American alligators are about as close to dinosaurs as you can get in modern times, and can and may grow up to 14 ft in length. While considerably smaller reptiles like lizards are able to regenerate their tails, the question of whether much bigger alligator can regrow their enormous tails has not been well studied. A team of researchers from Arizona State University and the Louisiana Department of Wildlife and Fisheries have uncovered that young alligators have the capacity to regrow their tails up to three-quarters of a foot, or 18% of the total body length.
An interdisciplinary team of scientists used innovative imaging techniques together with proven methods of studying anatomy and tissue organization to examine the construction of those regrown tails. They discovered that these fresh tails were complex structures with an essential skeleton comprising cartilage surrounded by connective tissue which has been interlaced with blood vessels and nerves. They speculate that regrowing their tails gives the alligators a practical advantage in their ancestral aquatic habitats.
“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 Cindy Xu, a recent PhD graduate from ASU’s molecular and cellular biology program and lead author of the paper. ” 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 spectrum of regenerative ability across species is fascinating, clearly there is a high cost to producing new muscle,” said Jeanne Wilson-Rawls, co-senior author and associate professor with ASU’s School of Life Sciences. “
“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 Manager with 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.”
Alligators, lizards, and humans all belong to a group of animals with backbones known as amniotes. While the interdisciplinary team has previous studied the capability of lizards to regenerate their tails, this discovering of regrowth of complex new tails in the alligator gives additional information about the process in amniotes.
“The ancestors of alligators and dinosaurs and birds split off around 250 million years ago,” said co-senior author Kenro Kusumi, professor and director of ASU’s School of Life Sciences and associate dean in the College of Liberal Arts and Sciences. “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.””If we understand how different animals are able to repair and regenerate tissues, this knowledge can then be leveraged to develop medical therapies,”
“If we understand how different animals are able to repair and Regenerate tissues, this understanding can then be leveraged to create Medical treatments,” explained Rebecca Fisher, co-author and professor with At the University of Arizona College of Medicine-Phoenix and ASU’s School of Life Sciences. The researchers hope their findings will help lead to treating diseases like arthritis.
Related Journal Article: https://www.nature.com/articles/s41598-020-77052-8