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Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies. peerReviewed

In opaque butterflies and moths, scales ensure vital functions like camouflage, thermoregulation, and hydrophobicity. Wing transparency in some species – achieved via modified or absent scales – raises the question of whether hydrophobicity can be maintained and of it dependence on scale microstructural (scale presence, morphology, insertion angle, and coloration) and nanostructural (ridge spacing and width) features. To address these questions, we assessed hydrophobicity in 23 clearwing species differing in scale micro and nanofeatures by measuring static contact angle (CA) of water droplets in the opaque and transparent patches of the same individuals at different stages of evaporation. We related these measures to wing structures (macro, micro, and nano) and compared them to predictions from Cassie-Baxter and Wenzel models. We found that overall, transparency is costly for hydrophobicity and this cost depends on scale microstructural features: transparent patches are less hydrophobic and lose more hydrophobicity with water evaporation than opaque patches. This loss is attenuated for higher scale densities, coloured scales (for erect scales), and when combining two types of scales (piliform and lamellar). Nude membranes show lowest hydrophobicity. Best models are Cassie-Baxter models that include scale microstructures for erect scales, and scale micro and nanostructures for flat scales. All findings are consistent with the physics of hydrophobicity, especially on multiscale roughness. Finally, wing hydrophobicity negatively relates to optical transparency. Moreover, tropical species have more hydrophobic transparent patches but similarly hydrophobic opaque patches compared to temperate species. Overall, diverse microstructures are likely functional compromises between multiple requirements. Significance Statement Water repellency is vital for terrestrial organisms. Yet, how microstructural diversity may impact hydrophobicity is unknown. Bridging the gap between biology and physics, we exploit the microstructural diversity found in clearwing butterflies and moths to assess its impact on hydrophobicity, and its ecological relevance. Within a physical framework, we bring experimental and modelling evidence for a major role of microstructures (scale morphology, insertion angle, coloration) and multiscale roughness in determining wing hydrophobicity, with a role of nanostructures restricted to flat scales and nude membrane. For the first time, we evidence some costs for transparency, and a trade-off between optics and hydrophobicity. Beyond novel biological results, this study gives new sources of bioinspiration for applied research on transparent materials in physics.

The mechanical properties of the cell's membrane control many biological processes. Giant Unilamellar vesicle (GUV) are an easy approach to reproduce cells membrane. Micropipette aspiration is a well-known technique used to characterize their mechanical properties, though it involves long time experimentation, and huge set up. Here we present a microfluidic platform that reproduce micropipette aspiration especially by its cylindrical trap form. The main advantage is the flexibility in terms of the shape we can fabricate, as well as the multiplexing micropipette, offering high throughput measurements and finally the ability to fabricate the elements composing the micropipette by hundreds at a time. We were able first to characterize simple lipid compositions such as DOPC, POPC and Brain SM, whose bending and stretching moduli are in very good agreement with the values reported in the literature. We also characterized the effect of cholesterol on DOPC membranes: cholesterol does increase the stretching modulus of DOPC membrane but does not affect its bending modulus, making therefore the membrane stiffer. Moreover, we characterized DOPC membrane challenged with co-polymers nanoparticles which are usually used for drug delivery and which showed a softening in the membrane which could be due to the permeation effect of the NP on the membrane. As this method is versatile, by changing the shape of the cylindrical micropipette to a cross section which allows the GUVs to be trapped with a residual flow around it, we were able to have a preliminary characterization of the effect of flow on the membranes' fluidity properties. Finally, we adapted the size of the micropipette in order to characterize the viscoelastic properties of spheroids made of cancer cells. We characterized the viscosity of pancreatic cancer cells and demonstrated that it is independent on the spheroids size., Les propriétés mécaniques de la membrane cellulaire contrôlent de nombreux processus biologiques. Les vésicules unilamellaires géantes (GUV) sont une approche facile pour reproduire la membrane cellulaire. L'aspiration par micropipettes est une technique bien connue utilisée pour caractériser leurs propriétés mécaniques, bien qu'elle implique une expérimentation de longue durée pour une mesure et une configuration complexe. Nous avons développé des plates-formes microfluidique visant à intégrer l'aspiration par micropipettes. Un avantage crucial de l'approche la plus avancée que nous avons mise en place est la flexibilité en termes de forme que nous pouvons fabriquer (en particulier forme de piège cylindrique). Cette approche permet également de multiplexer des micropipettes, offrant des mesures à haut débit, et enfin la possibilité de fabriquer les éléments composant la micropipette par centaines à la fois. Nous avons d'abord pu caractériser des compositions lipidiques simples telles que DOPC, POPC et Brain SM, dont les modules de courbure et d'étirement étaient en très bon accord avec les valeurs rapportées dans la littérature. Nous avons également caractérisé l'effet du cholestérol sur les membranes DOPC : le cholestérol augmentait le module d'étirement de la membrane DOPC mais n'affectait pas son module de courbure, rendant ainsi la membrane plus rigide. De plus, nous avons caractérisé la membrane DOPC contestée avec des nanoparticules de copolymères, généralement utilisées pour l'administration de médicaments. Ces nanoparticules ont induit un ramollissement de la membrane, qui pourrait être dû à l'effet de perméabilisation des NP sur la membrane, ou à leur insertion dans les membranes provoquant des défauts. Cette méthode étant polyvalente, en changeant la forme de la micropipette cylindrique en une section transversale permettant de piéger les GUV avec un écoulement résiduel autour d'elle, nous avons pu avoir une caractérisation préliminaire de l'effet de l'écoulement sur la fluidité des membranes. Enfin, nous avons adapté la taille de la micropipette afin de caractériser les propriétés viscoélastiques des sphéroïdes, agrégats de cellules cancéreuses 3D. Nous avons caractérisé la viscosité des cellules cancéreuses du pancréas et démontré qu'elle est indépendante de la taille des sphéroïdes.