The genus Macrobiotus

[Macrobiotus water bear (jpg)]

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Zoological systematics
WB web base #18

Macrobiotus water bear. Anterior part of the body. Image width ca. 150µm

The water bear genus  Macrobiotus  was established by C.A.S. Schultze from Greifswald, Germany, in 1834. He described the first species Macrobiotus hufelandi  within the new genus.
You will find a translation of the original text by Schultze   here !

The form and symmetry of the claws are considered as the most important characteristics of the genus Macrobiotus:


Claws of a Macrobiotus water bear. Redrawn on the basis of an illustration by Ernst Marcus (see literature).

Furthermore the elements of the buccal system are valuable taxonomic properties:


Buccal system of a Macrobiotus water bear (Macrobiotus cf. hufelandi). Explanations:
(1) Macroplacoids: solid bars within the pharyngeal bulb serve for chewing. Form and number are characteristic for individual species within the genus Macrobiotus
(2) Microplacoid, can be absent in some species
(3) Mouth tube. The mouth tube of the genus Macrobiotus is straight, not flexible and of large diameter.
(4) The two stylets are rigid and strongly curved. Their normal use is for piercing plant cells (video clip: stylets in action)
(5) Stylet sheaths guiding the stylets outward through the mouth tube. Note the slits through which the stylets will emerge from their sheaths
(6) Mouth opening, here typical round Macrobiotus "kiss" mouth
(7) Muscles of the pharyngeal bulb help to pump liquid food into the stomach; remaining particles are crunched by the macroplacoids
(8) Stylet supports. The flexible stylet supports are fixed on both sides of the buccal tube and work like a spring against the stylet muscles

Macrobiotus water bears move faster than the red Echiniscus water bears. Their body appears to be transparent or white (in incident light). Some of them can have a grey or brownish colour, but they are never red like those Echiniscus water bears on the title image of the WB web base. In 1986 Walter Maucci (see literature) counted 93 different species within the genus Macrobiotus worldwide.


Typical Macrobiotus tardigrade

The Water Bear web base is intended as an appetizer for microscope amateurs. For more reliable information on species determination you will need   special reference literature .

© Photomicrographs and illustration by  Martin Mach

Back to:
Zoological systematics
WB web base #18


Ernst Marcus: Bärtierchen. p. 6 (1928).

Walter Maucci: Tardigrada (Vol. XXIV of the series Fauna d'Italia). p. 180. Bologna 1986.