When an animal grows back a missing body part, the replacement is not as good as the original, new research confirms.
It's been known for a while that regenerated lobster claws and eyes tend to be much smaller, but now a study on regenerated lizard tails reveals that they are far from identical to the first ones.
"The regenerated lizard tail is not a perfect replica," Rebecca Fisher, an associate professor in Arizona State University's School of Life Sciences, and at the UA College of Medicine – Phoenix, said in a press release. "There are key anatomical differences including the presence of a cartilaginous rod and elongated muscle fibers spanning the length of the regenerated tail."
The findings are published in a pair of articles featured in a special October edition of the journal The Anatomical Record.
Fisher and her team studied the regenerated tails of the green anole lizard (Anolis carolinensis). This lizard likely evolved the regrowth ability since predators often bite the lizard's tail off. The little reptile can lose its tail in other ways too.
The researchers determined that the new tails have a single, long tube of cartilage instead of vertebrae, as in the original. Long muscles also span the length of the regenerated tail compared to shorter muscle fibers found in the original.
"These differences suggest that the regenerated tail is less flexible, as neither the cartilage tube nor the long muscle fibers would be capable of the fine movements of the original tail, with its interlocking vertebrae and short muscle fibers," Fisher said.
"The regrown tail is not simply a copy of the original, but instead is a replacement that restores some function."
The animal also has to expend quite a lot of energy to regrow the missing part. People who break off the claws on a living lobster and say, "They'll just grow back," are actually leaving that animal in a dangerous, impaired state.
On a happier note, it's still promising to know that some animals can achieve this feat in the first place. Perhaps the method could be extended to humans, once some key questions are answered.
"Using next-generation technologies, we are close to unlocking the mystery of what genes are needed to regrow the lizard tail," said Kenro Kusumi, an associate professor in ASU's School of Life Sciences in the College of Liberal Arts and Sciences, and co-author of the papers. "By supercharging these genes in human cells, it may be possible to regrow new muscle or spinal cord in the future."
"What is exciting about the morphology and histology data is that these studies lay the groundwork for understanding how new cartilage and muscle are elaborated by lizards," said Jeanne Wilson-Rawles, co-author and associate professor in the School of Life Sciences. "The next step is understanding the molecular and cellular basis of this regeneration."
It looks like the researchers have their eyes set on new therapeutic approaches to spinal cord injuries and diseases like arthritis.
(Image shows a green anole male with a regenerated tail (brown region); Credit: Inbar Mayaan)