A taxonomic reevaluation of freshwater ostracods (Crustacea,Ostracoda) referred to the genus Cypridopsis Brady, 1868 from Southeast Asia

A taxonomic reevaluation of five species of Southeast Asian freshwater ostracods formerly assigned to the genus Cypridopsis Brady, 1868 has resulted in the retention of Cypridopsis adusta Sars, 1903, Cypridopsis exigua Sars, 1903 and Cypridopsis dubia Sars, 1903 in Cypridopsis and transfer of Cypridopsis albida (Vavra) 1898 and Cypridopsis arsenia Tressler, 1937 to the genus Plesiocypridopsis Rome, 1965.     

On the rehabilitation of the clariid catfish genus Bathyclarias endemic to the East African Rift Lake Malawi

A morphological and osteological study on a large number of specimens, together with zoogeographical data, indicate that the genus Bathyclarias , previously synonymized with the genus Dinotopterus , is a valid genus. It is rehabilitated in this paper. Bathyclarias is endemic to Lake Malawi, while Dinotopterus is confined to Lake Tanganyika.     

Phylogeography and Evolution of the Tanganyikan Cichlid Genus <Emphasis Type="Italic">Tropheus</Emphasis> Based upon Mitochondrial DNA Sequences

Lake Tanganyika harbors the oldest and most diverse species flock of cichlid fish. Many species are subdivided into numerous genetically and phenotypically distinct populations. Their present distribution and genetic structure were shaped by a series of lake level fluctuations which caused cycles of isolation and admixis and promoted dispersal events. One of the best examples of this phenomenon is the genus Tropheus. We present a comprehensive mtDNA phylogeny based upon 365 individuals of 55 populations from all over Lake Tanganyika, which suggests an almost-contemporaneous origin of eight major mitochondrial lineages about 700 Ka ago. While the distribution of seven lineages is restricted to particular sections of the lake shore, one lineage was found to have a much more widespread distribution. This particular lineage is subdivided into four sublineages which seem to have originated from a single dispersal event about 400 Ka. By using a molecular clock estimate in combination with geological data we derived a hypothetical scenario for the colonization history of Tropheus. Thereby we show a high degree of concordance between major changes of the lake level in the recent history of Lake Tanganyika and three distinct diversification events in this genus.     

Phylogeography and Evolution of the Tanganyikan Cichlid Genus Tropheus Based upon Mitochondrial DNA Sequences

Abstract Lake Tanganyika harbors the oldest and most diverse species flock of cichlid fish. Many species are subdivided into numerous genetically and phenotypically distinct populations. Their present distribution and genetic structure were shaped by a series of lake level fluctuations which caused cycles of isolation and admixis and promoted dispersal events. One of the best examples of this phenomenon is the genus Tropheus. We present a comprehensive mtDNA phylogeny based upon 365 individuals of 55 populations from all over Lake Tanganyika, which suggests an almost-contemporaneous origin of eight major mitochondrial lineages about 700 Ka ago. While the distribution of seven lineages is restricted to particular sections of the lake shore, one lineage was found to have a much more widespread distribution. This particular lineage is subdivided into four sublineages which seem to have originated from a single dispersal event about 400 Ka. By using a molecular clock estimate in combination with geological data we derived a hypothetical scenario for the colonization history of Tropheus. Thereby we show a high degree of concordance between major changes of the lake level in the recent history of Lake Tanganyika and three distinct diversification events in this genus.     

Recent speciation between sympatric Tanganyikan cichlid colour morphs

Lake Tanganyika, Africa's oldest lake, harbours an impressive diversity of cichlid fishes. Although diversification in its radiating groups is thought to have been initially rapid, cichlids from Lake Tanganyika show little evidence for ongoing speciation. In contrast, examples of recent divergence among sympatric colour morphs are well known in haplochromine cichlids from Lakes Malawi and Victoria. Here, we report genetic evidence for recent divergence between two sympatric Tanganyikan cichlid colour morphs. These Petrochromis morphs share mitochondrial haplotypes, yet microsatellite loci reveal that their sympatric populations form distinct genetic groups. Nuclear divergence between the two morphs is equivalent to that which arises geographically within one of the morphs over short distances and is substantially smaller than that among other sympatric species in this genus. These patterns suggest that these morphs diverged only recently, yet that barriers to gene flow exist which prevent extensive admixture despite their sympatric distribution. The morphs studied here provide an unusual example of active diversification in Lake Tanganyika's generally ancient cichlid fauna and enable comparisons of speciation processes between Lake Tanganyika and other African lakes.     

