Macrobiotus tardigrade. Anterior part of the body.
Image width ca. 150µm
The definition of the genus Macrobiotus was established
by Schultze. In 1834 he described the first species of the genus
Macrobiotus, Macrobiotus hufelandi.
Have a look at Schultze's original text here !
The most important characteristic property of Macrobiotus tardigrades
are the kind of branching and the symmetry of the claws:
Claws of a Macrobiotus tardigrade. After Marcus (see literature)
The parts of the pharyngeal apparatus are important for taxonomy as well:
Fig.: Pharyngeal apparatus of a Macrobiotus tardigrade (Macrobiotus cf. hufelandi).
(1) Macroplacoids: calcified parts within the pharyngeal bulb
serve as chewing instruments.
Form and number of the macroplacoids can be
recognised easily and are often used to distinguish among different species
(2) So-called comma, can be absent in some species
(3) Mouth tube. The mouth tube of a Macrobiotus is always approximately straight,
unflexible and wide.
(4) Macrobiotus tardigrades have strong curved stylets which
serve as a tool to pierce plant cells see video: stylets in action
(5) Stylet sheaths. The stylet sheaths have slits at their front ends,
so the stylets are guided through them to the outside world.
(6) Mouth opening, here a round 'kissing' mouth;
(7) Muscles of the pharyngeal bulb
(8) Stylet supports. The stylet supports act like springs
working against muscles which are fixed to the pharyngeal bulb
Macrobiotus tardigrades as a rule move much more quickly than e.g.
the red, armoured echiniscus tardigrades (see title image of the Water Bear web base).
Their body colour is white or brownish in incident light, transparent in
transmitted light, never red. The stomach contents can be green.
Walter Maucci (see literature) counts about 93 Macrobiotus species worldwide.
Typical visual appearance of a Marcrobiotus tardigrade.
For an exact identification you will need dedicated, scientific literature (Ramazzotti/Maucci, see literature.).
The probably best and most modern taxonomic book is:
G. Ramazzotti und
W. Maucci: Il Phylum Tardigrada. Memorie dell'Istituto Italiano di Idrobiologia
41 (1983) p. 1-1012 [in Italian language only, but there
exists an English translation by professor Clark W. Beasley].
Ernst Marcus: Bärtierchen. p. 6 (1928)
Walter Maucci: Tardigrada (vol. XXIV in the series Fauna d'Italia). p. 180. Bologna 1986.