Cell News—Elephantnose, my eye!

With a penny for scale, this is the entire 48 X 48 “fish eye” array based on the Elephantnose fish eye for extreme low-light vision. Photo courtesy of Hongrui Jiang, University of Wisconsin, Madison.

An Elephantnose might sound like a stage prop from circus freak shows of a bygone era, but this very real creature, Gnathonemus petersii, is a popular aquarium fish that originally hails from murky rivers in West and Central Africa. Like other river fish from similar habitats such as the Knifefish, the Elephantnose primarily uses electric organs to navigate and locate prey along with eyesight well adapted for low-light conditions in dark and muddy water. This inspired Hongrui Jiang, an electrical engineer at the University of Wisconsin, Madison, who is also affiliated with the McPherson Eye Research Institute there, to develop an enhanced low-light imaging device based on the Elephantnose’s eye. With collaborators Hewei Liu and Yinggang Huang, Jiang described this biologically inspired photosensitivity enhancer (BPE) in a recent PNAS paper.

The Elephantnose’s ability to see in the dark (scotopic vision) is enhanced by crystalline cups that reside on the retina; the incoming light is reflected off the sidewalls of these cups and concentrated at the photoreceptors in the retina to create a brighter image. The University of Wisconsin team led by Jiang created an array of artificial eyes, 48 x 48 chambers made with reflective aluminum sidewalls coupled to image sensors that can work with current imaging technologies. They observed low-light images that were a three to four-fold improvement over conventional imaging, where low light is indistinguishable from background noise.

In addition to improved night vision goggles, the authors say that their BPE is useful for imaging in UV or near-infrared spectra, as well as all wavelengths in between. Cell imaging techniques such as bioluminescence, radioluminescence, and low-excitation fluorescence are low-light applications as well, and a world of low-light fluorescent proteins may open up if cell biologists follow their Elephantnose.

A popular aquarium fish, the elephantnose doesn’t really have a nasal trunk but it does possess eyes well adapted for hunting food in the low-light environment of murky rivers. Wikipedia photo