PhD Theses

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Survey of culicoides (diptera: ceratopogonidae) of East Africa: their taxonomy and distribution.
(University of East Africa, 1968) Khamala, Canute P. M.
Synonymy affecting the family name, Ceratopogonidae, is discussed: A historical review of the discovery of Culicoides in East Africa between 1900 and 1966 and the medical and veterinary importance of Culicoides as vectors of disease, particularly those caused by viruses and filariae, is given. A brief account of the morphological characters used in identification is given together with information on materials and methods used for collecting and studying the adult Culicoides captured. Sixty one species of Culicoides were found, 25 of which are new to science and 48 (including the new species) are recorded for the first time in East Africa. Among established species, the female of kibatiensis and the males of trifasciellus, expectator, brucei, guinquelineatus, albopunctatus and adersi are described for the first time. Reasons for grouping the 61 species into 15 "species groups" of closely related members and definitions of quantitative characters used in classification and identification are given. Separate keys for identifying slide-mounted female and male Culicoides that were collected from East Africa during this study, together with a detailed description of each taxonomic entity (established species being compared with published descriptions) are given. Confusing synonyms are fully discussed. A distribution list of East African Culicoides according to ecological zones is attempted. The generic identity of Ceratopogon imperfectus (= Culicoides imperfectus Goetghebuer) is fully discussed and a detailed description of Ceratopogon imperfectus is given.
A study on the growth and development op grasses with emphasis on their root systems
(University of Dar es Salaam, 1969) Taerum, Ragnar
The growth, of six grasses, grown as spaced plants under two ecologically different habitats in Kenya, were studied with the object of obtaining basic information on their growth and development. This information is an essential part of general research aimed at the improvement of stability and value of rangelands in East Africa. An introduct¬ion to the grass species and the experimental sites are given and methods employed are described. Plots of Cenchrus ciliaris var. biloela, Chloris gayana var. mbarara and Panicum maximum var. makueni were established at Muguga in April 1968 and sampled nine times until March 1969. In addition, at Muguga (2,086 m, high rainfall) and Kedong (1,878 m, low rainfall) the above mentioned grasses and Cenchrus ciliaris var. mbalambala,; Sragrostis superba and Theme da triandra were sampled five times from April 1967 to February 1968 and sub¬sequently during May to July of the same year.
Plankton analysis relative to the feeding habits of Sardinella in Dar es Salaam waters.
(University of Dar es Salaam, 1971) Okera, Wazir
This work has involved the study of the composition and temporal fluctuations of the in shore zooplankton and the role of the different zooplanktoners as food items of the two species of sardines. From December 1968 to January 1970, night zooplakton samples were collected in darkness and under artificial light from Msasani Bay and adjacent areas and once in the Sinda Kendwa waters using a planktonnet based on the designs of CF 70 and Indian Ocean Standard nets. Surface sea water temperature of the above areas was recorded on the sampling night and salinity determination of the water was carried out for the first seven months. Over approximately the same period of 14 months, the stomach content of the commercially important East Africa Sardinella gibbosa and Sardinella albella caught in the light fishery operating in Msasani Bay and Sida Kundwa waters was studied. Morphometrics, fat content and gonad condition of the two species of sardines were also recorded. The results show that the various species of calanoide are the most regularly abundant zooplanktoners, followed by larvaces, Cypridina simosa and Cory caeus spp;l Oithona spp; Sagita spp; Euterpina, Lucifer and Oncea spp, in that order. All these zooplanktoners had a mean percentage proportion in the plankton of more than 1%. Of the lawvac of benthic invertebrates, caridean lawvac were the most abundant (mean proportion of about 4%). The members of a great majority of zooplanktoners were generally higher during the North East Monsoon. Stomach contents of S albella and S. Gibbosa showed that these two species of sardines feed principlaly on about the same fifteen zooplanktoners which are also the more abundant. The sizes of the zooplanktoners consumed varied from about 0.5 mm to about 30mm and it is suggest that within the range or organisms consumed, either size nor shape seem to be of critical importance. Feeding was found to be continuous through out the sampling period. Fishes caught during the North East Monsoon months were found to have high fat content compared to those of South East Monsoon month whose gonads however were not mature than those of the N.E. M. months.
A quantitative study of the ecology of the Serengeti short grasslands
(University of Dar es Salaam, 1976) Banyikwa, Feetham Filipo
Most of the early research conducted within the Serengeti Ecosystem concentrated on large mammals and little work was done on the vegetation. The little study on the vegetation emphasized the vegetation as a source of food for the large mammals without considering the structure and function of the vegetation itself. This study therefore provides a quantitative investigation of the gross structure composition and function of the Serengeti short grasslands. The structural and functional properties of the Serengeti short grasslands were studied and characterized. Salinity, alkalinity and pH were found to be important soil factors which influenced the structure and composition of the grasslands. The distribution of the soil factors was in turn controlled by topography. Four grassland types and sixteen species types were recognized. The major findings were as follows: (i) The Serengeti short grasslands have developed in an environment characterized by erratic and unpredictable rainfall. Soil forming processes were therefore hampered, leading to the poorly developed soils. (ii) The Serengeti short grasslands developed on gently undulating plains with low landscape diversity, which supports a relatively low species diversity. (iii) The drainage basins, with relatively high species diversity, seem to be important in the context of grassland stability. (iv) The contagious distribution of species suggests a considerable amount of pattern diversity within these grasslands. The author finally concludes that the Serengeti short grasslands represent a floristic and functional continuous in of intergrading composition, biomass, diversity and productivity. These properties are in turn closely interrelated to herbivorous and the physical environment through complex feedback loops which have been operating over the long co-evolutionary history.
