Lenticular soil mounds in the Kenya highlands

Summary Soil mounds in moist grassland at moderate altitudes in the Kenya Highlands have recently been interpreted as being formed by burrowing molerats. Evidence is presented here that these mounds contain active nests of Odontotermes spp. and are likely to have been built by the termites.     

Mima mounds in Kenya–a case of mistaken identity

Earth mounds at seven sites in upland areas of Kenya were examined. Termite activity was recorded from 91% of mounds and the major termite genus present was Odontotermes. Generally, signs of the mole rat, Tachyoryctes splendens were few and were present on only 18% mounds. All termite activity was mound-centred but only at Kiserian were mounds obvious centres for mole rat activity. At Molo, where Tachyoryctes were abundant, neither mounds nor much sign of termite activity were observed. The data are discussed in relation to the work of Cox and Gakahu. No convincing evidence was found to support the conclusion made by these workers for a mole rat origin of large earth mounds. The weight of the data suggests that a termite origin for these mounds is more likely.     

Productivity of malaria vectors from different habitat types in the western Kenya highlands

Background

Mosquito Larval Source Management (LSM) could be a valuable additional tool for integrated malaria vector control especially in areas with focal transmission like the highlands of western Kenya if it were not for the need to target all potential habitats at frequent intervals. The ability to determine the productivity of malaria vectors from identified habitats might be used to target LSM only at productive ones.

Methods

Each aquatic habitat within three highland sites in western Kenya was classified as natural swamp, cultivated swamp, river fringe, puddle, open drain or burrow pit. Three habitats of each type were selected in each site in order to study the weekly productivity of adult malaria vectors from February to May 2009 using a sweep-net and their habitat characteristics recorded.

Results

All surveyed habitat types produced adult malaria vectors. Mean adult productivity of Anopheles gambiae sensu lato in puddles (1.8/m²) was 11–900 times higher than in the other habitat types. However, puddles were the most unstable habitats having water at 43% of all sampling occasions and accounted for 5% of all habitats mapped in the study areas whereas open drains accounted for 72%. Densities of anopheline late instars larvae significantly increased with the presence of a biofilm but decreased with increasing surface area or when water was flowing. Taking stability and frequency of the habitat into account, puddles were still the most productive habitat types for malaria vectors but closely followed by open drains.

Conclusion

Even though productivity of An. gambiae s.l. was greatest in small and unstable habitats, estimation of their overall productivity in an area needs to consider the more stable habitats over time and their surface extension. Therefore, targeting only the highly productive habitats is unlikely to provide sufficient reduction in malaria vector densities.     

Lifetime productivity of dairy cows in smallholder farming systems of the Central highlands of Kenya

Evaluation of lifetime productivity is sensible to target interventions for improving productivity of smallholder dairy systems in the highlands of East Africa, because cows are normally not disposed of based on productive reasons. Feeding strategies and involuntary culling may have long-term effects on productive (and therefore economic) performance of dairy systems. Because of the temporal scale needed to evaluate lifetime productivity, experimentation with feedstuffs in single lactations is not enough to assess improvements in productivity. A dynamic modelling approach was used to explore the effect of feeding strategies on the lifetime productivity of dairy cattle. We used LIVSIM (LIVestock SIMulator), an individual-based, dynamic model in which performance depends on genetic potential of the breed and feeding. We tested the model for the highlands of Central Kenya, and simulated individual animals throughout their lifetime using scenarios with different diets based on common feedstuffs used in these systems (Napier grass, maize stover and dairy concentrates), with and without imposing random mortality on different age classes. The simulations showed that it is possible to maximise lifetime productivity by supplementing concentrates to meet the nutrient requirements of cattle during lactation, and during early development to reduce age at first calving and extend productive life. Avoiding undernutrition during the dry period by supplementing the diet with 0.5 kg of concentrates per day helped to increase productivity and productive life, but in practice farmers may not perceive the immediate economic benefits because the results of this practice are manifested through a cumulative, long-term effect. Survival analyses indicated that unsupplemented diets prolong calving intervals and therefore, reduce lifetime productivity. The simulations with imposed random mortality showed a reduction of 43% to 65% in all productivity indicators. Milk production may be increased on average by 1400 kg per lactation by supplementing the diet with 5 kg of concentrates during early lactation and 1 kg during late lactation, although the optimal supplementation may change according to milk and concentrate prices. Reducing involuntary culling must be included as a key goal when designing interventions to improve productivity and sustainability of smallholder dairy systems, because increasing lifetime productivity may have a larger impact on smallholders’ income than interventions targeted to only improving daily milk yields through feeding strategies.     

