Panaque

Panaque are freshwater catfish from South America, part of the suckermouth armoured catfish family. They are among the very few vertebrates that eat a lot of wood, though algae and aufwuchs—scraped from rocks with their rasping teeth—are also important in their diet. In home aquariums, the scraping sound they make while feeding is easily heard.

Taxonomy

The genus was first proposed in 1889 by ichthyologists Carl H. Eigenmann and Rosa Smith Eigenmann, with Chaetostomus nigrolineatus as the type species. That species had been described in 1877 by Wilhelm Peters from the Guárico River in Venezuela. Some classifications place Panaque within the tribe Ancistrini of the subfamily Hypostominae, but Eschmeyer's Catalog of Fishes does not recognize tribes in that subfamily. The names Scobinancistrus and Panaqolus are sometimes treated as subgenera of Panaque.

Etymology

Valid species include Panaque armbrusteri, P. bathyphilus, P. cochliodon, P. nigrolineatus (royal panaque), P. schaeferi, P. suttonorum (blue-eye panaque), and P. titan. The genus name comes from the local Venezuelan name for the type species.

Distribution and habitat

These fish live in fast-flowing streams and rivers across the Magdalena, Orinoco, Amazon, Essequibo, and Lake Maracaibo drainages. They are weak swimmers but, like other armoured catfish, have a strong sucker-like mouth to hold onto submerged rocks and wood.

Physical characteristics

Panaque can be told apart from related genera by their spoon-shaped teeth, which are broader at the tips than at the bases. Other suckermouth catfish have teeth that stay the same width from base to tip. They also lack a buccal papilla—a flap of skin inside the mouth. Their barbels are very short, unlike those of predatory catfish, and can be seen as short pointed structures on either side of the sucker mouth.

Whether Panaque truly digest wood is debated. Some researchers point to their spoon-shaped teeth, angled jaws, and symbiotic gut bacteria as adaptations for wood consumption. Others argue that the fish get little energy from wood, lose weight on a wood-only diet, and have digestive tracts no different from related catfish, suggesting they are detritivores like other Loricariidae. In 2010, scientists from the US National Science Foundation claimed to have found a new wood-eating catfish species in Peru's Alto Purús National Park.

In aquariums, several Panaque species are popular.