Miombo woodland inventory design a response to fuel wood scarcity in Tabora, Tanzania
(University of Dar es Salaam, 1980) Temu, Augustin Basil
This study was conducted in Tabora Region Tanzanias where flue cured tobacco is grown mainly by small scale farmers as a cash crop. An analysis of the problems encountered in tobacco and low soil fertility were the basic ones. A comparison of possible alternative sources of energy showed that fuel wood was the most reliable and economically feasible source for the foreseeable future. This means that if the tobacco production in Tabora is to be sustained exploitation from the currently available woodlands has to be regulated and supplemented with fuel wood plantations. However the first task was to produce a method of making an inventory of the fuel wood resource in the woodland. 2,080 ha of woodland were demarcated in Ulyankulu Forest Reserve. Single tree volume tables were constructed for the six most abundant tree species using destructive sampling method and felling the trees. These tables were used to estimate standing volume of saw logs and fuel wood separately. Volume estimates for the less abundant tree species of similar morphology or by deriving simple tree volume tables from measurements taken on standing tees during the main inventory field work. Inventory results showed that the mean volume to 5cm top diameter (o.b) were 120cm3 93cm3, 116cm3 and 116m3 per ha for the four sub-populations with fuel wood forming slightly over 70% of the volume in each case. In conclusion the policy of reservation in large blocks for timber production is unsuitable for the current rural development strategies. The wood lands ought to be sub-divided into smaller more intensively managed units to cater for timber more fuel wood and other needs.
Studies on growth , dry matter production and nutrients accumulation in Pinus Caribesa mor seedling as influenced by mycorrhizal inoculation
(University of Dar es Salaam, 1982) Maghembe, Jumanne Abdallah
The aim of the study was to determine the range of the mycorrhizal fungi in pine plantations in Tanzania and study thair biology under nursery conditions* The study involwad a aurvoy of nycorrhizal fungi their isolation in pinus culture, and studies on raycorrhizae aynthaaizad with Pinus caribaea Survey of octowyccrrhizal fungi use node in 10 pine plantation and too arboreta. Characteristic taorphoicny of nycorrhizaa were observed and isolations were attempted using well established procedures modified according to detected fungal requirements and chemical availability . Over 25 species of fungi known to form aycorrhizae aith pines were identified. The main species were Tholcphora faricacrle, Sclcrodoraa dictyoaporms Suilus, luteus granulates, S. sibiricus, tyooperdon parlotura and Rhizopogon luteolus. The fungi seems to be well adapted to highland conditions but did not develop well under the conditions of Tanzania's hot, dry, coastal plain . Isolation of fungal sysmbionts in pure culture from mycorrhiae use possible with rhizopogon, lutcolus and Sclcrodoraa dictyoaporus only. These species and suillus granuletus and lycopordon peristum were isolated fromfungal aporocaps. Other fungi were not successfully isolated in pure culture . Synthesis of octosycorrhizes in pinus caribase was demonstrated with mycelial and basidispore inocule of thelephora terrestris and scleroderms dictyosporus Inoculation of Pinus caribaea aas also undertaken with Rhizapogon lutcolus selected on the basis of the ncrphology of infected pine rootlets. Thelophora tarroatria baaidioepcrcs formed atycorrhizea between pH 5.5 to 7 .4. Mycorrhizal formation was inhibited at pH 4.3 and pH 8.7. Under similar conditions, myccrrhizal formation by basidispores was inhibited by the fungicide "Perenox" at a fungicide concentration of 5 000 ppm or above. In fumigated soils, nycorrhizaa forced even at Paradox concentrations up to 7 500 ppm. Detailed studies on nutrient uptake in nursery seedlings showed superiority of mycorrhizal seedlings in the total uptake of nitrogen phosphorus, potassium calcium, magnesium and zinc over uninoculated controls However the concentrations of nitrogen and potassium were always lower in Inoculated seedlings compered to uninoculated ones due to growth dilutions. The concentration of calcium, magnesium, and zinc was not influenced by inoculation but phosphorus was consistently more abundant per unit weight in inoculated seedlings than the controls. Juvenile trachoid lengths in Pinus caribaea seedlings was significantly increased by inoculation with Rhizopagon lutcolus. This positive relation was improved by soil fumigation and fertilization with UPK. Soil fumigation and NPK fertilization improved the growth and nutriant status of Pinus caribaoa seedlings but ferlilization progressively ratarded mycorrhizal formation. KPK fertilizer progressively reduced soil pH and Increased both exchangeable potassium and available phosphorus. The increased exchangeable potassium resulted luxury consumption and retarded root growth. The increased soil acidity retarded magnesium uptake. Comparison between inocumulated and uninoculated seedlings in both eseptically and nursery raised pinus carribase seedlings showed mycorrhizal seedlings to the more robust healthy and superior in heath and dry matter production.Recommendation are made for further studies of heat tolerant mycorrhizal fungi such as pisolithus tinctorius and conocucum graniforms which might be more suitable for the hot lowland plains. The interaction of these fungi and fertilizer regimes need further studies in order to develop more effecint nursery practices.
Comparative biological and ecological studies of callosobruchus species in Tanzania with particular emphasis to Callosobruchus Chinensis (L.)
(University of Dar es Salaam, 1983) Mphuru, Athanasius N.
