typically found in small clusters (they are not schooling fish but enjoy the company of their species), but are cautious and nocturnal by nature and swim near the bottom where they feed around obstacles. They natively live in a tropical climate and prefer water with a 5.5 – 6.5 pH-but will tolerate 7.0 pH in aquaria, a water hardness of 5.0 dGH, and a temperature range of 75 – 86 °F (24 – 30 °C). Kuhli loaches are scavengers, so they will eat anything that reaches the bottom. They usually feed at night, but can be taught to feed in the day in the home aquarium.[3]
In the wild, the fish spawn communally in very shallow water. The kuhli loach is a bottom dweller that burrows into soft places. Its older generic name 'Acanthophthalmus' comes from the meaning 'thorn' or 'prickle-eye', after a spine beneath each eye.
The kuhli loach was originally described as Cobitis kuhlii by Achille Valenciennes in 1846 to commemorate Heinrich Kuhl's work as a naturalist and zoologist. In scientific literature, it has been referred to as Acanthophthalmus kuhlii. The genus name Acanthophthalmus is a junior synonym of Pangio.
While striped Pangio loaches are a common in aquaria, the true P. kuhlii is rarely, if ever, kept. This is due to the fact that they are endemic to Indonesia Java and Sumatra, where collection of ornamental fish is extremely rare.[4][5] There are many who doubt P. kuhlii has ever even made it into the private aquarium trade.
There are a number of species of the genus Pangio, primarily P. semicincta, that appear similar and are sold under the same name, require similar care, and are all excellently suited for household tanks. They tend to be hardy and long-lived in the aquarium and get along well with their own kind as well as others.
In an aquarium environment, especially if the gravel is suitably finely grained, Pangio species can burrow into the bottom and there remain unseen for long periods of time, emerging to eat during the night. If the gravel is later disturbed, a hobbyist might well find themselves faced with fish assumed lost a long time ago. Kuhlis may also occasionally swim into unprotected filter inlets, possibly leading to their deaths.[6]
Breeding in captivity requires plenty of hiding spaces and consistent water quality.[7]
The true Kuhli loach (Pangio kuhlii), occasionally referred to as eel loach, is a small eel-like freshwater fish belonging to the loach family (Cobitidae). They originate from the island of Java and Sumatera in Indonesia. This snake-like creature is very slender and nocturnal.
