Thursday, April 23, 2009

Water bears in space - and on my garage roof

The cushions of moss that grow on my garage roof are a rich source of microscopic wildlife, including these little tardigrades, also known as ‘water bears’ or ‘moss pigs’. These are up to a fifth of a millimetre long, with eight legs that end in claws that allow them to clamber amongst the leaves of mosses. Tardigrades feed on mosses in the same way that greenfly feed on larger plants, by spearing the plant with a hypodermic syringe-like stylet and draining out the sap - you can see the green cell contents inside the gut of one of the tardigrades in these pictures. The most amazing thing about tardigrades is that they are virtually indestructible. When their habitat begins to dry out they develop into a barrel-shaped resting cyst call a ‘tun’, and in this state can survive in a state of extreme dehydration for decades. While in the tun stage they can survive extreme environmental conditions – even extreme vacuum and cosmic radiation in space – see


  1. I was aware of microscopic living creatures but to see such a tiny creature so clearly, especially with the video, shows how intricate and fully formed they are. I always think of life this small being of the single or few cells type.

    A brilliant, informative entry. John

  2. Thanks John, it is astonishing how these tiny animals can be so complex. The largest species are only a little over a millimetre long.


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