TARDIGRADE KEY

Tag: Superfamily Isohypsibioidea

Thulyphoribius

Genus description from Camarda et al. 2025: “Peribuccal lamellae or papulae absent, although in PCM, sometimes, internal septa in the buccal ring are visible giving the appearance of the presence of lamellae or papular lamellae. Buccal cone with 6 papular peribuccal lobes visible only under SEM and only when the buccal cone is fully extended. […]

Cucumibius

Cucumibius habitus

Genus description from Tumanov et al. 2024 (supplement): “Body surface with numerous tubercles formed by protrusions of procuticle and covered by epicuticle with intracuticular pillars. Peribuccal structures consisted of six peribuccal lobes. AISM in the shape of crests, asymmetrical with respect to the frontal plane. The dorsal apophysis consists of the following parts: (i) a relatively massive […]

Chilibius

Genus description (of Hypsibius (Isohypsibius) sculptus, with minor edits) from Ramazzotti 1962: “Lunghezza circa 200 µm. La cuticola è scolpita e presenta una granulazione estremamente fine, diffusa ovunque, anche sulla superficie ventrale. Il tubo boccale è stretto ed il suo diametro esterno è di circa 2.5 µm in un Tardigrado di 200 µm. Sempre per […]

Ramajendidae

Ramajendidae from Tumanov 2022: “Same as for the type genus (Pilato & Binda, 1990). Claws of each leg very different from each other: external claw of the Hypsibius type with extremely long and slender primary branch; internal claw of the Isohypsibius type. Bucco-pharyngeal apparatus of the Isohypsibius type, Ramajendas variant. Pharyngeal apophyses and placoids present. […]

Weglarskobius

Genus description from Kaczmarek et al. 2020: “Legs short and robust. Internal and external claws on legs I–III different in size and shape. Internal claws I–III similar to Isohypsibius type, but with long basal part (as in the genus thulinius Bertolani, 2003), and lacking accessory points (or not visible under light microscopy). External claws I–III […]

Vladimirobius

Genus description from Kaczmarek et al. 2020: “Legs long and slender. Claws of Vladimirobius type—internal claws at least two times shorter than the external claws (measured from the base of the claw), very wide at the junction of primary and secondary branches, short and thin basal part, primary branches with a very prominent gibbosity-like projection […]

Ursulinius

Genus description from Gąsiorek et al. 2019: “Cuticle covered with large, mamillose, and sculptured gibbosities. Claw bases with well-developed pseudolunulae. Double cuticular bars under claws.” Citations: Gąsiorek, P., Stec, D., Morek, W. & Michalczyk, Ł. (2019) Deceptive conservatism of claws: distinct phyletic lineages concealed within Isohypsibioidea (Eutardigrada) revealed by molecular and morphological evidence. Contributions to […]

Dianea

Genus description from Gąsiorek et al. 2019: “Cuticle with numerous small but distinct, pointy gibbosities covered with reticulum. Claw branches forking at a wide angle; claw bases without pseudolunulae. No cuticular bars under claws.” Citations: Gąsiorek, P., Stec, D., Morek, W. & Michalczyk, Ł. (2019) Deceptive conservatism of claws: distinct phyletic lineages concealed within Isohypsibioidea […]

Halobiotidae

Halobiotidae from Gąsiorek et al. 2019: “Marine eutardigrades with six peribuccal lobes equipped with chemosensory organs. Two large, dome-shaped cephalic papillae present. Mouth opening surrounded by the peribuccal lamina. No ventral lamina on the buccal tube. AISM symmetrical, divided into the anterior semilunar hook and the posterior slight thickening. Claws with pseudolunulae.” Citations: Gąsiorek, P., […]

Grevenius

Genus description from Gasiorek et al. 2019: “Aquatic (limnic or intertidal) or hygrophilic. Cuticle smooth or rough, covered with evident protuberances or wrinkles, sometimes forming reticulum. Claw bases with pseudolunulae. Single bars or no cuticular bars under claws. Two rows of teeth in the oral cavity. Stylet furcae of the Hypsibius type.” Genus description excerpted […]

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?

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, focus on other characters first!

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?

Modified from Lindahl K, Balser S.  1999. Key to tardigrade genera [Internet]. Available from: https://sun.iwu.edu/~tardisdp/Keypage33.html