Using your head - cranial steering in pterosaurs

The vast majority of pterosaurs are characterized by relatively large, elongate heads that are often adorned with large, elaborate crests. Projecting out in front of the body, these large heads and any crests must have had an aerodynamic effect. The working hypothesis of the present study is that these oversized heads were used to control the left-right motions of the body during flight. Using digital models of eight non-pterodactyloids ("rhamphorhyncoids") and ten pterodactyloids, the turning moments associated with the head + neck show a close and consistent correspondence with the rotational inertia of the whole body about a vertical axis in both groups, supporting the idea of a functional relationship. Turning moments come from calculating the lateral area of the head (plus any crests) and determining the associated lift (aerodynamic force) as a function of flight speed, with flight speeds being based on body mass. Rotational inertias were calculated from the three-dimensional mass distribution of the axial body, the limbs, and the flight membranes. The close correlation between turning moment and rotational inertia was used to revise the life restorations of two pterosaurs and to infer relatively lower flight speeds in another two.

The spatiotemporal richness of hummingbird wing deformations

Animals exhibit an abundant diversity of forms, and this diversity is even more evident when considering animals that can change shape on demand. The evolution of flexibility contributes to aspects of performance from propulsive efficiency to environmental navigation. It is, however, challenging to quantify and compare body parts that, by their nature, dynamically vary in shape over many time scales. Commonly, body configurations are tracked by labelled markers and quantified parametrically through conventional measures of size and shape (descriptor approach) or non-parametrically through data-driven analyses that broadly capture spatiotemporal deformation patterns (shape variable approach). We developed a weightless marker tracking technique and combined these analytic approaches to study wing morphological flexibility in hoverfeeding Anna's hummingbirds (Calypte anna). Four shape variables explained >95% of typical stroke cycle wing shape variation and were broadly correlated with specific conventional descriptors like wing twist and area. Moreover, shape variables decomposed wing deformations into pairs of in- and out-of-plane components at integer multiples of the stroke frequency. This property allowed us to identify spatiotemporal deformation profiles characteristic of hoverfeeding with experimentally imposed kinematic constraints, including through shape variables explaining <10% of typical shape variation. Hoverfeeding in front of a visual barrier restricted stroke amplitude and elicited increased stroke frequencies together with in- and out-of-plane deformations throughout the stroke cycle. Lifting submaximal loads increased stroke amplitudes at similar stroke frequencies together with prominent in-plane deformations during the upstroke and pronation. Our study highlights how spatially and temporally distinct changes in wing shape can contribute to agile fluidic locomotion.

Analysis of current methods and Welfare concerns in the transport of 118 horses by commercial air cargo companies

BACKGROUND

Studies on equine air transport practices and consequences are scarce. This prospective study aimed to describe horse and air journey details and practices, document how horse behavior and health changed during the air transport phases, quantify the occurrence of welfare issues, and identify possible associations between horse and journey details, air transport practices, and welfare issues.

RESULTS

Data were collected from before departure to five days after arrival on 118/597 horses traveling on 32 commercial air journeys on different routes, varying in duration and conditions. Most horses were middle-aged warmblood females, 26% of which were pregnant, and being moved by air for sales. Before flying, most were quarantined (median: 18; IQR: 9-53 days), and their fitness for travel was certified by veterinarians. At the departure airports, external temperatures varied from - 6 °C to 33 °C, and horses were loaded by experienced flight grooms (median: 35; IQR: 15-40 years) into jet stalls (three-horse: 87%, two-horse: 13%). During the flights, horses were regularly watered (water intake median: 14 L) and fed ad libitum (feed consumption median: 8 kg). At the arrival airport, horses were unloaded from the jet stalls, and external temperatures ranged from - 5 °C to 32 °C. Then, all horses were transported to arrival quarantine by road. Air transport phases affected horses' health status and behavior; increased heart and respiratory rates and behaviors, such as pawing, head tossing, and vocalization, were mainly identified at departure and arrival. Horse interaction, nasal discharge, increased capillary refill time (CRT), and abnormal demeanor were observed more often one hour before landing while resting and normal capillary refill time were more often displayed five days after arrival (all P < 0.01). One hour before landing, horses with bad temperament and horses of unknown temperament were more likely to develop nasal discharge when transported in winter and autumn (P < 0.001). The likelihood of an increased CRT was associated with shorter flights in horses of unknown travel experience (P < 0.001). Ten horses were injured, and 11 developed pleuropneumonias (i.e., shipping fever).

CONCLUSIONS

Air transport is a complex procedure with several different phases affecting horse health and behavior. Therefore, experienced staff should carefully manage each horse before, during, and after air journeys to minimize welfare hazards.

Facial and trigeminal nerves neuropathy induced by atmospheric pressure changes: A meta-analysis

BACKGROUND

Barometric pressure changes during flight or diving may cause facial barotrauma. Neuropathy of the fifth (CN5) or the seventh (CN7) cranial nerves is a rare manifestation of this condition. The aim of this study was to analyze risk factors for baroneuropathies of CN5 and CN7.

METHODS

A search of PubMed and Cochrane Library databases was conducted to identify all published cases of CN5 and CN7 neuropathies. Only original case reports and series that documented events of neuropathies associated with the trigeminal nerve or facial nerve while flying, diving, or mountain climbing were included. Assessed variables included sex, medical history, age, setting (flight or diving), atmospheric pressure changes, number of episodes, symptoms, treatment, and recovery.

RESULTS

We identified a total of 48 articles described >125 episodes in 67 patients. Mean age was 33.5 ± 12.1 years with a male predominance (76.1 %). Cases were equally distributed between flight and diving (50.7 %, 46.3 %, respectively). CN5 involvement was observed in 77.6 % of patients, with ear pain and facial numbness as the most common symptoms. The latter was correlated with positive otolaryngology medical history. CN7 was involved in 88.1 % of patients. Flying, as opposed to diving was correlated with spontaneous resolution of symptoms (86.7 % vs. 42.3 % of cases resolved spontaneously, respectively, p = 0.001).

CONCLUSIONS

Flight is an equal risk factor to diving with respect to CN5 and CN7 barotrauma. Involvement of CN7 was observed in most cases, but possibly due to report-bias. Positive medical history is a risk factor for facial numbness.

Parental conscription and cumulative adverse experiences in war-affected children and adolescents and their impact on mental health: a comment following Russia's invasion of Ukraine in 2022

BACKGROUND

With Russia's invasion of the Ukraine on February 2022, Ukrainian children and adolescents have been exposed to several stressful life events. In addition to the confrontation with war, flight and parent-child separation due to flight and forced displacement, the majority underwent another challenge at the initial phase of the war: the fatherly separation due to conscription.

MAIN BODY

In the literature, the negative effects of exposure to war and flight/refuge, parent-child separation due to flight or forced displacement and parental deployment are well established. In the context of self-experienced war, the effects of parent-child separation caused by compulsory military service have not yet been sufficiently taken into account. However, the findings of the literature on the impact of these events on the mental health of children and adolescents show that they are at high risk for developing numerous psychological and behavioral problems.

CONCLUSION

As children's and adolescents' mental health might be severely affected by war and its consequences, interventional programs that address the special needs of those children and adolescents are crucial.

Influence of behavioural and morphological group composition on pigeon flocking dynamics

Animals rely on movement to explore and exploit resources in their environment. While movement can provide energetic benefits, it also comes with energetic costs. This study examines how group phenotypic composition individual speed and energy expenditure during group travel in homing pigeons. We manipulated the composition of pigeon groups based on body mass and leadership rank. Our findings indicate that groups of leader phenotypes show faster speeds and greater cohesion than follower phenotype groups. Additionally, we show that groups of homogenous mass composition, whether all heavy or all light, were faster and expended less energy over the course of a whole flight than flocks composed of a mixture of heavy and light individuals. We highlight the importance of considering individual-level variation in social-level studies, and the interaction between individual and group-level traits in governing speed and the cost of travel.

Air sacs are a key adaptive trait of the insect respiratory system

Air sacs are a well-known aspect of insect tracheal systems, but have received little research attention. In this Commentary, we suggest that the study of the distribution and function of air sacs in tracheate arthropods can provide insights of broad significance. We provide preliminary phylogenetic evidence that the developmental pathways for creation of air sacs are broadly conserved throughout the arthropods, and that possession of air sacs is strongly associated with a few traits, including the capacity for powerful flight, large body or appendage size and buoyancy control. We also discuss how tracheal compression can serve as an additional mechanism for achieving advection in tracheal systems. Together, these patterns suggest that the possession of air sacs has both benefits and costs that remain poorly understood. New technologies for visualization and functional analysis of tracheal systems provide exciting approaches for investigations that will be of broad significance for understanding invertebrate evolution.

