NE Tanzania Research Articles

An experimental hut evaluation of Olyset® nets against anopheline mosquitoes after seven years use in Tanzanian villages

BackgroundLong-lasting insecticidal nets (LLINs) are advocated by WHO for protection against malaria. Of the three brands of LLINs currently approved by WHO, Olyset® is the only one currently granted full recommendation. With this type of LLIN, the insecticide (permethrin) is incorporated into the polyethylene fibre during manufacture and diffuses from the core to the surface, thereby maintaining surface concentrations. It has not been determined for how long Olyset nets remain protective against mosquitoes in household use.MethodsExamples of Olyset nets, which had been in use in Tanzanian villages for seven years, were tested in experimental huts against naturally entering Anopheles gambiae and Anopheles funestus mosquitoes. Performance was compared with new Olyset nets, conventionally treated ITNs (either newly treated with alphacypermethrin or taken from local villages after 1.5 years of use) and untreated nets. All nets were artificially holed except for the seven-year Olyset nets, which had developed holes during prolonged domestic use.ResultsAnopheles funestus and An. gambiae in NE Tanzania are susceptible to pyrethroids. The new Olyset nets caused high mortality against An. funestus (73.9%) and An. gambiae (62.7%) in experimental huts. The seven-year Olyset nets caused 58.9% mortality against An. funestus and 40.0% mortality against An. gambiae. The freshly treated alphacypermethrin nets also caused high mortality against An. funestus (70.6%) and An. gambiae (72.0%); this decreased to 58.4% and 69.6% respectively after 1.5 years of use. The new Olyset nets inhibited blood-feeding by 40–50%. The 7 year Olyset nets showed no feeding inhibition over that shown by the untreated nets. The alphacypermethrin treated nets failed to inhibit blood-feeding after 1.5 years of use. However iHhhdn laboratory tunnel tests samples of all types of treated net including the 7 year Olyset inhibited blood-feeding by more than 95%.ConclusionAfter seven years of use Olyset nets were still strongly insecticidal. Mosquito mortality decreased by only 20–35% over this period. However, Olyset would not provide personal protection after seven years unless it was in good condition and all holes fully repaired.

Fingerprinting facies of the Tuff IF marker, with implications for early hominin palaeoecology, Olduvai Gorge, Tanzania

The top of Tuff IF marks the upper boundary of the Plio-/Pleistocene Bed I succession exposed in Olduvai Gorge, NE Tanzania, a tephrostratigraphic interval that is well known for remarkable Oldowan archaeological and vertebrate fossil assemblages, including early hominins. Geochemically, Tuff IF is characterized by a relatively consistent silica-undersaturated trachytic to phonolitic composition that relates both in terms of numerical ages (1.79 Ma) and compositional constraints to Olmoti volcano, located 22–38 km E of Olduvai Gorge. Measured Tuff IF sections are characterized by a thick unwelded pyroclastic flow in proximal settings and a succession of surges and ashfalls that interfingers with fluvio-lacustrine deposits of the Olduvai Basin in the medial to distal settings. Only in those areas with a relatively low topographic gradient, in distal reaches and beyond the toe of an Olmoti-sourced volcaniclastic fan, did the Tuff IF marker develop a typical threefold subdivision comprising: (1) primary surges and minor fallout, (2) reworked pumice units as lateral correlatives of proximally emplaced pyroclastic flows and (3) a succession of mass flows in conjunction with aeolian and fluvially reworked units. The pyroclastic marker unit is thus highly heterogeneous with regard to its vertical and lateral facies architecture and this has immediate effects on its preservation potential and in situ burial of fossils and stone artifacts. Even though the volcanically-related environmental perturbations were probably more severe at the eastern lake margin, the evidence for at least temporary freshwater sources and trees suggests environments conducive to hominin activities, but not during emplacement of Tuff IF pyroclastic flows and surges. This inference is supported by the presence of rich Oldowan stone artifact assemblages immediately preceding and following the deposition of Tuff IF, but only extremely sparse archaeological traces from one site in Tuff IF, restricted to the upper, fluvially reworked portion of Tuff IF. Tuff IF facies record the maximum of a regressive (drying) cycle that correlates with regional marine arid indicators. An ecological crisis covering ∼ 2000–3500 a of time during Tuff IF deposition resulted not only from the lethal effects of explosive volcanism but also from its coincidence with a pronounced period of climate induced drought. These combined effects appear to have made at least the eastern basin uninhabitable by hominins and other vertebrates for most of the time during which Tuff IF accumulated.

