Bergtrollus

Class : Eutardigrada

Order : Apochela

Family : Milnesiidae

Genus : Bergtrollus

Genus Bergtrollus

Bergtrollus, from Dastych 2011: “Semiterrestrial, medium- to large-sized milnesiids with a very long, telescopically protrusible tubular proboscis (‘snout’). Mouth cavity short. Buccal tube long, flexible, smooth (i.e., without net- /spiral-like strengthening), stylets thin and long. The claw system of Milnesium-type.

The buccal tube length of the new genus is intermediate between that of the genera Milnesioides and Limmenius, as is also the width of the tube. […] The shortest and the widest tube […] in the family have members of Milnesium. In Bergtrollus gen. n. the mouth cavity is short and wide […] resembling that of Milnesium […] but is different in shape and size from the cavity of the genera reported from the Southern Hemisphere, i.e., Milnesioides and Limmenius. The latter taxa, particularly Limmenius, have the mouth cavity distinctly narrower and longer ….

The insertion of the stylet supports in Bergtrollus gen. n. is similar to that in Milnesium and Limmenius and the supports in these genera are inserted at ca. 60 % of the buccal tube length […]. In Milnesioides the supports are inserted much more caudally, at ca. 80 % of the tube length […]. It should be noted that the insertion of the supports (the index values) is more similar in genera with different type of buccal tube (Milnesium vs. Limmenius) but is distinctly different in genera where the buccal apparatus is more similar, i.e., Milnesium vs. Milnesioides. […] As inferring from the presence of proboscis and the morphology of its buccal tube, the new genus could be considered as an intermediate form be- tween genera Milnesioides and Limmenius. Consequently, it could be placed as a “missing link” in such a position within prearranged series of the three remaining milnesiid genera, as illustrated but not commented by Claxton (1999: […]). Milnesioides has a broader but shorter mouth tube than Bergtrollus gen. n. but is somehow similar to the tube of Milnesium. On the other hand, in Limmenius the tube is very long, narrower and much more flexible than in the new genus. Moreover, in Limmenius the tube is provided with a net- /spiral-like strengthening. The organ is within the Milnesiidae the most advanced. The tube of the latter genus resembles such independently evolved organ of e.g., the genus Diphascon (the order Parachela, the Diphasconidae). The mouth cavity in Bergtrollus gen. n. is very short and wide and resem- bles that in Milnesium. The cavity differs markedly from those present in the both Southern Hemisphere genera, Milnesioides and Limmenius. Because of this, one can also hypothesise that the new taxon originated not within the southern (Gondwanan?) lineage to which Milnesioides and Limmenius might belong, but evolved independently from Milnesium-like ancestors within the northern (Laurasian) region.

DISTRIBUTION: Known only from the type locality in the Lyngen Alps, Northern Norway (the Arctic zone).”


Dastych H. 2011. Bergtrollus dzimbowski gn. n., sp. n., a remarkable new tardigrade genus and species from the nival zone of the Lyngen Alps, Norway (Tardigrada: Milnesiidae). Entomologische Mitteilungen aus dem Zoologischen Museum Hamburg. 15 (186): 335-359.

Claw Symmetry Relative To Median Plane Of Leg?

Image from Bingemer J, Hohberg K. 2017. An illustrated identification key to the eutardigrade species (Tardigrada, Eutardigrada) presently known from European soils. Soil Organisms. 89 (3): 127-149.

Stylet Support Insertion Point As Percentage Of Buccal Tube Length

Stylet support insertion point = ss divided by Buccal tube length, as %. Note anterior measurements begin at anterior margin of stylet sheaths, ss is centred where stylet supports reach buccal tube (this requires a good dorsal or lateral view for proper measurement)


Image from Tumanov DV. 2006. Five new species of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae). Zootaxa. 1122: 1-23.

Buccal Tube Long, Mouth At Anterior Of A Protrusible Snout

Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Pharyngeal Tube With Spiral Reinforcement

Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Peribuccal papillae?

Note: in a tardigrade with snout extended, the flex of the pharyngeal tube may not be obvious.


Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

(Lateral) cephalic papillae, peribuccal papillae, Milnesiidae - type claws, exceptionally wide (and usually short) buccal tube?

Cephalic image modified from Nelson DR, Guidetti R, Rebecchi L. 2009. Tardigrada. Ch. 14 in Ecology and Classification of North American Freshwater Invertebrates, Thorp JH, Covich AP (eds.), 3rd ed.

Claw image modified from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Pharyngeal tube flexible?

Note: in a tardigrade with snout extended, the flex of the pharyngeal tube may not be obvious.


Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Serrated / dentate cuff / collar on legs IV

Left image from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Right Image from Richters F. 1926. Tardigrada. in Krumbach T. 1927. Handbuch der Zoologie, 3rd band, Walter de Gruyter & Co.

Leg sensory structures

Typically papilla on leg IV (se4 in image) and variable shape on leg I


Image from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Trunk appendages

Appendages (after Cirrus A) labeled according to plate … B (Scapular plate), C (First segmental plate), D (Second segmental plate), E (terminal plate). “B” is lateral, “Bd” is dorsal

Be careful! There can be great variability within a population, with individuals (especially juveniles) lacking some appendages. When in doubt, choose “Unclear” to ignore this character!


Left image from Ramazzotti G, Maucci W. 1983. Il phylum Tardigrada(III edizione riveduta e aggiornata). English translation by C. W. Beasley, 1995. Memorie dell’ Istituto Italiano di Idrobiologia 41: 1-1012.

Right image cropped from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Cirrus A form

Images modified from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Lower image (Mopsechiniscus) modified from du Bois-Reymond Marcus E. 1944. Sobre tardigrados brasileiros. Communicaciones Zoologicas del Museo de Historia Natural de Montevideo. 1(13): 1-19 plus plates.

Terminal / caudal plate with two notches?

Images modified from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

First image (Echiniscus) modified from Richters F. 1926. Tardigrada. in Krumbach T. 1927. Handbuch der Zoologie, 3rd band, Walter de Gruyter & Co.

Inner & outer buccal cirri present

Image modified from Nelson DR, Guidetti R, Rebecchi L. 2009. Tardigrada. Ch. 14 in Ecology and Classification of North American Freshwater Invertebrates, Thorp JH, Covich AP (eds.), 3rd ed.

Pseudosegmental plate between last medial plate & terminal plate?

Note on 2nd image, what you see before the terminal plate is either no plate, or a full-width medial plate; don’t confuse the latter with a pseudosegmental plate!
Also, sometimes the pseudosegmental plate is paired, like segmental plates II & III. It’s still pseudosegmental!

Images from Clifford HF. 1991. Aquatic invertebrates of Alberta. University of Alberta Press, Alberta, Canada.

Segmental plates larger than intersegmental?

Image modified from Lindahl & Balser (1999), http://www.iwu.edu/~tardisdp/Keypage35.html

Any Paired Plates?

Images from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335