Microevolutionary change in viscerocranial bones under congeneric sympatry in the Lake Tanganyikan cichlid genus Tropheus

Hydrobiologia - The endemic Lake Tanganyika cichlid genus Tropheus lives at rocky shores all around the lake and comprises six species which are subdivided into about 120 morphologically similar...     

Four new species of Gomphocythere (Crustacea, Ostracoda) from Lake Tanganyika, East Africa

Four new species of the ostracod genus Gomphocythere are described from Lake Tanganyika (East Africa): Gomphocythere downingi n. sp. G. coheni n. sp., G. wilsoni n. sp., and G. woutersi n. sp. All species are endemic to the lake and are found within a variety of substrates and depths. The addition of these four new species brings the total number of endemic Gomphocythere species in Lake Tanganyika to nine. Other Gomphocythere species are known from water bodies throughout East and South Africa and in the Levant. Brooding is an important, but not a unique, preadaptation for the persistence and taxic prolific speciation of this lineage in Lake Tanganyika.     

Molecular phylogeny and speciation patterns in host-specific monogeneans (Cichlidogyrus,Dactylogyridae) parasitizing cichlid fishes (Cichliformes,Cichlidae) in Lake Tanganyika

Cichlidogyrus (including Scutogyrus) is the most speciose dactylogyridean monogenean genus known from African and Levantine cichlid fishes (Cichlidae). While its taxonomy is well established, little is known about the phylogenetic relationships and evolutionary history of this ectoparasite, especially from hosts belonging to one of the most impressive vertebrate radiations, the cichlid fishes from the East African Great Lakes and surrounding hydrological systems. Phylogenetic inference based on DNA sequences of the nuclear 18S, internal transcribed spacer 1 and 28S rDNA genes revealed that Cichlidogyrus parasitizing mainly West African cichlid tribes is paraphyletic with respect to species parasitizing hosts belonging to the East African cichlid radiation, which constitute a well-supported monophylum. Members of Cichlidogyrus from tylochromine and oreochromine hosts that colonised Lake Tanganyika only recently, cluster with their non-Lake Tanganyika relatives, indicating that they colonised Lake Tanganyika with their current host species, and did not jump over from any of the many cichlid species already present in the lake. The diversification of Cichlidogyrus in Lake Tanganyika seems to be driven by failure to diverge in old lineages of cichlids, cospeciation in more recently evolved ones, and host switching followed by parasite duplication at the level of the various host tribes. Evaluation of host specificity and structural evolution of haptoral and reproductive organs in Lake Tanganyika Cichlidogyrus revealed that strict specialist species together with larval hook size represent the ancestral state of haptor configuration, suggesting that members of Cichlidogyrus in this system evolved from a very simple form to a more complex one similarly to their West African congeners. Generalist species among Cichlidogyrus with a sclerotized vagina parasitizing ancient Lake Tanganyika lineages seem to have developed a different hook configuration, most probably to ensure successful colonisation of new, phylogenetically unrelated hosts.     

Marine incursion: the freshwater herring of Lake Tanganyika are the product of a marine invasion into west Africa

The spectacular marine-like diversity of the endemic fauna of Lake Tanganyika, the oldest of the African Great Lakes, led early researchers to suggest that the lake must have once been connected to the ocean. Recent geophysical reconstructions clearly indicate that Lake Tanganyika formed by rifting in the African subcontinent and was never directly linked to the sea. Although the Lake has a high proportion of specialized endemics, the absence of close relatives outside Tanganyika has complicated phylogeographic reconstructions of the timing of lake colonization and intralacustrine diversification. The freshwater herring of Lake Tanganyika are members of a large group of pellonuline herring found in western and southern Africa, offering one of the best opportunities to trace the evolutionary history of members of Tanganyika's biota. Molecular phylogenetic reconstructions indicate that herring colonized West Africa 25-50MYA, at the end of a major marine incursion in the region. Pellonuline herring subsequently experienced an evolutionary radiation in West Africa, spreading across the continent and reaching East Africa's Lake Tanganyika during its early formation. While Lake Tanganyika has never been directly connected with the sea, the endemic freshwater herring of the lake are the descendents of an ancient marine incursion, a scenario which may also explain the origin of other Tanganyikan endemics.     