Population stage structure, survival and recruitment in the endangered East African forest herb Saintpaulia

Climatic seasonality, local habitat quality, and edge effects created by forest fragmentation due to human activity may affect the performance of endangered rain forest understory herbs. Viability and seasonal dynamics of the populations of the endangered Saintpaulia confusa, S. difficilis, and S. grotei were studied in a protected seasonal submontane forest in NE Tanzania by examining plant life-history traits, population stage structure, and the effects of habitat quality on plant performance. The population stage structures were of the dynamic type. There was a lower frequency of seedlings (57.9%) and higher frequency of juvenile (13.3%) and adult plants (28.8%) in S. confusa than in S. difficilis (74%, 10.7% and 15.3%, respectively). Seedling recruitment occurred from May to August with an average of 54, 103 and 38 emerged seedlings per 1 m2 study plot (S. confusa, S. difficilis, and S. grotei, respectively). Presence of the seed bank was also an indication of the regeneration potential of the populations. Mortality was high during the dry and hot season from December to March. Survival was lowest in juvenile plants, higher in sterile adult plants and the highest in fertile adult plants. Because survival was the lowest on dry substrates under open canopy, our data suggest that forest fragmentation, by reducing shade and humidity, will increase mortality in Saintpaulia. Furthermore, since the mortality was highest in seedlings and juveniles, forest fragmentation is likely to impede the regeneration of the Saintpaulia populations.

Focal mechanisms and the stress regime in NE and SW Tanzania, East Africa

We report 12 new focal mechanisms from earthquakes in NE and SW Tanzania where the stress regime within the East African rift system is not well constrained. Focal mechanisms for events at the intersection of the Lake Tanganyika and Rukwa rifts in SW Tanzania indicate a complicated stress pattern with possible dextral strike‐slip motion on some faults but oblique motion on others (either sinistral on NW striking faults or dextral on NE striking faults). Within the Rukwa rift, focal mechanisms indicate normal dip‐slip motion with NE‐SW opening. In NE Tanzania where the Eastern rift impinges on the margin of the Tanzania Craton, fault motions are consistent with a zone of distributed block faults and sub E‐W extension. All twelve earthquakes likely nucleated within the crust.

Influence of topography on monthly rainfall distribution over East Africa

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 28:199-212 (2005) - doi:10.3354/cr028199 Influence of topography on monthly rainfall distribution over East Africa P. Oettli*, P. Camberlin Centre de Recherches de Climatologie, FRE 2740 CNRS, Université de Bourgogne, 6 Boulevard Gabriel, 21000 Dijon, France *Email: oettlip@u-bourgogne.fr ABSTRACT: statistical models were defined for explaining the spatial distribution of rainfall in eastern Africa (southern Kenya and NE Tanzania) on the basis of various topographical descriptors. The procedure is first presented for the month of April, and subsequently month-to-month changes in the role of topography on rainfall distribution are discussed. Predictors included quantitative estimates of slope, mean and standard deviation of elevation, and principal components that describe the topographical environments around the meteorological stations. Different window sizes were considered in order to account for processes of different scales. Linear models were defined for each mean monthly rainfall field, and cross-validated. Inclusion of interpolated residuals yield explained variances in the range of 53 to 89%. Results were compared to a simple interpolation of gauge rainfall. The models are particularly useful in areas with few rain gauges. Selected predictors, as well as their scales, change seasonally. North–south exposure contrasts are the main factor of rainfall variation, except in the northern summer. East-facing stations are wetter in the short rains season (October to December), and drier in the monsoon season. These variations coincide with seasonal atmospheric circulation changes above the region. Slopes also contribute to rainfall variability. At the scale of the study mean elevation had little effect; other predictors, especially exposure, actually describe the interaction between rainfall and topography more adequately. KEY WORDS: Rainfall · Geostatistical modelling · Orography · Kenya · Tanzania Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 28, No. 3. Online publication date: May 24, 2005 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2005 Inter-Research.

