Does scavenging extend the host range of entomopathogenic nematodes (Nematoda: Steinernematidae)?

Living and freeze-killed natural and laboratory hosts, with different susceptibility to entomopathogenic nematodes, were exposed to the larvae of Steinernema affine and Steinernema kraussei in two different experimental arenas (Eppendorf tubes, Petri dishes), and the success of the colonisation and eventual progeny production were observed. Both nematodes were able to colonise both living and dead larvae of Galleria mellonella (Lepidoptera) and adult Blatella germanica (Blattodea) even though the progeny production in dead hosts was lower on average. Living carabid beetles, Poecilus cupreus, and elaterid larvae (Coleoptera) were resistant to the infection, however, both nematodes were able to colonise and multiply in several dead P. cupreus and in a majority of dead elaterid larvae. By scavenging, EPNs can utilise cadavers of insects that are naturally resistant to EPN infection, and so broaden their host range.     

Parasites of Perccottus glenii Dybowski, 1877 (Actinopterygii: Odontobutidae) in the native and the introduced host range: Abundance–occupancy and abundance–variance relationships

The Chinese sleeper Perccottus glenii Dybowski, 1877 is an invasive fish species rapidly expanding in Siberia and Europe. Its native range encompasses the Far East region of Russia, northeastern China and northern North Korea. We studied species composition, prevalence, mean abundance and variance of mean abundance of macroparasites of the Chinese sleeper in the native and the introduced range. The species composition of the parasite component communities differed considerably in the native and the introduced range. The frequency distributions of prevalence, mean abundance and variance of mean abundance of the parasites did not demonstrate any significant differentiation between the two parts of the host range. However, an analysis of the abundance–occupancy and the abundance–variance relationships revealed that the parasite component communities in the two parts of the host range were quite distinct. In the native range, prevalence increased faster and variance increased more slowly with the increasing abundance of the parasites than in the introduced range. These features are mostly associated with considerably increased prevalence, abundance and aggregation of the host-specific cestode Nippotaenia mogurndae in recipient water bodies as compared with the native habitats.     

Moniliophthora perniciosa,the mushroom causing witches’ broom disease of cacao: Insights into its taxonomy,ecology and host range in Brazil

Witches' broom caused by Moniliophthora perniciosa is the main disease of cacao (Theobroma cacao) in Brazil. The fungus is known to occur on other host families and these populations have been addressed in the literature as biotypes: C (Malvaceae); H (Malpighiaceae); L (Bignoniaceae) and S (Solanaceae). No complete elucidation of the phylogenetic relationships of isolates obtained from this disparate host range appears in the literature. One member of H (ex Heteropterys acutifolia) has been described as a distinct species. But should other biotypes be also recognized as distinct taxa? In the present study, a survey yielding 24 isolates of M. perniciosa from ten hosts and covering a wide range of geographic regions in Brazil was undertaken. These isolates were compared with those from T. cacao using three DNA regions for the phylogenetic analyses: ITS, LSU and RPB1. Morphology was also examined. All isolates in this study were found to belong to M. perniciosa, including the population from H. acutifolia, formerly treated as Moniliophthora brasiliensis but reduced here to a synonym of M. perniciosa. This species ranged from pathogenic to a previously unreported occurrence as a non-pathogenic endophyte in the Atlantic rainforest tree Allophylus edulis (Sapindaceae). M. perniciosa was recorded on a range of solanaceous hosts (16 species) over a wide variety of ecosystems. The ecological and evolutionary significance of these novel findings are discussed.     

Is the host or the parasitoid in control?: effects of host age and temperature on pseudoparasitization by Microplitis rufiventris in Spodoptera littoralis

