Limb Regeneration in Cynops orientalis
A photo series by Jean-Sébastien Roy
These photos were taken at the indicated time points after amputation of the left forelimb. All photos show the same animal.
During the first 24 hours after the limb is cut off, the wound heals and is covered by a thin layer of epidermis. This step is very critical, as the wound must heal quickly to prevent infection. Also, regeneration requires special conditions obtained only when skin covers the wound. A few days after the amputation, we note that the newt tries to use its limb because, when he walks, the stump is moving as if the foot was there.
|Week 2. During the first two weeks, the cells around the amputation site are dedifferentiating, meaning that the cells are losing their specific characteristics (muscle, vascular tissue, connective tissue, etc.). The cells become like embryonic cells, able to build any part of the body. These dedifferentiated cells form a mass, called the blastema.|
|Week 3. The blastema continues to grow.|
|Week 4. The blastema continues to grow.|
|Week 5a. The final step is the transformation of the blastema into a functional limb. This step is called redifferentiation. At this time, the cells are taking their final form, becoming bones, muscle, nerves, etc. As in embryos, the cells that will make the bones start by becoming cartilage, and then bones.|
|Week 5b. This picture was taken the same day as 5a. Here we note the difference in size between the old part of the limb and the new one. This difference will disappear with time. We can also see the digits better than in the previous picture.|
|Week 6. Redifferentiation continues. The four digits and their bones are now formed. In the tank, we can see the newt really using the limb (walking with it) even though it’s not the same size as the others.|
|Week 7. When all parts of the limb are complete, the limb gradually grows to become as big as the others, and there’s not even a scar left.|