![\"Sigmops](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14796e-Sigmops-gracilis.jpg\")
<\/a><\/p>\nSigmops gracilis. Image credit: Wu Quancheng \/ Fisheries Research Institute, Council of Agriculture, Taiwan.<\/p>\n
Approximately 75% of marine organisms are bioluminescent, with specialized light-emitting organs called photophores.<\/p>\n
They use the light they produce for various purposes, like attracting mates, luring prey, or confusing predators.<\/p>\n
Bioluminescent fish also have specialized crystalline structures called guanine platelets that play a key role in how their light shines.<\/p>\n
While all bioluminescent fish have photophores and platelets, the number, location, and shape of these biological structures vary in different fish.<\/p>\n
In a new study, Hiroshima University researcher Masakazu Iwasaka<\/a> investigated light control mechanisms in the photophores of the bioluminescent deep-sea bristlemouth Sigmops gracilis<\/a>.<\/p>\n He found that layers of localized guanine platelets do more than just reflect the light, they scatter the light in complex ways.<\/p>\n \u201cWhile examining deep-sea fish on board a research vessel, I realized important insights could not be obtained using only laboratory-based materials,\u201d Dr. Iwasaka said.<\/p>\n \u201cThis experience led me to explore a new direction \u2014 biomimetics inspired by unknown phenomena observed in the field.\u201d<\/p>\n \u201cBoth my own observations and previous studies have shown that guanine crystals can form layers on the surfaces of photophores in some fish species.\u201d<\/p>\n \u201cIn this study, I confirmed strong anisotropic reflection \u2014 meaning the reflected light changes significantly depending on the direction the light comes from.\u201d<\/p>\n \u201cThis suggests a previously unrecognized role guanine crystals play in controlling light direction.\u201d<\/p>\n Sigmops gracilis\u2019 guanine platelets are needle-shaped structures clustered locally around its light organs.<\/p>\n When light hits the guanine crystals, their shape causes light scattering.<\/p>\n \u201cIn earlier work, I showed that guanine crystals from goldfish act like tiny mirrors, producing anisotropic reflection due to their slightly tilted orientation,\u201d Dr. Iwasaka said.<\/p>\n \u201cIn contrast, the higher-aspect-ratio crystals studied here behave more like prisms, redirecting light rather than simply reflecting it.\u201d<\/p>\n \u201cTheir layered arrangement exhibits properties similar to photonic crystals.\u201d<\/p>\n The layered crystalline guanine platelets provide insights into highly efficient biomimetic designs that maximize and recycle leaked light, rather than just reflecting emitted light.<\/p>\n The scientists used electromagnets to test different orientations of the guanine crystals and exposed them to an external light source to record the scattering results of different light angles.<\/p>\n Since these tiny structures perform in water, insights from the study could be useful in implanted biomedical device design.<\/p>\n \u201cWhile deep-sea fish are difficult to obtain, the research is highly worthwhile,\u201d Dr. Iwasaka said.<\/p>\n \u201cInvestigating guanine in various fish species will lead to a treasure trove of biomimetics knowledge.\u201d<\/p>\n