The reedfish, ropefish (more commonly used in the United States), or snakefish, Erpetoichthys calabaricus, is a species of fish in the bichir family and order. It is the only member of the genus Erpetoichthys. It is native to fresh and brackish waters in West and Central Africa. The reedfish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. It is threatened by habitat loss through palm oil plantations, other agriculture, deforestation, and urban development.
Studies
The Uptake of the oxygen: The employment of Gills, skin, and Lungs
Calamoichthys calabaricus (a type of reed fish) , an air-breathing fish, has been studied for its oxygen uptake and gas exchange mechanisms. The researchers wanted to know how this fish uses its gills, skin, and lungs to absorb oxygen and how short-term air exposure affects these processes. The fish's behavior of leaving the water voluntarily for brief terrestrial excursions is also investigated. There were some key findings for example, Calamoichthys can make frequent short trips to land, and some can stay out of the water for extended periods of time. The study measures the partitioning of oxygen uptake in water and discovers that the skin, along with the gills, plays an important role in obtaining oxygen from water. The lungs are also affected, but to a lesser degree.Calamoichthys exhibits a consistent increase in total oxygen consumption when exposed to air. The lungs are assumed to be the primary site of increased oxygen uptake during air exposure, with the skin also playing a role. The study emphasizes Calamoichthys' ability to maintain or increase oxygen uptake during air exposure, which is normal behavior. The importance of the skin in gas exchange is emphasized, and the fish's ability to control skin perfusion may be critical for effective gas exchange in variable humidity conditions. Further research into the physiology of air exposure in this primitive air-breathing fish species is yet to be discovered.
Description
The largest confirmed reedfish museum specimen was long, and three studies where more than 2,000 wild reedfish were caught (using basket traps, meaning that only individuals longer than were retained) found none that exceeded . Although sometimes claimed to reach up to long, this is incorrect.
Body elongation in fishes, such as eels, usually happens through the addition of caudal (tail) vertebrae, but in bichirs it has happened through the addition of precaudal vertebrae. Reedfish has evolved a more snakelike body by having twice as many precaudal vertebrae as the members of its sister genus Polypterus, despite having the same number of tail vertebrae. Pelvic fins are absent, and the long dorsal fin consist of a series of well-separated spines, each supporting one or several articulated rays and a membrane. The reedfish possesses a pair of lungs, enabling it to breathe atmospheric air. This allows the species to survive in water with low dissolved oxygen content and to survive for an intermediate amount of time out of water. The sexes are very similar in both median and maximum length, but females average heavier than males of a similar length, and they can be reliably separated by the shape of their anal fin. Reedfish are dark above and on the sides, with lighter orangish or yellowish underparts. Males are generally more olive-green in colour, whereas females generally are more yellowish-brown. Larvae have conspicuous external gills, making them resemble salamander larvae.
The genus name derives from the Greek words erpeton (creeping thing) and ichthys (fish).
Distribution and habitat
The reedfish inhabits slow-moving or standing, fresh or brackish, relatively warm tropical water, and usually in places with reeds or other dense plant growth. It occurs in Benin, Cameroon and Nigeria, spanning the area from the Ouémé River to the Sanaga River. There are old records from the Chiloango River in DR Congo and Cabinda in Angola, but these are unconfirmed and questionable.
Ecology
The reedfish is nocturnal, and feeds on annelid worms, small crustaceans (such as shrimp), insects (both adults and their larvae), snails and small fish. When moving through water slowly, it tends to use its pectoral fins, changing to an eel-like form of swimming (making more use of full-body movements and the caudal fin) when moving quickly. Unlike their sister genus Polypterus, which does not leave water voluntarily, reedfish are known to explore land both in the wild and in captivity if given the opportunity, slithering along like a snake and also taking food items on land. Prey captured on land is brought back to the water.