Panaque

Lore & Background

The genus Panaque was first formally proposed in 1889 by the German-born American ichthyologist Carl H. Eigenmann and his wife Rosa Smith Eigenmann, with Chaetostomus nigrolineatus designated as its type species. That species was first formally described in 1877 by Wilhelm Peters, with its type locality given as the Guárico River at Calabozo in the Apure River drainage, Guárico State, Venezuela. Some authorities regard this genus as being within the tribe Ancistrini of the subfamily Hypostominae, but Eschmeyer's Catalog of Fishes does not recognise tribes within the subfamily Hypostominae. Scobinancistrus and Panaqolus are sometimes considered to be subgenera of this genus.

Panaque are found in the Magdalena River, Orinoco River, Amazon River, Essequibo River, and Lake Maracaibo drainages. All come from tropical South America and inhabit fast-flowing streams and rivers. They are weak swimmers but possess a strong sucker-like mouth with which they can hold on to submerged rocks and wood. They may be distinguished from other related genera by their teeth, which are spoon-shaped, being clearly broader at their tips than at their bases. They also lack a buccal papilla, a flap of skin on the inside of the mouth. Unlike predatory catfish, these omnivorous catfish have very short barbels.

Along with species of the Hypostomus cochliodon group, it has been argued that Panaque are the only fish that can eat and digest wood. Possible adaptations include spoon-shaped, scraper-like teeth and highly angled jaws to chisel wood. Researchers have also identified symbiotic gut bacteria that may allow the fish to digest wood. However, others have argued that Panaque do not in fact digest wood, and actually lose weight when fed just wood; their digestive tracts are no different from those of related catfish, suggesting they are detritivores much like other Loricariidae.

Reader's Guide

Several species of Panaque have become popular aquarium fish. The brightly coloured Panaque nigrolineatus, known as the 'royal panaque' or 'royal pleco', is particularly popular, with a greyish-green base color, thick dark bluish-black stripes, fins edged with gold or cream, and red eyes. In captivity, royal plecos typically grow to around 30 centimeters in length. A second species, Panaque cochliodon, is familiar as the 'blue-eyed pleco', widely traded in the late 1980s and early 1990s but now only rarely exported from its native Colombia. It is associated with the binomina Panaque suttonorum and P. suttoni, though Panaque suttonorum is a different fish from Venezuela. Blue-eyed plecos reach a similar size, but many specimens are infected with a bacterium closely related to Rickettsia, causing high mortality immediately after import; once settled, they are no more difficult to keep than royal plecos.

All Panaque require much the same care: a mixed diet including green algae, fresh vegetables such as carrots, courgettes, and spinach, and many aquarists provide driftwood for them to graze upon. Meaty foods are not required. Because they are relatively big and produce an unusually large amount of waste, a high-capacity tank and filter are essential. Royal panaques tolerate a wider range of water chemistry than others, preferring somewhat soft, slightly acid water but tolerating hard, alkaline water. Behaviorally, they are peaceful and nocturnal bottom-dwellers, good residents in community tanks, but territorial, so groups should only be kept in very large tanks.

Did You Know?

• Panaque are among the very few vertebrates that feed extensively on wood.
• The genus was first formally proposed in 1889 by Carl H. Eigenmann and Rosa Smith Eigenmann.
• The blue-eyed pleco (Panaque cochliodon) was widely traded in the late 1980s and early 1990s but is now rarely exported from Colombia.