TARDIGRADE KEY

Tag: Family Hypsibiidae

Parahypsibius

Genus description from Gąsiorek et al. 2024: “Hypsibiids with Ramazzottius-like claws and rigid buccal tube bent posteriorly. Only posterior bars may be present. AISMs asymmetrical, dorsal AISM shorter and higher than ventral, with prominent apex and less evident caudal processes. Pharynx with two granular macroplacoids. Rudimentary elliptical sensory organs present on head. Cuticular sculpturing well […]

Beorn

Genus description from Cooper, 1964: “Mouth without discernible palps or other appendages, dorsally and laterally enclosed by a well-defined cuticular frontal element which caps and delineates the “head” ; no cephalic appendages, no lateral cirrus, no clava, and no discernible eye-spots. Body naked; cuticle evidently regionally thickened dorsally, annulated by transverse lines of flexion, but […]

Cryobiotus

Genus description from Dastych 2019: “Median sized to large, dark-brown or blackish-brown pigmented hypsibiids with smooth cuticle (*) and large eyespots. Internal organs largely hidden by dense pigmentation. Six peribuccal lobes around mouth opening, peribuccal papillae not observed. The anterior apophyses of the mouth tube (= taa) of “acute hook” type (“Acutuncus variant”: Pilato & […]

Kopakaius

Genus description from Zawierucha et al. 2023: “Dark pigmentation (not found in other representatives ofthe subfamily Diphasconinae), wide bucco-pharyngeal apparatus consisting of short rigid part and elongated flexible tube, straight stylet supports, absence of placoids. Hypsibius -type furcae. Dorsal oval apodeme (thickening, drop-like structure) absent at the border between the buccal and pharyngeal tube. Very […]

Kararehius

Genus description from Zawierucha et al. 2023: “Transparent body, bucco-pharyngeal apparatus consists of rigid and flexible part. Oval dorsal apodeme (thickening, drop-like structure) absent. Stylet furcae of the Hypsibius type. Three macro-placoids and elongated microplacoid in the pharyngeal bulb. Septulum absent. Claws of the Hypsibius type.” Citations: Zawierucha, K., Stec, D., Dearden, P.K. & Shain, […]

Hypsibiinae

Hypsibiinae from Pilato 1969: “Unghie di tipo Isohypsibius o di tipo Hypsibius. Apparato boccale di tipo Hypsibius o di tipo Macrobiotus; bulbo faringeo provvisto di placoidi.” Translated: Claws of Isohypsibius or Hypsibius type. Buccal apparatus of Hypsibius or Macrobiotus type; pharyngeal bulb with placoids. Hypsibiinae from Bertolani et al. 2014: “Completely rigid buccal tube. Apophyses […]

Diphasconinae

“Eutardigrades with buccopharyngeal apparatus of Diphascon-type and anterior apophyses shaped as “blunt” or “semilunar” hooks (see Pilato 1987). Posteriodorsal apodeme (“drop-like” structure) present or absent, pharyngeal apophyses present. Asymmetrical claws of Hypsibiidae-type. Eggs either deposited into [shedded] cuticle and smooth or layed freely and with ornamented shells.” Dastych H. 1992. Paradiphascon manningi gen. n. sp. […]

Hypsibiidae

Hypsibiidae from Pilato 1969: “Senza alcuna appendice cefalica. Le due diplounghie di ciascuna zampa sono disposte asimmetricamente rispetto al piano mediano della zampa stessa e posssono essere di tipo Isohypsibius o di tipo Hypsibius. In ogni zampa le due diplounghie sono talvolta quasi uguali fra loro ma molto spesso profondamente diverse per forma e dimensioni. […]

Hypsibius

Genus description from Gąsiorek et al. 2018: “Six weakly outlined peribuccal lobes present. Apophyses for the insertion of stylet muscles in the shape of symmetrical hooks; and with well-developed caudal processes pointing diagonally (backwards and sideways […]). Pharyngeal apophyses and placoids present. Stylet furcae with the triangular base, thin arms and enlarged apices (sensu Pilato […]

Borealibius

Genus description from Pilato et al. 2006: “Claws of Hypsibius type; buccal–pharyngeal apparatus with rigid buccal tube without ventral lamina; in their caudal margins, the walls of the anterior portion of the buccal tube form well-developed transversal crests with very pronounced AISMs, almost cylindrical in shape with a large rounded or bilobed projection pointing caudally […]

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