Going against the flow: bumblebees prefer to fly upwind and display more variable kinematics when flying downwind

Foraging insects fly over long distances through complex aerial environments, and many can maintain constant ground speeds in wind, allowing them to gauge flight distance. Although insects encounter winds from all directions in the wild, most lab-based studies have employed still air or headwinds (i.e. upwind flight); additionally, insects are typically compelled to fly in a single, fixed environment, so we know little about their preferences for different flight conditions. We used automated video collection and analysis methods and a two-choice flight tunnel paradigm to examine thousands of foraging flights performed by hundreds of bumblebees flying upwind and downwind. In contrast to the preference for flying with a tailwind (i.e. downwind) displayed by migrating insects, we found that bees prefer to fly upwind. Bees maintained constant ground speeds when flying upwind or downwind in flow velocities from 0 to 2 m s-1 by adjusting their body angle, pitching down to raise their air speed above flow velocity when flying upwind, and pitching up to slow down to negative air speeds (flying backwards relative to the flow) when flying downwind. Bees flying downwind displayed higher variability in body angle, air speed and ground speed. Taken together, bees' preference for upwind flight and their increased kinematic variability when flying downwind suggest that tailwinds may impose a significant, underexplored flight challenge to bees. Our study demonstrates the types of questions that can be addressed with newer approaches to biomechanics research; by allowing bees to choose the conditions they prefer to traverse and automating filming and analysis to examine massive amounts of data, we were able to identify significant patterns emerging from variable locomotory behaviors, and gain valuable insight into the biomechanics of flight in natural environments.

"Genome-Wide Analysis Reveals Novel Regulators of Synaptic Maintenance in Drosophila"

Maintaining synaptic communication is required to preserve nervous system function as an organism ages. While much work has been accomplished to understand synapse formation and development, we understand relatively little regarding maintaining synaptic integrity throughout aging. To better understand the mechanisms responsible for maintaining synaptic structure and function, we performed an unbiased forward genetic screen to identify genes required for synapse maintenance of adult Drosophila neuromuscular junctions. Using flight behavior as a screening tool, we evaluated flight ability in 198 lines from the Drosophila Genetics Reference Panel to identify Single Nucleotide Polymorphisms (SNPs) that are associated with a progressive loss of flight ability with age. Among the many candidate genes identified from this screen, we focus here on ten genes with clear human homologs harboring SNPs that are the most highly associated with synaptic maintenance. Functional validation of these genes using mutant alleles revealed a progressive loss of synaptic structural integrity. Tissue-specific knockdown of these genes using RNA interference (RNAi) uncovered important roles for these genes in either presynaptic motor neurons, postsynaptic muscles, or associated glial cells, highlighting the importance of each component of tripartite synapses. These results offer greater insight into the mechanisms responsible for maintaining structural and functional integrity of synapses with age.

Window films increase avoidance of collisions by birds but only when applied to external compared with internal surfaces of windows

Window collisions are one of the largest human-caused causes of avian mortality in built environments and, therefore, cause population declines that can be a significant conservation issue. Applications of visibly noticeable films, patterns, and decals on the external surfaces of windows have been associated with reductions in both window collisions and avian mortality. It is often logistically difficult and economically prohibitive to apply these films and decals to external surfaces, especially if the windows are above the first floor of a building. Therefore, there is interest and incentive to apply the products to internal surfaces that are much easier to reach and maintain. However, there is debate as to whether application to the internal surface of windows renders any collision-reduction benefit, as the patterns on the films and decals may not be sufficiently visible to birds. To address this knowledge gap, we performed the first experimental study to compare the effectiveness of two distinct window films when applied to either the internal or external surface of double-glazed windows. Specifically, we assessed whether Haverkamp and BirdShades window film products were effective in promoting the avoidance of window collisions (and by inference, a reduction of collisions) by zebra finches through controlled aviary flight trials employing a repeated-measures design that allowed us to isolate the effect of the window treatments on avoidance flight behaviors. We chose these two products because they engage with different wavelengths of light (and by inference, colors) visible to many songbirds: the BirdShades film is visible in the ultraviolet (shorter wavelength) range, while the Haverkamp film includes signals in the orange (longer wavelength) range. We found consistent evidence that, when applied to the external surface of windows, the BirdShades product resulted in reduced likelihood of collision and there was marginal evidence of this effect with the Haverkamp film. Specifically, in our collision avoidance trials, BirdShades increased window avoidance by 47% and the Haverkamp increased avoidance by 39%. However, neither product was effective when the films were applied to the internal surface of windows. Hence, it is imperative that installers apply these products to exterior surfaces of windows to render their protective benefits and reduce the risk of daytime window collision.

Built up areas in a wet landscape are stepping stones for soaring flight in a seabird

The energy exchange between the Earth's surface and atmosphere results in a highly dynamic habitat through which birds move. Thermal uplift is an atmospheric feature which many birds are able to exploit in order to save energy in flight, but which is governed by complex surface-atmosphere interactions. In mosaic landscapes consisting of multiple land uses, the spatial distribution of thermal uplift is expected to be heterogenous and birds may use the landscape selectively to maximise flight over areas where thermal soaring opportunities are best. Flight generalists such as the lesser black-backed gull, Larus fuscus, are expected to be less reliant on thermal uplift than obligate soaring birds. Nevertheless, gulls may select flight behaviours and routes in response to or in anticipation of thermal uplift in order to reduce their transport costs, even in landscapes where thermal uplift isn't prevalent. We explore thermal soaring over land in lesser black-backed gulls by using high-resolution GPS tracking to characterise individual instances of thermal soaring and detailed energy exchange modelling to map the thermal landscape which gulls experience. We determine that lesser black-backed gulls are regularly able to undertake thermal soaring, even in a wet temperate landscape below sea level. By examining the relationship between lesser black-backed gull flight, thermal uplift and land use, we determine that built up areas, particularly towns and cities, provide thermal uplift hotspots which lesser black-backed gulls preferentially make use of, resulting in more opportunities for energy saving flight through thermal soaring.

Seizure rescue medications are missing from in-flight medical emergency kits

OBJECTIVE

We aimed to inquire whether any seizure rescue medications are included in the in-flight medical emergency kits of the main airlines in the world. This data could help the airline authorities update their strategies in light of any shortcomings.

METHODS

First, we identified ten major airlines in the world. Then, we searched the Google engine with the following keywords: "name of the airline" and "in-flight medical emergency" or "first aid kit" or "emergency kit". In case there was no information on the web, we emailed the airlines and inquired about the contents of their in-flight medical emergency kits. We also investigated some of the major aviation organizations' websites [i.e., Aerospace Medical Association (AsMA), International Civil Aviation Organization (ICAO), and International Air Transport Association (IATA)].

RESULTS

None of the major airlines were equipped with easily applicable seizure rescue medications (i.e., buccal midazolam, a nasal spray of midazolam, or intranasal diazepam). The AsMA and ICAO recommend including injectable sedative anticonvulsant drugs in the in-flight medical emergency kits without any further specifications. The IATA does not provide specific recommendations for including seizure rescue medications in the in-flight medical emergency kits.

CONCLUSION

A seizure is a significant in-flight medical emergency event. The use of easily applicable seizure rescue medications during prolonged or repeated seizures is significantly associated with fewer sequelae for the affected person. Easily applicable seizure rescue medications should be included in the in-flight medical emergency kits, and the cabin crew should receive training on how and when to use them.

