Congo blind barb | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cypriniformes |
Family: | Cyprinidae |
Genus: | Caecobarbus Boulenger, 1921 |
Species: | C. geertsi |
Binomial name | |
Caecobarbus geertsi Boulenger, 1921 | |
Caecobarbus geertsi, the African blind barb or Congo blind barb (known as Nzonzi a mpofo in the local Kikongo language, meaning "blind barb"), is a species of cyprinid fish. [1] [3] This threatened cavefish is only known from Democratic Republic of the Congo, [1] and it is the only member of the monotypic genus Caecobarbus. [4] George Albert Boulenger described this fish in 1921 and it apparently lacks any close relatives in the Congo region. [5]
Despite its common name, "African blind barb", other blind cave cyprinids are indigenous to Africa, notably the Somalian Barbopsis devecchi and Phreatichthys andruzzii . [6]
The Congo blind barb is found only in the Thysville Cave system, a part of the lower Congo River basin (notably Kwilu and Inkisi tributaries) in the Democratic Republic of the Congo. [1] [3] The area where it is found covers about 120 km2 (45 sq mi), [3] and is located at an altitude around 700–850 m (2,300–2,800 ft) above sea level. [5] It was initially known from seven caves in the Thysville system and an additional seven were discovered in the 2000s (decade). [3] The caves where found have high levels of calcium bicarbonate in the water and high variations in flood levels, meaning that animals such as terrestrial cave insects are absent. [3]
In the seven caves where first discovered, the total population has been estimated at perhaps 7,000 individuals in the 1950s; no estimates are available for the seven more recently discovered populations. [3] Among the first seven, one has disappeared entirely following quarrying of limestone that began in the 1930s. [3] The caves where it lives are considered sacred by the locals, and this restricts access to most of them. A local law passed in 1937 limits fishing and the species has been listed on CITES since 1981, which limits international trade. [1] [3] Before its listing on CITES Appendix II, the species was often caught and exported for the freshwater aquarium trade, but few exports have happened after. [3] Currently, the main threat is habitat loss: The human population in its range is increasing and farming near the caves can result in sedimentation and pollution. [1] [3] The region was formerly covered in rainforest and grassland, which limited erosion. Other potentially serious threats are changes to the hydrology (for example, large-scale water extraction) of the small rivers that feed the caves and predation by Clarias catfish found in at least some places inhabited by the Congo blind barb. [3]
Like other cavefish, the Congo blind barb has reduced pigmentation and no externally visible eyes. [7] Because of the lack of pigment, it appears pale whitish-pink overall. The operculum and lateral line region are purplish-red due to the gills and lateral line veins, respectively. [3] The eye completely lacks a lens, and the retina and optical nerve are rudimentary and located deep inside the head. Despite this, the fish is photophobic, actively avoiding light. [3] Its maximum total length is 12 cm (4.7 in). [5] Minor differences have been described between the different cave populations; some have a spot on the opercular and one has a serrated dorsal fin spine. [3]
The Congo blind barb mainly relies on food items that flow into the cave during the rainy (flood) season, but it may also feed on small crustaceans. [3] Its longevity is estimated to be 9–14 years, but it may be able to live longer. [5] It is slow-growing and likely has a slow reproduction rate. [3] The adhesive eggs are spawned freely, ending up in crevices and pores in the bottom, which protects them from predation. [1]
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