Malagarasi River Research Articles

Revision of the Amphilius jacksonii complex (Siluriformes: Amphiliidae), with the descriptions of five new species.

The Amphilius jacksonii complex is revised, and five new species are described: A. ruziziensis n. sp. from the Ruzizi River drainage and northeastern tributaries of Lake Tanganyika; A. pedunculus n. sp. from the Malagarasi River drainage, Lake Rukwa basin, and upper Great Ruaha River drainage, Rufiji basin; A. frieli n. sp. from the upper Congo basin; A. crassus n. sp. from the Rufiji and Wami basins; and A. lujani n. sp. from the Lake Kyogo drainage, northeastern tributaries of Lake Victoria, and the Lake Manyara basin.

Implications of Land Use and Land Cover Changes on Hydrological Regimes of the Malagarasi River, Tanzania

A study was conducted to investigate the impacts of land use and land cover changes on hydrological regimes of the Malagarasi River. Remote sensing techniques were used to inventory land use and land cover changes in the watershed for over 18 years. Hydrological data collected from 1975 to 2002 at Mbelagule, a gauging station far downstream before Lake Tanganyika were analyzed to reveal the alterations and trends in flows for the pre-1980 and post-1980 periods after a large influx of refugees in the catchment. Results revealed that between 1984 and 2002, there was a in settlement and cultivated area steadily increased from 42.91 km 2 to 51.01 km 2 , woodland area declined from 405.48km 2 to 398.91km 2 and wetland area declined from 36.35km 2 to 19.91km 2 . River flows were found to be highly variable within and between the years, and sensitive to land use and land cover changes. There was a shift in the peaking of the river post-1980 period, with high flows attained earlier in April instead of May in the pre-1980 period. The dry season (June to October) flows for the post- 1980 period declined progressively when compared to the pre- 1980. A trend analysis on annual rainfall did not indicate a significant change in amount of rainfall received in the area, likewise for the annual discharges, but a downward trend was detected in dry season flows. The flow duration curve analysis indicated a progressive decline in flows for the post-1980 period unlike the former. The study concludes that the modification of the land use and cover has resulted in changes in temporal distribution of runoff. The study highlights the need to consider the effects of land use and land cover changes on ecosystems and water resources for an informed decision on proper planning and management of the catchment.

The Malagarasi River Does Not Form an Absolute Barrier to Chimpanzee Movement in Western Tanzania

The Malagarasi River has long been thought to be a barrier to chimpanzee movements in western Tanzania. This potential geographic boundary could affect chimpanzee ranging behavior, population connectivity and pathogen transmission, and thus has implications for conservation strategies and government policy. Indeed, based on mitochondrial DNA sequence comparisons it was recently argued that chimpanzees from communities to the north and to the south of the Malagarasi are surprisingly distantly related, suggesting that the river prevents gene flow. To investigate this, we conducted a survey along the Malagarasi River. We found a ford comprised of rocks that researchers could cross on foot. On a trail leading to this ford, we collected 13 fresh fecal samples containing chimpanzee DNA, two of which tested positive for SIVcpz. We also found chimpanzee feces within the riverbed. Taken together, this evidence suggests that the Malagarasi River is not an absolute barrier to chimpanzee movements and communities from the areas to the north and south should be considered a single population. These results have important consequences for our understanding of gene flow, disease dynamics and conservation management.

Gene Flow and Genetic Diversity of Chimpanzees in Tanzanian Habitats

Abstract: Tanzania is located at the southeastern end of the eastern chimpanzee (Pan troglodytes schweinfurthii) distribution. Except for two national parks, their habitats have been degraded due to human activities. To clarify the gene flow and genetic diversity of chimpanzees in Tanzania, we analyzed the mitochondrial sequences of chimpanzees in six sites (Lwazi, Wansisi, Mahale, Karobwa, Ugalla-Masito, and Gombe), some of which are now isolated. The southernmost habitat (Lwazi) was about 150 km away from the nearest habitat but, considering the geographic distance, the genetic distance of the chimpanzees between Lwazi and the other habitats was not high. In contrast, the genetic distance between the chimpanzees in the northernmost habitat (Gombe), and the other habitats was relatively high considering the geographic distance. The results suggest that the Malagarasi River, which runs between Gombe and the southern habitats, limits gene flow. The genetic difference analyses also suggest that the habitats...