Landing manoeuvres predict roost-site preferences in bats

Roosts are vital for the survival of many species, and how individuals choose one site over another is affected by various factors. In bats, for example, species may use stiff roosts such as caves or compliant ones such as leaves; each type requires not only specific morphological adaptations but also different landing manoeuvres. Selecting a suitable roost within those broad categories may increase landing performance, reducing accidents and decreasing exposure time to predators. We address whether bats select specific roost sites based on the availability of a suitable landing surface, which could increase landing performance. Our study focuses on Spix's disc-winged bats (Thyroptera tricolor), a species known to roost within developing tubular leaves. Since previous studies show that this species relies on the leaves' apex for safe landing and rapid post-landing settlement, we predict that bats will prefer to roost in tubular structures with a longer apex and that landing will be consistently more effective on those leaves. Field observations showed that T. tricolor predominantly used two species for roosting, Heliconia imbricata and Calathea lutea, but they preferred roosting in the former. The main difference between these two plant species was the length of the leaf's apex (longer in H. imbricata). Experiments in a flight cage also show that bats use more consistent approach and landing tactics when accessing leaves with a longer apex. Our results suggest that landing mechanics may strongly influence resource selection, especially when complex manoeuvres are needed to acquire those resources.

Evaluation of fatigue and sleep problems in cabin crews during the early COVID-19 pandemic period

Background

The COVID-19 outbreak has affected the aviation sector. The anxiety and fear caused by this newly emerging virus, whose effects are not fully known in the short and long term, may also cause problems in terms of flight safety. We aimed to evaluate fatigue and sleep problems associated with fear of COVID-19 during the early pandemic period in cabin crew.

Methods

This is a cross-sectional survey study consisting of 45 questions in total. Participants were cabin crew members on flight duty. An online questionnaire was sent to 2092 cabin crew in February–April 2021 via TASSA Cabin Crew Member's Association. The survey included questions about socio-demographic characteristics, flight times, flight types and COVID test history, as well as the international physical activity questionnaire-short form (IPAQ-SF), fatigue severity scale (FSS), Jenkins sleep scale (JSS) and fear of COVID-19 scale (FCV-19S).

Results

Out of 316 survey results obtained (response rate, 15%), 225 (71%) were included in the study, with a mean age (SD) of 32.54 (4.91) years, and 124 (55.1%) were women. According to IPAQ-SF, 27.6% of cabin crew were found to be inactive, 54.7% minimally active and 17.7% very active. According to FSS, pathological fatigue was found in 43.6%. The FSS score of the inactive group was higher than the others (Kruskal Wallis, p < 0.001). As the number of people living in the same house or flight time in the last 1 month increase, the fear of COVID-19 also increases (Spearman, p = 0.01 r = 0.171, and p = 0.049 r = 0.131). In addition, there was direct correlation between fear of COVID-19 and fatigue and sleep problems (Spearman, p = 0.001 r = 0.218, and p < 0.001 r = 0.26, respectively).

Conclusion

This study shows that fatigue and sleep problems increase as the fear of COVID-19 increases in cabin crew during the early pandemic period. Consequently, precautions and further studies are needed, as fatigue and sleep disorders may primarily be related to the anxiety, fear and uncertainty surrounding the COVID-19 pandemic.

Variation in the reproductive quality of honey bee males affects their age of flight attempt

Background

Honey bee males (drones) exhibit life histories that enable a high potential for pre- or post-copulatory sperm competition. With a numerical sex ratio of ∼11,000 drones for every queen, they patrol flyways and congregate aerially to mate on the wing. However, colonies and in fact drones themselves may benefit from a relative lack of competition, as queens are highly polyandrous, and colonies have an adaptive advantage when headed by queens that are multiply mated. Previous research has shown that larger drones are more likely to be found at drone congregation areas, more likely to mate successfully, and obtain a higher paternity share. However, the reproductive quality and size of drones varies widely within and among colonies, suggesting adaptive maintenance of drone quality variation at different levels of selection.

Methods

We collected drones from six colony sources over the course of five days. We paint marked and individually tagged drones after taking body measurements at emergence and then placed the drones in one of two foster colonies. Using an entrance cage, we collected drones daily as they attempted flight. We collected 2,420 drones live or dead, analyzed 1,891 for attempted flight, collected emergence data on 207 drones, and dissected 565 upon capture to assess reproductive maturity. We measured drone body mass, head width, and thorax width at emergence, and upon dissection we further measured thorax mass, seminal vesicle length, mucus gland length, sperm count, and sperm viability from the seminal vesicles.

Results

We found that drones that were more massive at emergence were larger and more fecund upon capture, suggesting that they are of higher reproductive quality and therefore do not exhibit a trade-off between size and fecundity. However, smaller drones tended to attempt initial flight at a younger age, which suggests a size trade-off not with fecundity but rather developmental maturation. We conclude that smaller drones may take more mating flights, each individually with a lower chance of success but thereby increasing their overall fitness. In doing so, the temporal spread of mating attempts of a single generation of drones within a given colony increases colony-level chances of mating with nearby queens, suggesting an adaptive rationale for high variation among drone reproductive quality within colonies.

Imbalance of flight-freeze responses and their cellular correlates in the Nlgn3-/y rat model of autism

BACKGROUND

Mutations in the postsynaptic transmembrane protein neuroligin-3 are highly correlative with autism spectrum disorders (ASDs) and intellectual disabilities (IDs). Fear learning is well studied in models of these disorders, however differences in fear response behaviours are often overlooked. We aim to examine fear behaviour and its cellular underpinnings in a rat model of ASD/ID lacking Nlgn3.

METHODS

This study uses a range of behavioural tests to understand differences in fear response behaviour in Nlgn3^-/y rats. Following this, we examined the physiological underpinnings of this in neurons of the periaqueductal grey (PAG), a midbrain area involved in flight-or-freeze responses. We used whole-cell patch-clamp recordings from ex vivo PAG slices, in addition to in vivo local-field potential recordings and electrical stimulation of the PAG in wildtype and Nlgn3^-/y rats. We analysed behavioural data with two- and three-way ANOVAS and electrophysiological data with generalised linear mixed modelling (GLMM).

RESULTS

We observed that, unlike the wildtype, Nlgn3^-/y rats are more likely to response with flight rather than freezing in threatening situations. Electrophysiological findings were in agreement with these behavioural outcomes. We found in ex vivo slices from Nlgn3^-/y rats that neurons in dorsal PAG (dPAG) showed intrinsic hyperexcitability compared to wildtype. Similarly, stimulating dPAG in vivo revealed that lower magnitudes sufficed to evoke flight behaviour in Nlgn3^-/y than wildtype rats, indicating the functional impact of the increased cellular excitability.

LIMITATIONS

Our findings do not examine what specific cell type in the PAG is likely responsible for these phenotypes. Furthermore, we have focussed on phenotypes in young adult animals, whilst the human condition associated with NLGN3 mutations appears during the first few years of life.

CONCLUSIONS

We describe altered fear responses in Nlgn3^-/y rats and provide evidence that this is the result of a circuit bias that predisposes flight over freeze responses. Additionally, we demonstrate the first link between PAG dysfunction and ASD/ID. This study provides new insight into potential pathophysiologies leading to anxiety disorders and changes to fear responses in individuals with ASD.

Ungulates and trains - Factors influencing flight responses and detectability

Wildlife-train collisions can have deleterious effects on local wildlife populations and come with high socio-economic costs, such as damages, delays, and psychological distress. In this study, we explored two major components of wildlife-train collisions: the response of wildlife to oncoming trains and the detection of wildlife by drivers. Using dashboard cameras, we explored the flight response of roe deer (Capreolus capreolus) and moose (Alces alces) to oncoming trains and explored which factors, such as lighting and physical obstructions, affect their detection by drivers. In a majority of cases, roe deer and moose fled from an oncoming train, at an average flight initiation distance (FID) of 78 m and 79 m respectively. Warning horns had unexpected influences on flight behaviour. While roe deer initiated flight, on average, 44 m further away from the train when warned, they usually fled towards the tracks, in the direction of danger. FID of moose, however, was unaffected by the use of a warning horn. As train speed increased, moose had a lower FID, but roe deer FID did not change. Finally, detection of wildlife was obstructed by the presence of vegetation and uneven terrain in the rail-side verge, which could increase the risk of collisions. Our results indicate the need for early detection and warning of wildlife to reduce the risk of collisions. We propose that detection systems should include thermal cameras to allow detection behind vegetation and in the dark, and warning systems should use cues early to warn of oncoming trains and allow wildlife to escape the railway corridor safely.

