Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants

Shi, Norman Nan; Tsai, Cheng‐Chia; Camino, Fernando; Bernard, Gary D.; Yu, Nanfang; Wehner, Rüdiger

doi:10.1126/science.aab3564

Cited by 602 publications

(401 citation statements)

References 25 publications

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“…Therefore, we cannot exclude the possibility that the high levels of constitutive HSC70 detected in whole-body extracts from C. bombycina stem from the localised accumulation of HSC70 in specific tissues. Moreover, hairs have elevated transmissivity in the mid-infrared range, allowing radiation to bypass the ant's protective coat more readily at those wavelengths (Shi et al, 2015). As a consequence, we may have observed similar mortality rates in the two species because our experimental design did not reproduce the natural balance of incoming solar energy.…”

Section: Heat Hardening and Thermotolerancementioning

confidence: 74%

“…Indeed, recent studies have shown that the dorsal side of C. bombycina workers (but not of C. mauritanica workers) is covered by a unique array of prism-shaped hairs that reflect incident sunlight and are responsible for the species' silver colour ( Fig. 1) (Shi et al, 2015;Willot et al, 2016). The hairs are thermally protective in the visible and near-infrared range of the electromagnetic spectrum, reducing the absorption of sunlight energy and leading to lower internal body temperatures in workers.…”

Section: Heat Hardening and Thermotolerancementioning

confidence: 99%

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Proteome stability, heat hardening, and heat-shock protein expression profiles in Cataglyphis desert ants

Willot

Gueydan

Aron

2017

Journal of Experimental Biology

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In ectotherms, high temperatures impose physical limits, impeding activity. Exposure to high heat levels causes various deleterious and lethal effects, including protein misfolding and denaturation. Thermophilic ectotherms have evolved various ways to increase macromolecular stability and cope with elevated body temperatures; these include the high constitutive expression of molecular chaperones. In this study, we investigated the effect of moderate to severe heat shock (37-45°C) on survival, heat hardening, protein damage and the expression of five heat tolerance-related genes (hsc70-4 h1, hsc70-4 h2, hsp83, hsc70-5 and hsf1) in two closely related Cataglyphis ants that occur in distinct habitats. Our results show that the highly thermophilic Sahara ant Cataglyphis bombycina constitutively expresses HSC70 at higher levels, but has lower induced expression of heat tolerance-related genes in response to heat shock, as compared with the more mesophilic Cataglyphis mauritanica found in the Atlas Mountains. As a result, C. bombycina demonstrates increased protein stability when exposed to acute heat stress but is less disposed to acquiring induced thermotolerance via heat hardening. These results provide further insight into the evolutionary plasticity of the hsp gene expression system and subsequent physiological adaptations in thermophilous desert insects to adapt to harsh environmental conditions.

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Section: Heat Hardening and Thermotolerancementioning

confidence: 74%

Section: Heat Hardening and Thermotolerancementioning

confidence: 99%

Proteome stability, heat hardening, and heat-shock protein expression profiles in Cataglyphis desert ants

Willot

Gueydan

Aron

2017

Journal of Experimental Biology

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“…Yu and co-workers recently reported the thermoregulatory strategies that enable Saharan silver ants to forage in the midday sun on the desert surface where temperatures can reach 70 • C (which is not survivable by their primary predators). It was found that a monolayer of densely packed hairs with peculiar triangular cross-sections, in some sense a biological "metasurface", enhances not only the ant body's reflectivity in the visible and near-infrared, where solar radiation culminates, but also its emissivity in the midinfrared [248]. The combined effect enables the ants to minimize absorption from solar radiation, and to efficiently dissipate heat back to the surroundings via blackbody radiation.…”

Section: Discussionmentioning

confidence: 99%

A review of metasurfaces: physics and applications

2016

Self Cite

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Abstract. Metamaterials are composed of periodic subwavelength metal/dielectric structures that resonantly couple to the electric and/or magnetic components of the incident electromagnetic fields, exhibiting properties that not found in nature. This class of micro-and nano-structured artificial media have attracted great interest during the past 15 years and yielded ground-breaking electromagnetic and photonic phenomena. However, the high losses and strong dispersion associated with the resonant responses and the use of metallic structures, as well as the difficulty in fabricating the micro-and nanoscale 3D structures, have hindered practical applications of metamaterials. Planar metamaterials with subwavelength thickness, or metasurfaces, consisting of single-layer or few-layer stacks of planar structures can be readily fabricated using lithography and nanoprinting methods, and the ultrathin thickness in the wave propagation direction can greatly suppress the undesirable losses. Metasurfaces enable a spatially varying optical response (e.g., scattering amplitude, phase, and polarization), mold optical wavefronts into shapes that can be designed at will, and facilitate the integration of functional materials to accomplish active control and greatly enhanced nonlinear response. This paper reviews recent progress in the physics of metasurfaces operating at wavelengths ranging from microwave to visible. We provide an overview of key metasurface concepts such as anomalous reflection and refraction, and introduce metasurfaces based on the PancharatnamBerry phase and Huygens' metasurfaces, as well as their use in wavefront shaping and beam forming applications, followed by a discussion of polarization conversion in fewlayer metasurfaces and their related properties. An overview of dielectric metasurfaces reveals their ability to realize unique functionalities coupled with Mie resonances and their low ohmic losses. We also describe metasurfaces for wave guidance and radiation control, as well as active and nonlinear metasurfaces. Finally, we conclude by providing our opinions of future developments in this rapidly developing research field.

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“…Desert silver ants have relatively high solar reflecting backs so they can find food in the fierce daytime heat to avoid night predators [104]. A most important example is leaves.…”

Section: Mimicking Natural Nanostructuresmentioning

confidence: 99%

Nanophotonics-enabled smart windows, buildings and wearables

Smith¹,

Gentle²,

Arnold³

et al. 2016

Nanophotonics

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Design and production of spectrally smart windows, walls, roofs and fabrics has a long history, which includes early examples of applied nanophotonics. Evolving nanoscience has a special role to play as it provides the means to improve the functionality of these everyday materials. Improvement in the quality of human experience in any location at any time of year is the goal. Energy savings, thermal and visual comfort indoors and outdoors, visual experience, air quality and better health are all made possible by materials, whose "smartness" is aimed at designed responses to environmental energy flows. The spectral and angle of incidence responses of these nanomaterials must thus take account of the spectral and directional aspects of solar energy and of atmospheric thermal radiation plus the visible and color sensitivity of the human eye. The structures required may use resonant absorption, multilayer stacks, optical anisotropy and scattering to achieve their functionality. These structures are, in turn, constructed out of particles, columns, ultrathin layers, voids, wires, pure and doped oxides, metals, polymers or transparent conductors (TCs). The need to cater for wavelengths stretching from 0.3 to 35 µm including ultraviolet-visible, near-infrared (IR) and thermal or Planck radiation, with a spectrally and directionally complex atmosphere, and both being dynamic, means that hierarchical and graded nanostructures often feature. Nature has evolved to deal with the same energy flows, so biomimicry is sometimes a useful guide.

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Keeping cool: Enhanced optical reflection and radiative heat dissipation in Saharan silver ants

Cited by 602 publications

References 25 publications

Proteome stability, heat hardening, and heat-shock protein expression profiles in Cataglyphis desert ants

Proteome stability, heat hardening, and heat-shock protein expression profiles in Cataglyphis desert ants

A review of metasurfaces: physics and applications

Nanophotonics-enabled smart windows, buildings and wearables

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