The hingemouth (Phractolaemus ansorgii) is a freshwater fish found only in western Central Africa. It is less commonly known as the “African Mudminnow”, “African mudfish”, “snake mudfish”, and “snake mudhead”. In Lontomba, it is called "mobili". It is best known for its unique oral anatomy.
Species description
The hingemouth is a small, olive-gray or brown fish with an elongated, semi-cylindrical body measuring up to 18 cm.
Its namesake mouth points upwards, the hingemouth’s jaw is jointed between the dentary and quadrate bones at the anterior tip of the head. When its mouth is closed, the dentary and attached upper jaws (the maxillae and premaxillae) lay back against the quadrate. When the mouth opens, the dentary swings upwards and outwards, projecting the upper jaws forward. Protrusion of the premaxilla is a trait of teleost fishes in general, and many teleost taxa have developed variations of the anatomy that enables protrusion, these are actually projections of the dentaries themselves. The proboscis is also lined with rows of keratinous projections.
Systematics
The hingemouth is currently considered the sole member of the family Phractolaemidae. Although no fossils directly related to the hingemouth have been found as of yet, the first kneriid fossil was discovered in 2002; comparisons of the fossil against modern hingemouth and kneriid specimens led some researchers to argue that the hingemouth should be subsumed into Kneriidae.
Distribution
thumb|Recorded occurrences of the hingemouth (Phractolaemus ansorgii)
Hingemouth are found in freshwater swamps In the dry season, they can be found in the benthos of floodplain pools and lagoons.
In a survey of the upper Ekole River in Nigeria that used local fishers to collect samples over several months, hingemouth comprised 0.77% of the catch. The study authors considered hingemouth relatively abundant, though not dominant, among the 70 different species observed. In another study, carried out in flooded forest swamps near Lake Tumba in the Democratic Republic of Congo, hingemouth represented 4.55% of the fish sampled. Their distribution across the Lake Tumba micro-basin was higher in areas with deeper, slower, warmer waters. Hingemouth also preferred areas with less plant debris on the bottom.
Biology
The hingemouth is a facultative air-breather,
Conservation status
Although the IUCN considers the hingemouth a species of least concern, it does experience anthropogenic threats, both directly via fishing and trade, and indirectly via damage to its habitat. For example, the upper Ekole River, where hingemouth are found in abundance, is subject to regular oil spills and other anthropogenic pollution. personal and commercial fishing does occur. The hingemouth is used ethnomedically by Ifa practitioners in Southwest Nigeria as both an antidote to malicious poisoning and a treatment for erectile dysfunction. Practitioners source the hingemouth from fish traders, fishermen, traditional doctors and pharmacists, and even catch the fish themselves. The hingemouth may be caught for food as well; at the time of Western discovery, the hingemouth was already being consumed by locals. although hobbyists report that it is not a commonly-kept species and that information on its care is difficult to find.