Comparative biological and ecological studies of Callosobruchus species in Tanzania with particular emphasis to Callosobruchus chinensis are presented. Five species of Callosobruchus were found to be associated with various types of stored legumes in Tanzania. These include C. analis. The morphological characters of taxonomic value of these species are described and illustrated and emphasis is placed on structures in the male genitalia. Distinct differences occurred between the various species of Callosobruchus. The shape, size, and number of chitinized plates in the saccus region of the genitalia varied greatly between different species. The number of these chitinized plates in C. chinenis, C. rhodesianus, C. analis and C. phaseoli were two six, four, and two, respectively. Similarly the length, width, and the number of setae at the tip of parameres of different species showed significant differences. The number of setae at the tip of lateral parameres of C. chinensis, C. rhodesianus, C. analis and C. phaseoli were 20, 7, 15, and 26, respectively. In C. maculatus the genitalia occurred in two forms. These two forms are described and the significance of this polymorphism is discussed.Samples collected from different parts of the country showed that they contained only one species and mixed populations were very rare. The significance of this and possible reasons for it are discussed. Distribution and host plants data of all the species are described. Studies on the distribution and relative abundance of Callosobruchus species in Tanzania indicate that C. phaseoli in that order. C. maculatus was the most abundant species in the drier areas of Tanzania especially in Morogoro, Dodoma, Singida, Tabora, Shinyanga and Mwanza regions while C. chinenis was the most important species in the high altitude areas including Mbeya, Iringa, Moshi and Arusha regions. Studies on host-plant relationships showed that C. phaseoli was found associated mainly with lablab (Labla niger), while C. analis was found associated mainly with chickpea (Cicer arietinum). C. chinensis was found associated with a wide range of legumes including Pigeon peas (Cajanus cajan), chick peas (cicer arietinum), Cowpeas (Vigna unguiculata) and green gram (Vigna aureus). C. maculatus showed food preference similar to those of C. chinensis except that this species also attacked Bambaranut (Voandzeia subterranea). The distribution of these pests is discussed in relation to the origin of the host plants. Studies on the life history of C. chinensis at 300C and 80% R.H. are also described. Measurements of the width and length of head capsule and length and width of larvae indicate that there are four distinct larval instars. The total developmental period from egg to adult averaged three weeks. The egg stage, the first, second, third and fourth larval and pupal stages lasted 4 to 5, 2 to 3, 2 to 3, 3 to 4, 5 to 6 and 5 to 6 days, respectively. From the measurements of the length and width of each successive instar the development of the larvae followed a geometric pattern. Longevity in C. chinensis adult was also measured in absence of food and presence of glucose solution and water at different temperatures. The adult was short-lived, living for only about a week. Food and water had little influence on the adult longevity. Temperature on the other hand greatly influenced the life span of adult. The significance of this is discussed. The weight losses, pattern of bruchid damage and the relationship between damage and losses are reported in these investigations. The weight loss due to one bruchid varied from 20 to 30mg. Bruchid damage had little influence on percentage germination. However, it greatly influenced the seedling vigour
Automatic measuring system for impendance investigation of Mos structures
(University of Dar es Salaam, 1985) Mhamilawa, Edward Eliah
A case is presented to explain the observed frequency dependency of some reported tinuous capacita Cp and conductance G versus bias voltage Vb characteristics of a MOS transistor junction, measured at high frequencies. Based on a discussion on the appropriate electrical model of a device at high frequencies, a series model is chosen for the design of an instrument for measuring parameters of MOS structures. The design principle of the instrument is based on a vector ratio method in which a high frequency signal is transduced by a probe using a special current to voltage transformer and a pair of synchronous detectors, For high accuracy, high frequencies used are down converted to suitable value of 10 kHz using a superheterodyne phase lock loop system and a pair of mixers. The realized instrument is versatile and of low cost. It has the capability of automatic plotting of continuous capacitance Cs with its series resistance Rs versus bias voltage Vb characteristics of semiconductor devices such as MOS capacitors, varactors and similar structures on an X-Y Y recorder. The main features of the instrument include the capability of measuring capacitances from 1 pF to 100 pF and resistances Pram 0 ohm to 1000 ohms in steps of four scale ranges with an accuracy of better than 2 per cent. A bias voltage ranging from -110 V to 1l0 V with a variable sweep range up to ± 10 V and different sweep speeds included together with selectable frequencies of 25, 50 and 100 MHz. Using the developed instrument a set of CS (Vb), Rs(Vb) characteristics of some semiconductor structures are measured and analysed. From the data the frequency dependency of the measured characteristics is observed to be low in agreement with the expected theoretical results. Typically the change of capacitance and its loss resistance of a MOS transistor junction, when frequency is changed from 25 MHz to 100 MHz, have dropped from 48% and 652% to 14% and 40% respectively.
Proterozoic gold-base metal veins in the Mpanda mineral field, Western Tanzania
(University of Dar es Salaam, 1987) Nanyaro, Japhet Tulule
Research work was carried out on gold veins and gold veins and gold-bearing base metal veins, collectively referred to as the gold-base metal veins - in the Mpanda Mineral Field (MMF), western Tanzania. The research covered wide-ranging aspects of the gold-base metal mineralization: petrography and geochemistry of the veins and the spatially associated granites; wall rock alterations; petrography and microthermometry of the fluid inclusions from the veins; sulphur and lead isotopes in the veins and granites; and Rb-r isotopic age determination on the granites and associated gneisses. The gold-base metal veins were emplaced in shear zones and related fissures which crass-cut Early Proteroeroic, high grade metamorphic rocks of the Ubendian System and post-Ubendian granites. The sheared rocks show progressive deformation and alteration zones subdivided into cryptic and visible alteration zones. The visible zone comprising sericite and Fe-rich chlorite and quartez} occurs adjacent to most mineralized veins while the cryptic zone (characterized by chlorite, epidote-zoisite, and calcite) occupies a broad area tbeyond the visible zone) which merges with the country rocks. The visible zone resulted from the influx of hydrothermal fluids (CO2-H2O) from depth which caused partial partial destruction of the cryptic alteration zone. During this process, the wall rock gained, among others, K, Rb, Si, CO2, H2O, and Cl, and Iost Fe, Mg, Mn, Ca, Ba, Cu, Pb, Z0, etc. Some of the elements lost from the walI rocks apparently became constituent components of the mimeraIized veins. Based on the mineral