Targeted elimination of species-rich larval habitats can rapidly collapse arbovirus vector mosquito populations at hotel compounds in Zanzibar.

Understanding the dynamics of larval habitat utilization by mosquito communities is crucial for the design of efficient environmental control strategies. The authors investigated the structure of mosquito communities found at hotel compounds in Zanzibar, networks of mosquito interactions with larval habitats and robustness of mosquito communities to elimination of larval habitats. A total of 23 698 mosquitoes comprising 26 species in six genera were found. Aedes aegypti (n = 16 207), Aedes bromeliae/Aedes lillie (n = 1340), Culex quinquefasciatus (n = 1300) and Eretmapodites quinquevitattus (n = 659) were the most dominant species. Ecological network analyses revealed the presence of dominant, larval habitat generalist species (e.g., A. aegypti), exploiting virtually all types of water holding containers and few larval habitat specialist species (e.g., Aedes natalensis, Orthopodomyia spp). Simulations of mosquito community robustness to systematic elimination of larval habitats indicate that mosquito populations are highly sensitive to elimination of larval habitats sustaining higher mosquito species diversity. This study provides insights on potential foci of future mosquito-borne arboviral disease outbreaks in Zanzibar and underscores the need for detailed knowledge on the ecological function of larval habitats for effective mosquito control by larval sources management.

Seasonal, Locality, and Habitat Variation in Assemblages of Carrion-Associated Diptera in Gauteng Province, South Africa.

Seasonal, spatial, and habitat responses of carrion-associated Diptera assemblages can provide valuable information about the presence or absence of species and their relative abundance, and thereby enhance understanding of their responses to environmental variables and how this may have an impact on forensic investigations. Three different nature reserves (localities) within the Municipality of Tshwane, South Africa, were selected to determine whether species assemblages of carrion-feeding flies differ between seasons, localities, and habitat types. A total of 59,511 adult Diptera, identified to 35 species in eight different families, were collected using modified Redtop hanging traps, baited with liver and fish, during four seasons in three different habitat types. Species assemblages differed temporally, with season being the main factor determining species diversity and not locality or habitat. However, savanna and human-disturbed habitats supported a higher abundance and species richness than grassland habitats. Areas adjacent to the localities, such as large urban expanses in Dinokeng or agricultural holdings in Rietvlei, led to an increase in the abundance and mean species richness of carrion-associated Diptera, and in increased numbers of pest or invasive species such as Chrysomya megacephala (F.). Despite this, the overall species assemblages present in human-disturbed areas were very similar to those recorded in natural habitats.

Desiccation resistance of wild and mass-reared Bactrocera tryoni (Diptera: Tephritidae).

In pest management programmes that incorporate the sterile insect technique (SIT), the ability of mass-reared insects to tolerate dry conditions may influence their survival after release in the field. In the present study, desiccation resistance of adult mass-reared Queensland fruit flies, Bactrocera tryoni (Frogatt) (Diptera: Tephritidae), that are routinely released in SIT programmes was compared with that of wild flies at 1, 10 and 20 days after adult eclosion. Under dry conditions without access to food or water, longevity of mass-reared B. tryoni was significantly less than that of their wild counterparts. Desiccation resistance of mass-reared flies declined monotonically with age, but this was not the case for wild flies. The sharp decline in desiccation resistance of mass-reared flies as they aged was likely explained by decreased dehydration tolerance. As in an earlier study, desiccation resistance of females was significantly lower than that of males but this was particularly pronounced in mass-reared females. Female susceptibility to dry conditions corresponded with declining dehydration tolerance with age and associated patterns of reproductive development, which suggests that water content of their oocyte load is not available for survival during periods of water stress.

Optimizing irradiation dose for sterility induction and quality of Bactrocera tryoni.

The current study is an important step toward calibrating, validating, and improving irradiation methods used for Bactrocera tryoni (Froggatt) sterile insect technique (SIT). We used routine International Atomic Energy Agency/U.S. Department of Agriculture/Food and Agriculture Organization quality control tests assessing percentage of emergence, flight ability, sex ratio, mortality under stress, reproductive sterility, and sexual competitiveness, as well as a nonstandard test of longevity under nutritional stress to assess the impact of a range of target irradiation doses (60, 65, 70, 75, and 80 Gy) on the product quality of mass reared B. tryoni used in SIT. Sterility induction remained adequate (>99.5%) for sterile male-fertile female crosses, and 100% sterility was achieved in fertile male-sterile female crosses and sterile male-sterile female crosses for each irradiation doses tested. There was significant increase in mortality under stress as irradiation dose increased, and reduced participation in mating by males irradiated at higher doses. The current target-sterilizing dose for SIT of 70-75 Gy is associated with significant reduction in fly product "quality". Our data suggest that adequate sterility and improved fly quality could be achieved through a small reduction in target sterilizing dose.

Gene microarray analysis reveals a novel hypoxia signal transduction pathway in human hepatocellular carcinoma cells.

The molecular details of hypoxia-induced cellular responses have been difficult to identify since there is as yet no known oxygen receptor. We used cDNA microarray technology to extend our studies pertaining to these molecular details in human hepatocellular carcinoma (Hep3B) cells that produce erythropoietin (Epo) in response to hypoxia. Of approximately 1200 genes in the array, those associated with integrin-linked kinase (ILK), fibronectin precursor and glycogen synthase kinase-3beta (GSK-3beta) were markedly stimulated after exposure of Hep3B cells to low oxygen (1%) for 6 h. Epo, HIF-1, and von Hippel-Lindau cDNAs were measured in parallel as markers of low oxygen responses in Hep3B cells. ILK is a serine, threonine protein kinase that interacts with the cytoplasmic domains of integrin beta1 and beta3. This interaction localizes ILK to focal adhesion plaques. ILK is stimulated by cell-fibronectin interaction as well as insulin. It is regulated in a phosphatidylinositol 3-kinase dependent manner and can phosphorylate protein kinase B (PKB/AKT) and GSK-3beta. As a result of these and other activities ILK has been shown to affect anchorage-independent cell survival, cell cycle progression and tumorigenesis in nude mice. ILK has also been implicated in the Wnt pathway and as a critical target in PTEN-dependent tumor therapies. To our knowledge this is the first report implicating the ILK pathway in low oxygen responses. Other genes identified as a result of the microarray analysis not previously known to change as a result of low oxygen treatment were elongation factor-1alpha, glycyl-tRNA synthetase, and laminin receptor protein-1. These findings were all corroborated by RT-PCR assays and in some instances Western blot analysis.