We compared the production of pseudoparasitization by Microplitis rufiventris females in most (third) and less (fourth) preferred instars of Spodoptera littoralis larvae at 20+/-1 and 27+/-1 degrees C. The parasitized hosts were classified into hosts producing parasitoids (type A hosts) and hosts producing no parasitoids, i.e., pseudoparasitized hosts (type B hosts). The latter were further classified into: (a) pseudoparasitized hosts with "well" arrested development (type B1 hosts); (b) pseudoparasitized hosts with partially arrested development (type B2 hosts); and (c) pseudoparasitized hosts that successfully pupated to apparently normal host pupae (type B3 hosts). The present series of experiments showed that parasitization by M. rufiventris was clearly affected by host instar, age within an instar and rearing temperature. Production of type B hosts was less when third instar S. littoralis larvae were exposed to the wasp females than when the host larvae were in fourth instar. The production of type A hosts was much greater when early or mid ages of an instar was stung by the wasp females comparing with stung late age of the same instar. Production of type B hosts may be due to one or overall of the following: (a) dosage dilution of M. rufiventris female's factors in the different age classes of the instar; (b) endocrine system (physiological state) at parasitization time, i.e., early vs late age of the instar; (c) growth rate of host larvae. The lowest production of type B hosts was at highest growth rate; and (d) temperature, larger proportions of type B hosts were produced at 27+/-1 than at 20+/-1degrees C. The three types host development (B1, B2 and B3) are possibly representing three levels of host resistance (host control) resulting in partial or complete failure of parasitoid control. Type A hosts represent complete success of parasitoid control. The results suggest that the impact of parasitoid factor(s) on developmental arrest is affected by host age at the time of parasitism and/or by temperature.     

Water-seeking behavior in insects harboring hairworms: should the host collaborate?

We explored the idea that hosts infected with manipulative parasitesmight mitigate the costs of infection by collaborating withthe parasite rather than resisting it. Nematomorphs are usuallyconsidered to be manipulative parasites of arthropods becausethey cause hosts to seek an aquatic environment, which is neededby the adult parasite. We placed infected cricket hosts in situationsof forced noncompliance and compared some fitness parameters(life expectancy, gonad development, and reproductive behaviors)in noncompliant hosts and hosts allowed to express parasite-inducedbehavior. Compared to uninfected controls, reduced survivalwas observed in both males and females from the two categoriesof infected hosts, collaborative or not. A substantial proportionof collaborative females produced eggs or had developed ovarieswhile such phenomena were never observed among noncollaborativeones. Collaborative females retained a nymphal phenotype, butadult males nevertheless courted and produced spermatophoresto such females. However, collaborative females had difficultiesmounting males, taking spermatophores and/or ovipositing. Incontrast to females, all males were entirely castrated by theparasite regardless of their behavior, collaborative or not.Thus, bringing the parasite into water does not effectivelymitigate the costs of infection for the host.     

Nucleic acids in circulation: Are they harmful to the host?

It has been estimated that 10(11) -10(12) cells, primarily of haematogenous origin, die in the adult human body daily, and a similar number is regenerated to maintain homeostasis. Despite the presence of an efficient scavenging system for dead cells, considerable amounts of fragmented genetic material enter the circulation in healthy individuals. Elevated blood levels of extracellular nucleic acids have been reported in various disease conditions; such as ageing and age-related degenerative disorders, cancer; acute and chronic inflammatory conditions, severe trauma and autoimmune disorders. In addition to genomic DNA and nucleosomes, mitochondrial DNA is also found in circulation, as are RNA and microRNA. There is extensive literature that suggests that extraneously added nucleic acids have biological actions. They can enter into cells in vitro and in vivo and induce genetic transformation and cellular and chromosomal damage; and experimentally added nucleic acids are capable of activating both innate and adaptive immune systems and inducing a sterile inflammatory response. The possibility as to whether circulating nucleic acids may, likewise, have biological activities has not been explored. In this review we raise the question as to whether circulating nucleic acids may have damaging effects on the host and be implicated in ageing and diverse acute and chronic human pathologies.     

Toxocara in the mouse: a model for parasite-altered host behaviour?

