TARDIGRADE KEY

Claxtonia

Gąsiorek, P., Morek, W., Stec, D. & Michalczyk, Ł. (2019) Untangling the Echiniscus Gordian knot: paraphyly of the “arctomys group” (Heterotardigrada: Echiniscidae). Cladistics, 35, 633-653.

Class: Heterotardigrada

Order: Echiniscoidea

Family: Echiniscidae

Click taxa for descriptions

Genus description from Gąsiorek 2019: “Small echiniscids with red granulate eyes. Only cephalic cirri present. Cirri A longer than 30% of body length. Two pairs of segmental plates and two median plates. Incisions (notches) on caudal (terminal) plate. Pseudosegmental and ventral plates absent. Sculpture composed of regular granulation, i.e. circular or polygonal, dense round epicuticular granules being extensions of large intracuticular pillars, often connected by striae, pseudopores only in some species. Parthenogenetic or gonochoristic.”

Genus description from Degma 2019: “Small echiniscids, with red granulate eyes. Only cephalic cirri present. Two pairs of segmental plates and two median plates. Incisions (notches) on caudal (terminal) plate. Pseudosegmental and ventral plates absent. Sculpture composed of regular, dense granulation, i.e. circular or polygonal epicuticular elevations being extensions of large intracuticular pillars, often connected by striae. If pseudopores are also present, they are distributed as a crown around each granule. Parthenogenetic or gonochoristic.”

Gąsiorek, P., Morek, W., Stec, D. & Michalczyk, Ł. (2019) Untangling the Echiniscus Gordian knot: paraphyly of the “arctomys group” (Heterotardigrada: Echiniscidae). Cladistics, 35, 633-653.
Gąsiorek, P., Morek, W., Stec, D. & Michalczyk, Ł. (2019) Untangling the Echiniscus Gordian knot: paraphyly of the “arctomys group” (Heterotardigrada: Echiniscidae). Cladistics, 35, 633-653.

Citations:

Degma, P., Meyer, H.A. & Hinton, J.G. (2019) Claxtonia goni, a new species of Tardigrada (Heterotardigrada, Echiniscidae) from the island of Maui (Hawaiian Islands, U.S.A., North Pacific Ocean), with notes to the genus Claxtonia Gąsiorek & Michalczyk, 2019. Zootaxa, 4933(4), 527-542.

Gąsiorek, P., Morek, W., Stec, D. & Michalczyk, Ł. (2019) Untangling the Echiniscus Gordian knot: paraphyly of the “arctomys group” (Heterotardigrada: Echiniscidae). Cladistics, 35, 633-653.

Restart Search

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