RT Journal Article
SR Electronic
T1 Gradients of orientation, composition and hydration of proteins for efficient light collection by the cornea of the horseshoe crab
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2022.02.21.481013
DO 10.1101/2022.02.21.481013
A1 Oliver Spaeker
A1 Gavin Taylor
A1 Bodo Wilts
A1 Tomáš Slabý
A1 Mohamed Ashraf Khalil Abdel-Rahman
A1 Ernesto Scoppola
A1 Clemens NZ Schmitt
A1 Michael Sztucki
A1 Jiliang Liu
A1 Luca Bertinetti
A1 Wolfgang Wagermaier
A1 Gerhard Scholtz
A1 Peter Fratzl
A1 Yael Politi
YR 2022
UL http://biorxiv.org/content/early/2022/02/21/2022.02.21.481013.abstract
AB The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. While this visual system has been extensively described before, the precise mechanism allowing vision has remained controversial. Correlating quantitative refractive index (RI) mapping and detailed structural analysis, we demonstrate how gradients of RI in the cornea result from the hierarchical organization of chitin-protein fibers, heterogeneity in protein composition and bromine doping, as well as spatial variation in water content. Combining the realistic cornea structure and measured RI gradients with full-wave optical modelling and ray-tracing approaches, we show that the light collection mechanism depends on both refraction-based graded index (GRIN) optics and total internal reflection. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle.One-sentence summary Structural hierarchy and protein hydration determine the optical performance of the cornea of L. polyphemus.Competing Interest StatementTS and MAKAR are employed by TELIGHT. All other authors declare that they have no competing interests.