Conch Snails Strangely Have Excellent Eyesight, Which Helps Them Quickly Leap Away From Predators
The ocean is full of surprises, with one of them being the abilities of the big-eyed conch snail. Usually, snails are thought of as slow-moving creatures that have poor eyesight—but conch snails are the exception. They have sharp eyesight, which they use to quickly leap away from predators.
Most snails have eyes that look like small black dots, but conch snails have eyes that are up to 10 times bigger than any of their relatives.
Their eyes can peer in all directions, helping them keep a lookout for predators in their tropical shallow-water habitats.
“Large, high-resolution eyes are normally a characteristic of predators that rely on vision to hunt prey,” said Dr. Alison Irwin, the lead author of the study from the University of Copenhagen.
“Given their significant evolutionary cost, we only expect to find such eyes in animals where they are vital for survival.”
“That means it’s really strange to find conch snails with such good eyesight. They’re algae-grazers, not predators, so they must be using their excellent vision for something else.”
The research team’s findings suggest that the vision of conch snails and their large-eyed relatives evolved along with their ability to move quickly.
Most snails crawl; however, conch snails possess a large foot that allows them to jump across the seabed. Their superb eyesight and agility help them avoid becoming victims to predators like cone snails.
“Cone snails are a famous marine predator with really toxic venom,” said Dr. Suzanne Williams, who supervised Dr. Irwin.
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“They fire venom in darts at their prey, which can include worms, fish, and some conch snails. Cone snails are, however, notoriously slow. This marriage of good vision and high speed allows these conch snails to dart out of danger and live to graze another day.”
Of the five senses, vision is one of the most important because it lets animals find food, detect changes in light, and navigate their surroundings.
Vision does take a significant amount of energy to maintain, though. As a result, only animals that really depend on eyesight have evolved it.
The team wanted to investigate how the differences between conch snails and their smaller-eyed relatives arose.
While conch snails have big, colorful eyes, their smaller-eyed relatives have a reduced lens, and their eyes are at the base of the tentacles instead of at the tips, limiting their vision.
The researchers used the DNA of snails borrowed from museums around the world to assemble a family tree. The tree contained two main branches: one with large-eyed snails and one with smaller-eyed snails. This indicates that large eyes evolved just once, shifting from the base of the tentacles to the tips.
The large-eyed snails appear to have inherited their big eyes from a common ancestor. Then, they got bigger within the conch snail family. They likely evolved better eyesight due to pressure from predators during the Mesozoic Era.
Snail-eating predators were becoming more common in tropical, shallow marine habitats, so large eyes would have been useful to help with escaping danger.
In addition, conch snails evolved to have another amazing feature: a curve in the shell. They can retract their eyes into their shell if they spot a predator they can’t jump away from.
The findings were published in Systematic Biology.
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