Photonic Crystal Light Collectors in Fish Retina Improve Vision in Turbid Water

Abstract

Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal-lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization.

Cross-modal object recognition and dynamic weighting of sensory inputs in a fish

“…This finding suggests that in the absence of any electrical input, the visual information was no longer overwritten and the behavioral output was driven by the visual input, supporting the hypothesis that when intact, the ability to discriminate between the objects visually was masked by the dominance of the active electric sense. At short range, the reliability of the electric sense exceeds that of the visual sense, which has a relatively low spatial resolution (minimal visual angle of about 3°) (26,39,40). In contrast, active electrolocation provides the fish with fine-scale 3D spatial information and additionally informs the fish about the electrical properties of an object (41,42).…”

“…S2). Red color was used because the cones of G. petersii are most sensitive to red light (absorption maximum: 615 nm) (26).…”

“…This finding suggests that these complex cognitive abilities are present in fish in addition to mammals, and therefore do not require a cerebral cortex. dim light and in turbid waters (26). Previous studies have shown that the visual and electrosensory inputs can be integrated when sensing the surroundings (27), and both senses provide spatial information (matching content) about objects.…”

“…Active electrolocation is a near-field sense, which works only at short distances from the fish (22). In addition to this active electric sense, G. petersii possess a visual system with highly specialized eyes (26). The visual system is adapted to the crepuscular and nocturnal activity of the fish and their habitat (turbid black water streams in Central and West Africa).…”

Deformable and conformal silk hydrogel inverse opal

“…Light waves in these energy regions are also efficiently reflected; this phenomenon is known by different names, such as opalescence, structural color, and photonic band gap. Creatures in nature have evolved to exploit the properties of PhCs, with examples including antireflective nipple arrays in compound eyes, and 3D cuticle PhCs for broad-angle reflection that many scientists have been trying to mimic (6,7). For biomedical application, artificial biomimetic PhCs are potentially useful as ocular prostheses or highly sensitive biosensors.…”