Marine biologists have made a groundbreaking discovery while studying the light-emitting organs of bioluminescent fish species. They identified needle-shaped guanine crystals that scatter and redirect light, providing potential inspiration for developing more efficient biomedical and optical devices.
Sigmapus gracilis. Image credit: Wu Quancheng / Taiwan Agriculture Commission Fisheries Research Institute.
Approximately 75% of marine organisms exhibit bioluminescence, featuring specialized light-emitting organs known as photophores.
These luminous organisms utilize emitted light for various purposes, including mate attraction, prey luring, and predator evasion.
Notably, bioluminescent fish possess unique crystal structures called guanine platelets that significantly contribute to their light emission.
While all bioluminescent fish have luminescent vacuoles and platelets, the quantity, placement, and shape of these biological structures differ across species.
In a recent study led by researchers from Hiroshima University, including Masakazu Iwasaka, the light control mechanisms within the luminescent vesicles of the deep-sea fish Sigmapus gracilis were investigated.
The team found that localized layers of guanine platelets not only reflect light but also scatter it in intricate patterns.
“During our deep-sea fish studies aboard a research vessel, we realized traditional lab materials might not yield the insights we needed,” Dr. Iwasaka noted.
“This epiphany led me to explore biomimetics, inspired by the unique phenomena observed in the field.”
“Both my own observations and prior research indicate that guanine crystals can form surface layers on luminescent vacuoles in select fish species.”
“Our findings confirmed significant anisotropic reflection, meaning the reflected light varies considerably based on the incident angle.”
“This suggests that guanine crystals have a previously unrecognized role in light directionality control.”
Guanine platelets in Sigmapus gracilis exhibit needle-like structures that cluster around the light organ.
Upon light interaction, the unique shape of the guanine crystals results in scattering effects.
“In previous research, I demonstrated that guanine crystals in goldfish function as tiny mirrors, where their slightly tilted orientation causes anisotropic reflections,” Dr. Iwasaka explained.
“Conversely, the elongated crystals in this study act more like prisms, redirecting light instead of merely reflecting it.”
“Their layered configuration exhibits qualities reminiscent of photonic crystals.”
The layered crystalline structures of guanine platelets reveal insights for highly efficient biomimetic designs aimed at maximizing and reusing leaked light rather than allowing mere reflection.
The researchers tested various orientations of the guanine crystals with an electromagnet and analyzed the scattering patterns generated by an external light source at different angles.
Given that these small structures operate underwater, the findings could significantly enhance the design of implantable biomedical devices.
Professor Iwasaka remarked, “While deep-sea fish are challenging to obtain for research, their value is immeasurable.”
“Examining guanine in diverse fish species will yield valuable knowledge in biomimetics.”
The results are published in this week’s issue of Biointerphases here.
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Masakazu Iwasaka et al. 2026. Biomimetic illumination enhancement inspired by guanine platelets on luminophoric surfaces of deep-sea bristle mice Sigmapus gracilis. Biointerphases 21, 031003;doi: 10.1116/6.0005382
Source: www.sci.news
