The genus Echiniscus

The definition of the genus  Echiniscus  is based on a description by  C.A.S. Schultze from Greifswald, Germany (year 1840, see literature).
Those Echiniscus water bears are among the most beautiful creatures on earth.
Of course you might buy a microscope just in order to look at the cells of an onion skin. There is no reason to despise onion skins but your first microscopic encounter with an Echiniscus water bear will be a real thrill. They show strange, jelly-like body fluid and a perfectly controlled  muscle movement .

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Issue #19

[echiniscus tardigrade jpg]

Portrait of an echiniscus water bear.
Typical body length ca. 0,3 mm.


The Echiniscus water bears belong to the order of the Heterotardigrada, i.e. armoured and 'hairy' tardigrades (see zoological systematics).
They bear body appendices which are called filaments, feelers, 'hairs' or thorns. Length and position of the body appendices are important criteria for species determination, as well as the number, form and surface characteristics of the armour plates.
The visual appearance of the  legs and claws   can be of taxonomic value, too.

A special nomenclature has been developped for the description of the armour plates and for the position of the body appendices:


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fig. 1: back of an echiniscus water bear, photomicrograph

fig. 2: back of an echiniscus water bear, nomenclature


Explanations: the roman numbers in fig. 2, left side, refer to the body plates I to IV.
K is the head plate, body plate I is sometimes called shoulder plate.
The red inscriptions S1 to S3 indicate the positions of the so-called intermediate plates which are closer to the body than the more massive body plates.
The capital letters A to E indicate the positions where filaments can be situated. In the example shown here filaments are present in positions A and C, they are lacking in positions B and D.
The filaments on level C are oriented in two different manners, laterally and dorsally, another position might be in-between (dorso-lateral). Furthermore we notice dorsal thorns in position D.


The properties, in particular the number and length of the filaments can vary among the individuals of a given species and furthermore depend on the age of the individual under consideration. For comparison just think of homo sapiens  who tends to loose some hair on top of the head with increasing age whereas additional hairs grow out of nose, ears and eyebrows.

A reliable species determination within the genus Echiniscus can be performed by a few professionals only. This is the point where the Water Bear web base reaches its limits and where you should consult the  scientific literature  .


Literatur:

C.A.S. Schultze: Echiniscus bellermanni, animal crustaceum. Berlin 1840.

WB web base #19


©Text and images by  Martin Mach