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Infected Females (infected + female)
Selected AbstractsWhat maintains noncytoplasmic incompatibility inducing Wolbachia in their hosts: a case study from a natural Drosophila yakuba populationJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2004S. Charlat Abstract Cytoplasmic incompatibility (CI) allows Wolbachia to invade hosts populations by specifically inducing sterility in crosses between infected males and uninfected females. In some species, non-CI inducing Wolbachia, that are thought to derive from CI-inducing ancestors, are common. In theory, the maintenance of such infections is not possible unless the bacterium is perfectly transmitted to offspring - and/or provides a fitness benefit to infected females. The present study aims to test this view by investigating a population of Drosophila yakuba from Gabon, West Africa. We did not find any evidence for CI using wild caught females. Infected females from the field transmitted the infection to 100% of their offspring. A positive effect on female fecundity was observed one generation after collecting, but this was not retrieved five generations later, using additional lines. Similarly, the presence of Wolbachia was found to affect mating behaviour, but the results of two experiments realized five generations apart were not consistent. Finally, Wolbachia was not found to affect sex ratio. Overall, our results would suggest that Wolbachia behaves like a neutral or nearly neutral trait in this species, and is maintained in the host by perfect maternal transmission. [source] EVOLUTION OF INCOMPATIBILITY-INDUCING MICROBES IN SUBDIVIDED HOST POPULATIONSEVOLUTION, Issue 2 2009Ralph Haygood Many insects, other arthropods, and nematodes harbor maternally inherited bacteria inducing "cytoplasmic incompatibility" (CI), reduced egg hatch when infected males mate with uninfected females. Although CI drives the spread of these microbes, selection on alternative, mutually compatible strains in panmictic host populations does not act directly on CI intensity but favors higher "effective fecundity," the number of infected progeny an infected female produces. We analyze the consequences of host population subdivision using deterministic and stochastic models. In subdivided populations, effective fecundity remains the primary target of selection. For strains of equal effective fecundity, if population density is regulated locally (i.e., "soft selection"), variation among patches in infection frequencies may induce change in the relative frequencies of the strains. However, whether this change favors stronger incompatibility depends on initial frequencies. Demographic fluctuations maintain frequency variation that tends to favor stronger incompatibility. However, this effect is weak; even with small patches, minute increases in effective fecundity can offset substantial decreases in CI intensity. These results are insensitive to many details of host life cycle and migration and to systematic outbreeding or inbreeding within patches. Selection acting through transfer between host species may be required to explain the prevalence of CI. [source] A tapeworm molecule manipulates vitellogenin expression in the beetle Tenebrio molitorINSECT MOLECULAR BIOLOGY, Issue 4 2006E. Warr Abstract Metacestodes of Hymenolepis diminuta secrete a molecule that decreases vitellogenin (Vg) synthesis in the beetle host, Tenebrio molitor. The 5608 bp T. molitor Vg cDNA represents a single-copy gene encoding a single open reading frame of 1821 amino acids with a predicted molecular mass of 206 kDa. Northern blot analysis revealed detectable levels of transcripts only in adult females. In vivo, Vg mRNA abundance was significantly higher in fat bodies from infected females compared with control females at all but the earliest time point. In vitro, Vg mRNA abundance was significantly increased in fat bodies incubated with live stage I,II parasites. The apparent conflict between increased Vg mRNA abundance and decreased Vg protein in fat bodies from infected females is discussed. [source] Phlebotomus (Adlerius) halepensis vector competence for Leishmania major and Le. tropicaMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2003J. Sádlová Abstract., In Eurasia, phlebotomine sandflies of the subgenus Adlerius (Diptera: Psychodidae) comprise about 20 known species. Some are suspected vectors of visceral leishmaniasis (VL) and at least one species has been implicated as a vector of cutaneous leishmaniasis (CL). We tested Phlebotomus (Adlerius) halepensis Theodor (Jordan strain) for CL vector competence, compared with three standard vectors: Phlebotomus (Phlebotomus) duboscqi N-L. from Senegal, Phlebotomus (Paraphlebotomus) sergenti Parrot from Turkey and the Neotropical Lutzomyia longipalpis (L. & N) (Jacobina strain). Sandfly females were membrane-fed on amastigote suspensions of Leishmania major Y. & S. and Le. tropica (Wright) (Kinetoplastida: Trypanosomatidae) and examined for parasite development 3, 6 and 10 days post-infection. Phlebotomus halepensis showed high susceptibility to both leishmanias, supporting typical suprapylarian parasite development similar to the other vectors. Phlebotomus