Ancestry to an endemic radiation in Lake Tanganyika? Evolution of the viviparous gastropod Potadomoides Leloup, 1953 in the Congo River system (Caenogastropoda,Cerithioidea, Paludomidae)

Providing another spectacular model for understanding speciation and radiation, the origin of the gastropod species flock in Lake Tanganyika (with an estimated age of approximately 12 Myr) remained enigmatic to date. Although, for a long time, an in situ radiation was assumed, Lake Tanganyika could have functioned as a reservoir for ancient African lineages, implying that the now lacustrine taxa originiated elsewhere. However, the fluviatile gastropod fauna of adjacent river systems in Central and East Africa is only poorly known. Here, we provide conchological, anatomical, phylogenetical, and biogeographical data on the fluviatile genus Potadomoides Leloup, 1953, which was hitherto regarded as ancestral to the entire Tanganyika gastropod radiation. The type species Potadomoides pelseneeri is restricted to the delta region of the Malagarasi River east of Lake Tanganyika, whereas three congeneric species (Potadomoides bequaerti, Potadomoides hirta, and Potadomoides schoutedeni) inhabit the Congo River with its tributaries Lualaba and Luvua, west of the Tanganyikan Rift. We describe and document, with scanning electron microscopy, the ontogenetic development of embryos of this uterine brooder as well as the detailed reproductive anatomy. Phylogenetic analysis of 44 morphological characters (including adult and embryonic shell, operculum, radula, reproductive tract) for 15 paludomid taxa could not support monophyly of the Tanganyika species flock. Instead, we found two major lineages that colonized Lake Tanganyika independently, one comprising the Nassopsinae Kesteven, 1903 (= Lavigeriinae Thiele, 1925) with the riverine Potadomoides plus the lacustrine Lavigeria and Vinundu, the second comprising the riverine Cleopatra together with the rest of the lacustrine species (except for Tiphobia horei). The analysis identifies Potadomoides as paraphyletic, with the uterine brooder P. pelseneeri being the sister taxon to the uterine brooder Lavigeria plus the oviparous Vinundu, but not to the entire Tanganyika species flock. We reconstruct the independent evolution of an fluviolacustrine taxon Nassopsinae for which we evaluate the synapomorphic characters, in particular those of reproductive biology, and discuss systematic and evolutionary implications of repeated origin of (ovo‐)viviparity in these limnic Cerithioidea. Finally, we outline a hypothesis on the evolutionary history of Potadomoides in the context of the gastropod radiation in Lake Tanganyika. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 367–401.     

Description of a commercially important pelagic species of the genus Diplotaxodon (Pisces: Cichlidae) from Lake Malawi, Africa

A new species of pelagic haplochromine cichlid of the genus Diplotaxodon is described from Lake Malawi, Africa. The species, which attains a size of 14cm s. L., feeds mainly on zooplankton, shows no sexual dimorphism in size or body proportions, breeds throughout the year and lives at depths of 20 to at least 120 m. Approximately 600 tonnes of the species were caught by trawlers in 1990–1991, in the south–eastern arm of the lake alone. It appears that this species is a major component of the pelagic community, and occupies an ecological role similar to that of the clupeid Limnothrissa miodon in Lake Tanganyika.     

Nuclear and mitochondrial data reveal different evolutionary processes in the Lake Tanganyika cichlid genus <Emphasis Type="Italic">Tropheus</Emphasis>

Background  

Cichlid fishes are notorious for their wealth of intra- and interspecific colour pattern diversity. In Lake Tanganyika, the endemic genus Tropheus represents the most impressive example for geographic variation in the pattern and hue of integument colouration, but the taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved. Previous studies of mitochondrial DNA sequence data revealed polyphyly of the six nominally described species and complex phylogeographic patterns influenced by lake level fluctuations and population admixture, and suggested the parallel evolution of similar colour patterns in divergent evolutionary lineages. A gene tree of a rapidly radiating group may be subject to incomplete and stochastic lineage sorting, and to overcome this problem we used multi-locus, nuclear AFLP data in comparison with mtDNA sequences to study diversification, migration and introgression in Tropheus colour morphs in Lake Tanganyika.     

Morphological and genetic differentiation of the African clupeid Limnothrissa miodon 34 years after its introduction to Lake Kivu