paragenesis and chemical data, the MMF veins fall into three subtypes of vein-deposits; gold, gold-base metaI, and base metal. The veins, however, have many common characteristics, e.g. omnipresent quartz plus siderite as the gangue mineraIs; uniform Pb isotopic ratios; and simiIar fluid inclusion properties. The data, therefore, indicate a common origin for the mineralized veins in the MMF. The differences in ore contents may be ettributable to the types of dominant Au/base metaI complexing ligands in the ore fIuid during the mineraIization process. The granites from the MMF are marginally peraluminous (Al2O3/(CaO + K2O + Na2O): 1.06 to 1.24 mol. %; normative corundum: O.94 to 3.34) and moderately potassic (K2O/Na2O:1.35 to 2.O wt. %). The granites show low initial Sr ratio (0.7025), a uniform whoIe rock sulfur isotope composition (mean F34S of +4.8 %.), and upper crust Whole rock lead isotope ratios (206Pb/ 204Pb: 15.B4 to 23.86; 207Pb/204Pb: 15.49 to 16.37; 208Pb/204Pb: 42.96 to B0.81). The granite data are interpreted as indicating an upper mantla/lower crust origin for the granite magma which became contaminated by upper crust material prior to consolidation. A whole rock Rb-Sr isochron gives an emplacement age for the MMF granites of 1846 ± 37 Ma (MSWD: 2.77). Pb-Pb data of galena Pb from the ore veins give a model age of 1567 Ma (STDEV. = 34) , interpreted as the time when the Pb was extracted from the source rocks and precipitated in the veins. The galena Pb isotopic ratios are uniform and have upper crust characteristics (206Pb/204Pb 16.26 to 16-39; 207Pb/204Pb: 15.49 to 15.598 208/204Pb =36.82 to 37.39). The data point to homogeneous crustal sources for the lead or extraction of the Pb from heterogeneous sources and subsequent thorough mixing before precipitation. The ore Pb isotopic characteristics differ sharply from those of the granites, ruling out a direct genetic relationship of the rocks and the vei ns. The sulfide sulfur 2 isotope composition ranges widely among the MMF deposits s34S-values -2 to +8.3 .3, but with a tight cluster for individual deposits. The sulfur data further indicate that S isotopic equilibrium was not attained by the mineralizing fluid. The origin of the vein sulfur is therefore, unclear, but a contribution from an upper mantle source is probable. The upper mantle S was then modified during the transportation deposition process leading to a broad scatter of 3'-values around O %.. in the vein-deposits. On the basis of the current data, the previously suggested derivation of the ore-vein fluids from the granitic magma is unable to account far the peculiarities of the MMF vein deposits. A self-consistent genetic model is proposed for the MMF mineralization in which crustal rocks contributed the bulk of the ore elements (Pb, Fe, Cu, Au, Ag, Si, etc.) and deep-level sources supplied carborn-dioxide and some reduced sulfur. In this modeI, an infIux of carbon-dioxide, from a deep-level melt, dehydrated the overlying crustal rocks, and flushed-out water and the ore elements from the rocks into the shear conduits. Cooling and fluid/wall rock reactions are among the factors which caused the ore-vein deposition as the hydrothermal fIuid flowed to the upper levels of the crust.
Synthesis of Thia-Strigol analogues (potential striga controlling agents)
(University of Dar es Salaam, 1987) Mhehe, George Lukando
The use of strigol analogues in the control of Striga and related weeds has been restricted due to the breakdown of these compounds in the soil. Efforts have therefore been directed towards modification of the structure of these compounds in order to enhance the stability under soil conditions, with retention of the desired biological activity. This thesis describes the synthesis of novel strigol analogues in which the enol ether unit in the strigol skeleton has been replaced by an enethiol ether moiely. This thesis describes the synthesis of a number of strigol analogues (Potential Striga controlling agents) in which the enol ether oxygen present in strigol and strigol analogues has been replaced by sulphur. The prepartations of three model analogues, viz.3- (benzylthiomethylidene) - dihydro -2- (3H) - rufanone, 3 - (1 - benzylthiothylidene) - dihydro -2- (3H)- furanone and 2-methyl-4- (2-oxotetrahydrofuran -3-methylidenethio) - but -2-in-4- olide are discribed. These are simple compounds but their preparations demonstrate the possibility of carrying out the desired coupling reaction. The achievement of this coupling, giving products with the correct -geometry around the enethiol double bond, paved a way to the enethiolhalobutenolide coupling reactions required in the synthesis of thia-strigol analogues. The synthesis ofthia-strigol analogues having an aromatic A-ring has been accomplished. The synthesis involved coupling of the sodiomethylidenethiolate derived from the parent lactone 3,3a,4 8b-tetrahydroindeno - /1,2-b/-2-furanone, with 5-chloro -or 5-broms-3-methyl-2-(5H)- furanone. The problems encountered during the coupling are also discussed. Two more strigol analogues have been synthesized using similar coupling procedures. Thioformylation of Corey's lactone, viz.3,3a, 6,6a-tetrahydro-butenolide afforded the bis-lactone strigolanalogue 3-methyl -5- (2-oxo-3,3a,6,6a-tetrahydro-2H-cyclopenta -/b/-furan-3- methylidenethio)-2-(5H)- furanone. In the same manner thioformylation of 2,3,3a,6a-tetrahydor-(4H)-cyclopenta/b/-furan-3-methylidenethio)2- (5H)- furanone. In the same manner thioformylation of 2,3,3a,6a-tetrahydro- (4H)- cyclopenta-/b/-furan-2-one, which is a double bond isomer of Corey's lactone afforded, after the usual coupling, the isometric analogue. The preparation of 6-methoxyindan-1- one-2-acetic acid, a precursor for ring substituted strigol analogue, is described.
Obstetric and gynaecologic case records and commentaries
(University of Dar es Salaam, 1987) Mlay, Joseph
This study deals with the diagnosis, prognosis and treatment of specified Gynaecological and Obstetric cases; giving also commentaries on the procedures process of treatment and the realized results. The Gynaecological Cases studied and treated in this dissertation included; spontaneous incomplete Abortion evacuation; Pelvic Peritoneal Schistosomiasis; benign Dermoid Cyst of left Ovary laparotomy; ruptured Pyosalpinx Laparotomy and drainage; Reptured Tubal Pregnancy with total salpinga Oophorectomy; Induced abortion perforation of the uterus repair; uterine fibrosis menorrhagia abbnominal hysterectomy; second degree uterine prolapse a cystocele and a rectocele; sexial Asault with resultant third Degree perneal Tea following Vesico Vaginal Fistula repair. The obstetric cases studied and handled in this study included: spontaneous rupture of a gravid uterus due to obstracted labour; caesarean section of conjoined Twins Subacute polyharaminious ;termination; intrapartum Eclampsia and home delivery of a viable foetus; spontaneous Intrapartum Dehiscence of previous caesarean scar delivery of live fetus tubaligation; failed manual removal of retained placenta laparatomy and removal of placenta through a lower transverse uterine incision in a well developed horn of uterus Bicornis; Retained second twin, severe chorioamnionitis caesarean ystererectomy; placenta pravia at 38 weeks of Gestation; Tripplets delivery by Caesarean section and Recurent mid and late trimester pregnancy wastage cerrival cerclage by McDonald’s method. Detailed commentaries are provided after each case is studied and treated as to the results and the general process.
