Japanese rice fish detect ultraviolet rays from sunlight directly with the pituitary gland and turn their bodies black for protection, a team has found.
The findings by the team, including University of Tokyo associate professor Shinji Kanda and Okayama University assistant professor Keita Sato, were published in the U.S. journal Science recently.
Recent research had found that vertebrates including fish have receptor proteins that can detect light in cells other than those in their eyes, but their purpose was unknown.
The team suspects that animals with almost translucent bodies may have yet more systems to detect light directly.
The surface of Japanese rice fish’s body has pigment cells that receive a hormone from cells in the pituitary gland and synthesize melanin.
Cells in the gland contain the so-called Opn5m receptor protein.
The team succeeded in observing the release of melanocyte-secreting hormone from Opn5m by shining light with the same wavelength as ultraviolet A on Japanese rice fish.
