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Pincushion Ray
The pincushion ray (''Dasyatis ukpam'') or thorny freshwater stingray, is a little-known species of stingray in the family Dasyatidae, found in the rivers and lakes of West and Middle Africa. A heavy-bodied ray measuring up to across, this species can be distinguished by its rounded pectoral fin disk, reduced or absent stinging tail spine, and—in adults—numerous stout thorns covering its back and tail. In lieu of a long tail spine as in other stingrays, the pincushion ray employs these thorny denticles in defense. Seldom encountered since it was originally described, this species has been assessed as Critically Endangered by the International Union for Conservation of Nature (IUCN). Taxonomy John Alexander Smith scientifically described the pincushion ray in 1863, in ''Proceedings of the Royal Physical Society of Edinburgh''. He named it ''ukpam'', as that is the local indigenous name for freshwater stingrays. Because he saw the single, reduced tail spine of this ray as an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Alexander Smith (zoologist)
John Alexander Smith (June 1818–17 August 1883) was a Scottish physician, antiquarian, archaeologist and ornithologist. Life He was born at 13 Hope Street, off Charlotte Square, in June 1818, the son of James Smith (architect), the last Master Mason of Scotland. He was educated at the High School in Edinburgh then studied medicine at the University of Edinburgh receiving his doctorate (MD) in 1840. He set up practice as a GP in Edinburgh's West End at 7 West Maitland Street. In 1863 he was elected a Fellow of the Royal Society of Edinburgh The Royal Society of Edinburgh is Scotland's national academy of science and letters. It is a registered charity that operates on a wholly independent and non-partisan basis and provides public benefit throughout Scotland. It was established i ... his proposer being John Hutton Balfour. From 1870 to 1873 he was Vice President of the Society of Antiquaries of Scotland. In 1874 he succeeded the late Dr Somerville as Treasurer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sanaga River
The Sanaga River (formerly german: Zannaga) is the largest river in Cameroon located in East Region, Centre Region and Littoral Region. Its length is about from the confluence of Djérem and Lom River. The total length of Sanaga-Djérem River system is about . Djerem is the longest source of Sanaga River with a total length of 464.5 km. Course The Sanaga River has its Source at the Adamawa Plateau. It is formed by the confluence of the Djérem River and Lom River in the north of the East Region. Djérem River has a total length of and Lom River has a total length of . Apart from those originating rivers, the largest tributary of Sanaga is Mbam River with a total length of . Climate The Sanaga River forms a boundary between two tropical moist forest ecoregions. The Cross-Sanaga-Bioko coastal forests lie to the north between the Sanaga River and the Cross River of Nigeria, and the Atlantic Equatorial coastal forests extend south of the river through southwes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiracle (vertebrates)
Spiracles () are openings on the surface of some animals, which usually lead to respiratory systems. The spiracle is a small hole behind each eye that opens to the mouth in some fish. In the jawless fish, the first gill opening immediately behind the mouth is essentially similar to the other gill opening. With the evolution of the jaw in the early jawed vertebrates, this gill slit was caught between the forward gill-rod (now functioning as the jaw) and the next rod, the hyomandibular bone, supporting the jaw hinge and anchoring the jaw to the skull proper. The gill opening was closed off from below, the remaining opening was small and hole-like, and is termed a spiracle. In many species of sharks and all rays the spiracle is responsible for the intake of water into the buccal space before being expelled from the gills. The spiracle is often located towards the top of the animal allowing breathing even while the animal is mostly buried under sediments. As sharks adapted a fast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes along the eyelid margin, which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration. "Palpebral" (and "blepharal") means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies. The appearance of the human upper eyelid often varies between different populations. The prevalence of an epicanthic fold covering the inner corner of the eye account for the majority of East Asian and Southeast Asian populations, and is also found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water. A contour line of constant salinity is called an ''isohaline'', or sometimes ''isohale''. Definitions Salinity in rivers, lakes, and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride, magnesium sulfate, potassium nitrate, and sodium bicarbonate which dissolve into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an example of a euryhaline invertebrate that can live in salt and brackish water. Euryhaline organisms are commonly found in habitats such as estuaries and tide pools where the salinity changes regularly. However, some organisms are euryhaline because their life cycle involves migration between freshwater and marine environments, as is the case with salmon and eels. The opposite of euryhaline organisms are stenohaline ones, which can only survive within a narrow range of salinities. Most freshwater organisms are stenohaline, and will die in seawater, and similarly most marine organisms are stenohaline, and cannot live in fresh water. Osmoregulation Osmoregulation is the active process by which an organism maintains its level of water co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brackish Water
