Time travellers

 

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When I was working on the book I’ve just finished I became a little fixated by the rotifers and I blogged about them previously, here and here. However, these two posts are not enough and I feel like I must discuss these tiny creatures at length such is their mind-boggling biology. One thing that particularly fascinates me about the rotifers and the other small animals of transient aquatic habitats is their ability to time travel. I don’t mean they have a glowing, whirring device at their disposal that transports them to a year of their choice, but they do have adaptations that are perhaps the next best thing. Namely, by entering a state of very deep quiescence (cryptobiosis) or persisting as resting eggs they slow their vital processes to such a degree that the spark of life is vanishingly faint – perhaps 0.01% of normal. This allows them to cross stretches of time effectively unaged between periods of favourable conditions when they can get on with feeding and reproducing. Exactly how long they can survive these periods of suspended animation is a bone of contention, but it’s certainly decades and possibly even centuries or millenia. Below are some photos illustrating these adaptations in rotifers and tardigrades.

The rotifer, Pompholyx sulcata. Attached to the rear-end of this rotifer is a large resting egg – a time-travelling adaptation of many rotifers species (Image courtesy of Michael Plewka).
The resting egg of a tardigrade. These eggs have a thick shell that is very often elaborately sculpted (image courtesy of Eye of Science/SPL).
A tardigrade entering the state of cryptobiosis. This complex dehydration process involves all the water molecules in the body of the animal being replaced with a simple sugar, typically trehalose (image courtesy of Microfield Scientific Ltd /SPL).
Following on from the image above, the process of cryptobiosis is almost complete and the tardigrade is now little more than a dried out husk (a tun) that can see out very long periods of unfavourable environmental conditions (Image courtesy of Eye of Science / SPL).

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