Tardigrades - just a funny joke?
time ago we received an e-mail by a pupil who had been laughed at
by his biology teacher who didn't believe in the existence of tardigrades
have asked us how to clean their jeans from tardigrades and whether
tardigrades might cause itching
An other reader
comes up with the question: tardigrades - a new hoax?
So, it seems that we have to clarify some facts here.
Water bears (= tardigrades) are real: but how
to prove their existence ?
Tardigrades are widely unknown to the public including
many scientists and, strange enough, even some biologists.
But when looking up the term 'tardigrade' in a good encyclopaedia you will
usually find a small entry at least.
Tardigrades are strange microscopic, multi-cellular animals. About 750
species are known to the scientific world. They always live in water:
in the oceans and in ponds but most typically in small droplets of
water bound by mosses or lichens. So you can bet that some tardigrades
will be very close to you, usually in a distance of less than 10 meters !
In order to prove their existence to anybody you might proceed as
described in our introductory chapter
on tardigrade collecting and simply present a few living tardigrades.
Most schools do have microscopes which as a rule can be used for a demonstration.
Some people are easily convinced by photographs
or videos , but as we all know,
nowadays a digital photograph or a video might be a fully synthetic product
far from reality.
We do not have a single report about a tardigrade seeking human contact
or annoying somebody, e.g. by biting into a person's skin.
Why are the tardigrades so much
They are so much miniaturized, everything being smaller by a factor
of 1000 when compared to humans or mammals but they still resemble so-called
higher animals like lizards or as their name indicates, even bears.
Water bear in full movement, exploring a tiny water droplet.
Body length ca. 0.3 mm.
Even after the invention of the microscope it took some time until the first
tardigrade was found - in the 18th century, by a German pastor, an early
Water bears have miniature legs, claws, muscles,
eyes, stomach, mouth and nerves. The relative size of a water bear is
demonstrated here .
Water bears show signs of youth
and high age . There are
both sexes and sexual behaviour as well.
Water bears have the strange ability to dry out fully and to
come back to active life just by
means of a droplet of water!
Perhaps it was not the full truth that tardigrades have not been annoying humans:
zoologists desperately tried to fit the tardigrades somewhere into the zoological
system but in the end resigned and gave them a phylum of their own, which is
really an honour when keeping in mind that e.g. the big group of vertebrates
has been devalued to a lower taxonomic ranking.
Though tardigrades like to spend their leisure time on the bottom of the oceans,
in glacier holes, hot springs and on top of the Himalayas, you will find them
also in the cities, in the humble green between the pavement stones -
you do not need to travel far to find them.
In short: is there something special about water bears?
- are real
- are very small (typically 0.3 to 0.5 mm) but not primitive
- have a precise muscle control and move like higher animals
- resemble little bears; some have claws like cats
- have a mouth, head, brain, legs, eyes, nerves, muscles ...
- live next door to you (for sure)
- are thought to be extraterrestrials, at least by some authors
- have strange eggs which look like miniature artwork
- can transform into a dry state which can return to life after years
- in dry state need only a drop of water to revive
- in dry state survive acid and solvent attack
- in dry state survive very high and very low temperatures
- in dry state survive high pressure and radioactive radiation
- have been found under 5 m layers of ice
- have been found in oceans 6000 m below the surface
- have been found on mountains, 6000 m high
- are a phylum (!) of its own
- are fascinating to look at under a microscope
- in return seem to look at you from under the microscope
- are a fine topic for biology courses
- are unknown to most of your neighbours, even to some biologists
- have escaped exploitation by man for centuries