Thursday, February 23, 2017

Those amazing (and cool) tardigrades

And now, apropos of nothing at all, here's an interesting article on one of my favourite animals, the tardigrade, also known as water bears or moss piglets.
These amazing little critters kind of look like the blissed-out caterpillar from "Alice in Wonderland", except that they are tiny, ranging from 0.05mm to 1.2mm, depending on the species (there are over 1,000 different species within the tardigrade phyllum).
Tardigrades have long plump bodies with scrunched-up heads. They have eight legs with four to eight claws on each "foot", and they can also use these legs to swim quite effectively in water. Their mouths can telescope outwards to reveal sharp teeth which they can use to grab onto food, although they mainly just suck the juices from algae, lichens and moss (a few species, however, are carnivorous, and even cannibalistic). Female tardigrades may lay anywhere between 1 and 30 eggs at a time, and some species reproduce asexually.
Typically, tardigrades prefer to live in the sediment at the bottom of a lake or on damp mosses or other wet environments, but they can live almost anywhere, and this is one of their coolest attributes. They have been shown to be able to withstand environments as cold as -200°C, or as hot as +149°C; they can survive boiling liquids, intense radiation, and pressures of up to six times the pressure in the deepest parts of the ocean; they can even survive in the vacuum and radiation of space without any protection (their bodies produce a special protein that protects their DNA from radiation damage). In fact, they are almost indestructible.
In some conditions, tardigrades survive by going into a death-like state called cryptobiosis: they retract their head and legs and curl into a dehydrated ball called a "tun". In this state, their metabolic activity can go as low as 0.01% of normal activity, and their organs are protected by a sugary gel called trehalose. When exposed to water again, they can "come back to life" within a few hours. In fact, they need to always have a thin coating of water around their bodies in order to prevent them from turning into a tun. They can survive in this tun state for at least 30 years, and possibly for more than 100 years. In low oxygen water, tardigrade also have another trick: they stretch out their bodies and slow down their metabolism so that their muscles can absorb enough oxygen to survive.
And in case, you are waiting for me to say, oh, by the way, tardigrades are being pushed to the edge of extinction by our profligate modern lifestyles, it turns out that they are not on any endangered list, and they have happily survived five previous mass extinctions, and so they are not going anywhere any time soon. Cool or what?

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