It isn’t just teeny lizards that have the ability to regenerate a lost tail; it looks like even the mighty American alligator can do it too.
In a new study, researchers from Arizona State University (ASU) and the Louisiana Department of Wildlife and Fisheries have shown how young American alligators (Alligator mississippiensis) can regenerate up to 24 centimeters of their chunky tails, around 6-18 percent of their total body length.
As reported in the journal Scientific Reports, the researchers used a bunch of advanced imaging techniques, methods for studying anatomy, and dissections to examine the structure of regrown tails in juvenile American alligators.This revealed that the regrown alligator tail is built out of cartilage surrounded by connective tissue, all interlaced with blood vessels and nerves, but appears to lack skeletal muscle.
This is slightly different to the regenerated tails of lizards, which feature skeletal muscle, but it does share similarities with regenerated limbs of some frogs and regenerated tails in the tuatara (an unusual species of reptile from New Zealand that looks like a lizard, but it is part of a totally distinct lineage).
However, this new study remains surprising due to the sheer size of American alligators. One of the dissected individuals studied in this research was a juvenile male that measured just under 180 centimeters (5 feet and 10 inches) from tail to snout, but adults are known to grow up to 4.6 meters (over 15 feet)
"What makes the alligator interesting, apart from its size, is that the regrown tail exhibits signs of both regeneration and wound healing within the same structure," Cindy Xu, lead study author and a recent PhD graduate from ASU's molecular and cellular biology program, said in a statement.
"Regrowth of cartilage, blood vessels, nerves, and scales were consistent with previous studies of lizard tail regeneration from our lab and others. However, we were surprised to discover scar-like connective tissue in place of skeletal muscle in the regrown alligator tail. Future comparative studies will be important to understand why regenerative capacity is variable among different reptile and animal groups."
Of course, not all animals can regenerate lost tails and the ability appears to be largely limited to amphibians and reptiles. While mammals can regenerate some tissues, they have a very limited capacity for regeneration. The researchers hope that this insight into alligators regenerating their tails could shed some light to when this ability emerged in the evolutionary tree.
"The ancestors of alligators and dinosaurs and birds split off around 250 million years ago. Our finding that alligators have retained the cellular machinery to regrow complex tails while birds have lost that ability raises the question of when during evolution this ability was lost. Are there fossils out there of dinosaurs, whose lineage led to modern birds, with regrown tails? We haven't found any evidence of that so far in the published literature," explains co-senior author Kenro Kusumi, professor and director of ASU's School of Life Sciences.
The team even suggests that this new knowledge about the regeneration of tissues could be used to help develop medical therapies in humans. It will be a long time until this idea has applications in the real world, but it’s certainly a promising prospect.