Would you prefer to stay alone or to live among bizarre relatives ?

In their unending fight for a strictly structured kingdom of animals scientists eagerly tried to fit the tardigrades into an already existing biological category - but failed to do so in the long run.

The German pastor J.A.E. Goeze had named his newly discovered animal "Kleiner Wasserbär", i.e. small water bear. A first Latin (i.e. international) term was introduced by the famous Italian biologist Lazaro Spallanzani already in 1776: he called the water-bears "Tardigrada" (slow-walkers).

When looking up the term "Tardigrada" in a modern biology textbook you will possibly come across  two  different entries. One entry links, as expected, to our water bears and the other - guess - to the sloths which have got the same label "Tardigrada"!
This one-way ambiguity was finalized as a bidirectional ambiguity when in 1795 Donndorf translated the French term "le tardigrade" (in this case meaning a water bear) to the German "Faulthier" (sloth).

The international term "Tardigrada" is fully established today and helps a lot to filter out e.g. the water bear publications among those publications which refer to the real big bears. On the other hand those old-fashioned, abandoned water bear designations are quite charming as well:

Wasserbär (German, "water bear")-- Brucolino (Italian, meaning "small grub") -- Acarus ursellus (Latin, "bear mite") -- das Faulthierchen (German, sloth, see above) -- Urslet ("little bear") -- Systolides marcheurs (French, "walking rotifer")-- Systolides sucteurs (French, "sucking rotifer")-- Blaracken (?) -- Moss piglets  -- Xenomorphida ----Trionychicum ursinum -- Arctisken (from "arctos", Greek word for bear)-- Arctisconia -- Water-sloths -- Bärwürmer (German, "bear worms") etc.

Though possibly ambiguous, already in 1776 the present name had been established. But the search for an appropriate position within the biological system of animals continued. An unending story of non-ideal and forced relationships began. Following   Leunis  (1861) the tardigrades belong to the Arachnoidea (spider animals), and within the spider animals to the so-called "Krustenspinnen" (crust spiders).
Of course, it was not possible to ask the tardigrades whether they actually agreed to this proposal. But, frankly speaking, would you like to be identified as a relative of this peculiar being shown below?

According to Leunis (1861) the first representative of the "Krustenspinnen": Pycnogonum, the "Spindelassel".

According to Leunis (1861) the second representative of the "Krustenspinnen":
our tardigrade !

The outer circle of relatives looks bizarre as well. Further members of the spider family are, according to Leunis:

"Tardigrade relative" (from Leunis, 1861):
European scorpion (Europäischer Skorpion)

"Tardigrade relative" (from Leunis, 1861):
Common book scorpion (Gemeiner Bücherskorpion)

"Tardigrade relative" (from Leunis, 1861):
Tarantula (Tarantelspinne)

"Tardigrade relative" (from Leunis, 1861):
Cochineal mite (Cochenille Milbe)

"Tardigrade relative" (from Leunis, 1861):
Cheese mite (Käsemilbe)

"Tardigrade relative" (from Leunis, 1861):
man-parasite scabies mite (Krätzmilbe des Menschen)

"Tardigrade relative" (from Leunis, 1861):
hair mite (Haarbalgmilbe des Menschen)

"Tardigrade relative" (from Leunis, 1861):
Common bird-parasite mite (Gemeine Vogelmilbe)

"Tardigrade relative" (from Leunis, 1861):
Wood tick (Holzbock)

Today we tend to be more generous and provide an own phylum for those tardigrades - far away from spiders, mites and scorpions.

Literature

Johannes Leunis: Schul-Naturgeschichte. Eine analytische Darstellung der drei Naturreiche, zum Selbstbestimmen der Naturkörper. 4th edition, first part, p. 247.
Hannover, Hahn'sche Hofbuchhandlung 1861.

Ernst Marcus: Tardigrada. p. 1. [synonym list] Berlin 1936.

J. Senebier: Über die vornehmsten mikroskopischen Entdeckungen in den drey Naturreichen. Translated by Johann August Donndorf. Leipzig 1795.

Lazzaro Spallanzani: Opuscoli di Fisica animale e vegetabile, Vol. 2. Modena 1776.

Volker Storch, Ulrich Welsch: Systematische Zoologie. 5th edition. Stuttgart 1997.

© 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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