The Argentine black and white tegu – Salvator merianae – is a sizeable lizard living in the tropical rainforests and savannas of east and central South America. Like almost all lizards, these omnivorous creatures have the ability to regenerate their tails if they suffer injury or are even lost completely. A young member of this species, as revealed in the journal Cuadernos de Herpetología, has trumped them all by setting a new record: It has managed to simultaneously regenerate six tails.
Regeneration is different from healing: tissue repair is often incomplete, with the damaged organ or body part fixing itself just enough to adapt to the wound caused by the injury. Regeneration, on the other hand, is where the damaged tissue is replaced by an exact copy soon afterwards. Parts of the human body have lost the ability to regenerate after suffering an injury. Small skin punctures can completely regenerate themselves; damaged heart tissue can only repair, not regenerate, itself.
Lizards, however, are quite different, in that they have remarkable regeneration abilities; they’re able to regenerate their entire tail after it has been injured or severed off. In many cases, lizards remove their tails as a defensive strategy in order to escape predators, who may have a grip on the tail at the time. This is a process known as “autotomy,” (Greek for self-severing) and it’s not just lizards that can do this: two species of spiny mice, the first mammals known to have the ability to self-amputate, can regenerate hair follicles, skin, sweat glands, cartilage and fur.
When threatened, a lizard severs its tail between two specific vertebrae, similar to the vertebrae found in a wide range of mammals. A fracture is generated within its tail along one of these intentionally weak structural points; bleeding is quickly clotted and shut off, and the cellular regeneration of the tail tissue begins rapidly from the remaining stub.
This particular young black and white tegu lizard appeared to have suffered a particularly damaging injury to its tail, likely caused by a sharp object, which failed to completely cut off the tail. The wound was deep enough, however, to stimulate multiple points along the tail where regeneration normally takes place, causing multiple tails to grow.
As reported by New Scientist, “this is the first case of ‘hexafurcation’ ever reported,” says Nicolás Pelegrin of the National University of Córdoba in Argentina, who has reported the discovery. Although lizards with two or three tails are found more commonly than you might think, this is a world first.
Having six tails does not provide it with any evolutionary advantage over its peers: If anything, its movement is now hampered, it may find social signaling a little trickier, and perhaps most unfortunately, its reproductive capabilities have likely been somewhat reduced.