A comparison of thermal sensitivities of wing muscle contractile properties from a temperate and tropical bat species

Endotherms experience temperature variation among body regions, or regional heterothermy, despite maintaining high core body temperatures. Bat forelimbs are elongated to function as wings, which makes them vulnerable to heat loss and exaggerates regional heterothermy. A tropical bat species, Carollia perspicillata, flies with distal wing muscles that are substantially (>10°C) cooler than proximal wing muscles and significantly less temperature sensitive. We hypothesized that the difference between proximal and distal wing muscles would be even more extreme in a temperate bat species that is capable of flight at variable environmental temperatures. We measured the contractile properties of the proximal pectoralis muscle and distal extensor carpi radialis muscle at a range of temperatures in the big brown bat, Eptesicus fuscus, and compared their thermal dependence with that of the same muscles in C. perspicillata. We found that, overall, temperature sensitivities between species were remarkably similar. The sole exception was the shortening velocity of the pectoralis muscle in E. fuscus, which was less temperature sensitive than in C. perspicillata. This decreased temperature sensitivity in a proximal muscle runs counter to our prediction. We suggest that the relative lability of body temperature in E. fuscus may make better pectoralis function at low temperatures advantageous.

Oh, snap! A within-wing sonation in black-tailed trainbearers

Vertebrates communicate through a wide variety of sounds, but few mechanisms of sound production, besides vocalization, are well understood. During high-speed dives, male trainbearer hummingbirds (Lesbia spp.) produce a repeated series of loud snaps. Hypotheses for these peculiar sounds include employing their elongated tails and/or their wings striking each other. Each snap to human ears seems like a single acoustic event, but sound recordings revealed that each snap is actually a couplet of impulsive, atonal sounds produced ∼13 ms apart. Analysis of high-speed videos refutes these previous hypotheses, and furthermore suggests that this sonation is produced by a within-wing mechanism- each instance of a sound coincided with a distinctive pair of deep wingbeats (with greater stroke amplitude, measured for one display sequence). Across many displays, we found a tight alignment between a pair of stereotyped deep wingbeats (in contrast to shallower flaps across the rest of the dive) and patterns of snap production, evidencing a 1:1 match between these sonations and stereotyped kinematics. Other birds including owls and poorwills are reported to produce similar sounds, suggesting that this mechanism of sound production could be somewhat common within birds, yet its physical acoustics remains poorly understood.

Traumatic events, daily stressors and posttraumatic stress in unaccompanied young refugees during their flight: a longitudinal cross-country study

BACKGROUND

Unaccompanied young refugees constitute an especially vulnerable population, reporting high rates of trauma and mental health problems. There is a significant gap in the literature on trauma and posttraumatic stress symptoms (PTSS) in unaccompanied young refugees who are still on the move and live in precarious circumstances such as refugee camps. This study therefore aimed to contribute to this gap by investigating pre- and peri-migration (potentially) traumatic experiences of unaccompanied young refugees; longitudinal trajectories of trauma, daily stressors and PTSS; and the impact of gender, trauma, and daily stressors on PTSS over time.

METHODS

This longitudinal, mixed-method, and multi-country study was conducted in various settings (e.g. refugee camps, reception centers) across nine European countries. A heterogeneous sample of N = 187 unaccompanied young refugees (78.4% male) from 29 different countries was assessed via interviews at 3 time-points during a period of 27 months. Data was analyzed via growth curve modelling.

RESULTS

Prevalence rates of (potentially) traumatic experiences ranged from 29.5 to 91.9%. Peri-migration traumatization remained stable over time (b = - 0.02; p = 0.371), but the number of reported daily stressors (b = - 0.24; p = 0.001) and PTSS scores significantly decreased over time (b = - 0.98; p = 0.004). Females reported higher PTSS compared with males at baseline (p = 0.002), but gender did not influence the longitudinal trajectory of PTSS. The pre-migration trauma load and daily stressors at baseline did not have a significant effect on PTSS at baseline or on the longitudinal trajectory.

CONCLUSIONS

This is the first study to document not only the high numbers of traumatic events for unaccompanied young refugees pre- and peri- migration, but also the continued traumatization during flight, as well as high rates of daily stressors and PTSS. Humanitarian and political assistance is urgently needed to curb the often life-threatening conditions unaccompanied young refugees face during migration.

Multi-modal locomotor costs favor smaller males in a sexually dimorphic leaf-mimicking insect

Background

In most arthropods, adult females are larger than males, and male competition is a race to quickly locate and mate with scattered females (scramble competition polygyny). Variation in body size among males may confer advantages that depend on context. Smaller males may be favored due to more efficient locomotion leading to higher mobility during mate searching. Alternatively, larger males may benefit from increased speed and higher survivorship. While the relationship between male body size and mobility has been investigated in several systems, how different aspects of male body morphology specifically affect their locomotor performance in different contexts is often unclear.

Results

Using a combination of empirical measures of flight performance and modelling of body aerodynamics, we show that large body size impairs flight performance in male leaf insects (Phyllium philippinicum), a species where relatively small and skinny males fly through the canopy in search of large sedentary females. Smaller males were more agile in the air and ascended more rapidly during flight. Our models further predicted that variation in body shape would affect body lift and drag but suggested that flight costs may not explain the evolution of strong sexual dimorphism in body shape in this species. Finally, empirical measurements of substrate adhesion and subsequent modelling of landing impact forces suggested that smaller males had a lower risk of detaching from the substrates on which they walk and land.

Conclusions

By showing that male body size impairs their flight and substrate adhesion performance, we provide support to the hypothesis that smaller scrambling males benefit from an increased locomotor performance and shed light on the evolution of sexual dimorphism in scramble competition mating systems.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-01993-z.

Compensation for wind drift prevails for a shorebird on a long-distance, transoceanic flight

BACKGROUND

Conditions encountered en route can dramatically impact the energy that migratory species spend on movement. Migratory birds often manage energetic costs by adjusting their behavior in relation to wind conditions as they fly. Wind-influenced behaviors can offer insight into the relative importance of risk and resistance during migration, but to date, they have only been studied in a limited subset of avian species and flight types. We add to this understanding by examining in-flight behaviors over a days-long, barrier-crossing flight in a migratory shorebird.

METHODS

Using satellite tracking devices, we followed 25 Hudsonian godwits (Limosa haemastica) from 2019-2021 as they migrated northward across a largely transoceanic landscape extending > 7000 km from Chiloé Island, Chile to the northern coast of the Gulf of Mexico. We identified in-flight behaviors during this crossing by comparing directions of critical movement vectors and used mixed models to test whether the resulting patterns supported three classical predictions about wind and migration.

RESULTS

Contrary to our predictions, compensation did not increase linearly with distance traveled, was not constrained during flight over open ocean, and did not influence where an individual ultimately crossed over the northern coast of the Gulf of Mexico at the end of this flight. Instead, we found a strong preference for full compensation throughout godwit flight paths.

CONCLUSIONS

Our results indicate that compensation is crucial to godwits, emphasizing the role of risk in shaping migratory behavior and raising questions about the consequences of changing wind regimes for other barrier-crossing aerial migrants.

Analysis and comparison of protein secondary structures in the rachis of avian flight feathers

Avians have evolved many different modes of flying as well as various types of feathers for adapting to varied environments. However, the protein content and ratio of protein secondary structures (PSSs) in mature flight feathers are less understood. Further research is needed to understand the proportions of PSSs in feather shafts adapted to various flight modes in different avian species. Flight feathers were analyzed in chicken, mallard, sacred ibis, crested goshawk, collared scops owl, budgie, and zebra finch to investigate the PSSs that have evolved in the feather cortex and medulla by using nondestructive attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). In addition, synchrotron radiation-based, Fourier transform infrared microspectroscopy (SR-FTIRM) was utilized to measure and analyze cross-sections of the feather shafts of seven bird species at a high lateral resolution to resolve the composition of proteins distributed within the sampled area of interest. In this study, significant amounts of α-keratin and collagen components were observed in flight feather shafts, suggesting that these proteins play significant roles in the mechanical strength of flight feathers. This investigation increases our understanding of adaptations to flight by elucidating the structural and mechanistic basis of the feather composition.

Perioperative air travel increases the risk of venous thromboembolism following lower limb arthroplasty

Purpose

Venous thromboembolism (VTE) is a significant complication following lower limb arthroplasty (LLA). There is a paucity of evidence with regard to air travel following LLA. Orthopaedic surgeons are often asked by patients regarding air travel following LLA, and there is a need for evidence to guide these patients.

Methods

This was a retrospective cohort study. We identified two cohorts, one travelling to and from the hospital by air and another, by land. All patients received routine preoperative and post-operative care, and thromboprophylaxis, as per our hospital guidelines. We collected baseline demographics, ASA score and incidence of VTE at 90 days using local patient records and a national joint registry. We also recorded data on flight time and overland distance of travel.

