Sexual dimorphism of arrestment and gregariousness in the bed bug (Cimex lectularius) in response to cuticular extracts from nymphal exuviae

Releaser pheromones have direct behavioural effects to arrest, attract or disperse insects, whereas interactions within groups of social insects are often influenced by primer pheromones. The behaviour of insects displaying intermediate levels of sociality is largely unexplored in this context. In the present study, both the gregariousness and arrestment (settling near the odour source) of bed bugs Cimex lectularius L. (Hemiptera: Cimicidae) in response to conspecific exuvial extracts are described. Adult males are arrested on filter papers with extracts derived from exuviae of fifth‐instar nymphs. Adult females and nymphs display no significant evidence for such behaviour. Adults of both sexes show no preference for extracts of male versus female fifth‐instar exuviae. Arrestment of adult males does not occur on papers treated with fourth‐instar exuvial extracts. Because the insects are assayed behaviourally in groups, an index is calculated describing how far bugs are away from being located independently of one another, as a measure of gregariousness. Adult males have lower values for this index (i.e. locations are closer to independence). Adult females, nymph cohorts and mixed age groups all have higher values for this index, which tend to increase over time. Females exhibit a clear increasing dose‐dependent relationship for this index. It is concluded that the extracts of fifth‐instar nymphal exuvia arrest males on refuges that possess the odour source. However, gregariousness is induced in females, without evidence of a tendency to assemble near the odour source.     

Effect of climate change on mast-seeding species: frequency of mass flowering and escape from specialist insect seed predators

Global surface temperatures are expected to increase by several degrees in the next century, with potentially large but poorly understood impacts on ecological interactions. Here we propose potential effects of increased temperatures on ecologically dominant New Zealand grasses (Chionochloa spp.) that mass flower and mast seed. Twenty-two years’ data from five masting Chionochloa species in New Zealand showed that the cue for heavy flowering was unusually high temperature in the summer of the year before flowering. Attack by predispersal insect seed predators was much reduced in mast years, apparently because predator populations were satiated. Increased temperatures would greatly decrease interannual variation in Chionochloa flowering, allowing seed predator populations to increase and potentially to devastate the seed crop annually. Similar responses are likely in masting species worldwide. This previously unrecognized effect of global warming could have widespread impacts on temperate ecosystems.     

Cavity selection for roosting,and roosting ecology of forest-dwelling Australian Owlet-nightjars (Aegotheles cristatus)

Abstract We compared a variety of attributes of tree cavities used for roosting by radio-tagged Australian Owlet-nightjars Aegotheles cristatus with randomly chosen prospective cavities to test which features are important for the species. Owlet-nightjars preferentially roosted in tree cavities closer to the ground, in trees with a significantly greater number of cavities and significantly closer to another tree with a cavity than expected by chance. There was also a significant interaction between cavity height and number of cavities in the tree. Tree size, decay stage and tree species were not statistically important cues used for making site choices. The requirements for Owlet-nightjars differ from those of most other Australian birds that use tree holes and also from most insectivorous bats. Telemetry data indicate that Owlet-nightjars move ～300 m between roost sites every 9 days on average. Individual birds used 2-6 different cavities during the 1–4-month period over which they were followed. The reasons for the relatively low levels of site fidelity are unknown.     

Regulation of Metamorphosis-Associated Changes in the Lipid Metabolism of Selected Vertebrates

SYNOPSIS. The life histories of many vertebrates include complex,postembryonic developmental pathways that involve morphologicaland physiological changes that adapt juveniles to a new habitat.A survey of such developmental pathways, including lamprey metamorphosis,salmonid smoltification, and anuran metamorphosis, reveals acommon strategy of lipid metabolism consisting of two distinctphases. The first phase is characterized by lipid accumulationin storage sites and resultsfrom lipogenesis prevailing overlipolysis. The second phase is characterized by lipid depletionfrom storage sites and results from lipolysis prevailing overlipogenesis. Regulation of lipid deposition and lipid mobilizationis essential for ensuring availability of lipid during timesof need. Lipogenesis is promoted by insulin and, in lampreyand anurans, also by thyroid hormones. Lipolysis is promotedby a number of hormones, including prolactin, growth hormone,adrenocorticotropic hormone, corticosteroids, somatostatins,and thyroid hormones. The coordinate regulation of development-associatedchanges in lipid metabolism results from interactions amonghormones and other internal and environmental cues.     

Effects of experimentally enhanced flows on fishes of a small Texas (U.S.A.) stream: assessing the impact of interbasin transfer

1. Completion of a large interbasin water transfer system in northern Texas (U.S.A.) provided the opportunity to test the effects of pre-planned, experimental increases (≈×30) in flow on the fish fauna of a small, low-gradient, natural stream that was included as part of the conveyance system. Water from Lake Texoma (Red River basin) was pumped via a 16-km pipeline to the headwaters of Sister Grove Creek (Trinity River basin), which then carried the donor water 50 km downstream to Lake Lavon.
2. Baseline (pre-transfer) data on the composition of fish assemblages at seven stations on the creek or at its confluence with the receiving reservoir were collected monthly for 3 years, and similar data were collected for 2 years during and after trial flows of Lake Texoma water to Sister Grove Creek. We also documented fish abundance at five creek stations immediately before and after three trial flow periods of 10–14 days each in summer and autumn.
3. Multivariate analysis of all routine monthly samples over the 5-year pre- and post-transfer period showed moderate changes in the fish fauna of the creek after initiation of the trial flows. Samples taken within a week before and after the artificial high flows showed little overall change in abundance of individual fish species, but at some stations the quantitative or qualitative change in composition of the local assemblage was substantial.
4. The trial flows lasted 2 weeks or less. Long-term effects of water transfer on the fish fauna of Sister Grove Creek can only be determined after the conveyance system goes into normal operation, with periods of artificial flow of longer duration.     

