TARDIGRADE KEY

Tag: Subfamily Euclavarctinae

Proclavarctus

Genus description from Renaud-Mornant 1983 translated from French by Fontoura et al. 2017: “Euclavarctinae with cephalic cirri composed of three parts: a cirrophore forming a narrow sheath, an elongated scapus with annulated base, and a short flagellum narrowed by a proximal notch; median cirrus and cirri A larger than the external and the internal cephalic […]

Parmursa

Genus description by Renaud-Mornant 1984, emended by Hansen 2007, in Fontoura et al. 2017: “Euclavarctinae with cuticular aliform expansions supported externally by dorsal cuticular ribs. Trapezoid head, completely proportionate to the arrangement of the cephalic sense organs. Cephalic cirri with a funnel-shaped scapus. Erect secondary clavae. Stylet supports absent.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, […]

Moebjergarctus

Genus description from Bussau 1992: “Halechiniscidae without dorsal segmental plates. Eleven cephalic sense organs present. Primary clavae club-shaped, bent forward. Secondary clavae spherical. Cephalic cirri separated into three parts: short cirrophore, long segmented scapus and short flagellum. Spines on the first three pairs of legs I, 11, 111. Small clavoid papillae on legs IV. Long […]

Exoclavarctus

Genus description from Renaud-Mornant 1983, translated from French by Fontoura et al. 2017: “Euclavarctinae with cephalic cirri showing a marked dimorphism; median cirrus and cirri A having a long flagellum; internal and external cephalic cirri with a very short flagellum. The cirrophore and the base of the scapus indistinguishable from one another forming a bulbous […]

Euclavarctus

Genus description from Renaud-Mornant 1975: “Halechiniscidae with compound cephalic cirri: including a funnel-like cirrophorus, a basal sheath, a large mean portion and a thin distal part. Two sets of unequally shaped clavae. Toes bearing an unspurred claw.” Genus description from Renaud-Mornant 1983, translated from French by Fontoura et al. 2017: “Euclavarctinae with cephalic cirri similar […]

Clavarctus

Genus description from Renaud-Mornant 1983, translated from French by Fontoura et al. 2017: “Euclavarctinae with reduced cephalic cirri having a short bulbous scapus and a short beveled flagellum. Cirrophore absent. Internal claws chelate-like due to the presence of a robust and elongate accessory spine.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, A., Kristensen, R.M. & Hansen, […]

Euclavarctinae

Euclavarctinae from Renaud-Mornant 1983 translated from French by Fontoura et al. 2017: “Halechiniscidae with unplated body without expansions. Conical head bearing two sets of unequally shaped clavae. Cirri A and primary clavae inserted separately. Tarsus weakly individualized. The claws are simple or internal claws with a dorsal accessory spur.” Citations: Fontoura, P., Bartels, P.J., Jørgensen, […]

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