Overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors

This article presents an overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors. It first briefly summarises some of the disease-causing pathogens vectored by insects and emphasises the need for innovative control methods to counter the threat of resistance by both the vector insect to pesticides and the pathogens to therapeutic drugs. Subsequently, the state of art of paratransgenesis is described, which is a particularly ingenious method currently under development in many important vector insects that could provide an additional powerful tool for use in integrated pest control programmes. The requirements and recent advances of the paratransgenesis technique are detailed and an overview is given of the microorganisms selected for genetic modification, the effector molecules to be expressed and the environmental spread of the transgenic bacteria into wild insect populations. The results of experimental models of paratransgenesis developed with triatomines, mosquitoes, sandflies and tsetse flies are analysed. Finally, the regulatory and safety rules to be satisfied for the successful environmental release of the genetically engineered organisms produced in paratransgenesis are considered

Dimensional modelling of the fuel outgassing phenomenon: Improving flammability assessment of aircraft fuel tanks

Fuel outgassing (oxygen evolution) within aircraft fuel tanks presents a serious flammability hazard. Time constants representing oxygen transfer rate, from the fuel into a tank’s ullage, are used to model the effect of outgassing on tank flammability. These time constants are specific to a single aircraft type and flight envelope and may not accurately represent fuel outgassing behaviour for other aircraft types with differing fuel tank configurations and flight envelopes. To improve current modelling practice for more accurate flammability analysis dimensional modelling has been used to determine the rate of oxygen evolution from Jet A-1 fuel in an aircraft fuel tank. Measurements of oxygen evolution rate, made on a dimensionally similar model, have been projected to an A320 aircraft. The evolution of oxygen from the fuel was found to increase monotonically with time. Fitting the test data with an inverse-exponential function enabled oxygen release rate and its associated time constant (t) to be determined. Dimensional modelling of aviation fuel outgassing using model fuel tanks will enable oxygen evolution rate from aviation fuel to be determined for a wide range of aircraft fuel tank configurations and environments without the need for flight testing. In turn the accuracy of flammability assessment of aircraft fuel tanks will be improved and significant cost savings made

A study of the effects of acid on the polymerisation of pyrrole, on the oxidative polymerisation of pyrrole and on polypyrrole

The polymer products arising from the hydrochloric acid treatment of aqueous pyrrole were shown to have spectroscopic data consistent with alternating pyrrole and pyrrolidine units with varying degrees of ring opening of the pyrrole units. The acid catalysed polymerisation of pyrrole offers a facile route to polymers with amine and carbonyl functional groups, which could be further derivatised. The products were polydisperse spheres; however the use of steric stabilisers induced monodisperse sphere formation and a concomitant ten fold decrease in size. Dilute nitric acid treatment of aqueous pyrrole gave polydisperse spheres (and ovoid shapes) in lower yield, plus a small proportion of curious particles which resembled pitted olives. The presence of acid in the reaction mixture of pyrrole and ferric ions was shown to have a relatively small effect on the conductivity of the resultant polypyrrole. The ability of polypyrrole to withstand harsh acidic conditions was assessed. Polypyrrole was shown to possess significant conductivity even after treatment with boiling concentrated hydrochloric acid

The Age-Specific Breeding Performance of Great Skuas on Shetland

The effect of age on the breeding performance of the great skua was examined between 1991 and 1993. There was a linear increase in clutch volume, aggression towards human intruders and fledging success with age while laying date became earlier with age. Clutch size and hatching success improved with age in a non-linear manner; increasing in younger birds before reaching a plateau in older birds. There was no effect of age on inter-nest distance nor on the condition of either the 'A' or 'B' chick. Female age was important in the advancement of laying date while male age was more important in increasing clutch volume. The latter result was possibly due to older males having a higher rate of courtship feeding. An improvement in food supply between 1989 and 1993 reduced the number of birds deferring breeding on territory, advanced laying date, increased clutch volume and greatly improved fledging success. The increase in clutch volume with improved food supply was statistically independent of laying date. Food supply had an additive effect on age specific laying dates but there was no significant interaction. There was a significant interaction of food supply and age on fledging success; in years of intermediate food supply fledging success improved with age, while in good years the fledging success of younger birds was elevated to a level similar to that found in older ones. This suggests that the fledging success of young birds was constrained by food supply to a greater extent than in older birds. Breeding experience had an effect on laying date, clutch size and clutch volume but did not affect hatching success. Age and experience were closely inter-related but separating the effects of these factors on breeding performance was not possible due to small samples of birds in which both age and experience were known. Despite this it seems that clutch size improved due to breeding experience rather than age. Improvements in laying date, clutch size and clutch volume were found in individual birds on successive breeding attempts following recruitment suggesting that individual birds improve breeding performance through a maturation process or a learning of skills beneficial to breeding. There was no evidence for an increase in reproductive effort with age, despite the fact that a decrease in survival was found with old age, which would provide a selective basis for such an increase in effort. There was also evidence to suggest that high fledgling production produced a cost of reproduction in terms of a decline in survival, this only being evident in old birds. Low clutch size and aggression was associated with increased mortality, this finding providing evidence that poor quality breeders have lower life expectation. The high mortality of poor quality birds which laid only one egg was especially evident in first time breeders. This effect could produce and increase in clutch size with age since birds laying a one egg clutch will die early while birds which lay 2 eggs will be represented in the population at older ages