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root '' brak''. Certain human activities can produce brackish water, in particular civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming. Brackish water is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment (see article on shrimp farms). Technically, brackish water contains between 0.5 and 30 grams of salt per litre—more often expressed as 0.5 to 30 parts per thousand (‰), which is a specific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Democratic Republic Of The Congo
The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in Central Africa. It is bordered to the northwest by the Republic of the Congo, to the north by the Central African Republic, to the northeast by South Sudan, to the east by Uganda, Rwanda, and Burundi, and by Tanzania (across Lake Tanganyika), to the south and southeast by Zambia, to the southwest by Angola, and to the west by the South Atlantic Ocean and the Cabinda exclave of Angola. By area, it is the second-largest country in Africa and the 11th-largest in the world. With a population of around 108 million, the Democratic Republic of the Congo is the most populous officially Francophone country in the world. The national capital and largest city is Kinshasa, which is also the nation's economic center. Centered on the Congo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boma, Kongo Central
Boma is a port town on the Congo River, some upstream from the Atlantic Ocean, in the Kongo Central province of the Democratic Republic of the Congo, adjacent to the border with Angola. It had an estimated population of 162,521 in 2012. Boma was the capital city of the Congo Free State and Belgian Congo (the modern Democratic Republic of the Congo) from 1 May 1886 to 1923, when the capital was moved to Léopoldville (since renamed Kinshasa). The port handles exports of tropical timber, bananas, cacao, and palm products. History Boma was founded by European merchants in the 16th century as an entrepôt, including for the slave trade. Trade was chiefly in the hands of Dutch merchants, but British, French and Portuguese firms also had factories there. No European power exercised sovereignty, though claims were from time to time put forward by Portugal. British explorer Henry Morton Stanley arrived here on 9 August 1877, after crossing Africa from east to west.Stanley, H. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Congo River
The Congo River ( kg, Nzâdi Kôngo, french: Fleuve Congo, pt, Rio Congo), formerly also known as the Zaire River, is the second longest river in Africa, shorter only than the Nile, as well as the second largest river in the world by discharge volume, following only the Amazon. It is also the world's deepest recorded river, with measured depths around . The Congo- Lualaba- Chambeshi River system has an overall length of , which makes it the world's ninth-longest river. The Chambeshi is a tributary of the Lualaba River, and ''Lualaba'' is the name of the Congo River upstream of Boyoma Falls, extending for . Measured along with the Lualaba, the main tributary, the Congo River has a total length of . It is the only major river to cross the Equator twice. The Congo Basin has a total area of about , or 13% of the entire African landmass. Name The name ''Congo/Kongo'' originates from the Kingdom of Kongo once located on the southern bank of the river. The kingdom in turn was nam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabon
Gabon (; ; snq, Ngabu), officially the Gabonese Republic (french: République gabonaise), is a country on the west coast of Central Africa. Located on the equator, it is bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo on the east and south, and the Gulf of Guinea to the west. It has an area of nearly and its population is estimated at million people. There are coastal plains, mountains (the Cristal Mountains and the Chaillu Massif in the centre), and a savanna in the east. Since its independence from France in 1960, the sovereign state of Gabon has had three presidents. In the 1990s, it introduced a multi-party system and a democratic constitution that aimed for a more transparent electoral process and reformed some governmental institutions. With petroleum and foreign private investment, it has the fourth highest HDI in the region (after Mauritius, Seychelles and South Africa) and the fifth highest GDP per capita ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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