Ebay tardigrades (I)
Obiously, the world wide tardigrade species distribution pattern is difficult to determine.
But there are very impressive national geographic distribution snapshots like
the dissertation by Hieronim Dastych "The Tardigrada of Poland".
You can imagine the tremendous work input by Hieronim Dastych and his
co-workers when taking into account that his publication is based upon 5,261 samples with
81,532 (!) tardigrade individuals. Similar deep-digging work appears to have
been performed in some other countries, e.g. in Italy, Austria, the Czech Republic,
Sweden, France, Denmark, Greenland, Russia, Switzerland, The United States,
Great Britain and Germany, with some of the publications dating back several
or many decades.
The geographic distribution situation might appear to be even more complex
when we think about how those national species distributions might change
with time. Remember, nowadays we find numerous reports about so-called
"alien" species - strange plants, frogs or shells that suddenly
conquer a foreign region and suppress local populations. Probably it would
turn out to be an endless task to follow the species distribution changes
of tardigrade populations with time in all countries, all over the world.
And of course this type of scientific work is far beyond the scope of our
very down-to-the-earth, popular magazine. But still we can try to
understand the contributing mechanisms behind those changes by which also new
tardigrade species might suddenly arrive in a region where they have not been met before.
It is well known that tardigrades are in fact travelling and it appears that
they can be found among the first pioneer animal species which settle in new, possibly
somewhat problematic regions. For example Fritz Heinis from Switzerland has shown already
in the first half of the last century that tardigrades were among the
limited number of new species that re-settled shortly after the terrible
19th century Krakatau vulcan catastrophy on an assumedly sterile ground.
The following quotation is based upon Heinis' results, too:
"A stone memorial was unveiled in 1904 and soon some
moss cushions were found on it. After only two years two tardigrade species
were discovered in those moss cushions. In 1927, i.e. after 23 years
5 tardigrade species were detected, which most probably have been transported
to the stone by air."