Whale sharks typically swim near the surface of the ocean to feed on plankton, but they can also dive into deep waters at depths of nearly 2,000 meters, and most of their biological characteristics remain a mystery to humans.
According to a new study by a group of Japanese scientists, whale sharks – the largest fish species on the planet, are capable of seeing clearly even in the dark depths of the ocean due to a mutation in their retinas.
A whale shark swimming off the coast of Nice, France. (Photo: AFP/TTXVN).
This mutation also leads to night blindness in humans, a type of vision impairment many people experience at night or in low-light environments.
The study indicates that the gene mutation in whale sharks’ eyes activates visual pigments that detect blue light—the only color that penetrates deep into the ocean, based on temperature changes.
Whale sharks typically swim near the ocean’s surface to feed on plankton, but they can also dive into deep waters at depths nearing 2,000 meters, and most of their biological characteristics remain a mystery to humans.
To better understand how these creatures can see in both the bright surface waters and the dark depths of the ocean, researchers focused on analyzing rhodopsin—a type of protein in the retinal cells that allows for vision in low-light conditions.
They discovered that the rhodopsin protein—which is usually sensitive to green light—has mutated in whale sharks to become more sensitive to blue light.
This change in amino acid composition allows whale sharks to see better in the light-deficient environment at the ocean floor, while a similar change in humans leads to night blindness.
Professor Shigehiro Kuraku from the National Institute of Genetics, who participated in the study, stated that while rhodopsin in whale sharks degrades upon exposure to heat, it still functions effectively in the cold waters of the deep ocean.
The light-sensitive pigments in whale sharks adapt according to temperature.
The research, conducted by scientists from the National Institute of Genetics, Osaka Metropolitan University, Okinawa Churashima Foundation, and RIKEN Center for Biosystems Dynamics Research, was published in the Proceedings of the National Academy of Sciences.
