A wrinkle in flight: the role of elastin fibres in the mechanical behaviour of bat wing membranes

Bats fly using a thin wing membrane composed of compliant, anisotropic skin. Wing membrane skin deforms dramatically as bats fly, and its three-dimensional configurations depend, in large part, on the mechanical behaviour of the tissue. Large, macroscopic elastin fibres are an unusual mechanical element found in the skin of bat wings. We characterize the fibre orientation and demonstrate that elastin fibres are responsible for the distinctive wrinkles in the surrounding membrane matrix. Uniaxial mechanical testing of the wing membrane, both parallel and perpendicular to elastin fibres, is used to distinguish the contribution of elastin and the surrounding matrix to the overall membrane mechanical behaviour. We find that the matrix is isotropic within the plane of the membrane and responsible for bearing load at high stress; elastin fibres are responsible for membrane anisotropy and only contribute substantially to load bearing at very low stress. The architecture of elastin fibres provides the extreme extensibility and self-folding/self-packing of the wing membrane skin. We relate these findings to flight with membrane wings and discuss the aeromechanical significance of elastin fibre pre-stress, membrane excess length, and how these parameters may aid bats in resisting gusts and preventing membrane flutter.     

Olfactory discrimination ability in short-tailed fruit bat,carollia perspicillata (Chiroptera: Phyllostomatidae)

The olfactory discrimination ability in a fruit-eating bat,Carollia perspicillata, was investigated. In a food-rewarded flight training procedure, four animals were taught to choose one of two odors simultaneously presented in a three-choice apparatus.Carollia chose the odor of ripe banana over that of unripe banana in a spontaneous choice test. With the same method, the bats significantly preferred undiluted banana odor compared to a dilution of 1 10, but did not express a preference between undiluted and 15 dilutions of ripe banana. In a series of reinforced choice tests, the positive stimulus (CS +) was the standardized odor of natural ripe banana. Prominent components of this complex odor were used as CS –, first in monomolecular form and later in combinations (odor cocktails) of increasing similarity to banana odor. In all these tests the bats easily discriminated the natural food odor from the artificial ones. Even a gas Chromatographic congruity of 57% between the major components of natural banana odor and an odor cocktail caused no impairment of the olfactory performance. The olfactory discrimination ability ofCarollia perspicillata supports the assumption that echolocating, frugivorous bats may use their sense of smell to find and select their food.     

中国传统建筑“蝠饰”及其文化意义探析

人类源自对自然力的敬畏产生了早期的吉祥文化,而蝙蝠图案装饰是中国古代吉祥文化中的一个重要组成部分。本文阐述了建筑吉祥图案的成因和蝙蝠图案的吉祥寓意,并重点从园林建筑两个层面深入剖析了蝙蝠装饰图案的具体艺术表现形式。     

Unpacking Pandora from Its Box: Deciphering the Molecular Basis of the SARS-CoV-2 Coronavirus

An enigmatic localized pneumonia escalated into a worldwide COVID-19 pandemic from Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This review aims to consolidate the extensive biological minutiae of SARS-CoV-2 which requires decipherment. Having one of the largest RNA viral genomes, the single strand contains the genes ORF1ab, S, E, M, N and ten open reading frames. Highlighting unique features such as stem-loop formation, slippery frameshifting sequences and ribosomal mimicry, SARS-CoV-2 represents a formidable cellular invader. Hijacking the hosts translational engine, it produces two polyprotein repositories (pp1a and pp1ab), armed with self-cleavage capacity for production of sixteen non-structural proteins. Novel glycosylation sites on the spike trimer reveal unique SARS-CoV-2 features for shielding and cellular internalization. Affording complexity for superior fitness and camouflage, SARS-CoV-2 challenges diagnosis and vaccine vigilance. This review serves the scientific community seeking in-depth molecular details when designing drugs to curb transmission of this biological armament.     

