Aged-Out

Honey bees challenge many of the ideas we have about ageing (imagine doing the most physically demanding work of your life at the very end, or your mother naturally living more than 30 times as long as you…). Science writer Dave Black takes a look at what we know about our honey bees’ ageing process.

By Dave Black

"By the time you're eighty years old you've learned everything. You only have to remember it."[i]

A recent birthday may have been the reason for wondering about what it means to be getting older, but I can’t remember. I couldn’t even properly remember this, from the deadpan, self-deprecating comedian George Burns. I had to look it up again.

Not that I’m eighty… yet.

Worn wings, a sign that a bee (bumble in this case) is nearing the end of life. Curiously, honey bees seem to ‘live life backwards’, carrying out the most physically exhausting work (foraging outside the hive) later in life. Photo: Rusty Burlew (www.honeybeesuite.com)

Why is it when the clock ticks the hands seem to only ever head in one direction, towards cellular damage and dysfunction? Can’t we expect more than ‘three-score years and ten’ without the labour and sorrow?[ii]  If Nature is so clever why doesn’t it select for organisms that don’t suffer from old age? It is odd that Nature’s ability to produce highly complicated creatures doesn’t seem to be accompanied by some imperative to preserve them.

The failure of natural selection

There is no reason to believe there are any particular genes whose presence or absence may have evolved to cause ageing. For most organisms hazards like disease, predation, and accidents are responsible for their death. The genetic traits that affect their reproductive fitness when they are young and reproducing matter most, because there will always be more youngsters than ‘veterans’, and adaptive variations that affect them later in life will be less subject to natural selection. It’s just statistics.

Characteristics that might be of benefit when you are old, but not when you are young, are only going to be useful if you live that long; few do, and if they do the probability of the trait being passed to any progeny with any frequency are very low.

A curious Disease

When biologists talk about ageing they call it ‘senescence’, which refers to an unavoidable, progressive, physiological deterioration of self-organizing systems that reduces reproductive performance, and increases the probability of dying.

One thing we have learnt in the last 40 years is that ageing is not actually just a matter of time, of chronology, and it’s not as universal, inexorable and inevitable as it first appears. It doesn’t happen in many plants, and in several laboratory animals we have been able to intervene, increasing their healthy life-span[iii]. There is even such a thing as ‘biological immortality’[iv].

Gaming the System

As is so often the case, honey bees challenge many of the ideas we have about ageing. For a start their clock can be gamed, the link between chronology and performance is at best tenuous. You may have come across the description ‘phenotypic plasticity’. It’s a very precise way of saying their behaviour and physical form can be ‘pliable’ (plastic); it changes to suit the circumstances. The task-specific ‘division of labour’ we notice as worker bees age (housekeeping, nursing, guarding, comb-building, and so on), and the associated physiological abilities, (producing wax for example) is flexible, even reversible[v].

What’s more, bees that inherit identical sets of genes can live for years, or only a few months. A worker or a queen can develop from the same egg but could have vastly different lifespans, depending on a dietary variation that begins in the larval stage. Queens develop faster, emerging as an adult five days earlier than a worker, but are heavier and live longer. Human siblings never have such disparate natural lifespans.

We might wonder if there is something special about the social insects, ants, termites, bees, and wasps, who all exhibit this range in life-span. Honey bee queens have been reported to live as long as eight years[vi]. A more credible estimate would be two to three years, still considerably longer than a honey bee worker where the longest report was 320 days, and a couple of months might be the usual expectation.

From Münch, D., Amdam, G.V., 2010. The curious case of aging plasticity in honey bees. FEBS Letters 584, 2496–2503. https://doi.org/10.1016/j.febslet.2010.04.007

Many species of ants also have very long-lived queens and in one species have been reported to live up to 13 years, which was 10 years more than their workers[vii]. Curiously, one recent honey bee study last year transplanted gut bacteria into microbiota-free bees from a sterile environment and found that the ones that received queen gut bacteria (rather than worker) extended their lifespan.[viii]

Now, clearly, honey bees are ‘born’, and then they die, but how much is their mortality due to the risks they face in later life (they are ‘killed’, or run out of ‘fuel’) and how much to senescence (they ‘age’)? One common thought is that after a while foraging bees, in some way, simply run out of the enzymes they require to fuel continued flight.

Curiously Benjamin Button[ix]

One of the ways we think about ageing is how it relates to nutrition and energy consumption. Honey bee foragers have lived life backwards, in that their huge metabolic and energetic turnover powering flight, a hundred times greater than a resting bee (and three times that of a hummingbird), occurs at the end of their lives. While we humans slave when we are young and then retire to potter around the house, they’re doing it the other way around. Their cells that use oxygen to ‘burn food’ and provide all this energy, the mitochondria, actually get better at it as foragers get older. In all the other animals that have been looked at the opposite is true, mitochondria senesce.

Honey bee foragers somehow escape the oxidative stress, protein degradation, and metabolic slow-down that we normally see in other animals[x].

Let Food be Your Medicine

Ultimately, we’d expect there would be some trade-off to make between basic survival and reproduction as there may rarely be enough food to support both[xi]. By ‘off-loading’ the energetic cost of caring for offspring and feeding them to near-relatives, honey bee queens can afford to produce large numbers of eggs for a long time.

