Corentin Jouault and the insects of the past

Student in Master 2 at the University of Rennes 1 and passionate about insects since always, Corentin Jouault tells us the secrets of fossilization in amber, and tells us about current ants. The interview is also available on mysciencework's youtube channel (with subtitles).

Can you introduce yourself?

Hello everyone, my name is Corentin Jouault, I am a student in Master 2 PPP, Master of Paleontology at the University of Rennes 1, and I study mainly fossil insects.


How are insects trapped in amber?

To defend itself, the tree will have a substance called resin; so we have the sap which is the "blood" of the tree, and the resin which is a defense mechanism, and when the tree is wounded, that is to say when an insect comes to pierce it or to make its nest in it, it will secrete resin and will engulf the insect, which in exceptional cases, will be fossilized. We will be able to study it, perfectly preserved, a few million years later.


How did ants evolve?

We know that the first ants, those found in the Cretaceous amber of Myanmar, are potentially eusocial, since we have morphological differences, we recognize queens and workers. But to say how we went from the supposed ancestor, which would be a kind of solitary ant-ape that would hunt on the ground, to the complex society as we know them today and as we observe them in the Cretaceous, is not possible for the moment. But maybe in ten years...


Have insects changed much over time?

There are certain families of insects found in amber that are totally extinct, they are no longer found today. On the other hand, I took the case of the ant just before, we know them since the middle of the Cretaceous, so about 100 Million Years ago, since they have not evolved much or not at all, morphologically, we can recognize them and say to ourselves "this is an ant", using the same criteria as if it was a contemporary ant, an ant that we can observe in our garden today.


If you had to present us an ant today, which one would it be?

It would be the Bulldog ants. They are ants known today only in the Australian region. There is also one in New Caledonia, and one on the Northern Islands. In the fossil record they were much more diversified. We know some in France, we know some in the United States, in South America. They are very nice because they jump, they make little jumps that can go up to 30 cm, or even a little higher, they have a very good sight, and they hunt very very well, so it is quite nice to observe, because it runs in all directions, it has a very powerful venom. And it is rather "primitive" in the organization, since when we take the cladograms of the evolution of ants, they are ants which are situated rather basally, hence occupying rather low places without this phylogeny.

It is rather interesting, in particular to understand this transition between eusocial models of early areas, and eusocial models of lineages which are a little more "evolved".


What can the study of ancient insects be used for?

The study of the fossil record in general, be it insects, plants or other, at first there will be something very concrete, for example when we talk about global warming, we all see, a great catastrophe is coming, the planet is warming up, etc. But how much it will impact on the future? But to what extent will it impact biodiversity? Will it be something very massive, very sudden or not? By studying insects, we can, thanks to the fossil record, see if at times there are diversification curves, times when species will diversify, we will see more species appear, or extinction phases, and for example, are these extinction phases correlated with a global warming phenomenon. This is the case, yes, and we can say to ourselves, by the principle of actualism, "ok, today we observe a similar phenomenon, the planet is warming up, so maybe this will lead to a massive reduction of species and to the disappearance of very interesting species, taxa.