The aerodynamic cost of flight in the short-tailed fruit bat (Carollia perspicillata): comparing theory with measurement

Aerodynamic theory has long been used to predict the power required for animal flight, but widely used models contain many simplifications. It has been difficult to ascertain how closely biological reality matches model predictions, largely because of the technical challenges of accurately measuring the power expended when an animal flies. We designed a study to measure flight speed-dependent aerodynamic power directly from the kinetic energy contained in the wake of bats flying in a wind tunnel. We compared these measurements with two theoretical predictions that have been used for several decades in diverse fields of vertebrate biology and to metabolic measurements from a previous study using the same individuals. A high-accuracy displaced laser sheet stereo particle image velocimetry experimental design measured the wake velocities in the Trefftz plane behind four bats flying over a range of speeds (3–7 m s⁻¹). We computed the aerodynamic power contained in the wake using a novel interpolation method and compared these results with the power predicted by Pennycuick''s and Rayner''s models. The measured aerodynamic power falls between the two theoretical predictions, demonstrating that the models effectively predict the appropriate range of flight power, but the models do not accurately predict minimum power or maximum range speeds. Mechanical efficiency—the ratio of aerodynamic power output to metabolic power input—varied from 5.9% to 9.8% for the same individuals, changing with flight speed.     

Contextualizing avian mortality: A preliminary appraisal of bird and bat fatalities from wind,fossil-fuel,and nuclear electricity

This article explores the threats that wind farms pose to birds and bats before briefly surveying the recent literature on avian mortality and summarizing some of the problems with it. Based on operating performance in the United States and Europe, this study offers an approximate calculation for the number of birds killed per kWh generated for wind electricity, fossil-fuel, and nuclear power systems. The study estimates that wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour (GWh) of electricity while fossil-fueled power stations are responsible for about 5.2 fatalities per GWh. While this paper should be respected as a preliminary assessment, the estimate means that wind farms killed approximately seven thousand birds in the United States in 2006 but nuclear plants killed about 327,000 and fossil-fueled power plants 14.5 million. The paper concludes that further study is needed, but also that fossil-fueled power stations appear to pose a much greater threat to avian wildlife than wind and nuclear power technologies.     

A quantitative comparison of bird and bat wakes

Qualitative comparison of bird and bat wakes has demonstrated significant differences in the structure of the far wake. Birds have been found to have a unified vortex wake of the two wings, while bats have a more complex wake with gradients in the circulation along the wingspan, and with each wing generating its own vortex structure. Here, we compare quantitative measures of the circulation in the far wake of three bird and one bat species. We find that bats have a significantly stronger normalized circulation of the start vortex than birds. We also find differences in how the circulation develops during the wingbeat as demonstrated by the ratio of the circulation of the dominant start vortex and the total circulation of the same sense. Birds show a more prominent change with changing flight speed and a relatively weaker start vortex at minimum power speed than bats. We also find that bats have a higher normalized wake loading based on the start vortex, indicating higher relative induced drag and therefore less efficient lift generation than birds. Our results thus indicate fundamental differences in the aerodynamics of bird and bat flight that will further our understanding of the evolution of vertebrate flight.     

Megachiropteran bats (pteropus) utilize human referential stimuli to locate hidden food.

Spontaneous point-following behavior has been considered an indicator of advanced social cognition unique to humans. Recently, it has been suggested that a close evolutionary relationship with humans could result in similar social skills in domesticated species. An alternative view is that the mechanism is not genetic domestication alone but instead a combination of phylogenetic and ontogenetic variables. Here we test the necessity of phylogenetic domestication by investigating the point-following behavior of a captive population of nondomesticated megachiropteran bats (Pteropus pumilus, Pteropus rodricensis, Pteropus conspicillatus, Pteropus vampyrus). Three of five subjects were highly successful in following an unfamiliar human's point to a target location, providing the first empirical evidence of cross-species social referencing in bats. The three successful bats were all born in captivity and socialized to humans early in life, whereas unsuccessful bats were wild-born individuals. This study provides evidence that referential point following is not restricted to domesticated animals and indicates that early experience may be important. Megachiropteran bats may prove to be a useful model for studying social behaviors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Role of body temperature variations in bat immune response to viral infections

The ability of bats to coexist with viruses without being harmed is an interesting issue that is still under investigation. Here we use a mathematical model to show that the pattern of body temperature variations observed in bats between day and night is responsible for their ability to keep viruses in check. From the dynamical systems point of view, our model displays an intriguing quasi-periodic behaviour that might be relevant in making the system robust by avoiding viral escape due to perturbations in the body temperature cycle.     

“蝙蝠纹”艺术符号创作思维中的“造字法”运用

从丑陋的蝙蝠原形到吉祥的蝙蝠纹样是一个极具中华文化特色的艺术符号生成过程。在此艺术符号的思考、表现与解读的过程中溶入了汉字造字法"形声"、"象形"、"指事"、"会意"、"假借"的思想。这种艺术符号的创作思维对于现代艺术设计具有启示。