Complex tail regeneration has been discovered in alligators

In a new study from Arizona State University, researchers have found that young alligators have the ability to regenerate their tails. Remarkably, the alligators can regrow the complex structures by up to three-quarters of a foot, or 18 percent of their total body length.

Adult male American alligators measure up to 15 feet in length. While it has been well-documented that much smaller reptiles such as lizards are capable of regrowing entire appendages, regeneration has not been studied extensively in alligators.

In collaboration with the Louisiana Department of Wildlife and Fisheries, the researchers used advanced imaging techniques to examine the structure of regrown alligator tails. The team discovered that the new tails had a central skeleton composed of cartilage surrounded by connective tissue that was interlaced with blood vessels and nerves. 

“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,” said study lead author Cindy Xu. “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.”

The discovery that alligators are regrowing complex new tails could provide experts with new insight about the regeneration process in amniotes – the large group of animals that have backbones including alligators and humans. 

“The ancestors of alligators and dinosaurs and birds split off around 250 million years ago,” said study co-senior author Professor Kenro Kusumi. “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.”

The researchers hope their work may ultimately lead to the development of new methods for repairing injuries and treating diseases such as arthritis.

“If we understand how different animals are able to repair and regenerate tissues, this knowledge can then be leveraged to develop medical therapies,” said study co-author Professor Rebecca Fisher.

“Staff biologists in our Alligator Research and Management Program have been pleased to partner with Dr. Kusumi at Arizona State University for many years,” said Ruth M. Elsey, a biologist at the Louisiana Department of Wildlife and Fisheries.

“We see alligators in the field with some indication of possible regrowth of tail tissue, but their expertise led to the current study detailing the histological changes associated with the capacity for possible partial tail regrowth or wound repair.”

The study is published in the journal Scientific Reports.

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By Chrissy Sexton, Earth.com Staff Writer