RP-Department of Zoological Sciences

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Contribution of hot spring cyanobacteria to the mysterious deaths of Lesser Flamingos at Lake Bogoria, Kenya
(Oxford University Press, 200-03-01) Krienitz, L; Ballot, A.; Kotut, K.; Wiegand, C.; Pütz, S.; Metcalf, J. S.; Codd, G. A.; Pflugmacher, S.
Cyanobacterial mats at hot springs on the shore of the alkaline Lake Bogoria, Kenya, were investigated regarding species community and cyanobacterial toxin content. The hepatotoxins microcystin-LR, -RR, -LF and -YR, and the neurotoxin anatoxin-a were present. The mats were dominated by Phormidium terebriformis, Oscillatoria willei, Spirulina subsalsa and Synechococcus bigranulatus. The concentration of microcystins in mat samples, ranged from 221 to 845 μg microcystin-LR equivalents g−1 DW of mat. Anatoxin-a concentrations ranged from 10 to 18 μg g−1 DW of mat. A contribution of the cyanobacterial toxins from the hot spring mats to the mass mortalities of Lesser Flamingos is suggested by: (a), the presence of hot spring cyanobacterial cells and cell fragments, and high concentrations of the cyanobacterial hepato- and neurotoxins in flamingo stomach contents and faecal pellets; (b), observations of neurological signs of bird poisoning at the lake. Cyanobacterial toxins in stomach contents, intestine and fecal pellets were 0.196 μg g−1 fresh weight (FW) for the microcystins and 4.34 μg g−1 FW for anatoxin-a. Intoxication with cyanobacterial toxins could occur by uptake of detached cyanobacterial cells from the mats, as the flamingos need to drink fresh or brackish water, and to wash their feathers daily, which they do in the vicinity of the hot springs, where salinity is lower than in the main body of water of the lake.
Factors Affecting Stem Borer Parasitoid Species Diversity and Parasitism in Cultivated and Natural Habitats
(Entomological Society of America, 201) Kairu, E. W.; Mailafiya, D. M.; Le Ru, B. P.; Calatayud, P.; Dupas, S.
The effects of biotic and abiotic factors on stem borer parasitoid diversity, abundance, and parasitism were studied in cultivated and natural habitats in four agroecological zones in Kenya. Comparing habitat types, we found partial support for the “natural enemy” hypothesis, whereby, across all localities, parasitoid diversity was higher in more diverse host plant communities in natural habitats, whereas parasitoid abundance was higher in cultivated habitats. For both habitats, parasitoid richness was mainly influenced by stem borer density and/or its interaction with stem borer richness, whereas parasitoid abundance was mainly affected by stem borer abundance. Parasitoid richness was higher in localities (with bimodal rainfall distribution) with increased spatial and temporal availability of host plants that harbored the borers. Across seasons, parasitoid richness was lower in both cultivated and natural habitats in the driest locality, Mtito Andei. Overall, parasitoid diversity was low in Suam and Mtito Andei, where maize cultivation was practiced on a commercial scale and intense grazing activities persist across seasons, respectively. Across localities, habitats, and seasons, stem borer parasitism was positively correlated with parasitoid richness and abundance. Furthermore, the interaction of rainfall and altitude influenced the presence and absence of parasitoids, and consequently, stem borer parasitism. Parasitism was positively and negatively correlated with temperature in cultivated and natural habitats, respectively. Overall, natural habitats seem to serve as important refugia for sustaining parasitoid diversity, which in turn can affect stem borer parasitism in the cereal cropping system.
Parasitization of Helicoverpa armigera (Lepidoptera: Noctuidae) by four Indigenous Trichogrammatid Species/Strains in a Mixed Cropping System of Tomato and Okra
(SCIENCEDOMAIN international, 201-02-21) Mueke, J. M.; Kalyebi, A.; Hassan, S.; Sithanantham, S.