halepensis infection rates were ,90% for Le. major and ,80% for Le. tropica, with high parasite densities. Development of infections was relatively fast, colonizing the thoracic midgut by 6 days post-bloodmeal in every case and reaching the stomodeal valve in >80% of flies. In late-stage infections, 10 days post-bloodmeal, nearly all P. halepensis females had cardia and stomodeal valve filled with very high numbers of parasites and some Le. tropica -infected females had promastigotes in the pharynx and proboscis. Host choice experiments in the laboratory showed that P. halepensis females fed readily on rat or rabbit and preferred the human forearm. In view of its vector competence and partial anthropophily, we infer that P. halepensis is a potential vector of cutaneous as well as visceral leishmaniases. [source] Vector competence of South African Culicoides species for bluetongue virus serotype 1 (BTV-1) with special reference to the effect of temperature on the rate of virus replication in C. imicola and C. bolitinosMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2002J. T. Paweska Abstract. The oral susceptibility of 22 South African livestock associated Culicoides species to infection with bluetongue virus serotype 1 (BTV-1) and its replication rate in C. imicola Kieffer and C. bolitinos Meiswinkel (Diptera: Ceratopogonidae) over a range of different incubation periods and temperatures are reported. Field-collected Culicoides were fed on sheep blood containing 7.5 log10TCID50/mL of BTV-1, and then held at constant different temperatures. Virus replication was measured over time by assaying individual flies in BHK-21 cells using a microtitration procedure. Regardless of the incubation temperatures (10, 15, 18, 23.5 and 30°C) the mean virus titre/midge, infection rates (IR) and the proportion of infected females with transmission potential (TP = virus titre/midge ,,3 log10 TCID50) were found to be significantly higher in C. bolitinos than in C. imicola. Results from days 4,10 post-infection (dpi), at 15,30°C, shows that the mean IR and TP values in C. bolitinos ranged from 36.7 to 87.8%, and from 8.4 to 87.7%, respectively; in C. imicola the respective values were 11.0,13.7% and 0,46.8%. In both species the highest IR was recorded at 25°C and the highest TP at 30°C. The time required for the development of TP in C. bolitinos ranged from 2 dpi at 25°C to 8 dpi at 15°C. In C. imicola it ranged from 4 dpi at 30°C to 10 dpi at 23.5°C; no individuals with TP were detected at 15°C. There was no evidence of virus replication in flies held at 10°C. When, at various points of incubation, individual flies were transferred from 10°C to 23.5°C and then assayed 4,10 days later, virus was recovered from both species. The mean virus titres/midge, and proportion of individuals with TP and IR, were again significantly higher in C. bolitinos than in C. imicola. Also the infection prevalence in C. magnus Colaço was higher than in C. imicola. Low infection prevalences were found in C. bedfordi Ingram & Macfie, C. leucostictus Kieffer, C. pycnostictus Ingram & Macfie, C. gulbenkiani Caeiro and C. milnei Austen. BTV-1 was not detected in 14 other Culicoides species tested; however, some of these were tested in limited numbers. The present study indicates a multivector potential for BTV transmission in South Africa. In C. imicola and C. bolitinos the replication rates are distinct and are significantly influenced by temperature. These findings are discussed in relation to the epidemiology of bluetongue in South Africa. [source] Evolutionary significance of fecundity reduction in threespine stickleback infected by the diphyllobothriidean cestode Schistocephalus solidusBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010DAVID C. HEINS Parasites may cause fecundity reduction in their hosts via life-history strategies involving simple nutrient theft or manipulation of host energy allocation. Simple theft of nutrients incidentally reduces host energy allocation to reproduction, whereas manipulation is a parasite-driven diversion of energy away from host reproduction. We aimed to determine whether the diphyllobothriidean cestode parasite Schistocephalus solidus causes loss of fecundity in the threespine stickleback fish (Gasterosteus aculeatus) through simple nutrient theft or the manipulation of host energy allocation. In one stickleback population (Walby Lake, Matanuska-Susitna Valley, Alaska), there was no difference in the sizes and ages of infected and uninfected reproducing females. Lightly- and heavily-infected females produced clutches of eggs, but increasingly smaller percentages of infected females produced clutches as the parasite-to-host biomass ratio (PI) increased. Infected, clutch-bearing sticklebacks showed reductions in clutch size, egg mass, and clutch mass, which were related to increases in PI and reflected a reduction in reproductive parameters as growth in parasite mass occurs. The findings obtained for this population are consistent with the hypothesis of simple nutrient theft; however, populations of S. solidus in other regions may manipulate host energy allocation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 835,846. [source] | ||||||||||||||||||||||