Caecobarbus geertsii

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Congo blind barb
Scientific classification e
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][2] This threatened cavefish is only known from Democratic Republic of the Congo,[1] and it is the only member of the monotypic genus Caecobarbus.[3] It was George Albert Boulenger who described this fish in 1921 and it completely lacks close relatives in the Congo region.[4]

Despite its common name, "African blind barb," there are other blind cave cyprinids indigenous to Africa, notably the Somalian Barbopsis devecchi and Phreatichthys andruzzii.[5]


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][2] The area where found covers about 120 km2 (45 sq mi),[2] and is located at an altitude of about 700–850 m (2,300–2,800 ft) above sea level.[4] It was initially known from seven caves in the Thysville system and an additional seven were discovered in the 2000s (decade).[2] 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.[2]


In the seven caves where first discovered, the total population has been estimated at perhaps 7,000 individuals in the 1950s; there are no estimates for the seven more recently discovered populations.[2] Among the first seven, one has disappeared entirely following quarrying of limestone that began in the 1930s.[2] 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][2] 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.[2] 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][2] 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 that are found in at least some places inhabited by the Congo blind barb.[2]


Like other cavefish, the Congo blind barb has reduced pigmentation and no externally visible eyes.[6] 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.[2] 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.[2] Its maximum length is 12 cm (4.7 in).[4] 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.[2]


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.[2] The longevity is estimated to be 9–14 years, but it may be able to live longer.[4] It is slow-growing and likely has a slow reproduction rate.[2] The adhesive eggs are spawned freely, ending up in crevices and pores in the bottom, which protects them from predation.[1]


  1. ^ a b c d e f g Moelants, T. (2010). "Caecobarbus geertsii". The IUCN Red List of Threatened Species. IUCN. 2010: e.T3449A9866689. doi:10.2305/IUCN.UK.2010-3.RLTS.T3449A9866689.en. Retrieved 13 January 2018. 
  2. ^ a b c d e f g h i j k l m n o p Vreven, E.; A. Kimbembi ma Ibaka; and S. Wamuini Lunkayilakio (2011). "The Congo blind barb: Mbanza-Ngungu's albino cave fish". In Darwall; Smith; Allen; Holland; Harrison; and Brooks. The diversity of life in African freshwaters: Underwater, under threat. IUCN. pp. 74–75. ISBN 978-2-8317-1345-8. 
  3. ^ "Caecobarbus geertsi". Integrated Taxonomic Information System. 
  4. ^ a b c d Froese, Rainer and Pauly, Daniel, eds. (2017). "Caecobarbus geertsi" in FishBase. July 2017 version.
  5. ^ Proudlove, G. (2006). Subterranean fishes of the world. ISBN 978-2-9527084-0-1. 
  6. ^ Proudlove, G. S.; Romero, A. (2001). "Threatened fishes of the world: Caecobarbus geertsii Boulenger, 1921 (Cyprinidae)". Environmental Biology of Fishes. 62: 238. doi:10.1023/A:1011803519256.