The Quaternary stratigraphy and its associated fossil fauna and flora of the Holili area, NE Tanzania

The basement for the Holili area (NE Tanzania) comprises gneisses of the Mozambique Belt. These rocks are overlain by a Middle Pleistocene (0.35 Ma) olivine basalt which is part of the Kilimanjaro volcanic massif. A red paleosol was formed from this basalt. This paleosol is covered successively by mudstone and calcareous tuffaceous gritty breccia. Some faunal fossil remains (bone fragments, a tooth and horns) and floral fossil remains ( angiosperm dicotyledon plant leaf impressions, twigs and wood) were discovered on the paleosol–mudstone–gritty breccia lithological boundary. The animal fossil remains were recovered from the paleosol surface while the plant fossil remains were recovered from within the mudstone that overlies the paleosol. A primitive hominid stone tool associated with chopped bones and a tooth were also discovered on the paleosol surface. The geological environment of Holili area and its associated fossil fauna and flora resembles other paleontological sites in Tanzania.

Trees of Amani Nature Reserve, NE Tanzania

Trees of Amani Nature Reserve, NE Tanzania

The Fruit of Sanrafaelia rufonammari Verdc. (Annonaceae)

I recently described (Verdcourt 1996) a new genus of Annonaceae from NE Tanzania from somewhat sparse material. Only extremely young fruits were available2 which, however, suggested that adult fruits would prove to be long and narrow. More material has now been collected in ripe fruit which confirms this and it has been thought advisable to refigure the species more adequately showing the fruit and seed (Fig. 1). The disposition of the corolla lobes is also shown. The collectors sent some coloured prints showing this but unfortunately they are not adequate for reproduction.

New Species of Bryophaenocladius Thienemann, 1934 from Tanzania, with Bare Squama (Diptera: Chironomidae)

Bryophaenocladius imberbus sp. n., B. mazumbaiensis sp. n., and B. usambarensis sp. n. are described and figured as male imago, based on specimens collected in the Usambara Mountains in NE Tanzania. All three species lack setae on squama.

Crustal Age Domains and the Evolution of the Continental Crust in the Mozambique Belt of Tanzania: Combined Sm-Nd, Rb-Sr, and Pb-Pb Isotopic Evidence

