TARDIGRADE KEY

Author: admin-flc

Insuetifurca

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Macrobiotus

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Mesobiotus

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Minibiotus

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Minilentus

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Paramacrobiotus

Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical (2112); AISM generally asymmetrical, due to the ventral lamina, with lateral caudal processes of crests and hooks.” Macrobiotoidea from Bertolani et al. 2014: “Double claws symmetrical with respect to the median plane of the leg (sequence 2112); double claw of each leg similar in shape and size; each […]

Diploechiniscus

From Vicente et al. 2013: “Echiniscids with dorsal plates I, II, III, IV (II and III paired), transversally subdivided median plates m1 and m2 and undivided plate m3 present; double sculpture in the dorsal plates, represented (under phase contrast) by dark polygonal and white circular grains; ventral plates present, especially evident in the anterior, head […]

Echiniscus

From Schultze 1840: “The body ovate-elongated, with armor plates, in nine distinct segments, eight feet affixed to alternate segments from the third to the ninth. The head with four thorn-like antennae, eyes simple and two.” Untranslated: “Corpus ovato-elongatum, scutatum, spinosum, in novem segmenta distinctum, pedes octo alternis segmentis a tertio ad nonum affixi. Caput antennis […]

Hypechiniscus

From Thulin 1928: “Echiniscidae with armor containing five median plates. End plate adjacent to the last median plate. Terminal notches present. Echiniscus gladiator MURRAY var. exarmatus MURR leads to this genus. The exarmatus form (from the Faroe Islands) that I have examined differs in some aspects from MURRAYS description: The animals are colorless with black […]

Testechiniscus

From Kristensen 1987: “Echiniscidae with black/brownish or ‘lipoid’ granular eyes; rigid buccal tube, large cuticular stylet supports, seven rows of sculptured ventral plates. Pseudosegmental plates absent. Paired segmental plates II and III with thinner anterior part. Caudal plate IV with a terminal indentation. Median plates 1 and 2 large, plate 3 small and reduced. Colour […]

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