Aims: Egg parasitoids, Trichogramma are recognised as natural enemies of many lepidoptera pests worldwide. In Kenya, a number of indigenous parasitoids species have been recovered. We evaluated the relative preference (parasitism) by four Trichogrammatid egg parasitoid species/strains, namely, T. sp. nr. mwanzai (L), T. sp. nr. lutea (H), T. sp. nr. mwanzai (M) and T. sp. nr. lutea (M) for the African bollworm Helicoverpa armigera on two of its host plants, tomato and okra usually intercropped in smallholder farms in Kenya. Study Design: Host parasitism on host plants. Methodology: Evaluations of parasitism for H. armigera by Trichogrammatid species/strains on Tomato and Okra in bioassays in both laboratory and field cages, in choice and no-choice conditions were undertaken. Results: In general, species/strains exhibited significant differences in parasitism for the host (F=2.8; df =3, 7; P= 0.05) but neither the host plant nor host plant x species/strain interaction affected parasitism. Chi-square analyses showed no significant preference by species/strains between the two host plants although there was greater tendency by the parasitoids to go for H. armigera on okra than tomato. Conclusion: The results give useful insights in planning for augmentation biological control of H. armigera in mixed farming agroecosystems. The four Trichogrammatids could effectively be used in augmentation programs in the tomato-okra cropping systems.
Some effects of mound-building termites on soils in Uganda
(Bioinfo Publications, 1976-09) Pomeroy, D. E.
Most large mounds in Uganda are built by termites of the genus Macrotermes. Except for those in valley bottoms they are composed of subsoil which is thought to be collected mainly from depths of 0.5 to 1.0 m, although the evidence is inconclusive. Mounds of both M. bellicosus and M. subhyalinus contain less sand than the subsoil when this is sandy, but only M. subhyalinus mounds contain less clay when the subsoil has a high clay content. In general both species tend to produce a stone-free topsoil whose physical properties are closer to a loam than the average subsoil. Mounds of both species in valley bottoms appear to be built from topsoil. The amounts of organic matter, nitrogen, calcium, phosphorus, and potassium in mounds were estimated together with their rates of turnover. In terms of the demands of two typical crop plants the quantities held in mounds and their rate of release to the surrounding topsoil were small. Only calcium was likely to be cycled in significant amounts. It seems that termites only slightly affect the physical and chemical properties of Ugandan soils, even where mounds are comparatively abundant.
Effects of temperature on growth in the regenerating tail of the scincid lizard, Mabuya striata
(Zoological Society of Southern Africa, 1977) Magon, D.K.
Experiments on effects of temperature on growth in the regenerating tail of Mabuya striata, artificially autotomized, suggest a faster rate of regeneration during hot weather than cold weather. limbs of newts and salamanders can generally be replaced both in adults and larvae. Amongst reptiles, however, regeneration of limbs is not a common phenomenon. In lizards, for example, limb regeneration occurs only as abnormal outgrowths (Goss 1969). A few lizards are known to restore lost tails, and there generated tail is almost a true substitute for the original tail, not only with respect to structure and function, but also to size. The period taken by a regenerating tail to achieve its original length varies from species to species as well as individual to individual. Such variation in the rate of growth of regenerates seems to be correlated with several factors, viz. the amount of tail autotomized, pressure applied at the time of autotomy, temperature, humidity, hormonal levels and diet (Moffat & BeUairs 1964; Bryant & Bellairs 1967; licht 1967; Maderson & licht 1968; Shah & Chakko 1968; Baiinsky 1970; Magon 197580 1975b). Much more experimentation will be necessary, however, before the effects of these factors can be quantified. The experiments described in this paper examine the influence of temperature on the growth in the regenerating tail ofthe scincid lizard, Mabuya striata, during the different seasons of the year, viz. hot season: December - February; rainy season: March - May & September - November; and cold season: June - August.
Histological observations on the changes in thyroid activity in the scincid lizard, Mabuya striata, during different phases of tail regeneration
(Zoological Society of Southern Africa, 1977) Magon, D.K.
