Dale Fort Blog Number 27

21 02 2014

TARDIGRADESTardi

Unless you have a microscope you’re not likely to be very familiar with Tardigrades.  The likelihood is that you are sitting pretty close to very large numbers of them.  These remarkable animals dwell in their millions among the mosses and lichens that develop and grow in the cracks between paving stones, in gutters and on rocks and stones.

They were not discovered until 1773 when the German naturalist Goeze described them as kleiner wasseba.   This means “little water bear”.  They have 4-8 limbs, each of which ends in a little claw.

Cuudly bear with text

Tardigrade means “slow walking” and this is what they do.  Under a low-power microscope they resemble bumbling-gaited microscopic bears.

Tardigirl with text

Most of the 1000-odd species feed on plants, sucking the juice out them using a pair of piercing stylets that emerge from the mouth.  Some of them are predators using the same method to eat other animals like nematode worms (See Blog 1).  Some consume microscopic creatures whole and some are cannibals.

Most species have separate sexes.  The males fertilize the eggs through a gonopore or sometimes eggs are laid on the ground and fertilized there.  Some species have no known males and reproduce by parthenogenesis (virgin birth, no chaps involved).

The most astonishing thing about these creatures is their ability to survive extreme conditions.  They are found at the tops of the highest mountains, and at the bottom of the deepest seas. They are found deep underground, in hot springs and from the poles to the equator.

They survive extreme environments by virtue of their capacity to adopt a “resting” stage called a tun . In this state, they can survive temperatures near to absolute zero or as high as 150oC; levels of radiation  a thousand times stronger than any other known animal; lack of oxygen equivalent to the vacuum of space and a decade or so without any water.

tardi tun and active

It may not be possible to detect any signs of metabolism during this phase.  All they need is a drop of water and a few hours and they’ll be back to normal.  This might cause us to redefine what we mean by death because “no metabolic activity” isn’t a bad definition (although “nature’s way of telling you to slow down” is funnier in my opinion).  This ability is known as cryptobiosis (hidden life) and an understanding of it leads to wildly exciting possibilities for space travel and organ transplants.  It also might help to explain why we’ve found it so difficult to establish if there’s life on Mars.  What if something like a tardigrade existed for long periods as a resting stage and only showed signs of life every few 100 years or so?  You’d have to be lucky to catch it when it was detectable with one probe every 20 years.  We need to send a tardigrade specialist to Mars.  I know of only one (hello Clive) and I don’t think he wants to go.  Some people go so far as to suggest that the ancestors of our current species might have been early colonisers of the earth from elsewhere in the cosmos.  They’ve certainly been on earth for a very long time. fossil evidence dates back to at least the Cambrian Period (530 million years ago).

Behold with text

If they can survive the vacuum of space and if say a meteorite impact could blast them into space (and several hundred meteorites that have been found on Earth are known to be bits of Mars) then it could be that the loonies are in fact correct and aliens are indeed among us.  They might still be arriving.

Celebrate these remarkable animals by building one for yourself:

Build your own tardigrade

Designed by Jane Cutting, Placement Student at Dale Fort a long time ago.

Keep a look out for Blog 28 when Nunzilla may return…..

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