The evolutionary consequences of an artificial introduction of the clupeid Limnothrissa miodon from Lake Tanganyika into Lake Kivu, East Africa were examined. In 1959, 57 400 fry (mixture of Limnothrissa and the related clupeid, Stolothrissa tanganicae ), were released into Lake Kivu to boost fisheries production. Comparisons were made between respective source and transplant populations 34 years later (1993) using morphometrics ('truss' method), allozymes (29 enzyme-coding loci) and mitochondrial (mt) DNA variation (RFLP analysis of PCR-amplified ND5/6 genes). Significant morphological and genetic differentiation between source and transplant samples was detected, with a distinct clustering of Kivu Limnothrissa on respective dendrograms, especially at the morphometric and mtDNA levels. Differentiation within Lake Tanganyika was, however, consistently higher than that between lakes. Allozymic diversity was similar in samples from both lakes (Lake Tanganyika: heterozygosity = 0.0658, mean number of alleles=1.44; Lake Kivu: heterozygosity = 0.0655; mean number of alleles = 1.48), however, a significantly lower mtDNA haplotype diversity was detected in Lake Kivu (Lake Tanganyika: 0.905; Lake Kivu: 0.755). Data suggest that high post-introduction mortality and various demographic factors reduced the effective population size of the introduced population to tens rather than thousands of individuals, resulting in a reduction in genetic diversity and founder effect.     

Brood parasitism of an open-water spawning cichlid by the cuckoo catfish

The cuckoo catfish Synodontis multipunctatus and S. grandiops are endemic to Lake Tanganyika and the only known nonavian vertebrates that exhibit obligate interspecific brood parasitism. Seven maternal mouth-brooding cichlid fish species are reported to be natural hosts of the parasitic catfish and share a common reproductive behaviour that the catfish exploits: cichlid females spawn eggs on the bottom, allowing the catfish female to place her eggs near the cichlid eggs, and the cichlid females collect the catfish eggs by mouth together with their own eggs. However, so far it has not been reported that the cuckoo catfish exploit different spawning behaviours. The genus Cyprichromis consists of five maternal mouth-brooding species endemic to Lake Tanganyika, most of which spawn and collect eggs in open water. This study reports that the cuckoo catfish also parasitizes the open-water spawning Cyprichromis coloratus, although it may not be a regular host.     

An initial measurement of photosynthetic productivity in Lake Tanganyika

Measurements of ¹⁴C uptake and oxygen evolution by phytoplankton in Lake Tanganyika provide the first direct estimates of the lake's primary productivity. These measurements at the expected nadir of the annual range suggest that Lake Tanganyika is as productive as other large, deep tropical lakes.     

On Lecane tanganyikae new species (Rotifera: Monogononta, Lecanidae)

A new species of rotifer, Lecane tanganyikae n.sp., is described from the littoral of Lake Tanganyika and some water bodies in the plain of the Rusizi river near Lake Tanganyika, Bujumbura Province, Burundi. The affiliation of the new species, especially in relation to L. elsa Hauer, is discussed.     

Seasonal Dynamics of Periphyton in a Large Tropical Lake

Tropical aquatic systems are generally assumed to have little seasonality in productivity patterns. However, this study indicated that there was substantial seasonal variation in epilithic productivity and biomass in tropical Lake Tanganyika, due primarily to seasonal patterns in lake hydrodynamics that influence nutrient availability. Although they support much of the lake’s biological diversity, epilithic algae made a minor contribution to the total energy budget in Lake Tanganyika. A comparison among large, oligotrophic lakes revealed no significant latitudinal trends in periphyton productivity or biomass. However, Lake Tanganyika has relatively low benthic algal biomass and is therefore more efficient at photosynthesis than the temperate lakes. The influence of wave action and consumer density and diversity may be important in moderating productivity of the epilithic community.     

Insights into the evolution of freshwater sponges (Porifera: Demospongiae: Spongillina): Barcoding and phylogenetic data from Lake Tanganyika endemics indicate multiple invasions and unsettle existing taxonomy

Sponges are a conspicuous element in many benthic habitats including in Africa's oldest, deepest lake, Lake Tanganyika. Despite their prevalence and pivotal ecological role as filter feeders, knowledge of the evolutionary history of sponges is in its infancy. Here, we provide the first molecular analysis targeting the evolution of sponges from Lake Tanganyika. Independent markers indicate the occurrence of several colonisation events which have shaped the current Tanganyikan lacustrine sponge biodiversity. This is in contrast to a range of previously studied organisms that have diversified within the lake from single lineages. Our tree reconstructions indicate the presence of two genera, Oncosclera and Eunapius, which are globally distributed. Therefore, we reject the hypothesis of monophyly for the sponges from Lake Tanganyika and challenge existing higher taxonomic structure for freshwater sponges.     

Ostracods (Ostracoda,Crustacea) from two freshwater lakes near Maarssen,The Netherlands

Summary In Lake Maarsseveen I (with the lowest trophic level) 15 ostracod species were collected, whereas 9 species were found in Lake Maarsseveen II.Physocypria kliei Schäfer, 1934, andCypridopsis obesa Brady and Robertson, 1869, are new to the Dutch fauna.