No battle scars
A tiny crustacean seems to have perfected regenerating its limbs.
Join Alba as she investigates this down to a cellular level.
Our Body
Broken bones mend themselves,
severe injuries heal,
and, over time,
all that remains of it
are the scars we carry.
Our bodies are amazing!
There is, however, one thing that our body
is just not equipped to do:
There is, however, one thing that our body
is just not equipped to do:
Grow back body parts.
Regeneration
It is the ability that some animals have to re-grow body parts.
Regeneration
It is the ability that some animals have to re-grow body parts.
To us, it is such an exotic trait, but it is indeed more common in animals than we tend to think.
Regeneration in lizards
Lizards may injure their tail and have to regenerate it. And each time, we see them regenerate a fully functional replica.
Regeneration in lizards
Lizards may injure their tail and have to regenerate it. And each time, we see them regenerate a fully functional replica.
But on closer inspection, we can spot defects.
In fact, the bony vertebrae of the lizard's tail is replaced by cartilage in the regenerated tail.
In some other cases,
the defects are more striking.
Regeneration in frogs
Tadpoles can regenerate their limbs perfectly.
Although, after they metamorph into frogs,
the same regenerated structure no longer
resembles the original one!
There is a tiny crustacean who seems to be able to regenerate perfect replica of its limbs.
There is a tiny crustacean who seems to be able to regenerate perfect replica of its limbs.
How is that possible?
There is a tiny crustacean who seems to be able to regenerate perfect replica of its limbs.
How is that possible?
And why can this small shrimp regenerate perfectly while other animals cannot?
Parhyale hawaiensis
This is Parhyale.
It does as other marine creatures do:
swimming, eating, mating...
These are tense situations, and Parhyale can sometimes lose a whole limb!
These are tense situations, and Parhyale can sometimes lose a whole limb!
But that's not really a problem for it, because it can simply regrow a seemingly perfect replicate.
These are tense situations, and Parhyale can sometimes lose a whole limb!
But that's not really a problem for it, because it can simply regrow a seemingly perfect replicate.
Leaving no trace of the battle injury.
Lets begin by comparing images of Parhyale‘s
uninjured limb with a regenerated one.
In just 3 weeks, it has grown a miniature replica of a limb.
In 6 months, the limb looks identical!
What's going on inside Parhyale to regenerate this identical limb?
What's going on inside Parhyale to regenerate this identical limb?
To answer this question, we need to peek
inside the animal and observe the process on a cellular level.
What's going on inside Parhyale to regenerate this identical limb?
To answer this question, we need to peek
inside the animal and observe the process on a cellular level.
Today, Alba's colleagues can observe
this process live, in extraordinary detail.
Live cell imaging
This technique revolutionised biology in the end of the 20th century, finally allowing us to observe the living cellular world.
Let's take a look at what we can observe!
To make a new leg in a constrained space, the tissues have to detach from the exoskeleton and retract.
Then, the cells start to divide multiple times and the missing parts are shaped back.
At the end of the video (approximately a week later) we can observe a miniature replica.
Now, parhyale makes a new armour that fits the new leg and gets rid of the old one.
What you see moving around are nuclei, doing many different things.
We know that these nuclei correspond to neurons, epidermal cells, muscle cells and many other types of cells needed by the limb.
Alba is asking: Does Parhyale regenerate all the different types of cells present in the uninjured limb?
Is the regeneration perfect, even at the cellular level?
UMAP
Alba is able to visualise the different types of cells in the limb onto a graph, called a UMAP.
UMAP
Alba is able to visualise the different types of cells in the limb onto a graph, called a UMAP.
Lets take a look at the UMAP for the uninjured limb.
Each dot represents a cell, and they are grouped by how similar they are in their function.
Alba was able to identify muscle cells, nerve cells, blood cells and a whole range of other types of cells.
Now let's bring up the UMAP for the regenerated limb.
Each dot represents a cell, and they are grouped by how similar they are in their function.
Alba was able to identify muscle cells, nerve cells, blood cells and a whole range of other types of cells.
Now let's bring up the UMAP for the regenerated limb.
Each dot represents a cell, and they are grouped by how similar they are in their function.
Alba was able to identify muscle cells, nerve cells, blood cells and a whole range of other types of cells.
Now lets bring up the U-Map for the regenerated limb.
The regenerated limb has all the different types of cells restored in it.
The regenerated limb has all the different types of cells restored in it.
This regeneration process is unbelievably flawless!
How can Pahryale recreate such a perfect replica of its limb?
How can Pahryale recreate such a perfect replica of its limb?
Are there different ways to create exactly the same limb?
How can Pahryale recreate such a perfect replica of its limb?
Are there different ways to create exactly the same limb?
Or is Parhyale mimicking the same mechanisms that it used for building a limb when it first grew into an adult?