Tiny But Perfectly Formed

Regular readers (assuming the plural is appropriate) will know that our remit is to explain new developments in cancer. So numerous, multi-faceted and remarkable are these that we have been obliged in the past to offer explanation, if not apology, for surfeits of superlatives. So there is no requirement to step outside the admittedly broad acres of cancer biology to inform, astonish and amaze. Nevertheless, a change is said to be as good as a rest and for this we will make a rather pathetic bipedal excursion into the six-legged world that makes up, we estimate, more than 90% of all the different life forms on earth.

Meet the family

Yes, it’s the insects that have caught our eye – specifically a species of planthoppers by the name of Issus coleoptratus. They’re members of the Issidae family which alone includes about 1000 distinct species – a staggering thought, although if you bear in mind that there are approaching 10 million insect species around, clearly each family needs to contribute its bit. The Issidae was first described by one Maximilian Spinola – who was indeed descended from the celebrated Genoese family, pre-eminent during the high-water period of that city-state between the 12th and 14th centuries.

Issus nymph. Photo by Malcolm Burrows

Issus nymph. Photo by Malcolm Burrows

The Issidae are common in Britain and Europe but they’re unusual in that, although they still have wings, they’ve lost the ability to fly. But if you didn’t know already you’ll have guessed that they’ve made up for this in terms of getting around by working hard on their leg muscles. So much so that the nymphs (which, delightfully, is what the insect folk call the immature form – just a couple of millimeters long before it metamorphoses into a grown-up) can jump up to 40 cm – more than 100 times their length.

As you might suppose, to achieve such calisthenic feats the nymphs need their back legs to be as coordinated as possible – not least to prevent them veering off in random directions, rather like the man-powered flight loonies who jump off London Bridge.

Electrical v. mechanical

Somewhat surprisingly, it’s emerged that electrical signalling via the nervous system isn’t good enough for this coordination. Malcolm Burrows and Gregory Sutton from Cambridge and Bristol Universities, respectively, have shown that to get both legs to kick off within 30 microseconds, the Issus make interacting gears that, in effect, lock their legs together. That’s an astonishing finding because although we know that proteins can do anything – form cables, bridges and travelators as well as pumps, rotating flagella and even motors (such as the ATP synthase of mitochondria) – a toothed wheel is a first. Even against a backdrop of such amazing, multi-component machines, it’s a staggering sight – the more so as Burrows and Sutton estimate that on take-off the gears whiz round to the tune of over 33,000 revolutions per minute!

Gearwheels of the flightless planthopper insect Issus

Gearwheels of the flightless planthopper insect Issus

There are, of course, other great leapers in the insect world but those that have been examined use friction for synchronization – grippy legs if you like. So it’s a bit of a mystery that this planthopper has come up with such a sophisticated locking system. But that’s not the only remarkable thing about these little chaps because as they grow into adolescents they go through a kind of moulting process in which they shed their exoskeleton for an upgrade – including progressively bigger gears. How incredible is that? But having gone to all this trouble the final amazing twist is that the gears vanish when nymph becomes adult! So for the rest of their lives they too rely on non-slip legs.

Burrows and Sutton hazard that, although mechanical gears are the most efficient way of linking both legs at kick-off, they carry a big risk for prolonged use – damage a tooth and the chances are you’ll end up on someone’s menu. So better a somewhat less efficient system that is not liable to failure. Exactly how I justified driving an Austin A35 for many years.

One Giant Leap For Mankind

So these marvellous juveniles, less than half a centimeter long, pull off a trick equivalent to me jumping the length of the Melbourne Cricket Ground with so much to spare I land somewhere in the stands. No question, it gives a new meaning to the term ‘jumping genes’ that, you may recall, are stretches of DNA that can be shifted around the genome. They were discovered 60-odd years ago in maize by Barbara McClintock who came from Hartford, Connecticut and remains the only woman to win the Nobel Prize for Physiology or Medicine on her own.

How Did You Know That?

Well, the thing is we now know that these athletic DNA fragments can sometimes land in the wrong place – meaning that they disrupt normal genes. If that sounds suspiciously like a type of mutation it is, and the insertion of a jumping gene can act as a cancer-promoter. By which ingenious piece of circuitry we bring ourselves back to cancer – where we should be – having nevertheless thoroughly enjoyed our visit to the insect Olympics.

References

Burrows, M. and Sutton, G. (2013). Interacting Gears Synchronize Propulsive Leg Movements in a Jumping Insect. Science 341, 1254-1256.

http://www.extremetech.com/extreme/166493-evolution-delivers-the-first-mechanical-gear-found-in-a-living-creature

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