The objective of this paper is to critically evaluate the significance of parasite-altered host behaviour in the Toxocara mouse model particularly in the light of the Manipulation Hypothesis. Murine behaviours were examined in both outbred and inbred strains of mice infected with different doses of Toxocara canis ova. Behaviours investigated included activity, exploration, response to novelty, anxiety, learning, memory and social behaviour. Subsequent modifications to the behaviour of infected mice were investigated with respect to dose administered and larval accumulation in the brain. There was substantial variation in the number of larvae recovered from brains of individual mice, which received similar doses of Toxocara ova. Furthermore, the numbers of larvae recovered at different doses differed significantly between an outbred and inbred strain of mouse. Alterations in infected host behaviour occurred and were related to the number of larvae recovered from the brain. For social behaviour in outbred mice, a high infection in the brain reduced levels of aggressive behaviour and increased levels of flight and defensive behaviours. In contrast, outbred mice with a low infection in the brain displayed a greater level of risk behaviour in respect of predator odour and the light/dark box compared to control or high infection mice. Post-infection, outbred mice were more immobile whereas inbred mice showed reduced immobility and increased digging and climbing. Impaired learning ability was observed in outbred mice with moderate and high levels of infection in the brain compared to control and low infection mice. Toxocara infection has an impact upon a diverse range of murine behaviours with little evidence for a specific and hence an adaptive alteration. Many of the effects on murine host behaviour by Toxocara are likely to be pathological side effects of infection rather than as a consequence of adaptive host-manipulation. Observed changes in murine behaviour may be relevant to human toxocariasis.     

What determines host range in parasitoids? An analysis of a tachinid parasitoid community

Despite the vast diversity of parasitic insects and their importance in natural and agricultural communities, our knowledge of what determines their patterns of association with hosts remains sparse. Unlike most parasites that tend to be specialized, parasitoid flies in the family Tachinidae exhibit a broad spectrum of host-specificity, with many species attacking a wide range of hosts. This variability in host-specificity makes them a useful model for examining the ecological and historical factors that determine host associations. We analyzed data collected from a 5-year rearing program of Lepidoptera in southern Arizona to investigate the factors that influence tachinid-host associations. After controlling for a strong effect of sample size, a significant portion of the remaining variance in host range was explained by differences among phylogenetic groups of tachinids and/or their correlated reproductive strategies. Relatively specialized tachinids tended to be associated with monophagous or narrowly oligophagous hosts and attacked them at relatively high frequencies, a pattern we suggest is related to host location efficiency. Cluster analysis indicated that host abundance, gregariousness, food-plant type, and morphology are all important determinants of tachinid host use. Little concordance was found between how tachinid species cluster according to characteristics of their hosts and their estimated phylogenetic relationships. Together, the results of this study suggest that ecological factors are important determinants of host use in these parasitoids and although phylogenetic history may influence the range of hosts used, its power to explain the ecological or taxonomic character of hosts used appears limited.     

Comparative proteome profiling of host–pathogen interactions: insights into the adaptation mechanisms of Francisella tularensis in the host cell environment

The intracellular pathogens have the unique capacity to sense the host cell environment and to respond to it by alteration in gene expression and protein synthesis. Proteomic analysis of bacteria exposed directly to the host cell milieu might thus greatly contribute to the elucidation of processes leading to bacterial adaptation and proliferation inside the host cell. Here we have performed a global proteome analysis of a virulent Francisella tularensis subsp. holarctica strain during its intracellular cycle within the macrophage-like murine cell line J774.2 using the metabolic pulse-labeling of bacterial proteins with ³⁵S-methionine and ³⁵S-cysteine in various periods of infection. The two-dimensional gel analysis revealed macrophage-induced bacterial proteome changes in which 64 identified proteins were differentially expressed in comparison to controls grown in tissue culture medium. Nevertheless, activation of macrophages with interferon gamma before in vitro infection decreased the number of detected alterations in protein levels. Thus, these proteomic data indicate the F. tularensis ability to adapt to the intracellular hostile environment that is, however, diminished by prior interferon gamma treatment of host cells.     

Ant associations in the Neotropical shrub Turnera subulata (Turneraceae): Costs or benefits to the host plant?