Performance of Toggenburg dairy goats in smallholder production systems of the eastern highlands of Kenya

The use of exotic dairy goats in breeding programmes for smallholder production systems is popular in Eastern Africa. However, information on the performance of exotic breeds within these systems is scarce. This paper presents information on performance of Toggenburg dairy goats under smallholder production systems in a medium to high agricultural potential environment in Kenya under a community-based set-up as part of the characterization of its adaptive and productive attributes. Environmental factors affecting growth of 646 goats born in the environment, and fertility and milk production of 160 does from 1997 to 2005 were evaluated. Genetic parameters were also estimated for early growth traits. The average birth weight (BW) for 607 kids was 3.27 kg. Corrected weaning weights (CW), and average daily gain to weaning (ADG) for 646 kids were 19.12 kg and 136 g/day, respectively. The results indicated that the smallholder farmers were able to maintain comparably high levels of milk production in the first three parities (LMY), with yields of 475 ± 9 l in 201 days for 160 does in the first parity, 507 ± 9 l in 264 days from 130 does in the second parity and 513 ± 13 l in 296 days for 82 does in the third parity. Kidding intervals though initially long decreased with time to reasonable levels (302 ± 117 days). The heritability estimates obtained were low (0.23 ± 0.13 for BW, 0.18 ± 0.11 for CW and 0.14 ± 0.11 for ADG). Genetic correlations between the traits were also low. Genetic and phenotypic trends indicated little change in BW, CW and LMY over the years. The phenotypic trend in the kidding interval showed a reducing interval over time. The results demonstrated that the Toggenburg goats were able to perform and thrive reasonably well under the low-input farming conditions.     

Performance of forecasting,warning and detection of malaria epidemics in the highlands of western Kenya

On the 4th July 2002 a leading national newspaper in Kenya, the Daily Nation, ran the headline 'Minister sounds alert on malaria' in an article declaring the onset of epidemics in the highlands of western Kenya. There followed frequent media coverage with quotes from district leaders on the numbers of deaths, and editorials on the failure of the national malaria control strategy. The Ministry of Health made immediate and radical changes to national policy on treatment costs in the highlands by suspending cost-sharing. Development partners and non-governmental organisations also responded with a large increase in the distribution of commodities (approximately 500,000 US dollars) to support preventative strategies across the western highland region. What was conspicuous by its absence was any obvious effort to predict the epidemics in advance of press coverage.     

On the biochemical significance of phosphoserine: a working hypothesis

The significance of the presence of free phosphoserine in living cells represents an intriguing problem. Its utilization for the synthesis of phosphoproteins and phospholipids has been ruled out. It is produced extensively by hydrolysis of phosphoproteins or phosphatidylserine since no phosphorylating enzyme for serine is present. So far the only significance of phosphoserine has been related to its participation in the exchange reaction with serine, the meaning of which is quite unclear. Evidence is presented that phosphoserine could modulate the activity of phospholipase A2, thus regulating the permeability properties of cellular and intracellular membranes which depend largely on phospholipase pattern. Phosphoserine in fact inhibits in a competitive way phospholipase A2 from cobra venom.     

The significance of antioxidants in the aphid-plant interaction: The redox hypothesis

The hypothesis is advanced that a redox system controls oxidation rates during the responses of plants to attack by sucking insects, that soluble antioxidants, such as ascorbate and glutathione, enhance the effectiveness of the plant's defensive system, and that oxidising enzymes in the saliva of aphids (and other phytophagous sucking insects) serve to counter it. Plants typically respond to wounding, including that caused by sucking insects, by mobilising and oxidising phenolic compounds. The initial phenolic monomers, and especially the monomerico-quinones to which many give rise on oxidation, are generally deterrent to insects. Their final oxidation products, however, are polymers and phenol-protein conjugates, which are non-toxic, but serve to seal off damaged cells. It is suggested that effective defence by the plant requires oxidation of phenolics at a controlled rate that maintains a deterrent titre of the monomers, while allowing a well ordered deposition of sealants. It is also suggested that the salivary oxidases of the insects hasten oxidation in the affected tissues, thereby decreasing concentrations of monomeric phenols and quinones. It is further suggested that sedentary species may also thereby disorganise the sealing off of affected tissues. A kinetic model is developed to show that inclusion of a reductive cycle in the sequential oxidation of phenolics increases the steady state concentrations of monomeric phenols for a given throughput. Conversely, an increase in oxidation rates diminishes the titre of monomers for the same throughput. In initial biological tests of the hypothesis, infiltration of stems of lucerne cultivars with ascorbate or glutathione reduced the reproductive rate of spotted alfalfa aphid,Therioaphis trifolii maculata (Buckton), and of blue-green aphid,Acyrthosiphon kondo Shinji, feeding thereon. Intrinsically non-deterrent concentrations of ascorbate synergised the deterrence of the plant phenolics chlorogenic acid and catechin to the apple aphid,Aphis pomi (de Geer), and the spotted alfalfa aphid,T. t. maculata, respectively.     

