Simcheong threw herself into the Indangsu to awaken her father's eyes with three hundred seon of rice. If she had found the rice paddy first, she might not have had to sacrifice her life. Scientists have found clues for reviving human eyes in the Pomacea canaliculata that live in rice paddies.
Professor Alice Accorsi from the Department of Molecular and Cell Biology at the University of California, Davis, noted on the 6th (local time) in the international journal "Nature Communications" that they confirmed the fact that Pomacea canaliculata and human eyes share anatomical structures and genetic characteristics.
In particular, Pomacea canaliculata can regenerate eyes lost or damaged due to accidents or diseases. Professor Accorsi stated, "By revealing the remarkable eye regeneration ability of Pomacea canaliculata, we can gain insight into understanding human eye damage and even potentially propose new methods for treatment or regeneration of human eyes."
◇A new eye grows just one month after being cut
Pomacea canaliculata is a mollusk belonging to the family Ampullariidae, which is similar to a snail. Its round shell is reminiscent of an apple, thus it is called the apple snail. When fully grown, it can reach a body length of 15 cm. Originally a freshwater snail native to South America, it was brought to Japan in 1983 for consumption and later used in eco-friendly farming methods. It is larger than the native rice snail, which is why it is named Pomacea canaliculata.
Humans possess camera-like eyes. At the front is the cornea, which acts as a protective shield, followed by the lens that gathers light. At the back is the retina, where millions of photoreceptor cells convert light into electrical signals. The optic nerve transmits these electrical signals to the brain, allowing us to see objects. Pomacea canaliculata also has camera-like eyes, similar to octopuses, squids, and spiders.
Remarkably, the eyes of Pomacea canaliculata can be fully regenerated, unlike those of humans. The research team confirmed that the eye regeneration process occurs over about a month. First, the wounds that caused the eye loss are treated to prevent further infection and fluid loss. This usually takes about 24 hours. Next, undifferentiated cells migrate to the area where the eye was and proliferate. For about a week and a half, these cells differentiate and form the structures of the eye, including the lens, retina, and cornea.
Fifteen days after losing the eye, the structures in the eye, including the optic nerve, are fully formed. However, it still does not function normally. The research team explained that the newly formed eye structures require a few more weeks to mature.
◇Finding the genes responsible for eye regeneration using gene scissors
The research team also investigated which genes are activated during the eye regeneration process. When the eye was severed, 9,000 genes started to operate at different rates compared to other specimens. After 28 days, 1,175 genes were still expressed differently in the regenerated eye. The research team explained that while it appears the eye is fully regenerated after a month, complete maturation may take more time.
Professor Accorsi expressed hope that clarifying the regeneration process of Pomacea canaliculata could also lead to recovery of vision for patients with eye damage. The research team first cut the pax6 gene in the embryos of Pomacea canaliculata using the CRISPR/Cas9 gene scissors to understand its function. The protein produced by the pax6 gene is known to regulate the development and organization of the brain and eyes in humans, mice, and fruit flies.
CRISPR gene scissors are enzyme complexes that cut genes. Guide RNA recognizes and binds to the DNA portion of the gene that needs to be cut, allowing the Cas9 protein to make the cut.
Similar to humans, Pomacea canaliculata has two identical copies of each gene, inherited one from each parent. The research team confirmed that if both copies of the pax6 gene in the snail do not function normally, the eye does not develop in the embryo. It was discovered that pax6 is essential for the initial eye development of Pomacea canaliculata.
The research team is now investigating whether pax6 also plays a role in eye regeneration. This involves experiments where the pax6 gene of fully grown Pomacea canaliculata is modified or its function suppressed to see if regeneration occurs properly. Along with this, they are also investigating genes that create specific structures of the eye, such as the lens and retina.
◇The snail that can regenerate even after losing its head
Mollusks like Pomacea canaliculata and snails have been known for their regeneration ability to survive even after being severed for centuries. In 1766, a researcher recorded that a severed garden snail could regenerate its entire head. Some sea slugs even cut off their own necks to separate their bodies from parasites.
Researchers at Nara Women's Hospital in Japan revealed in 2021 in "Current Biology" that they observed a sea slug cutting off its neck and later regenerating its body from the head. The head with tentacles moved and even ate after being separated from the body. After 1 to 3 weeks, the torso, including the heart, regenerated.
Professor Accorsi noted that Pomacea canaliculata are easy to raise in the laboratory and produce many offspring, making them suitable animals for eye regeneration research. He stated, "If we discover a gene group crucial for eye regeneration and these genes also exist in vertebrates, theoretically, it would be possible to activate those genes to regenerate human eyes."
◇References
Nature Communications(2025), DOI: https://doi.org/10.1038/s41467-025-61681-6
Current Biology(2021), DOI: https://doi.org/10.1016/j.cub.2021.01.014