The image-forming mirror in the eye of the scallop

Palmer, Benjamin A.; Taylor, Gavin J.; Brumfeld, Vlad; Gur, Dvir; Shemesh, Mordechai; Elad, Nadav; Osherov, Aya; Oron, Dan; Weiner, Steve

doi:10.1126/science.aam9506

Cited by 105 publications

(154 citation statements)

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“…Another interesting example demonstrating the importance of the guanine metabolite-based structures is the image-forming mirror in the eye of the scallop (Palmer et al 2017b). Scallops possess a visual system comprising up to 200 eyes, each containing a concave mirror, rather than a lens, to focus the light (Fig.…”

Section: Naturally Accruing Functional Metabolite Assembliesmentioning

confidence: 99%

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Functional metabolite assemblies—a review

et al. 2018

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Metabolites are essential for the normal operation of cells and fulfill various physiological functions. It was recently found that in several metabolic disorders, the associated metabolites could self-assemble to generate amyloid-like structures, similar to canonical protein amyloids that have a role in neurodegenerative disorders. Yet, assemblies with typical amyloid characteristics are also known to have physiological function. In addition, many non-natural proteins and peptides presenting amyloidal properties have been used for the fabrication of functional nanomaterials. Similarly, functional metabolite assemblies are also found in nature, demonstrating various physiological roles. A notable example is the structural color formed by guanine crystals or fluorescent crystals in feline eyes responsible for enhanced night vision. Moreover, some metabolites have been used for the in vitro fabrication of functional materials, such as glycine crystals presenting remarkable piezoelectric properties or indigo films used to assemble organic semiconductive electronic devices. Therefore, we believe that the study of metabolite assemblies is not only important in order to understand their role in normal physiology and in pathology, but also paves a new route in exploring the fabrication of organic, bio-compatible materials.

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Section: Naturally Accruing Functional Metabolite Assembliesmentioning

confidence: 99%

“…d Crystals in adjacent layers, stacked directly on top of each other, viewed in a fracture through the mirror. e TEM micrograph of a single, regular square crystal extracted from the eye (adapted from Palmer et al 2017b with permission)…”

Section: Figmentioning

confidence: 99%

Functional metabolite assemblies—a review

et al. 2018

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“…Two types of image-forming reflective eyes are found in nature: concave mirrored eyes and reflection superposition compound eyes. The former is epitomized by the scallop eyes, which produce well-resolved images by reflecting light from a concave, guanine crystal-based mirror located at the back of the eye onto the retina above it (8,9). Similar eyes are also found in deep-sea fish (10,11) and crustaceans (12,13).…”

Section: Introductionmentioning

confidence: 95%

Isoxanthopterin: An Optically Functional Biogenic Crystal in the Eyes of Decapod Crustaceans

Palmer¹,

Hirsch

Brumfeld

et al. 2017

Preprint

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The eyes of some aquatic animals form images through reflective optics. Shrimp, lobsters, crayfish and prawns possess reflecting superposition compound eyes, composed of thousands of square-faceted eyeunits (ommatidia). Mirrors in the upper part of the eye (the distal mirror) reflect light collected from many ommatidia onto the underlying photosensitive elements of the retina, the rhabdoms. A second reflector, the tapetum, underlying the retina, back-scatters dispersed light onto the rhabdoms. Using microCT and cryo-SEM imaging accompanied by in situ micro-X-ray diffraction and micro-Raman spectroscopy, we investigated the hierarchical organization and materials properties of the reflective systems at high resolution and under close to physiological conditions. We show that the distal mirror consists of three or four layers of sparse plate-like nano-crystals. The tapetum is a diffuse reflector composed of hollow nanoparticles constructed from concentric lamellae of crystals. Isoxanthopterin, a peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/240366 doi: bioRxiv preprint first posted online Dec. 28, 2017; pteridine analog of guanine, forms both the reflectors in the distal mirror and in the tapetum. The crystal structure of isoxanthopterin was determined from crystal structure prediction calculations and verified by comparison with experimental X-ray diffraction. The extended hydrogen bonded layers of the molecules results in an extremely high calculated refractive index in the H-bonded plane, n = 1.96, which makes isoxanthopterin crystals an ideal reflecting material. The crystal structure of isoxanthopterin, together with a detailed knowledge of the reflector superstructures, provide a rationalization of the reflective optics of the crustacean eye. SignificanceAquatic animals use reflectors in their eyes either to form images or to increase photon capture.Guanine is the most widespread molecular component of these reflectors. Here we show that crystals of isoxanthopterin, a pteridine analogue of guanine, form both the image-forming 'distal' mirror and the intensity-enhancing tapetum reflector in the compound eyes of some decapod crustaceans. The crystal structure of isoxanthopterin was determined, providing an explanation for why these crystals are so well suited for efficient reflection. Pteridines were previously known only as pigments and our discovery raises the question of which other organic molecules may be used to form crystals with superior reflective properties either in organisms or in artificial optical devices.peer-reviewed)

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“…The coloring portion under the dorsal body surface of adult male sapphirinids consists of arrayed guanine hexagonal plates exposing the (100) faces. A twin structure of three guanine hexagonal plates was characterized by transmission electron microscopy (TEM) with electron diffraction [27][28][29] . Recently, the presence of an amorphous state was reported to be important for the formation of specifically structured guanine crystals 5,6,27 .…”

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Guanine crystals regulated by chitin-based honeycomb frameworks for tunable structural colors of sapphirinid copepod, Sapphirina nigromaculata

Kimura

Takasaki

Hatai

et al. 2020

Sci Rep

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Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. in the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70-100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. the structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. the framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.Structural color is generated by a combined effect of diffraction, refraction, reflection, and interference of light due to submicron-scale periodic structures 1-6 . Several organisms have characteristic parts that exhibit specific structural colors. For example, we can observe specific colors on feathers of peacock, necks of pigeon, and wings of morpho butterfly 7-9 . Adult males Sapphirina nigromaculata, which are marine zooplanktons, show tunable structural colors originating from a layered structure of guanine hexagonal plates ~1.5 µm wide and cytoplasm under the dorsal body surface 10,11 . A feature of the biological structural color on the Sapphirinid copepod is tunability from achromatic to yellow, red, and blue 12-14 . The iridescence of male sapphirinids has been reported to be optimized to communicate with non-iridescent females having relatively larger twin lens-eyes in the water column 13,14 . The disappearance of the structural color in the males is probably utilized as a defense system against visual predators, such as pelagic fishes 10,11,13,14 . The tunability of the structural colors of planktons is very interesting not only for clarification of the biological function but also for the development of biomimetic display technologies. The variation in the structural color with change in the interplate distance was reported by detailed observation using a cryo-technique for electron microscopy and an optical simulation 5,6,10,11 .An ordered array of guanine hexagonal plates ~1.5 µm wide and ~80 nm thick in each domain are regulated by flat compartments in a chitin-based honeycomb framework. Understanding the essence of the organization and regulation of tunable structural colors of S. nigroaculata would shed light on biomimetic engineering for novel coloring and display devices. experimental Structural analysis of sapphirinid copepods. Plankton samplings were conducted at 35°08.9′N 139°10.5′E in the western part of the Sagami Bay in the south ...

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The image-forming mirror in the eye of the scallop

Cited by 105 publications

References 43 publications

Functional metabolite assemblies—a review

Functional metabolite assemblies—a review

Isoxanthopterin: An Optically Functional Biogenic Crystal in the Eyes of Decapod Crustaceans

Guanine crystals regulated by chitin-based honeycomb frameworks for tunable structural colors of sapphirinid copepod, Sapphirina nigromaculata

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