Results

Two hundred and forty-three patients travelled by air; mean flight time was 74 min. In total, 5498 patients travelled a mean 25.3 miles over land to the hospital. No differences in baseline demographics or ASA score were observed. Four patients developed a VTE in the flight group, with 32 patients suffering a VTE in the control group. There was a significant difference in the VTE rate between the flight and control groups (p < 0.05); the relative risk of developing a VTE in the flight group was 2.85.

Conclusions

In our cohort, perioperative short haul air travel is associated with an increased risk of VTE at 90 days following LLA. Orthopaedic surgeons must ensure that their patients are cognizant of the risks associated with perioperative air travel and take measures to minimise these risks.

Avoiding obstacles while intercepting a moving target: a miniature fly's solution

The miniature robber fly Holcocephala fusca intercepts its targets with behaviour that is approximated by the proportional navigation guidance law. During predatory trials, we challenged the interception of H. fusca performance by placing a large object in its potential flight path. In response, H. fusca deviated from the path predicted by pure proportional navigation, but in many cases still eventually contacted the target. We show that such flight deviations can be explained as the output of two competing navigational systems: pure-proportional navigation and a simple obstacle avoidance algorithm. Obstacle avoidance by H. fusca is here described by a simple feedback loop that uses the visual expansion of the approaching obstacle to mediate the magnitude of the turning-away response. We name the integration of this steering law with proportional navigation 'combined guidance'. The results demonstrate that predatory intent does not operate a monopoly on the fly's steering when attacking a target, and that simple guidance combinations can explain obstacle avoidance during interceptive tasks.

Evaluating the effects of water and food limitation on the life history of an insect using a multiple-stressor framework

Many environmental stressors naturally covary, and the frequency and duration of stressors such as heat waves and droughts are increasing globally with climate change. Multiple stressors may have additive or non-additive effects on fitness-related traits, such as locomotion, reproduction, and somatic growth. Despite its importance to terrestrial animals, water availability is rarely incorporated into multiple-stressor frameworks. Water limitation often occurs concurrently with food limitation (e.g., droughts can trigger famines), and the acquisition of water and food can be linked because water is necessary for digestion and metabolism. Thus, we investigated the independent and interactive effects of water and food limitation on life-history traits using female crickets (Gryllus firmus), which exhibit a wing dimorphism mediating a life-history trade-off between flight and fecundity. Our results indicate that traits vary in their sensitivities to environmental factors and factor-factor interactions. For example, neither environmental factor affected flight musculature, only water limitation affected survival, and food and water availability non-additively (i.e., interactively) influenced body and ovary mass. Water availability had a larger effect on traits than food availability, affected more traits than food availability, and mediated the effects of food availability. Further, life-history strategy influenced the costs of multiple stressors because females investing in flight capacity exhibited greater reductions in body and ovary mass during stress relative to females lacking flight capacity. Therefore, water is important in the multiple-stressor framework, and understanding the dynamics of covarying environmental factors and life history may be critical in the context of climate change characterized by concurrent environmental stressors.

Identification of key volatile organic compounds in aircraft cabins and associated inhalation health risks

The identification of key VOCs during flights is important in creating a satisfactory aircraft cabin environment. Two VOC databases for the building indoor environment (from 251 occupied residences) and the aircraft cabin environment (from 56 commercial flights) were compared, to determine the common compounds (detection rate (DR) > 70%) in the two environments and the characteristic VOCs (only those with high DR during flights) in aircraft cabins. Possible VOC emission sources in flights were also discussed. As TVOC is usually viewed as a general indicator of air quality, the prediction of TVOC concentration was carried out using BP neural network algorithm, and the average error between the predicted and measured values was 55.35 μg/m³ (R² = 0.80). Meanwhile, the VOCs' inhalation cancer/non-cancer risks to crew members and passengers were calculated on the basis of detection rates, exposure concentrations, and health risk assessments. Six compounds (i.e., formaldehyde, benzene, tetrachloroethylene, trichloromethane, 1,2-dichloroethane, and naphthalene) were proposed as the key VOCs in the existing aircraft cabin environment, presenting a risk to crew members that is higher than the US EPA proposed acceptable level (evaluated mean value > 1E-06). The estimated lifetime excess cancer/non-cancer risks for passengers were all below the assessment criteria. Based on a summary of various VOC limits in five built environments, hierarchical design of VOC concentration limits is recommended for the aircraft environment.

Distinct aging-vulnerable and -resilient trajectories of specific motor circuit functions in oxidation- and temperature-stressed Drosophila

In Drosophila, molecular pathways affecting longevity have been extensively studied. However, corresponding neurophysiological changes underlying aging-related functional and behavioral deteriorations remain to be fully explored. We examined different motor circuits in Drosophila across the lifespan and uncovered distinctive age-resilient and age-vulnerable trajectories in their established functional properties. In the giant-fiber (GF) and downstream circuit elements responsible for the jump-and-flight escape reflex, we observed relatively mild deterioration toward the end of lifespan. In contrast, more substantial age-dependent modifications were seen in the plasticity of GF afferent processing, specifically in use-dependence and habituation properties. In addition, there were profound changes in different afferent circuits that drive flight motoneuron activities, including flight pattern generation and seizure spike discharges evoked by electroconvulsive stimulation. Importantly, in high temperature (HT)-reared flies (29 °C), the general trends in these age-dependent trajectories were largely maintained, albeit over a compressed time scale, lending support for the common practice of HT rearing for expediting Drosophila aging studies. We discovered that shortened lifespans in Cu/Zn superoxide dismutase (Sod) mutant flies were accompanied by altered aging trajectories in motor circuit properties distinct from those in HT-reared flies, highlighting differential effects of oxidative vs temperature stressors. This work helps to identify several age-vulnerable neurophysiological parameters that may serve as quantitative indicators for assessing genetic and environmental influences on aging progression in Drosophila Significance statementComparisons of the aging trajectories of performance changes of several motor circuits in Drosophila revealed remarkably heterogeneous age-progressions. We identified "aging-resilient" and "aging-vulnerable" circuits in both normal control and flies with shortened lifespans due to either elevated rearing temperature or oxidative stress. Motor circuit components including flight motor neuron and the giant-fiber pathway responsible for the escape reflex showed only mild functional decline, whereas distinct trajectories throughout lifespan were seen in the flight pattern generator, interneuron inputs to the giant-fiber system, and circuits generating seizure discharge patterns. Notably, high-temperature rearing generally compressed aging trajectories while Sod mutation-induced oxidative stress led to distinct patterns of motor defects. Together, these results elucidate potentially salient neurophysiological markers for aging in flies.

The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.

Size constrains oxygen delivery capacity within but not between bumble bee castes

Bumble bees are eusocial, with distinct worker and queen castes that vary strikingly in size and life-history. The smaller workers rely on energetically-demanding foraging flights to collect resources for rearing brood. Queens can be 3 to 4 times larger than workers, flying only for short periods in fall and again in spring after overwintering underground. These differences between castes in size and life history may be reflected in hypoxia tolerance. When oxygen demand exceeds supply, oxygen delivery to the tissues can be compromised. Previous work revealed hypermetric scaling of tracheal system volume of worker bumble bees (Bombus impatiens); larger workers had much larger tracheal volumes, likely to facilitate oxygen delivery over longer distances. Despite their much larger size, queens had relatively small tracheal volumes, potentially limiting their ability to deliver oxygen and reducing their ability to respond to hypoxia. However, these morphological measurements only indirectly point to differences in respiratory capacity. To directly assess size- and caste-related differences in tolerance to low oxygen, we measured critical PO₂ (P_crit; the ambient oxygen level below which metabolism cannot be maintained) during both rest and flight of worker and queen bumble bees. Queens and workers had similar P_crit values during both rest and flight. However, during flight in oxygen levels near the P_crit, mass-specific metabolic rates declined precipitously with mass both across and within castes, suggesting strong size limitations on oxygen delivery, but only during extreme conditions, when demand is high and supply is low. Together, these data suggest that the comparatively small tracheal systems of queen bumble bees do not limit their ability to deliver oxygen except in extreme conditions; they pay little cost for filling body space with eggs rather than tracheal structures.

