Social insects: Military service slowed down

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Social insects: Military service slowed down
Social insects: Military service slowed down

Slowed down military service

Termite workers are true all-rounders - even outside of their colony-care activities: The animals are in an early stage of development and can therefore still embark on a career path to become soldiers or young producers. Two gene products decide where it goes.


In the caste system of social insects, everyone has a clear task: some provide for offspring, others for the well-being of all, and a third clique makes sure that they can do this in peace. Queen, worker, soldier - all specially matured specialists, it seems.

But when it comes to termites, the picture isn't quite right. These original insects also have a strictly hierarchical system, but the workers here are not the final stage of a development, but only an intermediate state - in principle young people before puberty. Because the animals involved in procuring food, excavating work and caring for the brood can still differentiate themselves into reproductive colony members or, after a further preliminary stage, strengthen the community's defense troops. The basis for or against a military career is a variant of the juvenile hormone, which is found in two to five times the amount in newly minted warrior individuals. On the other hand, if the hormone level remains constant, a prepubertal worker will simply hatch at the next moult.

Now finding a job in a welfare state shouldn't be left to chance – what's the point, for example, in a huge army without food suppliers and offspring? So there must be a genetic basis and control of the processes. Sought, found: In earlier studies, the working group led by Michael Scharf from the University of Florida in Gainesville discovered that two hexamerines play a crucial role. This group of proteins intervenes in numerous storage processes and the binding of hormones, especially in young insects. The researchers now wanted to know whether blocking the relevant genes promotes or inhibits the development of becoming a soldier.

So the researchers silenced the two genes using RNA interference and also injected their six-legged guinea pigs with a good dose of juvenile hormone to trigger a developmental spurt. In the control group-supplemented juvenile hormone but normal hexamerine production-more pre-stage soldiers matured, as expected. In hexamerine-blocked conspecifics without additional hormones as well, and to a similar extent. But the scientists in the third department reaped a veritable flood of soldiers, to which they had both administered hormones and switched off the hexamerines.

This marks the beginning of a new era of sociogenomic research in the highly underrepresented eusocial insect order Isoptera

(Xuguo Zhou et al.) The proteins do not trigger growing up, but rather suppress the leap into the defensive ranks. But in what way? Two possible explanations, each with good arguments, await closer examination. On the one hand, the hexamerins could serve as hormone scavengers: By binding the juvenile hormone and thus removing it from the insect metabolism, the immature termite bodies simply lack the necessary switch to turn on the transformation. Or the hexamerins have the task of signaling the nutritional status of the colony: if there is a lack of food supplies, workers are needed, not soldiers. In line with this, many hexamerins are produced more intensively during periods of intensive brood care, thus keeping the number of providers high.

But that's not the end of the story. Although it is still completely unknown how it works, the soldiers themselves seem to have an influence on the development fate of the workers: they keep the juvenile hormone levels low in their building mates and thus possibly promote the step towards young producers. This would mean that the hexamerines would be far more important than previously assumed. Accordingly, Scharf and his colleagues see their study as "the beginning of a new era of sociogenomic research in the highly underrepresented eusocial insect order Isoptera". In plain English: Termites are more exciting than many entomologists want to admit.

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