Population ecology of the Legume pod borer, Maruca Testulalis geyer (Lepidoptera: Pyralidae) in relation to its natural enemies on cowpea in Western Kenya.
(University of Dar es Salaam, 1988) Okeyo-Owuor, J. Barack
Studies were conducted at the International Centre of Insect Physiology and Ecology, Mbita Point Field Station (MPFS) farm and the Lambwe Valley farmer's field during 1983 - 1985, to determine the natural population changes of Maruca testulalis Geyer (Lepidoptera; Pyralidae). The role of natural enemies, host plants and climatic factors on natural population, development and survival of M. testulalis was investigated. Further investigations on the biology of Tetrastichus sesamiae (Chalcididae, Eulophidae} a gregarious pupal endo-parasitoid as well as bioassays on Nosema sp., a protozoan pathogen of the pest were conducted in the MPFS laboratory. It was found that M. testulalis colonised the crop at least 15 days after plant emergence when the first adult moths were recorded in the pheromone traps. The egg and larval populations started increasing steadily at the flower initiation stage reaching a peak between 42 and 54 DAPE at both sites. Only one generation of M. testulalis occurred on each crop of cowgea. From the partial ecological life tables it was found that total real mortality for the generations at MPFS and Lambwe ranged between 51.7 - 98.9% and 96.4 - 97.7% respectively indicating very low survival in this species. Several natural enemies were found associated with M. testulalis, including 7 parasitoids, five of which attacked pupae and 2 on larvae. No egg parasitoid was found. The major pathogenic microorganisms found on dead M. testulalis larvae and pupae were Nosema sp. and Bacillus sp. Observable parasitism played negligible role in causing mortality on M. testulalis being only 0.02 - 0.09 and 0.04 - 0.06% at MPFS and Lambwe respectively. Pathogens especially Nosema sp. and Bacillus sp. contributed significantly to mortality of M. testulalis at both sites. Disappearance designated as other losses not due to either parasitoids or pathogens also accounted for a large proportion of mortality. Analysis using key factor and correlation methods revealed that disappearance at the egg stage (ko) was the key-factor causing population change at MPFS, while in Lambwe, although, more observations are necessary for this analysis, the factor k3, representing disease at 3rd instar larval stage, was identified as the key factor. Temperature and rainfall also affected seasonal abundance of M. testulalis under field conditions. Under laboratory conditions, temperature was found to be an important factor affecting development and survival of the pest. Biological studies on T. sesamiae showed that the development period range from I4 - 18 days. Major factors identified to influence the biology and efficiency of the parasitoid includes quality of food, age of host pupae and different host species. Results from bioassay for pathogens showed that Nosema sp. was the most virulent naturally occurring pathogen on M. testulalis.
Finite elements for time-dependent convection-diffusion problems
(University of Dar es Salaam, 1988) Masenge, Ralph Wasili Peter
This thesis analyses and makes comparison (both theoretical and practical) between a number of numerical methods based on finite elements for solving stationary and time-dependent initial and boundary value problems governed by linear, scalar convection-dominated convection-diffusion equations. We set about achieving our objective by analysing the stability properties of the methods, deriving discretion error estimates and qualitatively assessing the computational complexity of implementing the methods. A number of test problems are presented and solved; the numerical results are discussed, and some specific conclusions are drawn in a concluding chapter.
Convection currents in bulk stred grain: detection, causes and consequences.
(University of Dar es Salaam, 1989) Uiso, Christian Basil Sawaki
The phenomenon of Iocalized moisture content build-up in bulk stored grain has been attributed to several processes including the existence of cyclic air convection currents which transfer moisture from warm to cooler parts of a bulk. Other moisture transfer mechanisms are not quantitatively considered in this study, although at the end of the second field trial period internal raining is explicitly considered to have contributed to the observed moisture and temperature distributions. A simple theoretical model has been derived to predict the airflow velocities for a given temperature difference predicted velocities ranged from 1.3x10-4MS-1 to 5.0x10-4MS-1 for temperature differences ranging from 7oC to 25oC, the higher velocity being induced by the larger temperature difference. The convection flow was first investigate experimentally in a laboratory apparatus which was set up using two cylindrical vertical columns of shelled maize interconnected at the top and bottom by two horizontal tubes containing air and maize respectively, Convection flow was detected by a tracer gas technique using sulphur directly proportional to the temperature difference in the range 17oC to 25oC and in good agreement with theoretical predictions. Moisture accumulation was detected in the top portion of the cool grain. Two field trials were conducted in a 250-tonne capacity steel silo, filled with maize, to confirm the existence of convection currents, measure their velocities and to field-test low air flow, remote moisture content and temperature measuring equipment were identified. Diurnal temperature changes were found to significantly penetrate the grain bulk to a depth of only 0.40m the surface. For the first time intergranular air convection in practical bulk storage due to such (virtual) temperature differences was detected and measured. Relatively strong downward (1.9x10-4 to 3.3x10-4MS-1 and weak upward (0.2x10-4 to 2.2x10-4MS-1) flows were measured near the silo walls and in the central bulk interior respectively, when the ambient was colder than the grain bulk. Big grain moisture content changes occurred in the whole bulk during the first field trial due to poor storage conditions. In the second field trial significant moisture content changes (from 13.5% to 26.0%) occurred in the top grain and along the silo walls near the top, initially due to the convective transport but later in the period also due to internal raining and dripping. Little moisture content change occurred in the grain bulk. Some recommendations were formulated for safe and long term storage of maize under the studied conditions and the scope for future academic work has been indicated.
