lukuga river begins in central africa near lake tanganyika.
which river begins in central africa near lake tanganyika?
lukuga river
most clupeids are marine and lake tanganyika was formed by rifting and has never had a connection with sea, the sub-family that the lake tanganyika sardine and its relative the lake tanganyika sprat, are members of, the pellonulinae are common in southern and western africa, for example "microthrissa royauxi" and "potamothrissa acuitirostris" in the congo basin. molecular phylogenetic reconstructions indicate that the ancestors of these freshwater pellonulines colonised west africa 25–50 million years ago, at the end of a major marine incursion in the region. pellonuline herring subsequently speciated in an evolutionary radiation in west africa, spreading across the continent and colonising lake tanganyika during its early formation. this shows that while lake tanganyika has never been directly connected with the sea, the endemic freshwater clupeids of the lake are descended from fish who radiated out of an ancient marine incursion.
lake tanganyika sardine
lake tanganyika is the site from which nearly all the cichlid lineages of east africa (including both riverine and lake species) originated. thus, the species in the lake constitute a single adaptive radiation event but do not form a single monophyletic clade. lake tanganyika is also the least speciose of the three largest african great lakes, with only around 200 species of cichlid; however, these cichlids are more morphologically divergent and ecologically distinct than their counterparts in lakes malawi and victoria, an artifact of lake tanganyika's older cichlid fauna. lake tanganyika itself is believed to have formed 9-12 million years ago, putting a recent cap on the age of the lake's cichlid fauna. many of tanganyika's cichlids live very specialized lifestyles. the giant or emperor cichlid ("boulengerochromis microlepis") is a piscivore often ranked the largest of all cichlids (though it competes for this title with south america's "cichla temensis", the speckled peacock bass). it is thought that giant cichlids spawn only a single time, breeding in their third year and defending their young until they reach a large size, before dying of starvation some time thereafter. the three species of "altolamprologus" are also piscivores, but with laterally compressed bodies and thick scales enabling them to chase prey into thin cracks in rocks without damaging their skin. "plecodus straeleni" has evolved large, strangely curved teeth that are designed to scrape scales off of the sides of other fish, scales being its main source of food. "gnathochromis permaxillaris" possesses a large mouth with a protruding upper lip, and feeds by opening this mouth downward onto the sandy lake bottom, sucking in small invertebrates. a number of tanganyika's cichlids are shell-brooders, meaning that mating pairs lay and fertilize their eggs inside of empty shells on the lake bottom. "lamprologus callipterus" is the most unique egg-brooding species, with 15 cm-long males amassing collections of shells and guarding them in the hopes of attracting females (about 6 cm in length) to lay eggs in these shells. these dominant males must defend their territories from three types of rival: (1) other dominant males looking to steal shells; (2) younger, "sneaker" males looking to fertilize eggs in a dominant male's territory; and (3) tiny, 2–4 cm "parasitic dwarf" males that also attempt to rush in and fertilize eggs in the dominant male's territory. these parasitic dwarf males never grow to the size of dominant males, and the male offspring of dominant and parasitic dwarf males grow with 100% fidelity into the form of their fathers. a number of other highly specialized tanganyika cichlids exist aside from these examples, including those adapted for life in open lake water up to 200m deep.
adaptive radiation