TARDIGRADE KEY

Tag: Superfamily Isohypsibioidea

Hexapodibius

Genus description amended by Schuster et al. 1980: “Peribuccal papulae and buccal lamellae absent; six peribuccal lobes present. Mucrones present; buccal tube short, rigid, without spiraled thickenings. Pharynx with apophyses and macroplacoids; without microplacoids and septulum. Cuticle without pores. Two small double claws of legs I-III of similar shape and size, not connected; without lunulae; sequence 2,1,2,1; […]

Haplomacrobiotus

Genus description from May 1948: “… la présence de deux griffes simples…” Translated: “…presence of two simple claws…” Note: May describes simple claws (lacking secondary branches) on all eight legs; Ramazzotti & Maucci report this on the first three legs only, with a tiny secondary branch on legs IV, barely visible (not from May, perhaps […]

Haplohexapodibius

Genus description from Pilato & Beasley 1987: “hind legs reduced to short stumps lacking claws. First three pairs of legs with two single claws. Bucco-pharyngeal apparatus with the buccal tube provided with the ventral strengthening bar. Mouth without peribuccal lamellae, provided with 6 peribuccal papulae and 6 peribuccal lobes. Pharyngeal bulb provided with apophyses and […]

Halobiotus

Genus description from Kristensen 1982: “Marine eutardigrades belonging to the family Hypsibiidae Pilato, 1969. The buccal tube has both a ventral list and a dorsal hook into which the stylet protractor muscles are inserted. The two double claws on each leg are heteronych. The external double claws with lunulae. The lunula of the internal claw […]

Thulinius

Genus description from Bertolani 2003: “Mouth opening with 12 small, partially fused peribuccal lamellae surrounded by six peribuccal lobes, sometimes subdivided into a larger number of irregular sublobes; crest-shaped apophyses for the insertion of the stylet muscles on the buccal tube, claws of Isohypsibius-typeRemarks. The three species are characterized by a buccal armature with a posterior […]

Pseudobiotus

Genus description from Schuster et al. 1980: “thirty small, irregular buccal lamellae present; peribuccal papulae absent. Buccal tube short, rigid, without spiraled thickenings; mucrones present. Buccal tube has anterior dorsal and ventral thickenings or crests. Pharynx with apophyses and macroplacoids; without microplacoids or septulum. Two double claws of each leg of similar size and shape; branches not […]

Paradiphascon

Genus description from Dastych 1992: “Semiterrestrial eutardigrades belonging to the family Hypsibiidae Pilato, 1969. Head segment provided with three flat lobes in its frontal (“facial”) part, i.e. a median and two lateral. Upper parts of lateral lobes shaped like a pair of roundish and flattened dome-tipped structures. Mouth opening surrounded by a flat ring of […]

Doryphoribius

Genus description from Schuster et al. 1980: “Without peribuccal papulae or buccal lamellae; six peribuccal lobes present. Buccal tube short, rigid, without spiraled thickenings; mucrones present. Pharynx with apophyses and macroplacoids; without microplacoids or septulum. Cuticle without pores. Two double claws of each leg of similar size and shape; not connected; without lunulae; sequence 2,1,2,1. Smooth eggs […]

Apodibius

Genus description from Dastych 1983: “Buccal apparatus of Macrobiotus-type, all legs strongly reduced and completely without claws or any sclerified structures.” Citations: Dastych H. 1983. Apodibius confusus gen. n. sp. n., a new water-bear from Poland (Tardigrada). Bulletin of the Polish Academy of Sciences, Biology. 31: 41-46.

Thalerius

Genus description from Dastych 2009: “Semiterrestrial, medium sized hypsibiids. Claw system of Hypsibius-type. The bases of external claws expanded posteriorly, each with a roundish, deep incision, the sides of the incision with a well formed tooth. Main branches of external claws thin and markedly long. At the base of each internal claw on legs I to […]

Digits

Note: If specimen has pads instead of digits, select “Pads”

Cephalic cirri flagellum form

Modified image from Renaud-Mornant 1982 0708 Renaud-Mornant J. 1982. Species Diversity in Marine Tardigrada. Proceedings of the Third International Symposium on the Tardigrada. 149-178

Note: If unsure of form, select “Present”

Cephalic cirri scapus form

Modified image from Renaud-Mornant 1982 0708 Renaud-Mornant J. 1982. Species Diversity in Marine Tardigrada. Proceedings of the Third International Symposium on the Tardigrada. 149-178

Note: If unsure of form, select “indistinct” for scapus

Cephalic cirri cirrophore form

Modified image from Renaud-Mornant 1982 0708 Renaud-Mornant J. 1982. Species Diversity in Marine Tardigrada. Proceedings of the Third International Symposium on the Tardigrada. 149-178

Note: If unsure of form, select “indistinct” for cirrophore

Secondary and tertiary clavae

Image from Fujimoto S, Hansen JG. 2019. Revision of Angursa (Arthrotardigrada: Styraconyxidae) with the description of a new species from Japan. European Journal of Taxonomy. 150: 1-19.

Note: Secondary clavae can have similar forms to primary clavae. However, secondary clavae can be flat structures of varying shapes around the mouth cone area

Generalized forms of primary clavae

Arthrotardigrada generalized primary clavae form

Note: Clavae forms can vary between species

Armoured plates?

Note: Specimen can have dorsal and ventral plates. Select those that apply

Additional digit accessory structures

Arthrotardigrada digit accessory structures

Note: Specimen can have some or none of these traits. Select those that apply.

Additional claw accessory structures

Arthrotardigrada claw accessory structures

Note: Specimen can have some or none of these traits. Select those that apply.

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