Zombifying virus drives caterpillars to suicide

This is neither a horror series nor a science fiction film. Much more often than one might imagine, viruses infect insects and drive them to suicide, in order to claim victims more quickly. Science Alert became interested in this phenomenon.

This type of virus has been around for hundreds of millions of years according to the scientific community. Of new research allow us to understand a little better their functioning, and more particularly that of a group called «nuclear polyhedrosis virus» (or VPN), which attacks the caterpillars Helicoverpa armigera or, in more common parlance, «tomato noctuelles».

While these caterpillars naturally head for the ground to metamorphose into butterflies, subjects infected with NPV tend to head for the tops of plants to die there. We now know a little more about this process: it is linked to the phototaxisor the reflex for certain species to move towards the light (positive phototaxis) or to move away from it (negative phototaxis).

Researchers from China Agricultural University conducted a series of experiments on these Tomato moths infected with a particular VPN: HearVPN. They deduced that the virus acts on phototaxis by hijacking the host’s visual perception to trigger upward climbing behavior in plants, which causes the death of infected larvae.

New scientific advances

old research already assumed that the infected caterpillars were looking for light. The news confirmed this hypothesis through experiments using LEDs. Further tests established that the caterpillars’ vision was being used at their expense, since those that were already blind before being infected were not affected as much as sighted caterpillars.

What is still a little unclear, however, is why this escalation benefits the virus. It is assumed that if the caterpillars die at the top of the plant, it is probably so that the virus can spread more easily a posteriori: perhaps thanks to the wind or predators.

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The researchers found the genes reacting to the virus (among others, those which naturally transform light into an electrical signal, for example). By observing them, they deduced that the VPN seems to act on the pre-existing attraction of insects for light, in order to turn it against them.

Source: Slate.fr by www.slate.fr.

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