|Panaque nigrolineatus in an aquarium|
C. H. Eigenmann & R. S. Eigenmann, 1889
W. K. H. Peters, 1877
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. 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.
There are currently seven recognized species in this genus:
- Panaque armbrusteri Lujan, Hidalgo & D. J. Stewart, 2010
- Panaque bathyphilus Lujan & Chamon, 2008
- Panaque cochliodon Steindachner, 1879
- Panaque nigrolineatus W. K. H. Peters, 1877 (Royal panaque)
- Panaque schaeferi Lujan, Hidalgo & D. J. Stewart, 2010
- Panaque suttonorum L. P. Schultz, 1944 (Blue-eye panaque)
- Panaque titan Lujan, Hidalgo & D. J. Stewart, 2010
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".
Distribution and habitat
Panaque are found in the Magdalena River, Orinoco River, Amazon River, Essequibo River, and Lake Maracaibo drainages. 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.
Xylophagy (wood consumption and digestion)
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. Possible adaptations to consuming wood 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 the wood they consume. 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. 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. 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.
In the aquarium
Several species of Panaque have become popular aquarium fish, in particular the brightly coloured Panaque nigrolineatus. This fish is known as the "royal panaque" or "royal plec", a reflection of its costliness and beauty when compared with the common plecs, Hypostomus spp. widely sold to aquarists as algae eaters. Royal plecs have a greyish-green background colour against which are set thick, dark bluish-black stripes. The fins are edged with gold or cream, and the eyes are red. In captivity, royal plecs typically grow to around 30 cm in length.
A second species, Panaque cochliodon, is familiar to many aquarists as the blue-eyed plec. This fish was quite widely traded in the late 1980s and early 1990s but is now only rarely exported from its native Colombia. Aquarium books often refer to the blue-eyed plec as Panaque suttonorum or Panaque suttoni, though Panaque suttonorum is in fact a quite different fish that only comes from Venezuela. Blue-eyed plecs reach a similar size to royal plecs, but because many specimens are infected with a bacterium closely related to Rickettsia, mortality immediately after import can be high. Once settled in and feeding, they are no more difficult to keep than royal plecs.
All Panaque catfish require much the same thing in captivity. Their main demand is for a mixed diet including green algae, fresh vegetables such as carrots, courgettes, and spinach, and clean bogwood. In the wild, these fish feed almost entirely on wood and algae, and the meaty foods enjoyed by other plecs are not required. Because they are relatively large for aquarium fish and produce an unusual amount of waste, a big tank with a good filter is essential. Royal panaques at least are adaptable as far as water chemistry goes and though they prefer somewhat soft, slightly acid water conditions they will tolerate hard, alkaline water as well.
In terms of behaviour, Panaque are peaceful and nocturnal, and make good residents in community tanks. Like most of the other armoured catfish, they are territorial, and groups should only be kept in very large tanks.
- Panaque respirometry paper
- Armbruster, Jon. "Panaque". Retrieved 2007-03-31.
- Froese, Rainer, and Daniel Pauly, eds. (2011). Species of Panaque in FishBase. December 2011 version.
- Revision of Panaque (Panaque), with Descriptions of Three New Species from the Amazon Basin (Siluriformes, Loricariidae) - bioone.org Retrieved 2011-01-03
- Chockley, Brandon R.; Armbruster, Jonathan W. (May 2002). "Panaque changae, a new species of catfish (Siluriformes: Loricariidae) from eastern Peru" (PDF). Ichthyol. Explor. Freshwaters. 13 (1): 81–90. Retrieved 2009-06-24.
- Nelson, J. A.; Wubah, D. A.; Whitmer, M. E.; Johnson, E. A.; Stewart, D. J. (1999). "Wood-eating catfishes of the genus Panaque: gut microflora and cellulolytic enzyme activities" (PDF). Journal of Fish Biology. 54 (5): 1069–1082. doi:10.1111/j.1095-8649.1999.tb00858.x.
- German, D. P. (2009). "Inside the guts of wood-eating catfishes: can they digest wood?" (PDF). Journal of Comparative Physiology B. 179 (8): 1011. doi:10.1007/s00360-009-0381-1.
- Govan, Fiona (2010-09-14). "Wood-eating catfish discovered in Peru". London: The Daily Telegraph, UK. Retrieved September 15, 2010.
- "PlanetCatfish::Catfish of the Month::May 1999". 2007-05-22. Retrieved 2007-07-01.
- PlanetCatfish • Frequently Asked Questions
- Khoo, L.; Dennis, P. M.; Lewbart, G. A. (1995). "Rickettsia-like organisms in the blue-eyed plecostomus, Panaque suttoni (Eigenmann & Eigenmann)". Journal of Fish Diseases. 18 (2): 157–164. doi:10.1111/j.1365-2761.1995.tb00273.x.