Environmental change and the phenology of European aphids

Aphids, because of their short generation time and low developmental threshold temperatures, are an insect group expected to respond particularly strongly to environmental changes. Forty years of standardized, daily data on the abundance of flying aphids have been brought together from countries throughout Europe, through the EU Thematic Network 'EXAMINE'. Relationships between phenology, represented by date of first appearance in a year in a suction trap, of 29 aphid species and environmental data have been quantified using the residual maximum likelihood (REML) methodology. These relationships have been used with climate change scenario data to suggest plausible changes in aphid phenology. In general, the date of first record of aphid species in suction traps is expected to advance, the rate of advance varying with location and species, but averaging 8 days over the next 50 years. Strong relationships between aphid phenology and environmental variables have been found for many species, but they are notably weaker in species living all year on trees. Canonical variate analysis and principal coordinate analysis were used to determine ordinations of the 29 species on the basis of the presence/absence of explanatory variables in the REML models. There was strong discrimination between species with different life cycle strategies and between species feeding on herbs and trees, suggesting the possible value of trait-based groupings in predicting responses to environmental changes.     

Supercooling point plasticity during cold storage in the freeze‐tolerant sugarbeet root maggot Tetanops myopaeformis

Abstract The sugarbeet root maggot Tetanops myopaeformis (Röder) overwinters as a freeze‐tolerant third‐instar larva. Although most larvae are considered to overwinter for only 1 year, some may exhibit prolonged diapause in the field. In the laboratory, they can live for over 5 years using a combination of diapause and post‐diapause quiescence. In the present study, the cold survival strategies of these larvae during storage is investigated by measuring their supercooling points in combination with survival data. Supercooling points (SCPs) change significantly during storage, highlighted by a marked increase in the range of SCPs recorded, although the ability to tolerate freezing is not affected. Additionally, a freezing event ‘re‐focuses’ the SCPs of aged larvae to levels similar to those seen at diapause initiation. This change in SCPs is dependant not only on the initial freezing event, but also on the parameters of the incubation period between freezing events. Finally, the temperatures of larval overwintering microhabitats are monitored during the 2007–2008 boreal winter. The results indicate that, although overwintering larva are physiologically freeze‐tolerant, they may essentially be freeze avoidant during overwintering via microhabitat selection.     

Breeding status, contaminant burden and helminth parasites of Northern Fulmars Fulmarus glacialis from the Canadian high Arctic

We studied the relationship between contaminant concentrations in livers, endohelminth prevalence and physiological indices of chronic stress (spleen size, heterophil/lymphocyte ratios) in Northern Fulmars Fulmarus glacialis collected during the breeding season in Nunavut, Canada. No blood parasites were found, similar to reports for other petrel species elsewhere. However, 54% of Fulmars had gastrointestinal helminths, principally cestodes (52% prevalence, mean intensity of 11 worms), nematodes (34% prevalence, 3.6 worms) and acanthocephalans (3%, eight worms). Both prevalence and intensity of helminth infections were lower for Arctic Fulmars than for Fulmars and other petrels found in southern parts of the species' range. Spleen size was not significantly related to either contaminant concentration or presence of parasites, suggesting that Fulmar health was generally unaffected by contaminant and parasite levels at the colony. However, we cannot rule out the possibility that Fulmars with higher parasitaemias or contaminant loads were in poorer condition and did not attend the breeding colony.     

A comparison of maternal effects and current environment on vital rates of Aphis nerii, the milkweed–oleander aphid

Abstract.  1. Non-Mendelian maternal effects, the effects of maternal phenotype or environment on offspring phenotype, have been documented in numerous taxa. By affecting offspring vital rates (birth, death, and movement), maternal effects have the potential to influence population dynamics. However, relatively few studies have directly linked maternal phenotype or environment to offspring vital rates. Additionally, even fewer studies have compared the magnitude of across-generation effects (i.e. maternal effects) to within-generation effects.
2. Because of their telescoping generations, aphids can be strongly influenced by maternal effects. The effects of maternal density and maternal host-plant species on offspring survival, fecundity, and alate formation were investigated experimentally in Aphis nerii , the milkweed–oleander aphid.
3. Additionally, the relative strength of maternal effects were compared with those operating within a generation. Therefore, in another set of experiments, the effects of current density and host-plant species (within-generation effects) on aphid vital rates were examined.
4. While maternal effects were present, within-generation effects were much stronger and more strongly influenced aphid vital rates. Within a generation, aphids exhibited density-dependent survival, fecundity, and alate formation and these effects varied among host-plant species.
5. These results indicate that while maternal effects have the potential to affect population dynamics, this potential is not always met. Additionally, the current environment, not the environment of previous generations, more strongly impacts population dynamics.     

Long-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit as well as biological realism. Regression analysis indicated that while the dual exponential and asymptotic models statistically and biologically fit more of the litter type–site combinations than the single exponential model, the latter was biologically reasonable for 27–65% of the cases depending on the test used. This implies that a slow phase is common, but not universal. Moreover, estimates of the decomposition rate of the slowly decomposing component averaged 0.139–0.221 year⁻¹ (depending on method), higher than generally observed for mineral soil organic matter, but one-third of the faster phase of litter decomposition. Thus, this material may be slower than the earlier phases of litter decomposition, but not as slow as mineral soil organic matter. Comparison of the long-term integrated decomposition rate (which included all phases of decomposition) to that for the first year of decomposition indicated the former was on average 75% that of the latter, consistent with the presence of a slow phase of decomposition. These results indicate that the global store of litter estimated using short-term decomposition rates would be underestimated by at least one-third.