Measurements of the follicle cells of the thyroid during different phases of regeneration of the tail in the scincid lizard. Mabuya striata. indicate a decrease in thyroid activity during the wound-healing phase and an increase at the end of the blastema phase. The significance of endocrine secretion of the thyroid has drawn the attention of a number of developmental biologists as the hormone thyroxine brings about various physiological changes during anuran metamorphosis. The regenerative power of these amphibians gradually diminishes as metamorphosis advances. It may be absent in the fully metamorphosed animals (Rose 1964), or sometimes restricted to wound healing or to the formation of a hypermorphic cartiJaginous spike (Richards et oJ. 1975). Further, PawlowskJ (1933), Peadorr (1953) and Schotte & Washburn (1954) showed that thyroidectomy, treatment with thiourea, or increased doses of thyroxine hinder amphibian regeneration. Nevertheless, Tassava (1969) and Bromley & Thornton (1974) presented data indicating that prolactin when present with thyroxine promotes limb regeneration. Thus these reports suggest some possible relationship of thyroxine to metamorphic changes and capacity for regeneration in the amphibians. However, the role of thyroxine and other thyroid secretions in regeneration of reptiles is still unknown. The following communication describes an attempt to examine histological differences in the thyroid activity in the normal scincid lizard, Mabuya striata. and those showing different stages of tail regeneration, with a view to assessing the role of thyroid secretion in the regenerative processes of this reptile
Reproductive Biology of Tilapia zillii (Gervais) in Lake Naivasha, Kenya
(Kluwer Academic Publishers, 1979) Siddiqui, A. Q.
Tilapia zillii breeds all year round in the equatorial Lake Naivasha with slightly high breeding intensity during wet months (March, May and July–August). A sex ratio of 1 : 1.28 was found between males and females. The smallest mature male and female were 9.0 and 11.0 cm respectively. The fecundity ranged from 2990 to 12344 eggs, with a mean of 6606 eggs. Fecundity showed a curvilinear relationship with total length (log F = 1.7034 + 1.6370 log L) and a linear relationship with body weight (F = 2197 + 28.76 W)
Changes in Fish Species Composition in Lake Naivasha, Kenya
(Kluwer Academic Publishers, 1979) Siddiqui, A. Q.
The fish species composition in Lake Naivasha has been modified during recent years. Out of seven introduced and one indigenous species reported in 1962, only three introduced ones are found today. The elimination of species has been brought about by predation and changing ecological conditions. The most common fish species today is Sarotherodon leucosticuus. The hybridization found by previous workers between S. leucostictus x S. spilurus niger has stopped, as S. s. niger is no longer found in the lake. Most of the hybrid characters have been lost by the few surviving hybrids due to backcrossing between hybrids and between hybrids and S. leucostictus. The hybrids now mostly resemble S. leucostictus.
Bushmeat in Nigeria as a Natural Resource with Environmental Implications
(Cambridge University Press, 1983) Martin, G. H. G.
The value of protein from wild animals (‘bushmeat’) in Nigeria was examined, especially with respect to the consumer market. Surveys were made of roadside sales, meat prices in markets, and bushmeat consumption by the general public. The results showed that, in the 1970s, over 50% of the population ate bushmeat regularly, and that bushmeat was popular with all income-groups. The results have wide environmental implications. The case is made for investigating in more detail than hitherto the potential for domestication and game-cropping. In addition to economic advantages resulting from careful management of animal wildlife as a renewable resource, there appear to be others—including major environmental ones through the maintenance of large-scale reserves.
A quantitative study of the life history of a fairy shrimp (branchiopoda: anostraca) in relation to the temporary nature of its habitat, a Kenyan rainpool
(Jstor, 1985) Hildrew, A. G.
