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A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes.

Publication ,  Journal Article
Holt, AL; Sweeney, AM; Johnsen, S; Morse, DE
Published in: Journal of the Royal Society, Interface
October 2011

Cephalopods possess a sophisticated array of mechanisms to achieve camouflage in dynamic underwater environments. While active mechanisms such as chromatophore patterning and body posturing are well known, passive mechanisms such as manipulating light with highly evolved reflectors may also play an important role. To explore the contribution of passive mechanisms to cephalopod camouflage, we investigated the optical and biochemical properties of the silver layer covering the eye of the California fishery squid, Loligo opalescens. We discovered a novel nested-spindle geometry whose correlated structure effectively emulates a randomly distributed Bragg reflector (DBR), with a range of spatial frequencies resulting in broadband visible reflectance, making it a nearly ideal passive camouflage material for the depth at which these animals live. We used the transfer-matrix method of optical modelling to investigate specular reflection from the spindle structures, demonstrating that a DBR with widely distributed thickness variations of high refractive index elements is sufficient to yield broadband reflectance over visible wavelengths, and that unlike DBRs with one or a few spatial frequencies, this broadband reflectance occurs from a wide range of viewing angles. The spindle shape of the cells may facilitate self-assembly of a random DBR to achieve smooth spatial distributions in refractive indices. This design lends itself to technological imitation to achieve a DBR with wide range of smoothly varying layer thicknesses in a facile, inexpensive manner.

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Published In

Journal of the Royal Society, Interface

DOI

EISSN

1742-5662

ISSN

1742-5689

Publication Date

October 2011

Volume

8

Issue

63

Start / End Page

1386 / 1399

Related Subject Headings

  • Spectrum Analysis
  • Scattering, Radiation
  • Refractometry
  • Optical Phenomena
  • Ocular Physiological Phenomena
  • Microscopy, Atomic Force
  • Microscopy
  • Loligo
  • General Science & Technology
  • Eye
 

Citation

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Holt, A. L., Sweeney, A. M., Johnsen, S., & Morse, D. E. (2011). A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes. Journal of the Royal Society, Interface, 8(63), 1386–1399. https://doi.org/10.1098/rsif.2010.0702
Holt, Amanda L., Alison M. Sweeney, Sönke Johnsen, and Daniel E. Morse. “A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes.Journal of the Royal Society, Interface 8, no. 63 (October 2011): 1386–99. https://doi.org/10.1098/rsif.2010.0702.
Holt AL, Sweeney AM, Johnsen S, Morse DE. A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes. Journal of the Royal Society, Interface. 2011 Oct;8(63):1386–99.
Holt, Amanda L., et al. “A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes.Journal of the Royal Society, Interface, vol. 8, no. 63, Oct. 2011, pp. 1386–99. Epmc, doi:10.1098/rsif.2010.0702.
Holt AL, Sweeney AM, Johnsen S, Morse DE. A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes. Journal of the Royal Society, Interface. 2011 Oct;8(63):1386–1399.
Journal cover image

Published In

Journal of the Royal Society, Interface

DOI

EISSN

1742-5662

ISSN

1742-5689

Publication Date

October 2011

Volume

8

Issue

63

Start / End Page

1386 / 1399

Related Subject Headings

  • Spectrum Analysis
  • Scattering, Radiation
  • Refractometry
  • Optical Phenomena
  • Ocular Physiological Phenomena
  • Microscopy, Atomic Force
  • Microscopy
  • Loligo
  • General Science & Technology
  • Eye