Flight system morphology and minimum flight temperature in North American cicadas (Insecta: Hemiptera: Cicadidae)

Thermal responses in cicadas have been studied for many years. The minimum flight temperature (MFT) does not show the same relationship to habitat and behavior as other thermal responses. We measured live mass, wing length, wingspan, wing area and wing loading in an attempt to correlate these morphological parameters to the MFT. We analyzed both intraspecific (in Magicicada cassinii (Fisher, 1852)) and interspecific relationships of the wing morphology and the ability of the cicadas to fly in a large number of North American cicada taxa (n=119). A total of 109 species and 10 subspecies from 17 genera, six tribes, and three subfamilies including all major North American habitats were studied. Analyses show that wing morphology (wing length, wingspan, wing area and wing loading) scales to body size as predicted by geometric similarity (all P<0.0001) for all species and wing area and wing loading (both P<0.0001) in M. cassinii. Mass (P=0.0105), wing length (P=0.0006), wingspan (P=0.0006), wing area (P=0.0055), and wing loading (P=0.0455) all demonstrate a significant correlation to MFT between species, as would be predicted by aerodynamic theory, but not within species. However, the low correlation coefficients suggest the flight system has minimal influence on the MFT of cicadas. Specific physiological adaptations appear to be responsible for the between species variability in MFT rather than being the result of modifications to the flight system morphology.

Corticosterone's roles in avian migration: Assessment of three hypotheses

While corticosterone (CORT) is often suggested to be an important hormone regulating processes necessary for avian migration, there has been no systematic assessment of CORT's role in migration. Prior to migration, birds increase fat stores and flight muscle size to prepare for the high energetic costs associated with long-distance flight. After attaining sufficient energetic stores, birds then make the actual decision to depart from their origin site. Once en route birds alternate between periods of flight and stopovers, during which they rest and refuel for their next bouts of endurance flight. Here, we evaluate three non-mutually exclusive hypotheses that have been proposed in the literature for CORT's role in migration. (1) CORT facilitates physiological preparations for migration [e.g. hyperphagia, fattening, and flight muscle hypertrophy]. (2) CORT stimulates departure from origin or stopover sites. (3) CORT supports sustained migratory travel. After examining the literature to test predictions stemming from each of these three hypotheses, we found weak support for a role of CORT in physiological preparation for migration. However, we found moderate support for a role of CORT in stimulating departures, as CORT increases immediately prior to departure and is higher when migratory restlessness is displayed. We also found moderate support for the hypothesis that CORT helps maintain sustained travel, as CORT is generally higher during periods of flight, though few studies have tested this hypothesis. We provide recommendations for future studies that would help to further resolve the role of CORT in migration.

The relationship between sternum variation and mode of locomotion in birds

BACKGROUND

The origin of powered avian flight was a locomotor innovation that expanded the ecological potential of maniraptoran dinosaurs, leading to remarkable variation in modern birds (Neornithes). The avian sternum is the anchor for the major flight muscles and, despite varying widely in morphology, has not been extensively studied from evolutionary or functional perspectives. We quantify sternal variation across a broad phylogenetic scope of birds using 3D geometric morphometrics methods. Using this comprehensive dataset, we apply phylogenetically informed regression approaches to test hypotheses of sternum size allometry and the correlation of sternal shape with both size and locomotory capabilities, including flightlessness and the highly varying flight and swimming styles of Neornithes.

RESULTS

We find evidence for isometry of sternal size relative to body mass and document significant allometry of sternal shape alongside important correlations with locomotory capability, reflecting the effects of both body shape and musculoskeletal variation. Among these, we show that a large sternum with a deep or cranially projected sternal keel is necessary for powered flight in modern birds, that deeper sternal keels are correlated with slower but stronger flight, robust caudal sternal borders are associated with faster flapping styles, and that narrower sterna are associated with running abilities. Correlations between shape and locomotion are significant but show weak explanatory power, indicating that although sternal shape is broadly associated with locomotory ecology, other unexplored factors are also important.

CONCLUSIONS

These results display the ecological importance of the avian sternum for flight and locomotion by providing a novel understanding of sternum form and function in Neornithes. Our study lays the groundwork for estimating the locomotory abilities of paravian dinosaurs, the ancestors to Neornithes, by highlighting the importance of this critical element for avian flight, and will be useful for future work on the origin of flight along the dinosaur-bird lineage.

Body size affects immune cell proportions in birds and non-volant mammals, but not bats

Powered flight has evolved several times in vertebrates and constrains morphology and physiology in ways that likely have shaped how organisms cope with infections. Some of these constraints probably have impacts on aspects of immunology, such that larger fliers might prioritize risk reduction and safety. Addressing how the evolution of flight may have driven relationships between body size and immunity could be particularly informative for understanding the propensity of some taxa to harbor many virulent and sometimes zoonotic pathogens without showing clinical disease. Here, we used a comparative framework to quantify scaling relationships between body mass and the proportions of two types of white blood cells - lymphocytes and granulocytes (neutrophils/heterophils) - across 63 bat species, 400 bird species and 251 non-volant mammal species. By using phylogenetically informed statistical models on field-collected data from wild Neotropical bats and from captive bats, non-volant mammals and birds, we show that lymphocyte and neutrophil proportions do not vary systematically with body mass among bats. In contrast, larger birds and non-volant mammals have disproportionately higher granulocyte proportions than expected for their body size. Our inability to distinguish bat lymphocyte scaling from birds and bat granulocyte scaling from all other taxa suggests there may be other ecological explanations (i.e. not flight related) for the cell proportion scaling patterns. Future comparative studies of wild bats, birds and non-volant mammals of similar body mass should aim to further differentiate evolutionary effects and other aspects of life history on immune defense and its role in the tolerance of (zoonotic) infections.

Psychophysiological response of military pilots in different combat flight maneuvers in a flight simulator

OBJECTIVE

To analyze the psychophysiological response during takeoff, landing, air-air attack and air-ground attack maneuvers.

METHODS

A total of 11 expert pilots (age=33.36 (5.37)) from the Spanish Air Force participated in this cross-sectional study. Participants had to complete in a flight simulator the following missions: 1) takeoff; 2) Air-air attack; 3) Air-Ground attack, and 4) Landing. The electroencephalographic activity (EEG) and heart rate variability (HRV) were collected during all these maneuvers.

RESULTS

Significant higher values of theta (during takeoff, air-air attack and air-ground attack) EEG power spectrum were obtained when compared to baseline. Significant difference in the P3 scalp location was observed between landing and takeoff maneuvers in the beta EEG power spectrum. Furthermore, significant lower values of HRV were obtained during takeoff, landing, air-air attack and air-ground attack when compared to baseline values. Also, landing showed a higher sympathetic response when compared to takeoff maneuver.

CONCLUSION

Takeoff, landing, air-air attack or air-ground attack maneuvers performed in a flight simulator produced significant changes in the electroencephalographic activity and autonomic modulation of professional pilots. Beta EEG power spectrum modifications suggest that landing maneuvers induced more attentional resources than takeoff. In the same line, a reduced HRV during landing was obtained when compared to takeoff. These results should be considered to training purposes.

A review: Learning from the flight of beetles

Some Coleoptera (popularly referred to as beetles) can fly at a low Reynolds number with their deployable hind wings, which directly enables a low body weight-a good bioinspiration strategy for miniaturization of micro-air vehicles (MAVs). The hind wing is a significant part of the body and has a folding/unfolding mechanism whose unique function benefits from different structures and materials. This review summarizes the actions, factors, and mechanisms of beetle flight and bioinspired MAVs with deployable wings. The elytron controlled by muscles is the protected part for the folded hind wing and influences flight performance. The resilin, the storage material for elasticity, is located in the folding parts. The hind wings' folding/unfolding mechanism and flight performance can be influenced by vein structures of hollow, solid and wrinkled veins, the hemolymph that flows in hollow veins and its hydraulic mechanism, and various mechanical properties of veins. The action of beetle flight includes flapping flight, hovering, gliding, and landing. The hind wing is passively deformed through force and hemolymph, and the attack angle of the hind wing and the nanomechanics of the veins, muscles and mass body determine the flight performance. Based these factors, bioinspired MAVs with a new deployable wing structure and new materials will be designed to be much more effective and miniaturized. The new fuels and energy supply are significant aspects of MAVs.

