Stuffed in a vacuum and bombarded by electrons, a tick waves hello

Not Exactly Rocket Science
By Ed Yong
Mar 15, 2012 5:59 PMNov 20, 2019 4:11 AM


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"I think it's saying, 'SPOON!'"

This movie has been filmed under conditions so harsh that they would kill virtually any animal. And yet, the star of the film is clearly alive – you can see it moving its legs, and after the shot was completed, it crawls away unharmed. It’s a tick, and it’s the first animal to be filmed with a scanning electron microscope

. These microscopes (known as SEM) can capture the most beautiful images of the tinier side of life, from pollen grains to insect feet to crawling cells

. But they’re not very good for looking at living things while they’re still alive. SEM microscopes work by firing a beam of electrons (the negative particles that form part of atoms), which rakes across the sample. Depending on the object’s shape and what it’s made of, the electrons scatter, reflect and absorb in different ways. The microscope collects this information to construct a picture of the object. The whole process happens in a vacuum, because air would distort the shape of the beam. And the specimen you’re trying to see also needs to be treated, which often involves drying, staining, and mounting. They’re often coated in a metal, such as gold, which helps to sharpen the resulting image. You can see why a living animal might not fare so well after being dried and slathered in metal, starved of air, and bombarded with a high-energy electron beam. But look at the video. The tick’s doing fine. Yasuhito Ishigaki from Kanazawa Medical University discovered the tick’s extreme endurance by accident, when he found the animals inside drying chambers

, connected to a vacuum pump. Even after 30 minutes with most of the air around them sucked away, the ticks survived. So Ishigaki put 20 live ticks (Haemaphysalis flava) in his SEM. He didn’t prepare them in any specific way, save for softly pasting them onto some conductive tape. He didn’t bother with any metal coating, since he knew that people have successfully looked at dead ticks under SEM without such coats. The animals lived. All of them waved their legs. That’s a clear sign of life, since dead ticks fold their legs tightly against their bodies. Clearer still, they got up and walked away after Ishigaki removed them from the microscope.

The electron beam does take its toll, though. While all the ticks survived for at least two days, they can last for several weeks if they never see an SEM, or even if they’re only exposed to the vacuum. In some cases, the ticks appeared to move their legs to avoid the incoming electron beam In itself, the videos don’t add very much to our understanding of ticks and mites (acarology, to those in the know). Since the 1970s, scientists have used SEM to study these tiny animals, and all we’re getting here is more detail about how they move. But the experiment certainly cements the tick’s status as one of life’s great survivors – a mantle it had not previously claimed. As Ishigaki writes, “It has been widely believed that no animal can live in vacuum condition.” Bacteria and lichens can certainly survive the vacuum of space, and in 2008, tiny creatures called tardigrades became the first animals to do so.

Tardigrades, or water bears, are famed for their Rasputin-like aversion to death, but they do so by drying out into a dormant inactive ball called a “tun”. By contrast, the ticks in Ishigaki’s experiment survived their ride in an SEM even though they were fully-hydrated and moving around. It’s not that ticks don’t need air. Indeed, some anti-tick chemicals work by blocking up the holes through which they breathe. It just seems that they can go without air for a long time, with no ill effects. Reference: Ishigaki, Nakamura, Oikawa, Yano, Kuwabata, Nakagawa, Tomosugi & Takegami. 2012. Observation of Live Ticks (Haemaphysalis flava) by Scanning Electron Microscopy under High Vacuum Pressure. PLoS ONE

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