Imagine the biologist Sayaka Mitoh’s surprise the day she finds a sea snail in her lab suddenly missing his body. Or its head really depends on your perspective. Either way, the sea snail was in two pieces, both of which looked alive, in the sense that they were both still moving. Somehow they kept alive for days and then weeks, even though the head was a cardiovascular and digestive system.
Among biologists, this type of body-splitting maneuver is known as autotomy – for example, lizards shed their tails to escape predation. But what the sacoglossan sea snail does next, places it in a class of its own. “We were surprised to see the head move just after the autotomy,” Mitoh says. “We thought it would soon die without a heart and other important organs, but we were again surprised to discover that it regenerates the whole body.”
That’s right: it drew a Deadpool. Only a few hours after the self-decapitation, the head begins to drag him to feed. After a day, the neck wound closed. After a week, it started to regenerate a heart. Within less than a month, the whole body grew again and the body without body was re-embodied. Several snails actually did this in Mitoh’s lab, so it’s a feature, not a mistake. One snail – apparently a showpiece – even beheaded himself two times.
However, the bodies previously owned do not retrieve it. As Mitoh puts it rather poetically in a new article describing the phenomenon in the magazine Current biology, ‘The bodies gradually shrank and turned pale, apparently from the loss of chloroplasts, and eventually decomposed. The heartbeat was visible just before the body disintegrated. ”
Before we get to the question of why on earth a sea snail would decapitate itself, let’s talk about the how, and those chloroplasts. Mitoh actually observed this behavior in several individuals of two different species of sacoglossan sea snail. This group of mollusks is – at least among biologists – known for its ‘valve toplasty’, or the way it steals its source of energy. In the algae that the animals eat, photosynthesis hums together in structures known as chloroplasts. Instead of digesting it, the sea snail ingests it in its own tissues. These chloroplasts can remain photosynthetically active for months, allowing their accepting sea snail to draw energy from the sun. The animal is very solar powered.