The results of ecological interactions depend on the costs and benefits involved in different ecological contexts. Turnera subulata is a shrubby plant with extrafloral nectaries that are associated with ants. Here, we test the hypotheses that the association between T. subulata and ants results in: (i) positive effects on host plant growth and reproduction; (ii) plant herbivory reduction and (iii) inhibition of the host plant visitation by beneficial organisms. Thirty experimental plots were established in northeastern Brazil, either in association with ants or without ants (N = 15 plots/treatment), with four plants each (total 120 plants). Vegetative growth (plant height and number of leaves), reproductive investment (flowers and fruits), herbivory rates and numbers of beneficial visitors were quantified during all phenological stages of the host plant. Data were analysed using generalized linear mixed models. At the host plant maturation stage, we found a trade‐off between growth and reproduction. Plants with ants had lower mean height; however, they invested more in reproduction (a higher number of flowers and fruits) compared to plants without ants. During the flowering stage, the abundance of sucking herbivores was higher in plots without ants but chewing herbivore abundance increased in the maturation stage in plots with ants. The cumulative proportion of leaves with herbivore damage did not differ between treatments, and the presence of ants reduced the number of beneficial visitors (e.g. pollinators and natural enemies) to the host plants. Our results show that association with ants results in some costs for the host plant, however, these costs appear to be offset by the defensive role of ants, which favours plant reproductive investment. In general, our results help to elucidate mechanisms involved in trophic interactions within the complex network of interactions involving ants and plants.     

Pristionchus uniformis,should I stay or should I go? Recent host range expansion in a European nematode

Pristionchus pacificus has been developed as a model system in evolutionary developmental biology, evolutionary ecology, and population genetics. This species has a well-known ecological association with scarab beetles. Generally, Pristionchus nematodes have a necromenic association with their beetle hosts. Arrested dauer larvae invade the insect and wait for the host's death to resume development. Only one Pristionchus species is known to frequently associate with a non-scarab beetle. Pristionchus uniformis has been isolated from the chrysomelid Leptinotarsa decemlineata, also known as the Colorado potato beetle, in Europe and North America, but is also found on scarab beetles. This unusual pattern of association with two unrelated groups of beetles on two continents requires the involvement of geographical and host range expansion events. Here, we characterized a collection of 81 P. uniformis isolates from North America and Europe and from both scarab beetles and L. decemlineata. We used population genetic and phylogenetic analyses of the mitochondrial gene nd2 to reconstruct the genetic history of P. uniformis and its beetle association. Olfactory tests on beetles chemical extracts showed that P. uniformis has a unique chemoattractive profile toward its beetle hosts. Our results provide evidence for host range expansion through host-switching events in Europe where P. uniformis was originally associated with scarab beetles and the nematode's subsequent invasion of North America.     

Disease ecology in the Galápagos Hawk (Buteo galapagoensis): host genetic diversity, parasite load and natural antibodies

An increased susceptibility to disease is one hypothesis explaining how inbreeding hastens extinction in island endemics and threatened species. Experimental studies show that disease resistance declines as inbreeding increases, but data from in situ wildlife systems are scarce. Genetic diversity increases with island size across the entire range of an extremely inbred Galápagos endemic bird, providing the context for a natural experiment examining the effects of inbreeding on disease susceptibility. Extremely inbred populations of Galápagos hawks had higher parasite abundances than relatively outbred populations. We found a significant island effect on constitutively produced natural antibody (NAb) levels and inbred populations generally harboured lower average and less variable NAb levels than relatively outbred populations. Furthermore, NAb levels explained abundance of amblyceran lice, which encounter the host immune system. This is the first study linking inbreeding, innate immunity and parasite load in an endemic, in situ wildlife population and provides a clear framework for assessment of disease risk in a Galápagos endemic.     

Thigh–calf contact: Does it affect the loading of the knee in the high-flexion range?

Recently, high-flexion knee implants have been developed to provide for a large range of motion (ROM>120°) after total knee arthroplasty (TKA). Since knee forces typically increase with larger flexion angles, it is commonly assumed that high-flexion knee implants are subjected to larger loads than conventional knee implants. However, most high-flexion studies do not consider thigh–calf contact which occurs during high-flexion activities such as squatting and kneeling. In this study, we hypothesized that thigh–calf contact reduces the knee forces during deep knee flexion as the tibio-femoral load shifts from occurring inside the knee towards the thigh–calf contact interface. Hence, the effect of thigh–calf contact on the knee loading was evaluated using a free body diagram and a finite element model and both the knee forces and polyethylene stresses were analyzed. Thigh–calf contact force characteristics from an earlier study were included and a squatting movement was simulated. In general, we found thigh–calf contact considerably reduced both the knee forces and polyethylene stresses during deep knee flexion. At maximal flexion (155°), the compressive knee force decreased from 4.89 to 2.90 times the bodyweight (BW) in case thigh–calf contact was included and the polyethylene contact stress at the tibial post decreased from 49.3 to 28.1 MPa. Additionally, there was a clear correlation between a subject's thigh and calf circumference and the force reduction at maximal flexion due to thigh–calf contact (R=0.89). The findings presented in this study can be used to optimize the mechanical behavior of high-flexion total knee arthroplasty designs.     