Combination of Nd and Sr model ages and Pb isotopes on leached feldspars reveals distinct model age provinces not recognized previously within the Mozambique Belt of Tanzania. Most boundaries of these age domains are overprinted by Neoproterozoic (Pan-African) tectonism and metamorphism. Granitoids from the Archean craton show Nd model ages of 2.7–3.1 Ga and very primitive Pb isotope systematics in feldspars. Amphibolite-facies migmatites and granulites from the Mozambique Belt have similar characteristics, yet their high 208Pb/204Pb values point to U loss in the Archean, possibly during high-grade metamorphism, and subsequent Pan-African reworking. Eclogite-facies metapelites of the Early Proterozoic Usagaran Belt likewise exhibit Archean Nd model ages, but higher Pb isotopic ratios are consistent with last recrystallization of feldspar at 2 Ga. Granulites with Nd model ages from 1 to 1.5 Ga only occur in NE Tanzania; because of their restricted range in Pb isotopic composition they are interpreted as juvenile additions during late Proterozoic time. Granulites of the W Uluguru Mts have Nd model ages between 2.1 and 2.6 Ga, and highly variable feldspar Pb isotope composition indicating possible derivation from cratonic and/or Usagaran material, reworked and mixed with a small proportion of younger Proterozoic material during the Pan-African orogeny. This could indicate the suture zone between a western Archean–proterozoic continental mass and juvenile arcterranes docking on from the east during subduction of the Mozambique Ocean. The combined isotope data provide strong evidence that parts of the East African crust grew by lateral accretion of Early and Mid Proterozoic segments onto an Archean nucleus. However, the Neoproterozoic (Pan-African) orogeny not only led to addition of new crust in the NE of Tanzania, but also reworked crustal material in most other parts of the Mozambique Belt. This juxtaposition of ancient with juvenile crustal segments is consistent with an active continental margin setting before or during orogenesis. Correlation with adjacent terranes indicates similar processes of mixing and limited juvenile addition prevailing throughout central Gondwana during the Pan-African orogeny.

First record of Manoa Fittkau and tribe Pseudochironomini Saether from the Afrotropical region (Diptera: Chironomidae: Chironominae)

AbstractManoa tangae sp. n. from the West Usambara Mts in NE Tanzania is described from male and female imagines. The species is the first Afrotropical representative of the tribe Pseudochironomini.

Physocrobylus tessa, a New Grasshopper Species from the East Usambara Mountains, NE Tanzania and Its Systematic Position (Acridoidea, Acrididae, Coptacridinae)

A new grasshopper species, Physocrobylus tessa, collected from the East Usambara Mountains (NE Tanzania) is described and the genus Physocrobylus Dirsh, 1951 is assigned to the subfamily Coptacridinae on the basis of external and internal characters. Some notes on the ecology of the species are made. Modified keys to the African genera of the subfamily Coptacridinae and to the two species of the genus are

Nutrient depletion in Ferralsols under hybrid sisal cultivation in Tanzania

Abstract. Sisal production in Tanzania has declined sharply in the past two decades because of a decrease in the area grown and a decrease in yields. As sisal is cultivated without manuring, depletion of soil fertility is considered one of the main causes of the declining yields. This paper presents a balance of the macronutrients N, P, K, Ca and Mg for sisal grown in a plantation in NE Tanzania on deep, red clay soils (Ferralsols). Annual fibre yields declined from 2.5 t/ha in the 1960s to about 1 t/ha in the 1980s. Hybrid sisal is a demanding crop and in ten years, with a total fibre yield of 11 t/ha, about 260 kg of N, 40 kg of P, 385 kg of K, 890 kg of Ca and 330 kg of Mg are removed in the harvested leaves. A comparison of soils after two and three 10‐yr cycles of sisal production showed that in the third cycle the pH decreased by 0.5 units and that exchangeable bases were decreased by fifty per cent or more. The amounts of K, Ca and Mg removed from the soil were similar to those in leaves. However, soil analyses could not detect changes in total N and available P, possibly because of the large amount of total N in the soil and the lack of precision in the N and P analyses. In the Ferralsols, potassium is likely to become deficient first, followed by magnesium and calcium. The soil has little available P, and an increase in soil acidity may decrease it further and also create aluminium and manganese toxicities. In order to maintain sisal production, fertilization with P, K, Ca and Mg is necessary, and to improve yields N must also be applied.

