Salamanders are the only amphibians that have tails in the adult stage of their life. Like Lizards, salamanders can lose part of most of their tail, and subsequently regenerate it. But have you ever wondered why this happens?
The main reason salamanders lose their tails is to defend themselves when they are grabbed by a predator or sense a threat. When a salamander detaches its tail, the tail whips and wiggles around on the ground, distracting the predator and giving the salamander time to escape.
Stem cells in the spinal cord then enable the salamander to regenerate a near-perfect clone of their tail, within a few weeks to a few months, depending on the species.
Salamanders Lose Their Tails as a Self-Defense Mechanism
Salamanders lose their tails as a self-defense mechanism to distract predators. This process is known as autotomy (meaning “self-severing” in Greek), or self-amputation.
Salamanders are born with a line of weakness in their tail, called a fracture plane, which is the spot along the tail that is meant to break and release.
In some species, such as the four-toed salamander (Hemidactylium Scutatum), the fracture plane is visible as an obvious constriction at the base of the tail.
If a salamander is grasped by a predator, (particularly if grabbed by the tail), the muscles along the fracture plane pull away from one another in a reflex muscle spasm.
The pulling apart of the muscles causes the tail to break off at the fracture plane.
Once detached, the tail whips around and wiggles on the ground, for up to 5 minutes in some species.
The dropped tail distracts the predator, buying the salamander enough time to scurry away.
Since the tail is no longer connected to the salamander, it is powered by anaerobic respiration and it is the action of nerves that keep it wriggling.
Fun fact: Salamander tail autotomy is so efficient that when the tail breaks off, the salamander suffers little to no blood loss.
Most Salamanders Only Lose Their Tails When the Tail Is Grasped With Sufficient Force
Some salamander species can voluntarily lose their tails even if little external force has been applied to the tail.
However, in most salamander species, tail loss is often the result of a predator grasping the tail and breaking it.
Salamanders Can Regenerate a Near-Perfect Clone of Their Tail
When a salamander loses its tail, stem cells in the spinal cord enable it to regenerate a tail that closely mimics the original, bone, nerve cells, and all.
Within the first few hours after tail loss, the salamander’s epidermal cells in the area migrate to cover the open flesh.
This layer slowly gets thicker over the next few days, forming something called an apical epithelial cap.
Cells within the salamander’s body, called ‘fibroblasts‘ also gather under that epidermal covering.
These Fibroblasts play a central role in wound healing and tissue repair and are undifferentiated.
This means that they’re free to become multiple types of cells, depending on which body part needs replacing.
After that initial process, the blastema develops from the mass of fibroblasts. Over time, the blastema will develop into the replacement tail.
Since salamanders lose not only flesh but also nerves when they drop their tails – nerve axon regeneration happens at the same time as tissue, bone, and muscle regeneration.
It is not uncommon to find salamanders in the wild with a partially regenerated tail.
In many salamander species, the tail that grows back is often lighter in color than the original tail.
How Many Times Can a Salamander Regenerate Its Tail?
A single salamander can drop and regenerate a few tails in its lifetime.
Salamanders are known to be able to regenerate limbs after an injury throughout their lives.
When a salamander loses its tail, it will always regrow a new one.
Losing the Tail Might Have Negative Effects
Despite its effectiveness at warding off predators, dropping the tail does come at an expense for the salamander.
Salamanders use their tails to help them move through the water, for predator defense, to attract mates, and also for balance.
Others, such as the long-toed salamander (Ambystoma macrodactylum) use their tails as fat storage, which is crucial to help hibernate and make it through the winter.
For this reason, autotomy is costly and is often only used when other defenses have failed.
The tail is too valuable to be dropped too easily, due to its numerous functions.
Some salamander species such as the Bolitoglossa rostrata of Mexico, have developed an adaptation to reduce the cost of tail loss.
These salamanders will delay autotomy until the predator moves its jaws up the tail or holds on for a long time.
This allows them to retain their valuable tails when other defenses, such as their toxic skin secretions, can ward off predators.
For every salamander, there is always a trade-off between the importance of having a tail and losing your life.
Prevention of Tail Loss in Salamanders
The easiest way to prevent tail loss is the handle salamanders correctly.
When picking up a salamander, never grab it by the tail. Instead, hold it with one hand with one hand under the belly and the other behind the forearms.
Doing this will prevent the salamander from being stressed, and shedding its tail in response.
What Other Animals Lose Their Tails?
Salamanders and lizards aren’t the only animals capable of self-amputation.
Over 200 species of invertebrates are capable of voluntarily shedding part of their bodies when necessary for survival.
For example, some spiders will shed a leg, if it is stung by bees or wasps.
In mammals, autotomy is known to be used by at least two species of African spiny mice.
These mice can release skin when captured by a predator, and later regenerate the lost skin; including hair follicles, sweat glands, and all – with little or no visible scarring.
Conclusion
Salamanders lose their tails as a defensive mechanism meant to distract predators
Although the tail has several important functions, sometimes being able to ditch the tail might just save a salamander’s life.
Photo credit: Michael McGuire (CC BY-NC 4.0)
Sources:
Wake DB, Dresner IG. Functional morphology and evolution of tail autotomy in salamanders. (PDF).
Elad Bassat, Elly M. Tanaka, The cellular and signaling dynamics of salamander limb regeneration, Current Opinion in Cell Biology, Volume 73, 2021, Pages 117-123, ISSN 0955-0674, https://doi.org/10.1016/j.ceb.2021.07.010.
Ducey, P. K., Brodie, E. D., & Baness, E. A. (1993). Salamander Tail Autotomy and Snake Predation: Role of Antipredator Behavior and Toxicity for Three Neotropical Bolitoglossa (Caudata: Plethodontidae). Biotropica, 25(3), 344–349. https://doi.org/10.2307/2388793
Fleming, P.A., Muller, D. and Bateman, P.W. (2007), Leave it all behind: a taxonomic perspective of autotomy in invertebrates. Biological Reviews, 82: 481-510. https://doi.org/10.1111/j.1469-185X.2007.00020.x
Tara Lynne Maginnis, The costs of autotomy and regeneration in animals: a review and framework for future research, Behavioral Ecology, Volume 17, Issue 5, September/October 2006, Pages 857–872, https://doi.org/10.1093/beheco/arl010