(1) Two cohorts of Streptocephalus vitreus (Brauer 1877) lived for 19 (short-rains cohort) and 32 days (long-rains cohort) in a temporary rainpool during two wet seasons in Kenya. On both occasions the pool dried up when many animals were still alive and producing eggs. The instantaneous growth rate was constant between the age of 3 and 17 days (27.0% dry weight day-') in the short-rains cohort, but declined with age in the long-rains cohort, being constant between day 3 and 5 (53.8% day-'), 9 and 19 (19-9% day-') and 19 and 32 (1.2% day-'). (2) Egg production began at the age of 17 days and at a mean dry weight of 300 ,ug in the short-rains cohort and at the age of 14 days and weight 440 ,ug in the long-rains cohort. A higher proportion of females produced eggs in the long than in the short-rains cohort and average clutch size differed (42.1 + 5.1 and 11.0 + 1.4 respectively). (3) There was a constant mortality rate in the long-rains cohort. Sex ratios were equal at first but favoured females after maturity. Males were preponderant in sample units containing one or two individuals, females in those with more than two individuals. In the long-rains cohort, average daily production was 5.70 mg dry weight m-2 day-' and the P/B ratio between age 3 and 32 days was 3.36. (4) More eggs hatched from soil cores taken near the edge of the pool than from those near the middle. Eggs either hatched within 3 days of immersion or not until they had been dried again. Egg hatching was very erratic and metanauplii emerged during each of nine periods of flooding the same soil cores. Hatching times were very variable even between eggs in the same clutch. (5) General aspects of the life-history strategy are discussed. Fairy shrimps are large in comparison with most other freshwater crustacea, do not co-exist with fish and, through their eggs, resist unfavourable circumstances rather than disperse. In S. vitreus there is extreme spreading of risk among the progeny and very rapid growth to maturity. Apparently in response to the unusually unreliable and hazardous nature of its habitat, reproduction begins relatively early and at a modest size. When circumstances allow, repeated copulations (probably with different males) produce further clutches of eggs.
Mima mound microtopography and vegetation pattern in Kenyan savannas
(Cambridge University Press, 1985-02) Gakahu, C. G.; Cox, G. W.
Earth mounds are important determinants of vegetation pattern in savannas, acting as foci for establishment of woody plants. In the Kenya highlands, mounds formerly attributed to termites have recently been found to be Mima mounds produced by rhizomyid mole rats. We investigated Mima mounds on black cotton soils near Kenyatta International Airport and on brown clay soils between Nairobi and Thika. At Kenyatta Airport, mounds had loamier, more granular soils than intermounds, and contained small rocks that mole rats can move. At the site between Nairobi and Thika, mound soils were more friable, higher in pH, and lower in carbon than intermound soils. Data from this and other studies indicate that Mima mound soils are more favourable for plant growth than those of true termite mounds. Mound vegetation exhibited lower coverage of grasses and greater coverage by forbs, shrubs, and bare ground, a pattern indicative of intense grazing and soil disturbance. Acacias, absent from most mounds, were abundant in the zone bordering the mound. This pattern may reflect the favourability of mound soils, combined with the effects of high grazing pressure. Future studies of savanna vegetation should distinguish between termite mounds and Mima mounds.
A population study of small rodents in a dry sub-humid grassland in Kenya
(Cambridge University Press, 1985-08) Martin, G. H. G.
Estimates were made of rodent longevity, population biomass and production in a dry sub-humid grassland area in Kenya, The results were based on a live-trapping study made over a 27-month period. During this time fourteen species of rodents and four species of insectivores were recorded from the area of the trapping grid. The most numerous species were Praomys natalensis, Mus triton, Mus minutoides and Lemniscomys striatus. Breeding took place in both wet seasons, coinciding with peaks in rodent populations. Densities ranged from 6.6 ha-1 to 52.4 ha-1, and estimates of net annual production varied from 5485 g ha-1 year-1 to 7221 g ha-1 year-1. Rodent populations appear to turn over every six to nine months. The results are discussed in relation to studies in other tropical grassland areas of Africa.
Studies of birds in a semi-arid area of Kenya. III The use of ‘Timed Species-counts’ for studying regional avifaunas
(Cambridge University Press, 1986-08) Pomeroy, D.; Tengecho, C. B.
