Thin Layer Interference may Reduce the Visibility of Transparent Phantom Midge Larvae (Chaoborus trivittatus) to Predators

Abstract
The body wall of transparent aquatic animals is constructed of materials which have a higher refractive index than water. Because of this, light will reflect from their surface, making their body contours visible to predators. Electron micrographs of cuticle from the transparent pelagic stage of the phantom midge Chaoborus trivittatus reveal thin layers less than a wavelength of light thick which could alter the spectral composition of this surface reflection by acting as an interference filter. This hypothesis is supported by measurements of the reflectance of the body surface of C. trivittatus. Reflectance was lower than expected at the wavelengths which maximize contrast in aquatic environments and higher than expected at ambient background wavelengths, suggesting that interference may reduce the visibility of Chaoborus to its predators by improving the spectral matching of its body reflection to the visual background.

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