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Young American alligators (Alligator mississippiensis) have the ability to regrow their tails up to 18% of their total body length, according to a study published in the journal Scientific reports. The study authors hope that their findings will help lead to the discovery of new therapeutic approaches for injury repair and the treatment of diseases such as arthritis.
Currency et al. present the first anatomical and histological evidence of repair of the regrowth tail in an archosaur, the American alligator (Alligator mississippiensis); the regrown alligator tails made up about 6-18% of the total body length and were morphologically distinct from the original tail segments. Image credit: Norbert Nagel / CC BY-SA 3.0.
“What makes the American alligator interesting, aside from its size, is that the regrown tail shows signs of regeneration and wound healing within the same structure,” said the author of the fist. Dr. Cindy Xu, A researcher at the School of Life Sciences at Arizona State University.
“The regrowth of cartilage, blood vessels, nerves and scales was consistent with previous studies on 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 varies between different groups of reptiles and animals.”
Dr. Xu and colleagues used advanced imaging techniques combined with proven methods of studying anatomy and tissue organization to examine the structure of regrown alligator tails.
They found that the new tails were complex structures with a central skeleton made up of cartilage surrounded by connective tissue that was intertwined with blood vessels and nerves.
“The spectrum of regenerative abilities between species is fascinating, clearly there is a high cost of producing new muscle,” said co-lead author Dr. Jeanne Wilson-Rawls, also of the School of Life Sciences at the Arizona State University.
The regrown alligator’s tail is different from the original tail; regrown scales are densely arranged and lack dorsal shields (top right); an unsegmented (yellow) cartilage tube replaces bone (light brown) in the regrown tail; furthermore the regrown tail is devoid of skeletal muscle (red) and instead there is an abundance of fibrous connective tissue (pink). Image credit: Arizona State University.
Alligators, lizards, and humans all belong to a group of animals with backbones called amniotes.
While the team previously studied the lizards’ ability to regenerate their tails, the new discovery of the regrowth of complex new tails in the alligator provides further insight into the process in amniotes.
“The ancestors of alligators, dinosaurs and birds separated about 250 million years ago,” said lead co-author Professor Kenro Kusumi, also of Arizona State University’s School of Life Sciences.
“Our discovery that alligators retained the cellular mechanism for regrowing complex tails while birds lost that ability raises the question of when in evolution this ability was lost.”
“Are there fossils out there of dinosaurs whose lineage has led to modern birds with regrown tails?”
“So far we have found no evidence of that in the published literature.”
“If we understand how different animals are able to repair and regenerate tissue, this knowledge can be harnessed to develop medical therapies,” said co-author Rebecca Fisher, researcher at the Arizona State University School of Life Sciences and the Department . of Basic Medical Sciences at the University of Arizona College of Medicine-Phoenix.
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C. Xu et al. 2020. Anatomical and histological analyzes reveal that tail repair is associated with regrowth in wild-caught young American alligators (Alligator mississippiensis). Ski Rep 10, 20122; doi: 10.1038 / s41598-020-77052-8
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