‘Times Species-counts’ are a simple method of comparing the avifaunas of extensive areas by sampling representative habitats. The method has been evaluated in south central Kenya but could be applied to most terrestrial regions of tropical Africa. The essential feature is that the observers move anywhere within a sample site of about 1 km2, recording all of the species seen in a fixed time, e.g. 1 h. Counts are made in all seasons and at various times of day. Reasonable estimates of the total number of species in an area can be derived from a series of 15 counts, but such estimates tend to be low in non-forested habitats because ‘wanderers’ (non-resident species) continue to be recorded almost indefinitely. Open sites have far fewer species than well-wooded areas. The numbers of resident species in non-forested terrestrial habitats is related both to the amount of woody vegetation and to a measure of plant growth. However, total species numbers seem to depend solely on the amount of woody vegetation. Road counts, from a vehicle, were compared to those made on foot. They are less satisfactory, especially for cryptic species.
Role of Sorghum Extract in Eliciting Oviposition on a Nonhost by the Sorghum Shootfly, Atherigona soccata Rondani (Diptera: Muscidae)
(Entomological Society of America, 1987-08) Hassanali, Ahmed; Saxena, K. N; Unnithan, G.C.; Bentley, M. D
The role of chemicals of sorghum plants in stimulating oviposition by the sorghum shootfly, Atherigona soccata Rondani, was investigated using the acetone extract of the susceptible sorghum CSH-1, which elicits high ovipositional response. Maize, not a host plant, treated with acetone extract of CSH-1 elicited as much egg-laying by the sorghum shootfly as did CSH-1. The activity of the extract on maize lasted for the maximum test period of 5 d. Results of these studies demonstrate the potential of the host-plant-produced oviposition stimulants for manipulating the ovipositional behavior of the sorghum shootfly as a strategy for the control of the pest.
Volatile components of banana pseudostem of a cultivar susceptible to the banana weevil
(Elsevier Ltd, 1991) Hassanali, Ahmed; Ndiege, I. O.; Budenberg, W. J.; Lwande, W.
Volatiles from banana (‘githumo’'cultivar) pseudostem were trapped using porapak S. The trapped volatiles were desorbed from porapak columns by elution with dichloromethane and analysed using GC and GC-MS. The volatile compounds identified included α-pinene, β-pinene, β-myrcene, limonene, α-cubebene, α-copaene, α-cedrene, β-caryophyllene and α-humulene
Feeding responses ofChilo partellus (Swinhoe) (Lepidoptera: Pyralidae) larvae to sorghum plant phenolics and their analogs
(Elsevier Ltd, 1991-01) Hassanali, Ahmed; Torto, B.; Saxena, K. N.; Nokoe, S.
Phagostimulatory responses of third-instar larvae ofChilo Partellus to phenolic components identified in an ethyl acetate extract of the leaf whorls of 3-week-old plants ofSorghum bicolor cultivar IS 18363 were studied in no-choice bioassays. The major components in the extract were identified as 4-hydroxybenzaldehyde and 4-hydroxybenzoic acid, with 4-hydroxy-3-methoxycinnamic acid, 3,4-dihydroxycinnamic acid, and 4-hydroxycinnamic acid present in minor amounts. All but 4-hydroxycinnamic acid were stimulatory at the doses tested. 4-Hydroxybenzaldehyde was more stimulatory than other potential biogenetic analogs. Hydroxybenzoic acids generally elicited greater feeding response than cinnamic acids, and the pattern of oxygen substitution in the benzene ring was related to bioactivity.
The effects of experimental Trypanosoma (Trypanozoon) (brucei) evansi infection on the fertility of male goats.
