Panaque
The genus Panaque contains a small number of small to medium-sized South American suckermouth armoured catfishes that are notable for being among the very few vertebrates that feed extensively on wood.[1] In addition, algae and aufwuchs are an important part of the diet, and they use their rasping teeth to scrape this from rocks. These fish are also popular aquarium fish, where the sound of scraping as these fish forage for food is easily audible.
The name Panaque is a Latinisation of a native Venezuelan name for these fish. It is pronounced "pan ack" in Britain and Europe, but often as "pan aki" or "pan a kay" in America. The Japanese call these fish "pana koo ee".[citation needed]
Panaque are found in the Magdalena River, Orinoco River, Amazon River, Essequibo River, and Lake Maracaibo drainages.[5] All Panaque come from tropical South American and inhabit fast-flowing streams and rivers. They are weak swimmers but like other armoured catfish possess a strong sucker-like mouth with which they can hold on to submerged rocks and wood.
Like other members of the armoured catfish family (Loricariidae), all Panaque have sturdy, armoured bodies covered in toughened plates of skin called scutes. These are not scales; like all catfish, Panaque lack scales. As well their armour, these catfish have very sturdy dorsal and pectoral fin spines. They use these defensively, either to wedge themselves into cracks from which predators cannot pull them, or else to prevent large predators from swallowing them. Another characteristic typical of the armoured catfish family is an iris. Most fish are unable to regulate the amount of light that enters the eye since they have irises that cannot change size. Both male and female Panaque develop bristles, known as odontodes, on the side of head immediately before and onto the pectoral fins.
Unlike predatory catfish, these omnivorous catfish have very short barbels. These barbels can be seen in the photograph of mouth of a Panaque shown here; they are the short pointed structures on either side of a suckermouth. This sucker-like mouth allows them to attach to rocks and remain stationary with very little expenditure of energy.
Along with the species of the Hypostomus cochliodon group (formerly the genus Cochliodon), it has been argued that Panaque are the only fish that can eat and digest wood.[5] Possible adaptations to consuming wood include spoon-shaped, scraper-like teeth and highly angled jaws to chisel wood.[5] Researchers have also identified symbiotic gut bacteria that may allow the fish to digest the wood they consume.[6] However, others have argued that Panaque do not in fact digest wood, and in fact take up very little energy from the wood they consume and actually lose weight when fed just wood.[7] Furthermore, their digestive tracts are no different from those of related catfish and they do not hold wood particles in the gut longer than other catfish, suggesting Panaque are not physically adapted to eating wood, and are in fact detritivores much like other Loricariidae.[7] In September 2010 scientists from the US National Science Foundation claimed to have discovered a new species of wood-eating catfish in the Alto Purús National Park, Peru.[8]
