Nothing Wrong With Second Hand, Babbitty Makes Full Recovery
If you have ever visited Pacific Science Center’s animal exhibits before, you have likely noticed our axolotls. They tend to stand out from other animals, thanks in no small part to their unusual appearance and a permanent happy expression on their faces. Our axolotl ambassadors Flopsy, Simpkin, and Babbitty, like all axolotls, are amphibians, a class of animals that also includes salamanders (their close relatives) and frogs. Amphibians are known for their peculiar life cycles: they begin their lives underwater, breathing through gills and rarely (if ever) going on land. As they grow, they metamorphose into a different form. By the time they are adults, they breathe air like any land-dwelling animal, and can survive just fine outside of the water. This is where they get their name. “Amphibian” comes from the Greek “amphi,” meaning both, and “bios,” meaning life–which describes perfectly a group of animals that live one life in the water and another on land.
Axolotls, however, are peculiar–they spend their entire lives underwater! This is because they have evolved an adaptation that prevents them from metamorphosing into an adult form. They are permanently juveniles, which is why they have those feathery gills on their heads that allow them to breathe underwater. Imagine living your whole life without ever growing up. I would imagine there are many different opinions about whether or not that would be a good or bad thing, but axolotls seem to be just fine with it. In fact, it may contribute to one of their most interesting abilities: regeneration. This species is well-known in the scientific and medical communities for their ability to completely regenerate almost any part of their body, without even leaving a scar. Babbitty, our young albino axolotl, was injured while on exhibit, causing her to lose one of her front limbs. While this might be a severe problem for most animals, for Babbitty, growing back her limb only took a little more than a month. Volunteer Terry took photos of her periodically while she was healing, so now we can take a look at Babbitty’s arm as she grew it back.
The exact mechanics of regeneration are complicated, and many scientists today are conducting research on the phenomenon, hoping to get a better understanding of how the healing can be so close to perfection and happen so quickly. Most animals (including humans) can only regenerate very specific parts of the body, such as skin, hair, fingernails, and parts of the liver. However, even when we do regenerate, there is a limit to the amount of damage we can recover from. For axolotls, almost any body part can heal so well that there is no visible evidence that the part was ever injured in the first place.
Researchers have discovered that they can even regenerate parts of the spinal cord, an injury that would cause permanent and/or extensive damage to most other vertebrates.
Okay, so we all agree that this is quite an amazing ability. “But,” you say, “I am a scientist! I need to know how it works!” You are absolutely justified in saying that, and I commend you for it. Plus, as it turns out, the mechanism behind axolotl regeneration is a genius and incredible feat of evolution. But, in order to understand it, we need to understand how body parts develop in the first place. The answer: stem cells.
All living things are made up of cells. Each cell in a multicellular organism is specialized to be part of a larger part of the body. When a cell is developing, however, it is something called a pluripotent stem cell. This means it has the potential to be one of many different kinds of cells. The type of cell it will become is determined by many factors, especially the kind of cells that are next to it. In most organisms, once a pluripotent stem cell has differentiated (i.e. developed into one specific kind of cell), it will perform only that function until it dies.
However, axolotl cells can do something amazing: when a body part is damaged, the cells at the site of the injury can actually revert to being pluripotent stem cells. That’s right: they can “de-differentiate” and then re-develop into whatever type of cell needs to be replaced in order for that body part to heal. These cells can then reproduce in order to restore the part to its original glory!
As expected, Babbitty fully recovered from her injuries and now has a brand new front leg that looks good as new. Unfortunately, soon after reintroducing her to the exhibit, we noticed Flopsy, our oldest and largest axolotl, exhibiting aggressive behaviors towards her. Axolotls, especially older, more mature individuals, can be territorial and defensive of their food towards newcomers. It is possible that during Babbitty’s time off-exhibit, Flopsy forgot who she was, and acted as if she was a brand new intruder. So for the time being, Babbitty will be living in our office in her own private tank. Don’t worry, though. Axolotls are mostly solitary animals, so she is perfectly happy swimming around on her own. Congrats, Babbitty. It turns out she barely even needed us to lend a hand!
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