Imagine the biologist Sayaka Mitoh’s surprise the day she discovered that a sea slug in her lab was suddenly missing her body. Or his head really depends on your point of view. Either way, the sea slug was in two pieces, both of which looked alive, in that they were both still on the move. Somehow they went on living for days and then weeks, even though the head lacked the heart and digestive system.
Among biologists, this kind of body-splitting maneuver is known as autotomy – lizards, for example, lose their tails to escape predation. But what the Sacoglossal Sea Slug does next puts it in a class of its own. “We were surprised to see the head move right after the autotomy,” says Mitoh. “We thought he would soon die without a heart and other important organs, but we were again surprised to find that he regenerated the whole body.”
That’s right: he shot a Deadpool. Within hours of being self-decapitated, the head began to drag itself around for food. After a day, the neck wound had healed. After a week, he started to regenerate a heart. In less than a month, the whole body had grown back and the disembodied slug was embodied again. Several slugs actually did this in Mitoh’s lab, so it’s a feature, not a bug. A slug – apparently a show-off – even self-decapitated twice.
Previously possessed bodies, however, do not. As Mitoh puts it poetically enough in a short story paper describe the phenomenon in the newspaper Current biology, “The bodies gradually shrank and turned pale, apparently from the loss of chloroplasts, and decomposed. The heartbeat was visible just before the body decomposed.
Now, before we get to the question of why on Earth would a sea slug beheaded, let’s talk about the How? ‘Or’ Whatand these chloroplasts. Mitoh actually observed this behavior in several individuals of two different species of Sacoglossal Sea Slug. This group of mollusks is famous – at least among biologists – for its “kleptoplasty”, or the way it steals its source of energy. In the algae that animals eat, photosynthesis buzzes in structures called chloroplasts. Instead of digesting them, the sea slug actually incorporates them into its own tissues. These chloroplasts can remain photosynthetically active During months, allowing their foster sea slug to draw energy from the sun. The animal is fine solar energy.