Queen bees also experience a different diet, royal jelly, which has been shown to increase the lifespan of worker honey bees and of some other animals commonly used in gerontological research, like Caenorhabditis elegans (a flatworm), drosophila (a fly), and mice[xii]. Probably why some people swear by it.

The discovery, 80 years ago, that ageing can be ameliorated by nutritional restriction (restricted but adequate) in the same animals led to research investigating the cellular neural pathways that both detect nutrient status and direct the responses to it. It’s nutrient sensing or ‘signalling’ networks that are largely responsible for establishing that nutrition ‘trade-off’, and they evolved at a very early evolutionary stage in the development of multi-celled animals.

Work published by Michael Klass in 1983, when he was screening chemically created mutants of C. elegans for short and long-lived variants, detected a single gene mutation that caused the worms to remain healthy and youthful for far longer, double the normal lifespan[xiii]. It turned out to be the important discovery and the gene was deemed partly responsible for a nutrient signalling ‘pathway’ also shown in drosophila, and later in bees[xiv].

Another such pathway (the Target Of Rapamycin (TOR) pathway) can be ‘switched off’ by a drug (rapamycin) to mimic the effects of dietary restriction. The drug is currently under clinical trial studying longevity in dogs, and is just one of a new class of ant-cancer/anti-ageing drugs under development targeting nutrient sensing.

Meals Shared

These signalling networks are proving to be central to senescence in many types of animals. The challenge for bee scientists is to describe the interaction between nutrient sensing pathways, the bee’s juvenile hormone (JH, which regulates growth, reproduction, and longevity, and caste determination) and the fat-body produced anti-oxidant protein vitellogenin (Vg).

It’s the last of these that may prove to be fundamental to the honey bee’s peculiar take on ageing. The fact that vitellogenin is a widely shared royal-jelly protein and therefore indicative of the temporal social relationships at play in the colony, and that it suppresses (and can be suppressed by) juvenile hormone, (effectively an ageing hormone in insects), links the honey bee’s unusual social arrangements to its volatile longevity[xv].

For ‘bees, you’re as old as the company you keep.

References

[i]Comedian and entertainer, George Burns (1896-1996)

[ii]“The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away”. King James Bible, Psalms, 90:10.

[iii]Gems, D., Partridge, L., 2013. Genetics of Longevity in Model Organisms: Debates and Paradigm Shifts. Annu. Rev. Physiol. 75, 621–644. https://doi.org/10.1146/annurev-physiol-030212-183712

[iv]https://en.wikipedia.org/wiki/List_of_longest-living_organisms - visited 16/04/2025

[v]Münch, D., Baker, N., Rasmussen, E.M.K., Shah, A.K., Kreibich, C.D., Heidem, L.E., Amdam, G.V., 2013. Obtaining Specimens with Slowed, Accelerated and Reversed Aging in the Honey Bee Model. JoVE 50550. https://doi.org/10.3791/50550

[vi]This rather starting statistic was reported once in a Russian beekeeping magazine, that 35% of queens in normal colonies survived 4-6 years, and that three queens lived 8 years or more. It’s been uncritically cited in many scholarly papers since. Bozina, K.D., 1961. How long does the queen live? Pchelovodstvo 38, 13.

[vii]Page, R.E., Peng, C.Y.-S., 2001. Aging and development in social insects with emphasis on the honey bee, Apis mellifera L. Experimental Gerontology 36, 695–711. https://doi.org/10.1016/S0531-5565(00)00236-9

[viii]Wang, H., Chen, W., Lei, L., Zhang, W., Liu, Z., Wang, Y., Xu, B., 2024. Queen bee gut microbiota extends honeybee lifespan by inhibiting insulin signaling. Appl Environ Microbiol 90, e01799-23. https://doi.org/10.1128/aem.01799-23

[ix]The Curious Case of Benjamin Button, by F. Scott Fitzgerald, Collier's Magazine, May 27, 1922. Film, 2008, directed by David Fincher.

[x]Menail, H.A., Cormier, S.B., Léger, A., Robichaud, S., Hebert‐Chatelain, E., Lamarre, S.G., Pichaud, N., 2023. Age‐related flexibility of energetic metabolism in the honey bee Apis mellifera. The FASEB Journal 37, e23222. https://doi.org/10.1096/fj.202300654R

[xi]Maklakov, A.A., Chapman, T., 2019. Evolution of ageing as a tangle of trade-offs: energy versus function. Proc. R. Soc. B. 286, 20191604. https://doi.org/10.1098/rspb.2019.1604

[xii]Yang, W., Tian, Y., Han, M., Miao, X., 2017. Longevity extension of worker honey bees ( Apis mellifera ) by royal jelly: optimal dose and active ingredient. PeerJ 5, e3118. https://doi.org/10.7717/peerj.3118

[xiii]Partridge, L., 2010. The new biology of ageing. Phil. Trans. R. Soc. B 365, 147–154. https://doi.org/10.1098/rstb.2009.0222

[xiv]Ament, S.A., Corona, M., Pollock, H.S., Robinson, G.E., 2008. Insulin signaling is involved in the regulation of worker division of labor in honey bee colonies. Proc. Natl. Acad. Sci. U.S.A. 105, 4226–4231. https://doi.org/10.1073/pnas.080630105

[xv]Münch, D., Amdam, G.V., 2010. The curious case of aging plasticity in honey bees. FEBS Letters 584, 2496–2503. https://doi.org/10.1016/j.febslet.2010.04.007