TARDIGRADE KEY

Tag: Family Halechiniscidae

Quisarctus

Genus description from Fujimoto 2015 in Fontoura et al. 2017: “Generic diagnosis as that of the family.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, A., Kristensen, R.M. & Hansen, J.G. (2017) A dichotomous key to the genera of the marine Heterotardigrades (Tardigrada). Zootaxa, 4294, 1–45. Fujimoto, S. (2015) Quisarctus yasumurai gen. et sp. nov. (Arthrotardigrada: Halechiniscidae) […]

Quisarctinae

Quisarctinae from Fujimoto 2015 in Fontoura et al. 2017: “Halechiniscidae with cylindrical body; primary clava and lateral cirrus arise from common cirrophore; primary clava longer than lateral cirrus; secondary clava undeveloped; leg IV sense organ as papilla; legs terminate in digits without folds, peduncles, proximal pads, pretarsi or wrinkles; internal digits longer than external digits; […]

Paradoxipus

Genus description from Kristensen & Higgins 1989: “Halechiniscinae with four similar toes (digits) on each foot. Each toe with proximal suction disc and distal claw. Complete set of cephalic cirri present; primary clavae and lateral cirri arising from distinct lateral extension; buccal clavae, in form of bent sausage-shaped structures situated posterolateral to the mouth opening, […]

Orzeliscus

Genus description from du Bois-Reymond Marcus 1989: “Head with median cirrus ; lateral cirri and clavæ arising from common bases. Each leg ends with 4 toes that are provided with peg-shaped terminations.” Citations: du Bois-Reymond Marcus, E. (1952) On South American Malacopoda. Bol. Fac. Fil. Cien. Letr. S. Paulo Zool. 17: 189-209. Fontoura, P., Bartels, […]

Opydorscus

Genus description from Renaud-Mornant 1989 in Fontoura et al. 2017: “Orzeliscinae with cuticular pillars ranging in size from 2–8 µm dorsally and exceeding 10 µm laterally. Ventral cuticle finely punctuated by small pillars. Head with small lateral expansion below the insertion of cirrus A. Complete set of cephalic cirri. Secondary clavae weakly distinct around the […]

Mutaparadoxipus

Genus description from Gross et al. 2014 in Fontoura et al. 2017: “Orzeliscinae with adhesive pads of different lengths; legs I–III: digits 1–3 with both proximal adhesive pad and distal claw, digit 4 with adhesive pad only; legs IV: digits 2 and 3 with proximal adhesive pad and distal claw, digits 1 and 4 with […]

Orzeliscinae

Orzeliscinae from Gross et al. 2014 in Fontoura et al. 2017: “Halechiniscidae with triangular tarsus bearing four digits. Elongated digits with proximal paddle- or spatula-shaped adhesive organs. Complete set of cephalic appendages present. Secondary clavae occurring as flattened papillae or bent, sausage-shaped structures. Stylet supports present.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, A., Kristensen, R.M. […]

Halechiniscus

Genus description from Grimaldi de Zio et al. 1990: “Flat head extending into lateral lobes ; claws either simple or with distal dorsal spur ; calcar always absent ; peduncles absent ; medial cirrus present, primary clava may be longer than the lateral cirrus.” Citations: Grimaldi de Zio, S., D’Addabbo Gallo, M. & Morone De […]

Chrysoarctus

Genus description from Renaud-Mornant 1984 translated from French by Fontoura et al. 2017: “Halechiniscinae with straight tibia and enlarged fan-shaped tarsus. Digits inserted side by side without peduncles. Simple claws with a small external calcar. Small papillae on fourth pair of legs.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, A., Kristensen, R.M. & Hansen, J.G. (2017) […]

Halechiniscinae

Halechiniscinae from Grimaldi de Zio et al. 1990: “Halechiniscidae usually with complete set of cephalic appendages with cylindrical tibia followed by a small tarsus ; claws either simple or with a dorsal spur ; peduncles absent ; sense organ of the fourth pair of legs (P4) short and non-branched ; vestigial secondary clavae.” Citations: Grimaldi […]

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