The neuroendocrine regulation of larval development in the maize-stem borer, BusseolaFusca (fuller) (Lepidoptera: Noctuidae)
(University of Dar es Salaam, 1989) Njau, Marcelian Anton
Busseolafusca {Lepidoptera:Noctuid is one of the most important insect pests of maize and sorghum in Africa, south of the Sahara. Last instar larvae of this species survive the dry season in the stalks and stubbles of their host plants by undergoing diapause. The present study was done with the main objective of investigating the involvement of the neuroendocrine system during the development of the last instar larvae with respect to non-diapause and diapause development. The main aspects studied were the biology of last larval instar, histology, ultrastructure and physiology of the components of the larval neuroendocrine system, particularly the type-A neurosecretory cells, corpus cardiacum, corpus allatum and prothoracic glands. Endocrine involvement in the regulation of development during the last instar larvae and in induction, maintenance and termination of diapause development were also investigated. Studies on the biology of the last larval instar showed that two types of development, namely, non-diapause and diapause occur in Busseolafusca. The non-diapause form of development is characterized by the feeding phase and post feeding phase and the diapause form of development is characterized by the feeding phase and post-feeding phase and the diapause form of development is characterized by only a long, non-feeding phase. The structure of the components of the endocrine system revealed that both in non-diapause and diapause larvae, the type-A neurosecretory cells in the brain and the prothoracic glands were structurally comparable with insignificant differences. However, the corpora allata were structurally different in non-diapause and diapause larvae. The corpora allata in non-diapause development had cells which completely lacked glycogen-like deposits which were found allata of diapause larvae. The mitochondria of the cells of the corpora allata in non diapause development were not conspicuous and did not contain dense bodies. On the other hand, the mitochondria of the cells of the corpora allata in diapause larvae were large and pleomorphic and contained bodies within the mattrix. The corpora allata in non-diapause larvae were slightly smaller in size than those of diapause larvae. However, the prothoracic glands in non-diapause larvae were larger than those in diapause larvae. The titres of juvenile hormone in non-diapause larva (as determined by Dysdercusbioassay}, was very low the average score was 0.8 out of 3.0, while that in the diapause larvae was high (average score of 2.8). The titres of the moulting hormone in non-diapause last instar larvae were 170, and 500ng/ml on days one, four and seven respectively; in diapause larvae the titre was generally low with a monthly mean titre of less than 200ng/ml. Injection of the juvenile hormone analogue resulted in induction of diapause in non-diapause larvae. Elevation of the moulting hormone titres by experimental injection of ecdysone into the diapause larvae triggered moulting but it was usually a larval-larval (stationary moult. Injection of the moulting hormone in isolated abdomens of diapause larvae observations indicated that diapause development was not due to deficiency of moulting hormone. Diapause can be initiated and maintained by high titres of juvenile hormone. Precocene showed no allatocidal effect on the corpus allatum of the diapause larvae. Fluoromevalonate treatment of the late diapause larvae at a dosage of l0ug per individual prevented larval moult and delayed pupation relative to the non-treated larvae. At a dose of 5ug per individual, larval moults occurred and pupation was not delayed but the resultant adults were deformed. In conclusion, this study has shown that non-diapause development in the last larval instar is characterized by two distinctive behavioural phases whereas diapause development has only one behavioural phase. Also, diapause development in Busseolafusca lasts up to the pre-pupal stage of the last instar. In addition, type-A neurosecretory cells stain less with advance of time in non-diapause and diapause development during the last instar while the presence of glycogen in the corpora allata of the diapause larvae signified the storage of metabolites for use during the long period of diapause. Ecdysonetitres in the emolymph during non-diapause and diapause development were quite normal and so were the JH titres in non-diapause development. However, the persistent high titres of JH in the haemolymph during diapause development indicates that ease development in Busseolafusca is primarily controlled by the juvenile hormone. Thus, both ecdysone and juvenile hormone are involved in the regulation of the type of development which occur during the last larval instar of Busseolafusca.
Radiation relationship over natural surface in Tanzania, with special attention to Longwave radiation
(University of Dar es Salaam, 1990) Jiwaji, Noorali Tayabali
Measurement techniques of incident solar radiation are well established. Reliable measurements of shortwave radiation are presently made on a research and routine basis in Tanzania. Measurements of other components of the radiation balance or their combinations, such as net short-wave, net long wave and net all wave radiation, and long wave radiation from the atmosphere and from specified surfaces are, however, generally not available in the tropics. Empirical or semi-theoretical estimations of these parameters are made on the basis of studies conducted mainly in temperate climates. Longwave emissions from a surface or the atmosphere depend upon their effective (or apparent) temperature which in turn depends on the energy balance of the surface or the atmosphere under prevailing climatic factors. Hence long wave measurements are important in determining the state of a surface or the atmosphere. In this study, various components of the radiation balance have been measured at two places with different climates, (dry, semi-arid at Dodoma; and humid Dar es Salaam) in Tanzania, above three natural surfaces: natural grass, short (meteorological station) grass, and bare soil under clear skies and a few cloudy sky conditions. Various radiation relationships with respect to net all wave radiation have been presented. These have been used to evaluate heating coefficients for the natural surfaces. This parameter, first proposed by Monteith and Szeicz (1961), quantifies the long wave