Biological significance of liver cell polyploidy: an hypothesis

The liver cell polyploidy phenomenon, a characteristic of many species of mammals, is reviewed. The liver parenchyma of adult animals represents a mixed population of mononuclear and binuclear cells with different number of chromosome sets and, therefore DNA content per nucleus. The polyploid hepatocytes are formed during postnatal liver growth as a result of a change from normal mitoses to polyploidizing ones. Hence, the polyploidization of hepatocytes is regarded as an equivalent of cell multiplication.An hypothesis of the biological significance of liver cell polyploidy is based on the fact of a high level of spontaneous chromosome aberrations in mitotic hepatocytes. Ploidy increase is known to give resistance against different kinds of genome alteration. Polyploidization of the liver cells ensures protection against deleterious consequences of the aberrant genome formation resulting from aberrant mitoses.Some implications of the hypothesis are discussed: the reasons for species-specific differences of liver cell polyploidy; the mechanisms of hepatocyte radioresistance; the relation of polyploidy to liver cell aging. The prerequisite factors for unbalanced cell genome formation are adduced: DNA and chromosome damage as the first step in the process, stimulation of mitosis as the second one. The aberrant polyploid genome of hepatocytes is assumed to be the cytogenetic basis for some chronic liver diseases in man.     

The adaptive significance of reptilian viviparity in the tropics: testing the maternal manipulation hypothesis

Abstract Phylogenetic transitions from oviparity to viviparity in reptiles generally have occurred in cold climates, apparently driven by selective advantages accruing from maternal regulation of incubation temperature. But why, then, are viviparous reptiles so successful in tropical climates? Viviparity might enhance fitness in the tropics via the same pathway as in the temperate zone, if pregnant female reptiles in the tropics maintain more stable temperatures than are available in nests (Shin's maternal manipulation hypothesis). Alternatively, viviparity might succeed in the tropics for entirely different reasons than apply in the temperate zone. Our data support the maternal manipulation hypothesis. In a laboratory thermal gradient, pregnant death adders (Acanthophis praelongus) from tropical Australia maintained less variable body temperatures (but similar mean temperatures) than did nonpregnant females. Females kept at a diel range of 25–31d?C (as selected by pregnant females) gave birth earlier and produced larger offspring (greater body length and head size) than did females kept at 23–33d?C (as selected by nonpregnant snakes). Larger body size enhanced offspring recapture rates (presumably reflecting survival rates) in the field. Thus, even in the tropics, reproducing female reptiles manipulate the thermal regimes experienced by their developing embryos in ways that enhance the fitness of their offspring. This similarity across climatic zones suggests that a single general hypothesis‐maternal manipulation of thermal conditions for embryogenesis‐may explain the selective advantage of viviparity in tropical as well as cold‐climate reptiles.     

Spiroplasma species in the Costa Rican highlands: implications for biogeography and biodiversity

More than 1,000 Spiroplasma isolates have been obtained from horse flies and deer flies (Diptera:Tabanidae) in the United States and Canada. However, the spiroplasma biota of Central America is poorly known. In August of 1995 and 1998, 13 isolates were obtained in 14 attempts from horse flies of a single species, Poeciloderas quadripunctatus, taken in the Costa Rican highlands (1,100–2,000 m). The majority of the “isolates” proved to be mixtures of two or more Spiroplasma species, but after filter cloning, single strains emerged that were designated as representatives of the 13 accessions. Six distinct spiroplasma serogroups were identified from these isolations. Three of the strains are putative new species with no serological relationship to any other Spiroplasma species. A fourth strain is a putative new species that may be distantly related to S. helicoides, a southeastern U.S. species. These four strains are accorded herein status as representatives of new serogroups: strain BARC 4886 (group XXXV); strain BARC 4900 (group XXXVI); strain BARC 4908 (group XXXVII); and GSU5450 (group XXXVIII). A fifth Spiroplasma species was very closely related to S. lineolae, known previously only from the Georgia (U.S.) coast. The sixth was most closely related to subgroup VIII-3, known from Texas and the southeastern U.S. Discovery of six spiroplasma species in only 13 attempted isolations reflects diversity seldom equaled in southeast Georgia, and never elsewhere in the U.S. These results are consistent with a hypothesis that spiroplasma diversity increases from north (Nova Scotia) to south (Georgia and Costa Rica). The discovery of significant affinity between some spiroplasmas of the southeastern U.S. and the Costa Rican highlands was unexpected, but may reflect a climatically complex Pleistocene history.