Cloning of AAC(3) and AAD(2″) genes fromAcinetobacter: differential expression in the host strain

The mechanism of resistance to gentamicin and tobramycin in a clinical isolate ofAcinetobacter baumannii, in which aminoglycoside-modifying enzymes were not detected, was investigated. For increase of the resistance gene product, DNA prepared from theA. baumannii isolate was cloned into pUC18 and introduced intoEscherichia coli by transformation. Gentamicin-resistant transformants were screened for aminoglycoside-modifying enzymes. This approach identified two genes encoding AAC(3) and AAD(2) activity, respectively. To determine whether both genes are expressed in the hostAcinetobacter strain, we extracted total cellular RNA from this strain, and Northern blots were hybridized with the cloned AAC(3) and AAD(2) structural genes. mRNA transcribed from the AAC(3) gene alone was detected. This shows that cloning a functional resistance gene is not sufficient in itself to investigate mechanisms of resistance in bacterial strains without detectable aminoglycoside-modifying activity. Furthermore, this study suggests a potential limitation of antibiotic resistance gene probes for studying mechanisms of resistance.     

Genetic Differentiation in Tetranychus Urticae (Acari: Tetranychidae): polymorphism,host races or sibling species?

Based on allozyme electrophoresis at the Pgm locus and nuclear ribosomal DNA (ITS2) sequences, we studied the genetic variation of the two-spotted spider mite Tetranychus urticae Koch collected on rose bay, Nerium oleander L. (Apocynaceae), from several localities around the Mediterranean basin. In addition, we compared these results with those of Navajas et al. (1998) and Tsagkarakou (1997) who collected from several other host plants from the Mediterranean. In the western part of this area (Spain, France, Tunisia), we found the individuals collected from rose bay to be clearly genetically differentiated from other samples. No evidence of such host-associated differentiation was detected in the eastern Mediterranean (Italy and Greece). The genetic differentiation of mites collected on rose bay was investigated further by studying the reproductive incompatibilities between populations in Greece and in France and a laboratory strain reared on bean, Phaseolus vulgaris, in France. Reciprocal crosses performed between these strains revealed variable levels of incompatibility, spanning from partial to complete reproductive isolation. In all cases incompatibility was asymmetric. We designed a test based on double-mating to establish the fertilization status of females in fully incompatible crosses. These crosses showed that the females had been inseminated, which suggests that the barrier to reproduction is not of a prezygotic behavioral nature. The data raises the question of the relative role of ecological factors (host plant) and geographical distance, in the ongoing differentiation process potentially leading to speciation.     

Plants,microbes, and odorants involved in host plant location by a specialist moth: who's making the message?

The grape berry moth (GBM), Paralobesia viteana (Clemens) (Lepidoptera: Tortricidae), is a specialist pest insect of cultivated grape, Vitis spp. (Vitaceae), in the eastern USA. A blend of volatile compounds has been isolated from plant material that attracts female GBM in the flight tunnel and field. However, the origin of the volatile cue is potentially complicated by the presence of microbes (bacteria and fungi) living on the surface of the plant. Microbial volatile organic compounds can affect insect behavior, and therefore must be considered to fully understand olfaction‐mediated behaviors. We report here the chemical and behavioral analysis of the volatile profiles produced from both the sanitized and control shoot treatments. The sanitization treatment removed 96.4% of the surface microbes up to 24 h, covering the duration of the behavioral assays and volatile collections. Overall, the surface microbes did not significantly contribute to the volatile profile of the grape shoots, as all of the peaks in the volatile profile of sanitized shoots were found in the profile of control shoots. In flight tunnel assays, female GBM displayed the same level of upwind oriented flight to sanitized shoots (flew upwind 57.4%, landed 30.9%) as they did to control shoots (flew upwind 57.8%, landed 31.0%), suggesting further that surface microbes did not contribute to the production of the previously identified blend of behaviorally active volatiles for GBM.