Long-Wavelength Reflecting Filters Found in the Larval Retinas of One Mantis Shrimp Family (Nannosquillidae)

Abstract

Animals are known to exploit either transmissive coloured filters or reflectors for adaptive visual benefits. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of stomatopod crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153 ± 5 nm. Axial illumination of these intrarhabdomal structures in vivo produces a narrow-band of yellow reflectance (mean peak reflectivity at 572 ± 18 nm). While analogous visual structures are not known in nature, the optical performance of these intrarhabdomal structural reflectors is similar to synthetic devices used in the optical industry, such as band gap filters, laser mirrors, or fiber Bragg gratings. The interaction of these structural filters with wavelengths of light between 475 nm and 520 nm and the animal's visual ecology together suggest that these structures may help improve the detection of pelagic bioluminescence in shallow water at night.

Angular‐Independent Photonic Pigments via the Controlled Micellization of Amphiphilic Bottlebrush Block Copolymers

“…The degree of order of the porous internal architecture of the microspheres was quantified with the structure factor -i.e., the Fourier's transform of the centre of the pores. [48,49] The structure factor allows for direct estimate of the average distance between pores and their spatial organization.…”

A tunable reflector enabling crustaceans to see but not be seen

“…The cellular extensions that interdigitate the rhabdoms are found in both the dorsal and ventral sides. This suggests that the reflective cells may serve a secondary function that directly enhances vision—either as an additional screen between photoreceptors ( 20 ) to improve acuity or as a lateral tapetum-like structure that improves sensitivity during activity in dim light environments ( 21 ).…”

Colour vision in stomatopod crustaceans

“…The compound eyes of the planktonic larvae of mantis shrimps are quite simple, resembling those of most crustacean larvae (but see [48,49]). This fundamental design is amenable to remodelling into the various types of adult eyes ( [50]; see also [51]).…”