property of a surface with respect to net all wave radiation of that surface, depending on the prevailing environmental conditions above and within the surface. This parameter has a good theoretical basis and would allow the long wave properties of various surfaces to be calculated on a routine basis. However various studies conducted have been inconclusive with regards to its consistency, such that even its validity has been questioned. Instrument related problems and variations in downward long wave radiation have been cited to explain the inconsistency of measured values of heating coefficients. From hourly averages of radiation balance components, our evaluations of heating coefficients indicate that they behave with explainable consistency over the various natural surfaces. More conclusions about this parameter could not be drawn as we did not collect data over longer periods. Hourly means of downward long wave radiation, derived as a residual from measurements using an adapted Swissteco radiometer, were found to have a systematic, instrument related error, proportional to incident shortwave radiation, which we corrected by checking the internal consistency of our data set. The corrected diurnal variation of hourly means of downward long wave radiation under clear sky conditions in the semi-arid climate of Dodoma was found to have an anomalous minimum around midday, which we could confirm by examining data from other studies. An overall, Swanbank-type daily atmospheric emissivity relationship (e.g. equation 4.14) has been established for estimating daily or longer term mean downward long wave radiation (equation 4.17). When this equation was compared with several other empirical Swanbank-type formulae from the literature, it was found that most of these relationships fall within a narrow band on a plot of (calculated) downward long wave radiation versus equivalent black body radiation at screen level air temperature (figure 4.17). Since the various Swanbank-type formulae had been established using data taken over different locations and climates, this result implies that daily or longer term average atmospheric emissivities may have a rather limited range of variation. From our limited set of cloudy sky measurements, and other published data, the conurbation of clouds to total downward long wave radiation from the atmosphere has been determined and was found to be close to some other values found in the literature. Using monthly mean climatologically data for Dar Es Salaam and Dodoma, several empirical atmospheric long wave radiation formulae (including the “Penman” long wave formula, equation 2.35) have been compared in order to rationalize the net long wave term in the Penman evaporation formula (equation 4.27) for use under our tropical conditions. It is proposed that “Penman” long wave formula should be replaced, in the tropics, by the Brustsaert formula (equation 2.36) which has been derived using sound theoretical principles. For a minimum data input approach to evaporation calculations, the Brutsaert formula may be used as a general calibration equation; from which a Swanbank-type formula may be established for a particular location using accurate values of air temperature and vapour pressure at screen level for that location. Solar radiation, Tanzania
Effect of intercropping sorghum and cowpea on their lepidopteran stem and pod borer populations build-up with particular emphasis on ChiloPartellus (swinhos) (Lepidoptera: pyralidae) in South Kenya.
(University of Dar es Salaam, 1990) Minja, Eliaineny Mose
Polyculture of intercropping is widely practiced in Eastern Africa. Normally crops with widely differing growth habits such as legumes and cereals are interplanted. Such crop mixtures may however, lead to increased or decreased pest incidences depending on crop combination, location, season and cropping pattern. The results described in this thesis involved field studies on sorghum stem and cowpea pod borers in relation to cropping patterns and microclimatic factors in 1986-88. Five cropping patterns were investigated: cowpea and sorghum monocrops, cowpea and sorghum sown simultaneously in the same plot, and cowpea sown before and after sorghum in the same plots. Crops were planted in randomized blocks replicated thrice at ICIPE Mbita point field station (MPFS) and on a farmer’s field on Rusinga Island. Chilopartellus (Swinhoe) (Pyralidae) egg counts were made on twenty sorghum plants. Chilo moths were released on caged field plants to study oviposition. Sorghum plants were artificially infested with eggs to study larval establishment. Stem borer larval and pupal populations were monitored on destructively sampled sorghum plants. Pod borer egg and larval counts were made weekly. Pupae were sampled every five days. Dead borers and other arthropods on plant samples were noted. Soil arthropods were sampled weekly using pitfall traps to monitor potential predators. Light intensity was recorded at ground level using a quantum radio meter (LI-1905). Canopy temperature and humidity were recorded. C. partellus, Busseolafusca (Fuller) (Noctuidae), Eldanasaccharina (Walker) (pyralidae) and Sesamiacalamistis (Hmps.) (Noctuidae) were recorded on sorghum throughout the study. Stem borer larval and pupal populations appeared to increase with the age of sorghum. Monocrop sorghum had a significantly higher number of borers and leaf damage than intercrops. There was a significant delay in borer colonization and establishment on sorghum sown after cowpea than the other cropping patterns. Monocrop cowpea had a significantly higher number of Marucatestulalis (Geyer) (Pyralidae) eggs, larvae, pupae and damaged pods than intercrops. Borer colonization and establishment was delayed in cowpea sown after sorghum. Diseases and parasites were the predominant mortality factors in larvae and pupae respectively. Soil arthropods were fewer in sorghum monocrop than intercrops. Furthermore, light intensity, temperature and humidity variations within crop canopies were higher in monocrop than intercrops. Cowpea and sorghum grain yields seemed to have been adversely affected by late planting. However, it appeared that if both crops are to be produced efficiently on a piece of land, then cowpea could be sown before sorghum. In conclusion therefore, intercropping appeared to have substantial influence in disrupting borer colonization and establishment as well as favoring predators and parasites.
A study on the ability of freshwater bacteria and ciliates to fix nitrogen and decompose Azolla for rice growth.