Physiological demands and nutrient intake modulate a trade-off between dispersal and reproduction based on age and sex of field crickets

Animals adjust resource acquisition throughout life to meet changing physiological demands of growth, reproduction, activity and somatic maintenance. Wing-polymorphic crickets invest in either dispersal or reproduction during early adulthood, providing a system in which to determine how variation in physiological demands, determined by sex and life history strategy, impact nutritional targets, plus the consequences of nutritionally imbalanced diets across life stages. We hypothesized that high demands of biosynthesis (especially oogenesis in females) drive elevated resource acquisition requirements and confer vulnerability to imbalanced diets. Nutrient targets and allocation into key tissues associated with life history investments were determined for juvenile and adult male and female field crickets (Gryllus lineaticeps) when given a choice between two calorically equivalent but nutritionally imbalanced (protein- or carbohydrate-biased) artificial diets, or when restricted to one imbalanced diet. Flight muscle synthesis drove elevated general caloric requirements for juveniles investing in dispersal, but flight muscle quality was robust to imbalanced diets. Testes synthesis was not costly, and life history investments by males were insensitive to diet composition. In contrast, costs of ovarian synthesis drove elevated caloric and protein requirements for adult females. When constrained to a carbohydrate-biased diet, ovary synthesis was reduced in reproductive morph females, eliminating their advantage in early life fecundity over the dispersal morph. Our findings demonstrate that nutrient acquisition modulates dispersal-reproduction trade-offs in an age- and sex-specific manner. Declines in food quality will thus disproportionately affect specific cohorts, potentially driving demographic shifts and altering patterns of life history evolution.

When it's hot and dry: life-history strategy influences the effects of heat waves and water limitation

The frequency, duration and co-occurrence of several environmental stressors, such as heat waves and droughts, are increasing globally. Such multiple stressors may have compounding or interactive effects on animals, resulting in either additive or non-additive costs, but animals may mitigate these costs through various strategies of resource conservation or shifts in resource allocation. Through a factorial experiment, we investigated the independent and interactive effects of a simulated heat wave and water limitation on life-history, physiological and behavioral traits. We used the variable field cricket, Gryllus lineaticeps, which exhibits a wing dimorphism that mediates two distinct life-history strategies during early adulthood. Long-winged individuals invest in flight musculature and are typically flight capable, whereas short-winged individuals lack flight musculature and capacity. A comprehensive and integrative approach with G. lineaticeps allowed us to examine whether life-history strategy influenced the costs of multiple stressors as well as the resulting cost-limiting strategies. Concurrent heat wave and water limitation resulted in largely non-additive and single-stressor costs to important traits (e.g. survival and water balance), extensive shifts in resource allocation priorities (e.g. reduced prioritization of body mass) and a limited capacity to conserve resources (e.g. heat wave reduced energy use only when water was available). Life-history strategy influenced the emergency life-history stage because wing morphology and stressor(s) interacted to influence body mass, boldness behavior and immunocompetence. Our results demonstrate that water availability and life-history strategy should be incorporated into future studies integrating important conceptual frameworks of stress across a suite of traits - from survival and life history to behavior and physiology.

Bats and birds as viral reservoirs: A physiological and ecological perspective

The birds (class Aves) and bats (order Chiroptera, class Mammalia) are well known natural reservoirs of a diverse range of viruses, including some zoonoses. The only extant volant vertebrates, bats and birds have undergone dramatic adaptive radiations that have allowed them to occupy diverse ecological niches and colonize most of the planet. However, few studies have compared the physiology and ecology of these ecologically, and medically, important taxa. Here, we review convergent traits in the physiology, immunology, flight-related ecology of birds and bats that might enable these taxa to act as viral reservoirs and asymptomatic carriers. Many species of birds and bats are well adapted to urban environments and may host more zoonotic pathogens than species that do not colonize anthropogenic habitats. These convergent traits in birds and bats and their ecological interactions with domestic animals and humans increase the potential risk of viral spillover transmission and facilitate the emergence of novel viruses that most likely sources of zoonoses with the potential to cause global pandemics.

Resilin matrix distribution, variability and function in Drosophila

Background

Elasticity prevents fatigue of tissues that are extensively and repeatedly deformed. Resilin is a resilient and elastic extracellular protein matrix in joints and hinges of insects. For its mechanical properties, Resilin is extensively analysed and applied in biomaterial and biomedical sciences. However, there is only indirect evidence for Resilin distribution and function in an insect. Commonly, the presence of dityrosines that covalently link Resilin protein monomers (Pro-Resilin), which are responsible for its mechanical properties and fluoresce upon UV excitation, has been considered to reflect Resilin incidence.

Results

Using a GFP-tagged Resilin version, we directly identify Resilin in pliable regions of the Drosophila body, some of which were not described before. Interestingly, the amounts of dityrosines are not proportional to the amounts of Resilin in different areas of the fly body, arguing that the mechanical properties of Resilin matrices vary according to their need. For a functional analysis of Resilin matrices, applying the RNA interference and Crispr/Cas9 techniques, we generated flies with reduced or eliminated Resilin function, respectively. We find that these flies are flightless but capable of locomotion and viable suggesting that other proteins may partially compensate for Resilin function. Indeed, localizations of the potentially elastic protein Cpr56F and Resilin occasionally coincide.

Conclusions

Thus, Resilin-matrices are composite in the way that varying amounts of different elastic proteins and dityrosinylation define material properties. Understanding the biology of Resilin will have an impact on Resilin-based biomaterial and biomedical sciences.

Metabolic reduction after long-duration flight is not related to fat-free mass loss or flight duration in a migratory passerine

Migratory birds catabolize large quantities of protein during long flights, resulting in dramatic reductions in organ and muscle mass. One of the many hypotheses to explain this phenomenon is that decrease in lean mass is associated with reduced resting metabolism, saving energy after flight during refueling. However, the relationship between lean body mass and resting metabolic rate remains unclear. Furthermore, the coupling of lean mass with resting metabolic rate and with peak metabolic rate before and after long-duration flight have not previously been explored. We flew migratory yellow-rumped warblers (Setophaga coronata) in a wind tunnel under one of two humidity regimes to manipulate the rate of lean mass loss in flight, decoupling flight duration from total lean mass loss. Before and after long-duration flights, we measured resting and peak metabolism, and also measured fat mass and lean body mass using quantitative magnetic resonance. Flight duration ranged from 28 min to 600 min, and birds flying under dehydrating conditions lost more fat-free mass than those flying under humid conditions. After flight, there was a 14% reduction in resting metabolism but no change in peak metabolism. Interestingly, the reduction in resting metabolism was unrelated to flight duration or to change in fat-free body mass, indicating that protein metabolism in flight is unlikely to have evolved as an energy-saving measure to aid stopover refueling, but metabolic reduction itself is likely to be beneficial to migratory birds arriving in novel habitats.

A simple and reliable method for longitudinal assessment of untethered mosquito induced flight activity

Aedes aegypti adult females are key vectors of several arboviruses and flight activity plays a central role in mosquito biology and disease transmission. Available methods to quantify mosquito flight usually require special devices and mostly assess spontaneous locomotor activity at individual level. Here, we developed a new method to determine longitudinal untethered adult A. aegypti induced flight activity: the INduced FLight Activity TEst (INFLATE). This method was an adaptation of the "rapid iterative negative geotaxis" assay to assess locomotor activity in Drosophila and explore the spontaneous behavior of mosquitoes to fly following a physical stimulus. Insects were placed on a plastic cage previously divided in four vertical quadrants and flight performance was carried out by tapping cages towards the laboratory bench. After one minute, the number of insects per quadrant was registered by visual inspection and categorized in five different scores. By using INFLATE, we observed that flight performance was not influenced by repeated testing, sex or 5% ethanol intake. However, induced flight activity was strongly affected by aging, blood meal and inhibition of mitochondrial complex I. This simple and rapid method allows the longitudinal assessment of induced flight activity of multiple untethered mosquitoes and may contribute to a better understanding of A. aegypti dispersal biology.

In-Flight Emergency: A Simulation Case for Emergency Medicine Residents

INTRODUCTION

In-flight medical emergencies are common occurrences that require medical professionals to manage patients in an unfamiliar setting with limited resources. Emergency medicine (EM) residents should be well prepared to care for patients in unusual environments such as on an aircraft.

