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