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Heatwaves are increasingly common globally and are known to have detrimental impacts on animal morphology and behaviour. These impacts can be severe, especially if heatwaves occur during development, even on animals that can regulate the temperature of their developing young. The onset and duration of heatwaves are stochastic and therefore may affect all or only part of development. In the heterothermic bumblebee Bombus terrestris, elevated temperatures over the entirety of development cause morphological changes in adults, despite their capability to regulate brood temperature. However, the effects of heatwaves that occur during a short period of development are unclear. We test the impact of elevated developmental temperature during the latter fraction of development on the behaviour and morphology of adult worker B. terrestris. We show that exposure to elevated temperature over a portion of late development is sufficient to impair the initial behavioural responses of workers to various sensory stimuli. Despite this, exposure to elevated temperatures during a period of development did not have any significant impact on body or organ size. The negative effect of elevated developmental temperatures was independent of the exposure time, which lasted from 11–20 days at the end of the workers’ developmental period. Thus, heat stress in bumblebees can manifest without morphological indicators and impair critical behavioural responses to relevant sensory stimuli, even if only present for a short period of time at the end of development. This has important implications for our understanding of deleterious climactic events and how we measure indicators of stress in pollinators., Frontiers in Ecology and Evolution, 9, ISSN:2296-701X

Simple Summary Pollinating insects rely on a range of senses such as vision, olfaction, gustation, and mechanosensation to utilise, locate, and fly between floral resources. The size of different sensory organs determines their sensitivity and provides an indication of their relative importance—larger organs can enhance sensitivity by increasing the number or size of sensing structures. However, increasing the relative size of an organ would require additional energy for developing and maintaining it. This likely leads to a trade-off between the energy invested into different sensory systems within individuals. To explore how the size of the sensory organs vary with body size in insect pollinators and how the energetic investment is divided, we performed a series of morphological measurements on the eyes, antennae, proboscis, and wings of male and female Pieris napi butterflies with a range of body sizes. We found that only antenna (in females) and wing size (in males and females) increased with body size. Males also had larger eyes and antennae compared to females regardless of body size. Our results provide insights into how the sensory morphology of these butterflies varies with body size and sex, and highlights unusual instances of organs that do not scale with body size. Abstract In solitary insect pollinators such as butterflies, sensory systems must be adapted for multiple tasks, including nectar foraging, mate-finding, and locating host-plants. As a result, the energetic investments between sensory organs can vary at the intraspecific level and even among sexes. To date, little is known about how these investments are distributed between sensory systems and how it varies among individuals of different sex. We performed a comprehensive allometric study on males and females of the butterfly Pieris napi where we measured the sizes and other parameters of sensory traits including eyes, antennae, proboscis, and wings. Our findings show that among all the sensory traits measured, only antenna and wing size have an allometric relationship with body size and that the energetic investment in different sensory systems varies between males and females. Moreover, males had absolutely larger antennae and eyes, indicating that they invest more energy in these organs than females of the same body size. Overall, the findings of this study reveal that the size of sensory traits in P. napi are not necessarily related to body size and raises questions about other factors that drive sensory trait investment in this species and in other insect pollinators in general.

Imaging the visual systems of bumblebees and other pollinating insects may increase understanding of their dependence on specific habitats and how they will be affected by climate change. Current high-resolution imaging methods are either limited to two dimensions (light- and electron microscopy) or have limited access (synchrotron radiation x-ray tomography). For x-ray imaging, heavy metal stains are often used to increase contrast. Here, we present micron-resolution imaging of compound eyes of buff-tailed bumblebees (Bombus terrestris) using a table-top x-ray nanotomography (nano-CT) system. By propagation-based phase-contrast imaging, the use of stains was avoided and the microanatomy could more accurately be reconstructed than in samples stained with phosphotungstic acid or osmium tetroxide. The findings in the nano-CT images of the compound eye were confirmed by comparisons with light- and transmission electron microscopy of the same sample and finally, comparisons to synchrotron radiation tomography as well as to a commercial micro-CT system were done., Journal of Microscopy, 283 (1), ISSN:0022-2720, ISSN:1365-2818

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Fibre bonds play an essential role in optical and mechanical properties of paper. Much research has focused on the strength of the bonds but the area of the individual fibre bonds has recently been of interest as well. Many of the research methods rely on optical tools which are restricted by the used wavelength of light. Since the bonding happens in the nanometer scale the highest optical resolution of 200 nm may not be accurate enough to capture the smallest variations in distance between the fibres in the intersection area.X-ray computed tomography utilises X-rays in studying the inner structure of materials. The method is based on X-ray absorption imaging that produces a spatial distribution of attenuation according to the density variation in the sample. After imaging the sample from different angles a reconstruction algorithm is used to recreate a three-dimensional model of the imaged sample. Novel X-ray devices surpass the optical methods in terms of resolution and, in particular, facilitate obtaining a detailed three dimensional image of the sample.X-ray nanotomography has previously been found to be a competent tool in the study of individual fibre bonds . As a continuation to the previous study, the method was used to successfully image 26 individual cellulose fibre bonds made of springwood and summerwood fibres of bleached softwood kraft pulp refined to 25o SR. Various dimensional properties of spring-to-springwood, summer-to-summerwood and spring-to-summerwood bonds were measured, most importantly the relative contact area (RCA, apparent contact area/overlapping area). The RCA values showed a wide variation from 6.4% to 85% with an average value of 57.7 %. Although the summerwood bonds had a somewhat smaller overlapping area and contact area than springwood bonds there were no significant differences in the RCA between the bond types. This suggests that the effect of absolute and relative contact area on the strength differences between the bond types seems to be minor. Typically the contact area in the bond was composed of several separate areas and the edge areas had a clearly higher probability to remain unbonded. The total thickness of the overlapping area correlated with the contact probability probably due to the effect of varying wet pressing pressure.

Sustainable wood fiber based materials as wood plastic composites (WPCs) are promising alternatives to engineering plastics and/or glass fiber reinforced materials in the construction and automotive sectors. However, due to the poor bonds of hydrophilic wood fibers with the hydrophobic matrix, moisture content (MC) variations cause hygroexpansion and strength reduction in WPCs as well as moisture-induced creep in the final products. In this context, a better understanding of the microscale phenomena in WPCs is needed for the assessment of their material properties and image-based modelling represents a promising approach [1]. This work presents a FEM modelling based on X-ray computed micro-tomography for the evaluation of hygroexpansion in polylactic acid (PLA) composites reinforced by birch pulp fibers. Water absorption tests were conducted on dog bone tensile test specimens containing 40% fibers to measure the levels of water uptake reached after 1 day, 7 days and 28 days immersion. Micro-tomographic images were acquired from a cylindrical sample of approximately 2 mm diameter cut from the middle web of the dry composite specimen [2]. Two-dimensional FEM meshes were created by using the oof2 open source software (https://www.ctcms.nist.gov/oof/oof2/) and FEM analyses of representative volume elements (RVEs) were carried out by using Abaqus code. The elastic moduli of fibers was assumed to be a parabolic function of MC starting from the reference in dry state. The hygroexpansion was simulated by assigning moisture changes to the RVE and hygroexpansion coefficients to the matrix and in the directions of fibers. The results in terms of elastic moduli and hygroexpansion were found in agreement with the measurements at different levels of water uptake.