The ecophysiological significance of calcium bicarbonate in the urine of subterranean rodents: testing a hypothesis

1. A comparative study of calcium and bicarbonate in the urine was carried out on the subterranean mole rat Cryptomys hottenttus and the terrestrial vlei rat Otomys irroratus. 2. The two species were kept on two different diets; carrots, a high calcium diet (41 mg/ 100 kg) or potatoes, a low calcium diet (14 mg/ 100g). 3. The results show that the urine of the mole rat contained high values of calcium bicarbonate on either diet. 4. The urine of the vlei rat showed high values of calcium bicarbonate only when kept on the high calcium diet. 5. From these results we assume that in subterranean rodents excretion of calcium bicarbonate is an adaptive mechanism to unload CO2 without increasing its concentration in the hypercapnic environment.     

Biodiversity in Ramogi Hill, Kenya, and its evolutionary significance

The bulk of Kenyan forests are in the afromontane biogeographical region, but the Lake Victoria basin and its biota have been referred to by many biogeographers as an eastern fragment of the Guineo-congolian forest. The Ramogi Hill forest in the lake basin receives an annual rainfall of less than 400 mm. Although much of its biota is typical of the Guineo-congolian region, several species of insects, birds, mammals and plants have been known to occur in the lowland forests of the Kenyan coast. The presence of taxa in these forests has been attributed to past geological changes and climatic fluctuations during the pleistocene period. Migration and dispersal of taxa have been suggested to have been through Kenya Rift or via the southern route of Rukwa Rift. The biodiversity studies conducted indicate that Ramogi Hill has low animal diversity compared to other forests. However, the importance of Ramogi Hill may be linked to its biological resources, and cultural and religious values accrued by the surrounding local communities. The preservation of Ramogi Hill as a reference point for biodiversity and sacred sites will depend a lot on the influence and participation of communities in biodiversity conservation and management programmes.     

In poor families, mothers' milk is richer for daughters than sons: A test of Trivers-Willard hypothesis in agropastoral settlements in Northern Kenya

The Trivers–Willard hypothesis predicts the unequal parental investment between daughters and sons, depending on maternal condition and offspring reproductive potential. Specifically, in polygynous populations where males have higher reproductive variance than females, it predicts that mothers in good condition will invest more in sons, whereas mothers in poor condition will invest more in daughters. Previous studies testing this hypothesis focused on behavioral investment, whereas few examined biological investment. This study investigates the Trivers–Willard hypothesis on both behavioral and biological parental investment by examining breastfeeding frequencies and breast milk fat concentrations. Data from exclusively breastfeeding mothers in Northern Kenya were used to test hypotheses: Economically sufficient mothers will breastfeed sons more frequently than daughters, whereas poor mothers will breastfeed daughters more frequently than sons, and economically sufficient mothers will produce breast milk with higher fat concentration for sons than daughters, whereas poor mothers will produce breast milk with higher fat concentration for daughters than sons. Linear regression models were applied, using breastfeeding frequency or log‐transformed milk fat as the dependent variable, and offspring's sex (son = 1/daughter = 0), socioeconomic status (higher = 1/lower = 0), and the sex‐wealth interaction as the predictors, controlling for covariates. Our results only supported the milk fat hypothesis: infant's sex and socioeconomic status interacted (P = 0.014, n = 72) in their relation with milk fat concentration. The model estimated that economically sufficient mothers produced richer milk for sons than daughters (2.8 vs. 0.6 gm/dl) while poor mothers produced richer milk for daughters than sons (2.6 vs. 2.3 gm/dl). Further research on milk constituents in relation to offspring's sex is warranted. Am J Phys Anthropol , 2012. © 2012 Wiley Periodicals, Inc.