Phylogenetic relationships among small <i>barbus</i>,<i> barbus</i> (actinopterygii: Cyprinidae) from malagarasi and Pangani river basins, Tanzania

The phylogenetic relationships among “Barbus” species (Barbus jacksonii, B. paludinosus and B. trimaculatus) from Malagarasi and Pangani River systems were examined by partial mitochondrial cytochrome b (cyt.b) gene. Sequences of the same samples from elsewhere in Africa obtained from the South African Institute of Aquatic Biodiversity (SAIAB’s) collection were also included in the analysis. Molecular technique was necessary due to phenotypic plasticity and extensive overlap of morphological features among the “Barbus species”. The findings of this study revealed that B. paludinosus from hale and Pangani populations occurred in two distinct genetic lineages though separated by a distance of approximately 10 km apart. Similar results were also noted amongst the population of B. paludinosus in Songati and Muumbara located on Lake Sagara in Malagarasi River basin. B. trimaculatus and B. jacksonii were indistinguishable such that it is envisaged that the two species are one and the same. The Barbus spp. from Africa included in the current study showed genetic affinity to neither European Barbus spp. nor South African redfins of the Pseudobarbus to conclude that the studied species of barbs are taxonomically quite different that needs further investigation to warrant renaming.

Integrated assessment of land use and cover changes in the Malagarasi river catchment in Tanzania

Malagarasi river catchment represents one of the largest and most significant transboundary natural ecosystems in Africa. The catchment constitutes about one third of the catchment area of Lake Tanganyika and contains ecosystems of both national and international importance (i.e. Muyovozi Wetland Ramsar site). It has been increasingly said that increased anthropogenic activities have had negative impacts on the Muyovozi wetland in particular and other catchment resources. Nevertheless, these beliefs are little supported by quantitative data. A study on the dynamics of land use and cover in the Malagarasi river catchment therefore investigated long-term and seasonal changes that have occurred as a result of human activities in the area for the periods between 1984 and 2001. Landsat TM and ETM+ images were used to locate and quantify the changes. Perceptions of local people on historical changes and drivers for the changes were also collected and integrated in the assessment. The study revealed a significant change in land use and cover within a period of 18 year. Between 1984 and 2001, the woodland and wetland vegetation covers declined by 0.09% and 2.51% per year. Areas with settlements and cultivation increased by 1.05% annually while bushed grassland increased at 1.93% annually. The perceived principal drivers for the changes were found to include fire, cultivation along rivers and lake shores, overgrazing, poor law enforcement, insufficient knowledge on environmental issues, increasing poverty, deforestation and population growth. The human population growth rate stands at 4.8% against a national figure of 2.9%. The most perceived environmental problems include drying of streams and rivers, change in rainfall, loss of soil fertility, soil erosion and reduced crop yield. The study concludes that, there has been significant changes in land use and cover in the catchment and these require concerted actions to reverse the changes. The study highlights the importance of integrating remote sensing and local knowledge in understanding the dynamics catchment resources and generating information that could be used to overcome the catchment management problems.

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.

Environmental assessment of mercury contamination from the Rwamagasa artisanal gold mining centre, Geita District, Tanzania

