Their severed heads get around just fine until they regenerate perfectly functioning, parasite-free new bodies, scientists say.
When Ms. Mitoh peered into its tank to get a better look, she noticed something even more shocking: The severed head of the creature was moving around the tank, munching algae as if there was nothing unusual about being a bodiless slug.
Ms. Mitoh also saw signs that the sea slug’s wound was self-inflicted: It was as if the sea slug had dissolved the tissue around its neck and ripped its own head off. Self-amputation, known as autotomy, isn’t uncommon in the animal kingdom. Having the ability to jettison a body part, such as a tail, helps many animals avoid predation. However, no animal had ever been observed ditching its entire body.
The head wounds the sea slugs created during autotomy took only one day to heal. Organs such as the heart took an average of one week to regenerate. For most of the sea slugs, the regeneration process took less than three weeks to complete.
“We’ve known for a long time that sea slugs have regenerative capabilities, but this really goes beyond what we had thought,” said Terry Gosliner, senior curator of invertebrate zoology at the California Academy of Science.
Dr. Gosliner, who has discovered over one-third of all sea slug species known to exist, suspects that the impressive regenerative capability of these sea slugs may relate to another impressive biological talent they possess.
Having this ability, which is known as kleptoplasty, could be what allows these sea slugs to survive long periods of time without their bodies.
“It’s so interesting to see so many features of regeneration in the animal kingdom brought together in one organism,” Dr. Kusumi said.
Much remains to be learned about drivers and biological mechanisms that allow Elysia marginata and Elysia atroviridis to sever their own heads and regenerate their bodies, but Ms. Mitoh and other scientists believe that improving our understanding of this strange phenomenon could one day lead to advances in regenerative medicine and other fields.
Until the solar-powered slugs’ secrets are revealed, Ms. Mitoh will continue spending her days watching her beloved sea slugs behead themselves. It’s grisly work, but someone has to do it.
Source: New York Times