Lake Ejagham is a small lake near Eyumodjock in the Southwest Region of

Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...

. Unlike many other lakes in the region, it is not a

volcanic lake A volcanogenic lake is a lake formed as a result of volcanic activity. They are generally a body of water inside an inactive volcanic crater (Volcanic crater lake, crater lakes) but can also be large volumes of molten lava within an active volcan ...

, but is likely a solution basin formed by

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

during the last Ice Age. This highly isolated lake is roughly

oval An oval () is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas of mathematics (projective geometry, technical drawing, etc.), it is given a more precise definition, which may inc ...

in shape, lacks an inflow, but has an outflow into the Munaya River (part of the Cross River system).Schliewen, U.K., Tautz, D., and Pääbo, S. (1994). ''Sympatric speciation suggested by monophyly of crater lake cichlids.''

Nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

368(6472): 629-632. The outflow is impassable to most fishes because of a waterfall.

Biology

Despite its very small size, it supports 7

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

species of coptodonine and oreochromine cichlid fishes ('' Coptodon deckerti'', '' C. ejagham'', '' C. fusiforme'', '' C. nigrans'', '' Sarotherodon lamprechti'', and '' S. knauerae''). Of these, 6 were only

scientifically described A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it diffe ...

in 2010 and 2011, and have therefore not been rated by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

, but they likely face the same threats as ''C. deckerti'' (the single older species that has been rated by the IUCN). Neumann, D., Stiassny, M. L. J, & Schliewen, U. K. (2011). ''Two new sympatric Sarotherodon species (Pisces: Cichlidae) endemic to Lake Ejagham, Cameroon, west-central Africa, with comments on the Sarotherodon galilaeus species complex.'' Zootaxa 2765: 1–20 ''C. deckerti'' is considered

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

due to

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

and

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...

from human activities. It could also be threatened by large emissions of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

(CO₂) from the lake's bottom (compare

Lake Nyos Lake Nyos ( ) is a crater lake in the Northwest Region of Cameroon, located about northwest of Yaoundé, the capital. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcan ...

), although Ejagham is too shallow to contain very high amounts of this gas.Freeth, S.J.; C.O. Ofoegbu; and K.M. Onuoha (1992). Natural Hazards in West and Central Africa, pp. 50—51. A species of catfish from the genus ''

Parauchenoglanis ''Parauchenoglanis'' is a genus of claroteid catfishes native to Africa. The range of the genus ''Parauchenoglanis'' stretches from the coastal lowlands of Benin and Nigeria to the Okavango and upper Zambezi River systems in Botswana and Zambia ...

'' has been introduced to the lake, and this probably presents a serious threat to the endemic cichlids. The Ejagham cichlids are commonly considered a prime example of

sympatric speciation Sympatric speciation is the evolution of a new species from a surviving Common descent, ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, ''sympatric'' and ''sympatry'' are ter ...

within its two genera. Studies indicate a level of secondary

gene flow In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic variation, genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...

between the lake's species and relatives from nearby regions, and this likely facilitated the

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

(i.e., the Ejagham species not strictly the result of sympatric speciation).Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422.

References

Ejagham Southwest Region (Cameroon) {{Cameroon-geo-stub

Biology

See also

References