The reflection superposition compound eye: new paradigms in biomineralization?

The reflection superposition compound eye, found in decapod crustaceans represents a spectacularly complex natural optical device based on biominerals. The eye contains a multilayer reflector in the distal part of the eye to focus light onto the retina and a reflecting tapetum layer which increases light sensitivity.

Using an array of physical techniques, including the use of synchrotron radiation we will determine the chemical identity of photonic crystals isolated from the eyes of the crayfish C. quadricarinatus and the prawn M. rosenbergii. We recently determined that magnesium lactate dihydrate, a previously unknown biomineral is present in the reflector material. Using cryo-SEM, we will determine the ultrastructural arrangement of photonic crystals in the distal and tapetal layers under life-like conditions. We will relate the crystal structure, crystal morphology and eye ultrastructural properties to understand better the overall optical function of the eye.

In collaboration with Prof. Amir Sagi (Ben-Gurion University), we will study the mechanism of crystal formation by observing changes in the distal reflecting layer in the eye of M. rosenbergii during development from larvae to adult. By studying gene expression during ontogeny a list of 'candidate genes' will be drawn up and their possible role in the biomineralization pathway will be explored by a series of gene silencing experiments.

A deeper understanding of the reflector materials in the eye could yield applications in material optics and uncover new paradigms in biologically controlled crystal formation which will have a wide impact in the fields of biomineralization, materials science and pharmacy.