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Insects are the most abundant and diverse group of animals on earth.
They inhabit nearly every corner of the planet. From the depths of Lake Baikal...
...to the heights of the Mount Everest, and from the wet Amazon rainforest to the hot Sahara desert.
At Naturalis Biodiversity Center and Leiden University...
...we're curious to find out how insects became so adaptable.
Many aspects contribute to their success. Their small size allows them to reproduce quickly.
Their ability to fly allows them to travel great distances.
But we're now starting to believe that to a great extent their success depends on the serosa.
The serosa is a waterproof layer of cells...
...that prevents the embryo from drying out while it's developing inside the egg.
Without it, insects would likely not have been able...
...to leave the aquatic environment and conquer land.
Nearly all insects develop a serosa in the embryonic stage...
...and normally they cannot survive without it.
But, amazingly, the embryos of the red flour beetle can do just that...
...but only if the circumstances are just right.
These beetles are extremely well adapted to living in dry circumstances.
They do not drink a single drop of water during their entire life.
Red flour beetles depend on a gene called "zen1" to form the serosa.
In the lab we injected female pupae with RNA that blocks the activity of this gene.
It doesn't have a direct effect on the females, but their offspring do not develop a serosa.
Next we experimented with hatching conditions. In a moist environment eggs hatch just fine...
...but it turns out that embryos are only able to survive dry conditions if they have a serosa.
So we found that the serosa protects the embryo from drying out.
Almost all insects living on land develop a serosa.
Because of this, we believe it was important for the survival of the very first insects...
...to lay their eggs on land, about 500 million years ago.
Their crustacean relatives, which do not develop a serosa, have been far less succesful...
...on land. And that's why we believe...
...it is the serosa that allowed insects to conquer land and become so incredibly succesful.