(University of Dar es Salaam, 1990) Magingo, Francis Stanislaus Sholastika
Results are presented on the following investigations: 1.The nitrogen fixation capacity of & methanogenic bacterium previously isolated from the anaerobic freshwater ciliate Metopus striatus McMurrich. 2.The conditions for isolation and growth of monocultures of two freshwater sapropelic ciliates: Metopus pulcher and Caenomorpha lata. 3.Rate of anaerobic decomposition of Azolla by sapropelic bacteria alone and sapropelic bacteria in combination with the above ciliates. 4.The influence of Azolla at different levels of decomposition on rice growth. The results of nitrogen fixation by Methanobacterium formicicum showed that pure cultures of the bacterium could utilize molecular nitrogen as the sole source of nitrogen for growth as monitored by methane production and culture turbidity measurements. The rate of methane production by the bacterium was correlated to the nitrogen gas concentrations. In the absence of any nitrogen gas or any other nitrogen source the bacteria completely stopped growing. It was also found that the presence of selenium and molybdenum in the culture medium was vital for growth of the bacterium under nitrogen fixing conditions. Two freshwater sapropelic ciliates, Metopus pulcher and Caenomorpha lata were isolated and monocultures of these could survive by feeding them with a mixed population of sapropelic bacteria and ground Azolla as the only source of organic material in the culture medium. Starting with 50 cells per ml of each ciliate type in 50 ml size carrel flasks, the monocultures grew to 700 and 280 cells per ml for M. pulcher and C. lata, respectively. Ways of ensuring a good monoculture of an anaerobic sapropelic ciliate are discussed. The cytoplasm of both ciliates contained large numbers of methanogenic endosymbionts and microbodies, as revealed by fluorescent and transmission electron microscopy. However, in M. pulcher the endosymbiont isolated was of the Methanobacterium type while in C. lata, there were two types of endosymbionts isolated viz., Methanosarcina and Methanobacterium. The biochemical pathways of these ciliates are discussed. The role of freshwater sapropelic bacteria and ciliates in the anaerobic decomposition and the release of fixed nitrogen of the freshwater floating fern Azolla was studied. The decomposition of Azolla was quantified in terms of methane production, changes in ammonium-N and decrease in fibres. The decomposition rate was faster when the Azolla was anaerobically decomposed by sapropelic bacteria and ciliates together rather than when only bacteria were present. Reasons for the faster Azolla decomposition in the presence of bacteria together with ciliates are discussed. In order to assess the importance of the decomposed Azolla on improving the soil fertility, an investigation was done on growth of rice plants by adding Azolla in different stages of decomposition. Dry weights and total nitrogen of rice plants grown without Azolla; with undecomposed Azolla; with Azolla decomposed by sapropelic bacteria alone; or with Azolla decomposed by sapropelic bacteria together with ciliates were measured. Significantly higher amounts of dry weight and total nitrogen were observed for rice plants grown with Azolla decomposed by sapropelic bacteria together with sapropelic ciliates Caenomorpha lata and Metopus pulcher. This was followed by rice plants grown with Azolla decomposed by bacteria only. Rice plants grown with undecomposed Azolla and no Azolla at all, had significantly the lowest amounts of dry matter and total nitrogen.
Anaerobic degradation of cereal residues by a rumen derived process
(University of Dar es Salaam, 1990) Kivaisi, Amelia Kajumulo
The conversion of lignocelluloses into biogas in a Rumen Derived Anaerobic Digestion (RUBAD) process was studied. Anaerobic degradation of lignocelluloses in conventional digesters is a slow process mainly due to low enzymatic activity present and lignin protects the degradable polysaccharides against enzymatic attack. On the contrary, the rumen degrades lignocelluloses efficiently because ruminants employ many highly cellulolytic microbial species. Hence the RUDAD-process has a potential to degrade lignocelluloses. However, lignin has been shown to inhibit rumen microorganisms in vitro. To examine the performance of rumen microorganisms in degrading lignocelluloses, various materials with lignin contents between 0 and 34% of total solids were tested in batch cultures and in the RUDAD-process. An increase in lignin content resulted in decrease of degradability. The effects of externally added lignin or lignin monomeres on in vitro degradation of filter paper cellulose by rumen micro-organisms and on their cellulose activity were studied in batch cultures. Addition of these compounds in concentrations comparable to natural conditions showed minor inhibitory effects. It appeared that the decrease of degradability with increasing lignin content was caused by lignin forming a physical barrier to enzymatic attack on the degradable polysaccharides. Rumen micro-organisms were further tested for degrading various cereal residues in a one-phase process. Under standard rumen conditions, and loading rates varying between 9.8g of volatile solids per litre per day, total fibre degradation efficiencies were in the 42-57% range irrespective of the loading rates applied. Optimum degradation of barley straw fibre (16% lignin) was obtained under conditions similar to those found in the rumen in vitro. In all of the experiments 40-60% loss in lignin was observed based on fibre analysis. The degradation efficiency of the straw in a two-phase process was 50%. The fermentation products of the first phase were converted to biogas in the second phase. The two-phase process was demonstrated to be stable for over three months with straw as the sole substrate for anaerobic digestion. To check if lignin was solubilized during the degradation of lignocelluloses the presence of soluble lignin derived compounds in the reactors fed barley straw was determined by Ultraviolet Spectral Characteristics and Pyrolysis Mass Spectrometry. Most of these compounds were shown to be released from the cell walls by the action of rumen micro-organisms. Determination of the association between rumen ciliates and methanogenic bacteria on the bias of coenzyme F42O-2 was attempted. The ease of extracting and quantifying the coenzyme makes the assay a much better method of assessing the extent of association than direct microscopically enumeration of methanogens.
The feeding ecology and behaviour of the red colobus monkey (colobus badius kirkii )
(University of Dar es Salaam, 1991) Mturi, Fatina Athumani
Feeding ecology and behavior of the Zanzibar red colobus monkey, colobus badius Kirkii was studies between January 1980 and April 1981 in Zanzibar (Tanzania). This involved an intensive systematic study of twelve month on two monkey group (I and II) in Jozani Forest reserve, and of eight month on another group (III) in Kichanga. Opportunistic observations were made on these and other monkey group in in Jozani, Pete, Muungwi and Muungoni. C.b Kirkii was observed to range in ground water forest, coral rag forest and thicket, mangrove forest, scrub, abandoned coconut and mango plantations, and other cultivated areas. Kirkii had a diverse and was selective in its feeding. It also fed on exotic and crop species and was condemned as vermin. Main items in Kirkii diet were leaf buds, young leaves unripe truits and seeds, and young floral parts. Ripe succulent fruits and mature leaves were avoided. Foods high in protein or fermentable carbohydrates and also digestible were selected. Alkaloids and condensed tannis showed little influence on food selection. The three study groups showed differences in food choice and selectivity. These were attributed to interference competitions. Food habit of Kirkii was similar to those of other red colobus. Like most red colobus, c.b. Kirkii ranged in heterosexual social groups that varied in size and day range lengths of group I and II varied thought-out the study period, and were not influenced by diet, food abundance, or rainfall. Day range lengths were positively related to intergroup encounters in group II. Range use in group I and II was not uniform. It was positively related to the abundance of food trees in group I. Ecological and behavioral factors influenced food selection and ranging in groups of c.b Kirkii is threatened by habitat destruction by human activity. Its survival can be guaranteed by protecting their natural habitat through adequate conservation measures

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