Predation on roseate tern eggs by European starlings in the Azores

Predation by the European starling (Sturnus vulgaris) was the main reason for roseate tern (Sterna dougallii) hatching failure on Vila islet, Azores, one of the species’ largest colonies in Europe. Observations showed that single or small groups of starlings were responsible for predation events and that tern nest defense against starlings was generally ineffective. Daily nest survival rate was 94.2% in 2002 and 90.0% in 2003. Nesting success was estimated using a simulation model that allowed for renesting following failure and was 0.42 in 2002 and 0.17 in 2003. These values are considerably lower than the 0.97 nesting success at Rockabill, Ireland, one of the main European colonies, for the period 2000-2003. The sensitivity and importance of the roseate tern population in the Azores are discussed in relation to predation. Management strategies to reduce predation could include non-lethal control of starlings, destruction of starling nests and prevention from nesting in the vicinity of tern colonies

Linking extreme interannual changes in prey availability to foraging behaviour and breeding investment in a marine predator, the macaroni penguin

Understanding the mechanisms that link prey availability to predator behaviour and population change is central to projecting how a species may respond to future environmental pressures. We documented the behavioural responses and breeding investment of macaroni penguins Eudyptes chrysolophus across five breeding seasons where local prey density changed by five-fold; from very low to highly abundant. When prey availability was low, foraging trips were significantly longer and extended overnight. Birds also foraged farther from the colony, potentially in order to reach more distant foraging grounds and allow for increased search times. These extended foraging trips were also linked to a marked decrease in fledgling weights, most likely associated with reduced rates of provisioning. Furthermore, by comparing our results with previous work on this population, it appears that lowered first-year survival rates associated, at least partially, with fledging masses were also evident for this cohort. This study integrates a unique set of prey density, predator behaviour and predator breeding investment data to highlight a possible behavioural mechanism linking perturbations in prey availability to population demography

Dietary divergence is associated with increased intra-specific competition in a marine predator

Optimal foraging theory predicts that when food is plentiful all individuals should take a small range of preferred prey types, but as competition increases less preferred prey will be included in the diet. This dietary switching may not be uniform among individuals, which produces discrete dietary clusters. We tested this hypothesis for gentoo penguins at Bird Island, South Georgia, using stable isotope analysis and biologging. Competition, in the form of the density of foraging dives, increased markedly from incubation to chick-rearing owing to increased foraging effort. Birds responded behaviourally by exploiting a greater portion of the available foraging radius and increasing dive depths. Dietary niche width doubled and two discrete dietary clusters appeared; one comprising birds that consumed mostly krill and another that ate a greater proportion of demersal fish. There were no differences in morphology between the dietary classes, but birds in the fish class had a tendency to dive deeper, which suggests a behavioural basis for specialization. Our findings are consistent with the hypothesis that intra-specific competition expands the population’s dietary niche width and drives divergence in diets among individuals

Long term movements and activity patterns of an Antarctic marine apex predator: the Leopard Seal

Leopard seals are an important Antarctic apex predator that can affect marine ecosystems through local predation. Here we report on the successful use of micro geolocation logging sensor tags to track the movements, and activity, of four leopard seals for trips of between 142–446 days including one individual in two separate years. Whilst the sample size is small the results represent an advance in our limited knowledge of leopard seals. We show the longest periods of tracking of leopard seals’ migratory behaviour between the pack ice, close to the Antarctic continent, and the sub-Antarctic island of South Georgia. It appears that these tracked animals migrate in a directed manner towards Bird Island and, during their residency, use this as a central place for foraging trips as well as exploiting the local penguin and seal populations. Movements to the South Orkney Islands were also recorded, similar to those observed in other predators in the region including the krill fishery. Analysis of habitat associations, taking into account location errors, indicated the tracked seals had an affinity for shallow shelf water and regions of sea ice. Wet and dry sensors revealed that seals hauled out for between 22 and 31% of the time with maximum of 74 hours and a median of between 9 and 11 hours. The longest period a seal remained in the water was between 13 and 25 days. Fitting GAMMs showed that haul out rates changed throughout the year with the highest values occurring during the summer which has implications for visual surveys. Peak haul out occurred around midday for the months between October and April but was more evenly spread across the day between May and September. The seals’ movements between, and behaviour within, areas important to breeding populations of birds and other seals, coupled with the dynamics of the region’s fisheries, shows an understanding of leopard seal ecology is vital in the management of the Southern Ocean resources

Immune Reactions of Vector Insects to Parasites and Pathogens

This overview initially describes insect immune reactions and then brings together present knowledge of the interactions of vector insects with their invading parasites and pathogens. It is a way of introducing this Special Issue with subsequent papers presenting the latest details of these interactions in each particular group of vectors. Hopefully, this paper will fill a void in the literature since brief descriptions of vector immunity have now been brought together in one publication and could form a starting point for those interested and new to this important area. Descriptions are given on the immune reactions of mosquitoes, blackflies, sandflies, tsetse flies, lice, fleas and triatomine bugs. Cellular and humoral defences are described separately but emphasis is made on the co-operation of these processes in the completed immune response. The paper also emphasises the need for great care in extracting haemocytes for subsequent study as appreciation of their fragile nature is often overlooked with the non-sterile media, smearing techniques and excessive centrifugation sometimes used. The potential vital role of eicosanoids in the instigation of many of the immune reactions described is also discussed. Finally, the priming of the immune system, mainly in mosquitoes, is considered and one possible mechanism is presented