Ultrastructure and Life Cycle of Merocinta davidii gen et sp. nov, a Dimorphic Microsporidian Parasite of Mansonia africana (Diptera: Culicidae) from Tanzania

Mansonia africana larvae were sampled at three sites in NE Tanzania, between June and September 1987. At each site between 2.5 and 5.7% were infected with a multisporous microsporidian parasite. The ovoid spores measured 2.5 × 1.5 μm. Meronts were diplokaryotic with electron-dense, thickened unit membranes. Repeated division of the diplokarya gave rise to multinucleate plasmodia, the plasma membrane of which was entirely surrounded by two other membranes interpreted as host endoplasmic reticulum. Both membranes were studded with ribosomes. Meronts became ribbon-like before division, the endoplasmic reticulum dividing with the parasite. At the onset of sporogony the two nuclei of the diplokaryon separated and the electron-dense coat was sloughed off. Nuclear division and cytoplasmic division gave rise to uninucleate sporoblasts and spores. Adult M. africana collected at one of the three sites were infected with two diplokaryotic microsporidia, designated Type A and Type B, which differed only in the size of the spores. Spores of Type A measured 3.4 × 1.8 μm and those of Type B measured 6.6 × 2.9 μm; both types were binucleate. Type A infected 10.8 and Type B 5.8% of the adults collected. Mixed infections were not observed. In transovarial transmission trials, larvae were not successfully reared from adults infected with Type B. However, 11.3% of progeny from females infected with Type A exhibited multisporous microsporidian infections indistinguishable from those found in larvae collected at that site, showing that the multisporous parasite in larvae and the Type A infection of adults represent different stages in the life cycle of a single species. The morphology and life cycle of this microsporidian exclude it from all other related genera and it is attributed here to a new genus and given the name Merocinta davidii.

Light Microscope and Ultrastructural Observations of a Microsporidian Parasite of Mesocyclops rarus (Copepoda: Cyclopoida) in Tanzania

A dimorphic microsporidian infection was found in Mesocyclops rarus copepods collected at three sites near Muheza in NE Tanzania. The mean prevalence of infection varied between 0 and 24.3% at the three sites. Both spore types were pyriform and varied in size but not ultrastructure. The smaller ones measured 8.9 × 3.9 μm and the larger 15.0 × 6.3 μm. They were always found together in the same host individual and therefore assumed to be the same species. Ultrastructurally both types showed marked similarities to those of the copepod phase of Amblyospora spp. which cause polymorphic infections in copepods and mosquitoes. Although it was not demonstrated in transmission experiments, the infection in M. rarus is possibly conspecific with one of two dimorphic infections in Mansonia africana mosquitoes (either Tricornia muhezae or Merocinta davidii) recently described from the same sites.

Tectonics of the lower crust: a view from the Usambara Mountains, NE Tanzania

In the Pare and Usambara Mountains, NE Tanzania, approximately 4000 km 2 of granulites display regular moderate northeast dips of layering and foliation and down-dip plunge of pervasive stretching lineation. Folds, other than scarce tight microfolds, appear to be absent; thrusts, only mapped in the North Pare Mountains, are probably numerous elsewhere. The granulites pass up, without any evidence of stratigraphic, structural or metamorphic break, into slightly lower-grade metasediments, including conspicuous marbles. These rocks show major tight folds. Comparison with the Turoka Fold in south Kenya, here re-interpreted as a sheath fold, supports interpretation of the stretching lineation in the Usambara granulites and overlying metasediments as the transport direction, transverse to the N-S Mozambique Belt. The regional lineation pattern indicates correlation of the transverse Usambara and Turoka lineations with those transverse to the Mozambique Belt farther north in Kenya. These are dated at ∼830 Ma; it is concluded that the Usambara stretching lineation, foliation and associated structures were also formed at that time. The fabrics show that this intense deformation took place in granulite facies conditions. The gradual change from their intense planar and linear deformation to the slightly more inclined fold and thrust deformation in the overlying metasediments is interpreted as implying an initially nearly flat shear zone in the lower crust during the Mozambique Belt orogeny; continuing movement imbricated and refolded the initially flat foliation, giving the northeastward dip across the granulites. The curved trend of the stretching lineation through the Usambara Mountains is attributed to strains during the late Mozambiquian deformations.