Once more, we will discuss the water bear Cornechiniscus cornutus.
This time we will have a look at the impressive sensory instrumentation in the head and 'nose' region. It must be assumed that those 'hairs' or filaments and papillae found on heterotardigrades species and in particular the horns of Cornechniscus are mechanical and possibly also chemical sensors.
Scientists have tried to check this out by teasing the Echiniscus water bears with their pipettes and needles but apparently the reactions of the water bears to this impertinence have remained a little bit unclear. But there is histological evidence that some of those papillae are directly connected to the nervous system. So it appears highly probable that most of the protrusions and filaments function in a similar way as e.g. the whiskers of a cat.

Sketch of the head of Cornechiniscus cornutus,
as seen from below.

CMI: cirrus medialis internus
CME: cirrus medialis externus
P: papilla cephalica
H: horn
Sp: buccal tube
St: stylets

Nota bene: the papilla cephalica (P) looks a little bit similar to an eye in the sketch but the lens-shaped eyes are positioned much deeper in the head and have been omitted here (but they are visible in the next foto, just below).

View from top on the head of Cornechiniscus cornutus. The curved profile of the eyes is noticeable from this perspective.

Once more, the head of Cornechiniscus cornutus, as seen from the ventral side.
Depth of focus problems hinder us from showing all the cephalic appendices in a single photograph:
in this case the mouth opening and the cirri externi can be seen clearly but the papillae and the cirri interni are somewhat nebulous.

Focus on the cirri externi of Cornechiniscus cornutus.

Cornechiniscus cornutus  has papillae at its hind legs:

Posterior part of the body of Cornechiniscus cornutus,
ventral view.
P: Papilla

Though it might sound not very thrilling to you: the structure of the armour plates in general is being discussed to a great extent in the scientific literature with respect to species identification and we will have a short look at it now:

Armour plates of Cornechiniscus cornutus, dorsal view, schematically.
The main plates I to III are coloured in grey. In the case of Cornechniniscus there is an additional fourth main plate, shown in red.
For comparison you might look at the regular echiniscus armour plate arrangement of "typical" Echiniscus tardigrades,
where this fourth plate is missing.

Previously, the tardigrades with a fourth main plate were put in a common systematic group called "Pseudechiniscus". Therefore the original designation of Cornechiniscus cornutus
has been Pseudechiniscus cornutus.

What remains to be discussed? First of all there are some contradictory statements in the scientific literature. As microscope amateurs we will probably not be able to resolve them:

Marcus  states a value of 216 µm as the maximum body length of C. cornutus, probably following the original publication by Ferdinand Richters, Dastych names values between 172 and 290 µm,
whereas  Maucci  writes about a "Lunghezza fino a 460 µm".

In the small sample of the Sümeg population the maximum body length was ca. 290 µm. Probably we simply have to accept that at other locations C. cornutus giants exist. In any case we can enjoy (adore ;-) the tardigrades also without those body length values.

By the way: our German language magazine version has been included in the  Media Index of the University of Exeter where it can be found among similar publications like "Hamster & Co" and "Marder Online" (marten online).

Literature:

Ernst Marcus: Bärtierchen (Tardigrada). p. 114. Jena 1928.
Walter Maucci (Ed.): Tardigrada. p. 165. Bologna 1986.
Hieronim Dastych: The Tardigrada of Poland. p. 58. Warszawa 1988.

© 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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