(Veterinary Research Communications, 1991-02) Ngeranwa, J.J.N.; Mutiga, E R; Agumbah, G J; Gathumbi, Peter Karuri; Munyua, W K
The effects on the fertility of small East African male goats of intravenous infection with Trypanosoma (t) (b) evansi were studied. Six infected bucks developed erratic, low but persistent parasitaemia, the packed cell volume dropped gradually but significantly (p less than 0.001) and they became emanciated. Half of these bucks developed clinical orchitis. Two bucks died of the disease during the experiment. Semen from all the infected bucks deteriorated in quality and quantity and those with clinical orchitis became totally aspermic. Spermatozoal abnormalities and the number of dead spermatozoa rose significantly. Later in the disease, the testicles of the infected bucks atrophied. Histologically, the testicles from the infected animals became devoid of spermatozoa, the testicular blood vessels contained microthrombi and there was infiltration of inflammatory cells. Subsequently, diffuse calcification set in, with calcium deposits obliterating most of the seminiferous vesicles and ducts and also the epididymal ducts.
Densities of Prodiamesa olivacea (Neigen) (Diptera: Chironomidae) in a Second Order Stream, the Laan (Belgium): Relation to River Dynamics
(Kluwer Academic Publishers, 1992) Janssens De Bisthoven, L.; Van Looy, E.; Ceusters, R.; Gullentops, F.; Ollevier, F.
Larval densities ofProdiamesa olivacea were examined in the Laan stream for one year and matched against stream discharge and coarse organic detritus (COD) content of the sediments. The sediment grain size partitioning for the 12 monthly sampling dates was also assessed. The substrate was mainly composed of fine sand (high discharge periods) or silt (low discharge periods) and a never absent COD component which fluctuated seasonally within a narrow range. The discharge fluctuations showed some negative impact on densities of early instarP. olivacea. The absolute and relative densities ofP. olivacea were high throughout most of the study period and showed emergence periods in April–May and September–October.
Pathogenesis of Trypanosoma (brucei) evansi in small east African goats.
(Research in Veterinary Science, 1993-05) Ngeranwa, J.J.N.; Gathumbi, Peter Karuri; Mutiga, E R; Agumbah, G J
Trypanosoma evansi is the cause of surra, a camel disease which is the most important single cause of economic losses in camel rearing areas. Sheep and goats herded with camels are the most likely hosts for T evansi. Upon intravenous infections goats developed erratic parasitaemia, lost weight and their packed cell volume dropped significantly (P < 0.001). Trypanosomes were demonstrated by direct microscopy in extravascular locations such as synovial, peritoneal and cerebrospinal fluids and also in lymph by subinoculations into mice. The carcases were emaciated and pale. Histologically there was lymphatic tissue hyperplasia, muscular atrophy and nephrotic changes. Two animals had necrotic foci in the liver, kidneys, lymph nodes, spleen and lungs and also bronchopneumonia. Histologically there was depopulation of lymphocytes in lymphatic tissues, destruction of hepatocytes in the liver with infiltration by inflammatory cells in the liver, lymph nodes, spleen and the kidneys.
The Effect of Intercropping on Relative Resistance and Susceptibility of Cowpea Cultivars to Maruca Testulalis Geyer when in mono and when Intercropped with Maize
(Cambridge University Press, 1993-06) Mueke, J. M.; Gethi, M.; Omolo, E. O.
Field studies to investigate the effect of intercropping on the relative resistance and susceptibility of cowpea cultivars to Maruca testulalis impure stands and intercropped with maize, were conducted at the International Centre of Insect Physiology and Ecology (ICIPE). It was clearly indicated that intercropping affected the relative resistance and susceptibility of cowpea cultivars. The resistance of TVU 946 to Maruca was reduced when the cultivar was under maize. This was attributed to the phenological changes observed, i.e. when planted with maize there was a significant (P = 0.05) increase in length of the pods and peduncles and significant (P = 0.05) reduction in the number of branches. Weekly mean temperatures and relative humidities indicated that there were significant differences between cropping patterns. Similarly there was a significant reduction in the photosynthetic active radiation incident on cowpea canopy in all the intercropped plots. This suggested that both intercropping and microenvironmental differences observed, reduced resistance in cultivar TVU 946 by probably acting directly on the crop, thus rendering it more susceptible.

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