Cities within cities - tardigrade populations within human cities -

Internet pages come in different flavours - and in different languages. Most pages, of course are in English, but there are also valuable offers in other languages. One of them is Rolf Schuster's   tardigrade dissertation  which can be downloaded in full text without costs (PDF, in German language 2.47 MB).

The German title reads:

Rolf Schuster: Faunistische und ökologische Untersuchungen an moosbewohnenden Tardigraden. 163 S. Dissertation. Hinterzarten/Schwarzwald 2003. The dissertation shows how to measure tardigrade populations numbers in a scientific manner.

As most of you will not be able to read in German language we will present instead a much more primitive own approach to a question like: "How many tardigrades do live unnoticed in a city like Munich, Germany (i.e. together with 1.3 million human inhabitants)?"

We will skip the Munich city highway, the subway and the densely populated moss cushions and have a look at a more typical city surface area type with a high area coverage: autumn leaves on pavement.

Leaves on the pavement of a typical Munich backyard area

Leaves on the pavement of a typical Munich backyard area,
as seen from a little bit closer.

Similar leaves, already immersed in water, in a petri dish

We assume that the leaves are not an ideal habitat for the tardigrades but that they will partially reflect some tardigrade presence from trees, walls and pavement. And in fact we did find tardigrades in the leaves, not many, and only individuals belonging to the single species  Ramazzottius oberhaeuseri .

Tardigrade Ramazzottius oberhaeuseri, from a Munich backyard (1).
Body length ca. 0.25 mm.

Young tardigrade Ramazzottius oberhaeuseri, from a Munich backyard (2).
Body length ca. 0.2 mm.

Tardigrade Ramazzottius oberhaeuseri, from a Munich backyard (3).
Anatomical details: Anterior body with buccal apparatus.
Please note that this species has no eye spots.

Well, just three samples, each with only one or two individuals of a single species, this is nothing when compared to Rolf Schuster's sophisticated dissertation and it is definitely not enough for reliable population statistics. Therefore we have peeped into the dissertation in order to compare our own results with the more scientific results and we were quite surprised that the magnitude looked similar:
On page 126 of the dissertation we did find a table with the individuum numbers per area unit that have been measured by various scientists.
The minimum tardigrade inhabitant numbers for leaves and soil listed are in the range between 0.1 and 1.3 tardigrades/cm². For a 40 m x 40 m backyard and a pessimistic population density of 0.1 tardigrades/cm² this sums up to a 1.6 Mio. (!) tardigrade community. Possibly some more or less. Being on the optimistic trail we might enlarge our calculation for the Munich city surface area and get ca. 100 billion tardigrades for Munich. And continued up to perfect crazyness we calculate for the earth surface area (without oceans) 125.000.000.000.000.000 tardigrades. You are invited to perform your own counter-measurements and counter-calculations. But do not forget the oceans - otherwise everything might be false ;-)

Merry Christmas and Happy 2008 for all our readers!

Literatur

Rolf Schuster: Faunistische und ökologische Untersuchungen an moosbewohnenden Tardigraden. 163 p. Dissertation. Hinterzarten/Schwarzwald 2003.

Roberto Guidetti, Roberto Bertolani und Diane R. Nelsnon: Ecological and Faunistic Studies on Tardigrades in Leaf Litter of Beech Forests. Zoologischer Anzeiger 238 (1999) p. 215 - 223.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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