Niger stingray
One of two freshwater stingrays in Africa, critically endangered.
The Niger stingray, also called the smooth freshwater stingray (Fontitrygon garouaensis), belongs to the Dasyatidae family and lives in rivers across Nigeria and Cameroon. Its pectoral fin disk is thin and nearly circular, with a snout tip that sticks out slightly. The skin is mostly smooth, with small or no dermal denticles. This ray grows up to 40 cm (16 in) wide. It eats aquatic insect larvae and reproduces through ovoviviparity. The long, stinging spine on its tail can cause a painful injury. The International Union for Conservation of Nature (IUCN) lists it as Critically Endangered because its numbers are dropping in some areas due to heavy fishing and habitat degradation.
Alfred Stauch and M. Blanc first described the species in 1962 in the journal *Bulletin du Muséum National d'Histoire Naturelle (Série 2)*. The name *garouaensis* comes from Garoua, Cameroon, where the type specimen was caught. They placed it in the genus *Potamotrygon*, which would have made it the only member of that genus outside South America. In 1975, Thomas Thorson and Donald Watson examined new specimens and, based on physical and physiological traits, moved it to *Dasyatis*.
Along with the pincushion ray (*F. ukpam*), the Niger stingray is one of only two freshwater stingrays in Africa. It is known from just three river systems: the Benue and lower Niger in Nigeria, and the lower Sanaga and Cross rivers in Cameroon. Reports from Lagos Lagoon remain unconfirmed. It has only been found in fresh water, though it might tolerate varying salinities.
The pectoral fin disk is almost circular, only about 5% longer than wide, with 122–124 internal rays on each side. It is flatter than any other stingray in the region, no more than 11% as thick as wide. The front edges are slightly concave, and the snout tip sticks out a little. The eyes are medium-sized and protruding, with small spiracles behind. The nostrils are covered by a skin flap with a fringed rear edge that reaches the small mouth. The upper jaw has 16–18 tooth rows, the lower jaw 14–28. Teeth are small and close-set; females have oval, blunt teeth, while males have triangular teeth with a sharp, backward-pointing cusp. Five papillae line the mouth floor. The pelvic fins are roughly triangular, and the tail is whip-like, twice as long as the disk is wide.
Quick Facts
- Genus
- Fontitrygon
- Species
- garouaensis
Facts from the source article.
Lore & Background
The Niger stingray was originally described in 1962 by Alfred Stauch and M. Blanc in the journal Bulletin du Muséum National d'Histoire Naturelle. They assigned it to the genus Potamotrygon, which would have made it the only representative of that genus outside South America. In 1975, Thomas Thorson and Donald Watson examined new specimens and concluded, on morphological and physiological grounds, that it belongs to Dasyatis. The specific epithet garouaensis refers to the city of Garoua, Cameroon, where the type specimen was caught.
This ray is known only from three river systems: the Benue and lower Niger River, the lower Sanaga River, and the Cross River. Records from Lagos Lagoon are unconfirmed. It has only been found in fresh water, though the possibility that it may be euryhaline cannot be discounted. The pectoral fin disk is nearly circular, about 5% longer than wide, and more flattened than any other stingray in the region. The skin is mostly smooth, with small or absent dermal denticles. The tail bears one or more stinging spines that can inflict a painful wound.
The Niger stingray feeds almost exclusively on aquatic nymphs of mayflies, stoneflies, and caddisflies. It is ovoviviparous, with females having a single functional ovary on the left side. Males mature at under 26.4 cm across in the Sanaga River, and females at 26–30 cm across. Males live up to five years, females up to seven years.
Reader's Guide
The Niger stingray is significant as one of only two freshwater stingray species in Africa, alongside the pincushion ray (Fontitrygon ukpam). Its osmoregulatory system retains substantial amounts of urea, though much less than marine species, and its ampullae of Lorenzini are smaller and simpler than those of marine stingrays, reflecting constraints of the freshwater environment. Compared to Potamotrygon stingrays, which have speciated dramatically in South America, the Niger stingray and its relatives may be more recent colonizers of fresh water.
The species has been assessed as Critically Endangered by the IUCN. Its numbers are declining in some areas, particularly in the Niger-Benue river system where it was historically most common. The possible disappearance from its type locality near Garoua was reported to have resulted from drought. A substantial number can still be found in the Sanaga River, though the population trend there is unknown. The ray faces heavy fishing pressure and habitat degradation, pressures likely to increase as its range becomes more heavily populated. It is caught incidentally and sold fresh or smoked for human consumption. The tail spine is known to the Hausa people as kunaman ruwa or 'water scorpion'.
Did You Know?
- Its specific epithet garouaensis refers to Garoua, Cameroon, where the type specimen was caught.
- Males live up to five years and females up to seven years.
More in Reef Sharks and Rays, Part 2 1-24
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