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Seminar Details

The structural basis for the brilliant colors of the sapphirinid copepods and the neon tetra fish

Date

28/05/2015

Lecturers

Dvir Gur - Weizmann Institute

Abstract

In animals colors are produced by either pigment coloration or structural colors. Structural colors are caused by the interaction of light with structures that have periodicities comparable to the visible light wavelengths. This leads to selective reflection of particular wavelengths through interference. Many taxa have independently evolved ways to produce structural colors using intra-cellular arrays of guanine crystals interspersed with cytoplasm. One of the most striking examples of such photonic arrays are the male sapphirinid copepods, small marine crustaceans that produce a variety of different colors. In order to understand how the different colors are produced, we designed a fully correlative experiment in which the reflectance of individual copepods was first measured using a tailor made microscope, and then the thicknesses of the crystal and cytoplasm layers were measured using cryo-SEM on the same individuals. Using this approach we were able to demonstrate that variations in cytoplasm layer thickness are mainly responsible for the different reflected colors. Furthermore, we show a strong angular dependence of the copepod color on the orientation relative to the incident light, which can account for its appearance and disappearance during spiral swimming in the natural habitat.

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