This study presents the results of an environmental assessment of mercury (Hg) contamination in the Rwamagasa artisanal gold mining area, northwest Tanzania, and the potential downstream dispersion along the River Malagarasi to Lake Tanganyika. At the time of sampling, generally low concentrations of Hg (<0.05 mg/kg) occurred in most cultivated soils although higher Hg (0.05–9.2 mg/kg) was recorded in urban soils and vegetable plot soils where these are impacted by Hg-contaminated water and sediment derived from mineral processing activities. Hg in vegetable and grain samples is mostly below the detection limit of 0.004 mg/kg Hg, apart from 0.007 and 0.092 mg/kg Hg in two yam samples and 0.011 to 0.013 mg/kg Hg in three rice samples. The standardized (i.e., standardized to 10 cm length) Hg concentrations in Clarias spp. increase from about 0.01 mg Hg/kg for the River Malagarasi delta to 0.07, 0.2, and 1.6 mg/kg, respectively, for the Rwamagasa ‘background’, moderately and most contaminated sites. For piscivorous ( Lates, Brycinus, and Hydrocynus spp.), insectivorous ( Barbus spp.), and planktivorous ( Haplochromis spp.) fish species, the 10-cm standardized Hg concentrations increase from about 0.006 mg/kg for the River Malagarasi-Lake Tanganyika area to 0.5 and 3.5 mg/kg, respectively, for the Rwamagasa moderately and most contaminated sites. The low concentrations of Hg in fish from the Malagarasi River delta and Lake Tanganyika indicate that Hg contamination from the Rwamagasa area does not have a readily discernible impact on the biota of Lake Tanganyika. Many of the fish samples from Rwamagasa exceed guidelines for human consumption (0.5 mg/kg) as well as the WHO recommended limit for vulnerable groups (0.2 mg/kg). Tissue total Hg (THg) of all fish collected from the River Malagarasi-Lake Tanganyika subarea is well below these guidelines. Potential human exposure through consumption of 300 g/day of rice grown on Hg-contaminated soils is 5.5 μg/week. Consumption of 250 g Nile perch ( Lates spp.), 500 g tilapia ( Oreochromis spp.), and 250 g of catfish ( Clarias spp.) each week would result in an intake of 65 μg Hg/week for people consuming only fish from the Mara and Mwanza regions of Lake Victoria and 116 μg Hg/week for people in the Rwamagasa area consuming tilapia and Nile perch from Lake Victoria and catfish from mining-impacted streams. This is lower than the Provisional Tolerable Weekly Intake (PTWI) of 300 μg for Hg in the diet set by the WHO and the FAO. Inadvertent ingestion of soil containing 9 mg Hg/kg at a rate of 80 mg/day would give an additional estimated weekly intake of 5 μg THg, whereas the persistent and purposeful consumption of soil (geophagia) at a rate of 26 g soil/day would produce an additional chemical exposure of 230 μg Hg/day.

Neolamprologus devosi sp. n., a new riverine lamprologine cichlid (Teleostei, Cichlidae) from the lower Malagarasi River, Tanzania

Neolamprologus devosi sp. n., a new species of riverine lamprologine cichlid is described from the lower Malagarasi River, Tanzania. The new species is tentatively placed within the poorly defined genus Neolamprologus, though generic reassignment may be necessary once ongoing work on the phylo-geny and classification of lamprologines is completed. Notably, Neolamprologus devosi sp. n. does not present characters diagnostic of Congo (ex-Zaire) River lamprologines, and contrary to previous suggestions appears to be phylogenetically distinct from those taxa. This raises questions regarding the number of putative riverine colonizations of lamprologines from a lacustrine source.

Distribution and density of wild chimpanzees on the northern bank of the Malagarasi river, Tanzania

Distribution and density of wild chimpanzees on the northern bank of the Malagarasi river, Tanzania

Notes on the Discovery and Biology of Glossina brevipalpis Newst. in the Mosso Region (Urundi)

Glossina brevipalpis Newst. is recorded for the first time in Ruanda-Urundi, where it has been found in the riverine forest of the upper Malagarasi river in the south-east of the territory.Resting places of both male and female flies have been found to be on tree trunks, between six and twelve feet up, in heavily shaded riverine thickets.The species is clearly crepuscular. It is suggested that the male's habit of resting on paths toward sunset is due to thermotropism rather than to phototropism, or that it may be related to passage of game.Numerous puparia have been found in a late-dry-season breeding ground; these have hatched readily.The animals encountered near the habitat of G. brevipalpis.Infections by trypanosomes have been found in proboscis, gut and salivary glands, but experiments on transmission of these trypanosomes from the wild flies to goat, guineapig and rabbit have thus far failed. Research is at present being carried on to determine the nature of the trypanosomes, of which there are probably several.

A Transverse Zoo-geographical Barrier on the East Side of Lake Tanganyika

No outstanding discontinuity of animal distribution as one proceeds from north to south down the east side of Lake Tanganyika would be inferred from most maps of the region. It is obvious only that along much of the Lake shores the land rises to above 5,000 ft., which has been generally accepted as the approximate lower level of the Highland life-zone in Central Africa. The latest maps1, which are a great advance on their predecessors, show plainly that on the east side of the Lake the highland country falls into three parts: (a) the narrow strip north of Kigoma, which, through Urundi, is continuous with the Kivu and Mufumbiro mountain area, and on the south is separated by the depression centring round the Malagarasi River from (b) the much-dissected Kungwe, Mahari, Baholoholo high country, separated on the south by the low gap round Karema from (c) the Ufipa Plateau, which is continuous with the highlands on the Northern Rhodesian border and round the head of Lake Nyasa.