METHODS

We developed a simulation case for EM residents featuring a 55-year-old male passenger who suffers a cardiac arrest secondary to a tension pneumothorax. We conducted this case eight times during a 5-hour block of scheduled simulation time. Participants included EM residents of all training levels from one residency program. We arranged the simulation lab as an airplane cabin, with rows of chairs representing airplane seats and a mannequin in a window seat as the patient. Residents were expected to manage cardiac arrest and perform needle thoracostomy on the patient. Residents also evaluated and treated a flight attendant with a near syncopal episode. Throughout the case, residents were expected to practice teamwork skills, including leadership, communication, situational awareness, and resource utilization. Participants were debriefed and completed voluntary anonymous evaluations of the session.

RESULTS

Seventeen EM residents participated in the simulation. Overall, all 17 found the simulation to be a valuable educational experience. In addition, all agreed or strongly agreed that they felt more prepared to respond to an in-flight emergency after participating in the simulation.

DISCUSSION

This simulation was determined to be a valuable part of EM resident education. The challenges presented and skills practiced in this in-flight medical emergency simulation case are transferable to other resource-limited environments.

Obstacle avoidance in bumblebees is robust to changes in light intensity

Flying safely and avoiding obstacles in low light is crucial for the bumblebees that forage around dawn and dusk. Previous work has shown that bumblebees overcome the limitations of their visual system—typically adapted for bright sunlight—by increasing the time over which they sample photons. While this improves visual sensitivity, it decreases their capacity to resolve fast motion. This study investigates what effect this has on obstacle avoidance in flight, a task that requires the bees to reliably detect obstacles in the frontal visual field and to make a timely diversion to their flight path. In both bright and dim light, bumblebees avoided the 5 cm diameter obstacle at a consistent distance (22 cm) although in dim light they approached it more slowly from a distance of at least at least 80 cm. This suggests that bumblebees have an effective strategy for avoiding obstacles in all light conditions under which they are naturally active, and it is hypothesised that this is based on a time-to-contact prediction.

A simple threat-detection strategy in mice

BACKGROUND

Avoiding danger and accessing environmental resources are two fundamental, yet conflicting, survival instincts across species. To maintain a balance between these instincts, animals must efficiently distinguish approaching threats from low-threat cues. However, little is known about the key visual features that animals use to promptly detect such imminent danger and thus facilitate an immediate and appropriate behavioral response.

RESULTS

We used an automatic behavior detection system in mice to quantify innate defensive behaviors, including freezing, flight, and rearing, to a series of looming visual stimuli with varying expanding speeds and varying initial and final sizes. Looming visual stimuli within a specific "alert range" induced flight behavior in mice. Looming stimuli with an angular size of 10-40° and an expanding speed of 57-320°/s were in this range. Stimuli with relatively low expanding speeds tended to trigger freezing behavior, while those with relatively high expanding speeds tended to trigger rearing behavior. If approaching objects are in this "alert range," their visual features will trigger a flight response; however, non-threatening objects, based on object size and speed, will not.

CONCLUSIONS

These results indicate a simple strategy in mice that is used to detect predators and suggest countermeasures that predators may have taken to overcome these defensive strategies.

Maximum aerodynamic force production by the wandering glider dragonfly (Pantala flavescens, Libellulidae)

Maximum whole-body force production can influence behavioral outcomes for volant taxa, and may also be relevant to aerodynamic optimization in microair vehicles. Here, we describe a new method for measuring maximum force production in free-flying animals, and present associated data for the wandering glider dragonfly. Flight trajectories were repeatedly acquired from pull-up responses by insects dropped in mid-air with submaximal loads attached beneath the center of body mass. Forces were estimated from calculations of the maximum time-averaged acceleration through time, and multiple estimates were obtained per individual so as to statistically facilitate approximation of maximum capacity through use of the Weibull distribution. On a group level, wandering glider dragonflies were here estimated to be capable of producing total aerodynamic force equal to ∼4.3 times their own body weight, a value which significantly exceeds earlier estimates made for load-lifting dragonflies, and also for other volant taxa in sustained vertical load-lifting experiments. Maximum force production varied isometrically with body mass. Falling and recovery flight with submaximal load represents a new context for evaluating limits to force production by flying animals.

Floral vibrations by buzz-pollinating bees achieve higher frequency, velocity and acceleration than flight and defence vibrations

Vibrations play an important role in insect behaviour. In bees, vibrations are used in a variety of contexts including communication, as a warning signal to deter predators and during pollen foraging. However, little is known about how the biomechanical properties of bee vibrations vary across multiple behaviours within a species. In this study, we compared the properties of vibrations produced by Bombus terrestris audax (Hymenoptera: Apidae) workers in three contexts: during flight, during defensive buzzing, and in floral vibrations produced during pollen foraging on two buzz-pollinated plants (Solanum, Solanaceae). Using laser vibrometry, we were able to obtain contactless measures of both the frequency and amplitude of the thoracic vibrations of bees across the three behaviours. Despite all three types of vibrations being produced by the same power flight muscles, we found clear differences in the mechanical properties of the vibrations produced in different contexts. Both floral and defensive buzzes had higher frequency and amplitude velocity, acceleration and displacement than the vibrations produced during flight. Floral vibrations had the highest frequency, amplitude velocity and acceleration of all the behaviours studied. Vibration amplitude, and in particular acceleration, of floral vibrations has been suggested as the key property for removing pollen from buzz-pollinated anthers. By increasing frequency and amplitude velocity and acceleration of their vibrations during vibratory pollen collection, foraging bees may be able to maximise pollen removal from flowers, although their foraging decisions are likely to be influenced by the presumably high cost of producing floral vibrations.

The aerodynamic force platform as an ergometer

Animal flight requires aerodynamic power, which is challenging to determine accurately in vivo Existing methods rely on approximate calculations based on wake flow field measurements, inverse dynamics approaches, or invasive muscle physiological recordings. In contrast, the external mechanical work required for terrestrial locomotion can be determined more directly by using a force platform as an ergometer. Based on an extension of the recent invention of the aerodynamic force platform, we now present a more direct method to determine the in vivo aerodynamic power by taking the dot product of the aerodynamic force vector on the wing with the representative wing velocity vector based on kinematics and morphology. We demonstrate this new method by studying a slowly flying dove, but it can be applied more generally across flying and swimming animals as well as animals that locomote over water surfaces. Finally, our mathematical framework also works for power analyses based on flow field measurements.

Movement assay for the undergraduate neuroscience laboratory

Described is a design for easy-to-construct apparatus that measures movement of flying insects suitable for the undergraduate teaching laboratory. The system does not require the purchase of specialized scientific equipment or software. The apparatus can be constructed and operated without advanced knowledge in electronics or programming. The goal of this apparatus was to expand upon previous research detecting insect flight in response to radiation. We improved upon the quantification and resolution of flight across differing intensities of white light. All of this was achieved using low-cost and commonly available materials and open-source software to collect and analyze data. The only substantial prerequisites for this design are a PC with a 3.5 mm microphone input and an understanding of basic electrical connections. The apparatus was validated with comparative physiological data from two different species of butterfly.

Supplemental oxygen therapy recommendations in patients with sickle cell disease during air travel: A cross-sectional survey of North American health care providers

INTRODUCTION

Air travel may expose patients with sickle cell disease (SCD) to an increased risk of disease-related complications. Several factors are felt to contribute including prolonged hypoxia, dehydration, temperature changes, and stress. The Canadian Paediatric Society (CPS) position statement, published in 2007, recommends that SCD patients use supplemental oxygen on flights. While the National Heart, Lung and Blood Institute (NHLBI) recommend that SCD patients dress warmly, stay hydrated, and move about the cabin. Other guidelines do not make specific recommendations.

METHODS

A cross-sectional online survey was circulated through the Canadian Hemoglobinopathy Association (CanHaem) and American Society of Pediatric Hematology and Oncology (ASPHO) listservs to North American health care practitioners (HCPs). Participants were asked to share their air travel recommendations for patients with SCD. Similarly, a patient survey regarding experiences with air travel was circulated through the Sickle Cell Disease Association of Canada (SCDAC) and the Sickle Cell Foundation of Alberta (SCFOA) listservs and discussion boards.

RESULTS

Although air travel is perceived to be a risk factor for sickling complications, only 18% of HCPs recommend supplemental oxygen. Most HCPs advise patients to increase hydration, carry analgesics, and wear warm clothes to prevent sickling complications. The patient survey was limited by a low response rate.

CONCLUSION

The majority of HCPs are not routinely recommending prophylactic oxygen to patients with SCD during air travel.