Crisp and Young, Like the Queen
Freiburg, Mar 30, 2021
Is it possible to age only just before death? Some termites have this ability, which is linked to their social status as well. An evolutionary biologist and ecologist at the University of Freiburg, Prof. Dr. Judith Korb, is investigating which social factors and molecular processes of termites let some enjoy persistent youth, while others age and die quickly. She has just published the volume “Ageing and Sociality” as a co-author. It looks at similar phenomena in the entire animal kingdom. The mechanisms for sustained youth are present in humans as well.
The queens of some species of termite remain fit and fecund nearly till the day they die –in some cases, as long as twenty years. Photo: Pisut/stock.adobe.com
Is it possible to escape the vagaries of aging? “Queens and kings of the species Cryptotermes secundus do not age at all until shortly before they die,” says Judith Korb. An evolutionary biologist and ecologist of the Institute of Biology I of the University of Freiburg is publishing together with a colleague from the University of Regensburg, Prof. Dr. Jürgen Heinze, the volume “Ageing and Sociality.” In the anthology, researchers from all over the world describe how the social lifestyles of insects, birds, and mammals influence their aging. For the Cryptotermes termites Korb works with, too, social factors determine persistent youth. For them, it is a royal privilege.
Social role changes
Molecularly, all Cryptotermes secundus (Csec) that belong to one colony are basically the same. But observations preliminarily support that the workers tend to age gradually – they experience senescence just as people do. By contrast, the queens are fit and fertile until just before they die. They can suddenly lie dead in the colony, even after just laying an egg. Their protein synthesis runs at full tilt, right up until the end. Yet apparently, a major share of the new proteins don’t work or are destroyed by oxidative stress. Korb explains, “Physiologically, it goes up and down. The entire system seems to be collapsing.” With two colleagues, Korb recently published these results as a preprint on the biology server bioRxiv.
Csec’s home is in Australia. Their colonies are made up of 200 to 300 totipotent individuals. That means they can change their social role, the evolutionary biologist explains. She continues, “All the Csec queens and kings were workers at one time.” The latter more or less are elevated to royalty as a result of colonial need. Therefore, they become fertile, grow wings, and swarm out to establish new colonies. Korb says the social life within these colonies is quite simple. She elaborates, “For me, the Csec colonies are not superorganisms.” Yet her second lab animal, the Macrotermes bellicosus (Mbel), does form these. In their homeland in West Africa, the Mbel termites build enormous colonies with several million individuals and a complex social structure. Their realm is organized according to work. The queen and king are responsible for reproducing, soldiers defend the colony, and workers build and maintain the termite nest and bring in grass and leaves. The queen can produce up to 20 thousand eggs a day. “She simply can’t do any more than that,” says the ecologist. “The queen lays one egg after another,” she adds. The workers and soldiers, on the other hand, are irreversibly sterile. Their totipotence is lost in the egg or early larval stage.
Patience and breeder’s success
Mbel regents can live as long as twenty years. Their Csec counterparts only make a maximum of thirteen. Do the royal termites become older the less totipotent their workers and the larger their colonies are? In Csec colonies, royals and workers have lives of similar duration, in as far as their possible role reversals can be cleanly separated. The Mbel workers, by contrast, live only two or three months. They die at much a younger age relative to the royal couple. So do the royals live proportionally longer the more socially refined the termite colony of a species is? “It looks like this pattern exists,” says Korb, while urging caution. “The available data is still weak,” she adds.
Only a few groups world-wide are examining the aging of termites, a factor that is related to the insects as well. The expert says “There’s no trick you can use to make them age faster.” Her 15-member team sometimes needs to exercise a great deal of patience as they wait to examine an old royal couple. And termite colonization unfolds in a complicated way in some respects. “Mbel colonies cannot be transplanted,” says Korb. They breed a very delicate symbiotic fungus that cannot be moved from one place to another. Every laboratory colony goes back to a royal pair that has been freshly caught and feels relaxed and at home. Transporting them from West Africa stresses them so much that they lose their desire to breed the fungus. The Csec is easier to take care of. In its Australian homeland it colonizes dead mangrove trees. “They spend their entire lives in them,” says Korb. When being transported in sawed blocks of wood, the animals are never away from home.
Preserved mechanisms of aging
Korb's team is also investigating why termite societies of varying complexity have developed through evolution, why there are so many termite species in the tropics, and how the insects communicate with each other using scent. Korb is the spokeswoman of “so-long,” a group being supported by the German Research Foundation (DFG) which provided the impetus for the current anthology. The book is all about aging in the entire animal kingdom. “The mechanisms behind it seem to be strongly maintained across species boundaries,” says Korb. In one contribution, researchers analyzed publications on social helper systems and life expectancies of North American birds. That’s what determines – to put it lightly – that socially fouler fowl live shorter lives.
But getting back to termites. Kolb would like to work out more precisely the relationship between aging patterns and sociality by looking at termite species whose degree of sociality is between that of Mbel and Csec. She is hoping to investigate at a molecular level the aging and non-aging process of Mbel and Csec more closely. Together with two of her team members, in 2018 she demonstrated that working Mbel age rapidly because they have certain, movable elements of their DNA. Royal pairs inhibit this “jumping” gene to beat evolution. Lots of sex, and high levels of fecundity, usually bring other animals to an earlier demise.
It would also be exciting to uncover completely the secret of the nearly eternal youth of Csec royals. To be bright-eyed and bushy-tailed to the last or penultimate day sounds alluring, and humans also have the same, responsible signal pathways. “They're just wired differently and the processes are a long way from being understood,” says the ecologist. She goes on to point out an interesting question. Would genetic manipulation to maintain youth actually be ethical? “It would be possible already, probably with genetic scissors – if we really understood all the relevant processes,” muses Korb, looking into the future. “But until then, lots and lots of water will have flowed down Freiburg’s Dreisam river.”
Jürgen Schickinger