Fully-functional, disembodied heads are the stuff of nightmares and science fiction. But they are also the stuff of proper zoological investigations, one of which featured in a gruesomely fascinating viral video, says Stuart Blackman.
Frozen by biologists at Nara Women's University, Japan, it shows a seaslug chewing off its entire body at the neck - heart, and all. The severed head then glides around its tank, grazing normally, before regenerating a whole new body within a matter of weeks.
It's an extreme case of autotomy - the self-inflicted removal of a body part - which, while not common, is widespread throughout the animal kingdom.
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Most famously, many lizards drop their tails to escape the clutches of predators, while sea cucumbers can startle assailants by ejecting their intestines explosively through their anus.
The males of certain money spiders increase their running speed by gnawing off one of their two bulky sex organs.
But the seaslugs take things to a higher level. Such drastic measures may be the only way to rid themselves of parasites infecting their body. It's likely that the disembodied heads are able to survive the ordeal only because their tissues contain photosynthetic algae that fuel the regeneration process.
