Milnesium

Class : Eutardigrada

Order : Apochela

Family : Milnesiidae

Genus : Milnesium

Genus Milnesium

From Doyère 1840: “Téte portant à sa partie antérieure et latérale deux appendices palpiformes très courts; bouch terminée par une ventouse entourée de palpes. Peau molle, coupée transversalement par des sillons, en anneaux de formes variables. Quatre paires de pattes. Anneaux du tronc bisegmentés.”

(translated): Head bearing anteriolaterally two very short palpiform appendages; mouth closed by a sucker surrounded by palpi. Soft skin, cut transversely by furrows into rings of variable shapes. Four pairs of legs. Bisegmented trunk rings.

From Ramazzotti & Maucci: Milnesiidae; there are present six buccal lamellae and six large peribuccal papillae; buccal tube wide, short, rigid; stylet supports short, large; there are present stylet sheaths; pharynx without apophyses and placoids. Branches of the claws separate, the secondary branch short, two-part or three-part.


Smooth cuticle group: almatyense, antarcticum, asiaticum, brachyungue, dujianensis, eurystomum, jacobi, longiungue, reductum, swolenskyi, tardigradum, tetralamellatum

Sculpted cuticle group: alabamae, katarzynae, reticulatum, krzysztofi

Alberta:
tardigradum (subsp. tardigradum) Doyère, 1840 spurs on all? (but possible variability in point B)(amended by Michalczyk et al. 2012)

Canada:

North America / Nearctic:
n sp (Nelson et al)

Other:
alabamae Wallendorf & Miller, 2009 Highly punctuated cuticle. BT 1/2 length of that in tardigradum & narrow.
almatyense Tumanov, 2006 smooth, no eyes (one example with poorly developed eyespots). 6 pb pap, 6 pb lam. Primary branch with hard-to-see accessory points. Outer claws I-III lack basal spur, both of IV lack basal spur. I-III have elongated cuticular thickening near claw base.
antarcticum Tumanov, 2006 very large (constricted >800µm). Reddish-brown, smooth, with eyes. 6 pb papillae, 6 pb lamellae. “Large, massive” claws. Basal spurs on all
asiaticum Tumanov, 2006 Slightly reddish or white, smooth, eyes in most. 6 pb pap, 6 pb lam. PB has poorly-developed a.p. Cuticular thickening on I-III. 3 points on all
brachyungue Binda & Pilato, 1990 spurs on all
barbasosense Meyer & Hinton, 2012
beasleyi Kaxzmarek, Jakubowska & Michalczyk
dujiangensis Yang, 2003 no primaries?
eurystomum Maucci, 1991 short, v wide tapered mouth
granulatum Ramazzotti, 1962 spurs on all? Variable. fine granulation caudally or over entire dorsum (amended to species level)
jacobi Meyer & Hinton 2010 very broad, cylindrical bt & posterior ss
katarzynae Kaczmarek, Michalczyk & Beasley, 2004 285-295µm sculpted. no basal spurs
krzysztofi Kaczmarek & Michalczyk, 2007 Similar to katarzynae but has spurs on internal I-III & external IV. Like katarzynae, has reticulated cuticle. 320-537µm
lagniappe Meyer, Hinton & Dupré, 2013 Like reticulatum but larger, no gibbosities, wider BT & longer claws, more posterior SS
longiungue Tumanov, 2006 long claws. White, smooth, eyes usually. 6 pb pap, 6 pb lam. V. long & slender claws. No a.p. Strongly reduced basal spur but present on all.
reductum Tumanov, 2006 reduced basal spurs & accessory points. Slightly reddish or white, smooth, eyes usually. 6 pb pap, 6 pb lam. PB has no a.p. No basal spurs on outer claws. I-III have cuticular thickening
reticulatum Pilato, Binda & Lisi, 2002 Has dorsal gibbosities, has eyes
swolenskyi Bertolani & Grimaldi, 2000 {fossil species} Very short claws (1/2 length)
tardigradum trispinosa Rahm, 1931 spurs on all? Variable. 3 spines on dorsum, caudal, just ant of IV
tetralamellatum Pilato & Binda, 1991 3pts on inner/ant, 2 pts on outer/post claws
zsalakoae Meyer & Hinton 2010 very long thin primaries

Key from Tumanov 2006: (missing alabamae (punctuated, & small bt), jacobi, krzysztofi (sculpted), lagniappe, swolenskyi (fossil), zsalakoae; tardigradum subspecies not distinguished)
Key to the determination of recent species of the genus Milnesium. (adult females)
1. Claws of all legs without main branches……………………………. Milnesium dujiangensis
– Claws of all legs with main branches ………………………………………………………………… 2
2. Cuticle reticulated ………………………………………………………………………………………… 3
– Cuticle smooth ………………………………………………………………………………………………. 4
3. *Check alabamae & krzysztofi here* With gibbosities on dorsal surface and eyespots. Inner claws of all legs with basal spurs ………………………………………………………………………………………..Milnesium reticulatum
– Without gibbosities and eyespots. Claws of all legs without basal spurs ………………….. …………………………………………………………………………………………Milnesium katarzynae
4. Buccal tube wide and short, with its diameter decreasing to the caudal end. Its diameter in the region of mouth opening exceed 30 µm…………………Milnesium eurystomum
– Buccal tube cylindrical, with diameter lesser then 30 µm …………………………………….. 5
5. Without accessory points on main claw branches………………………………………………… 6
– With accessory points on main claw branches …………………………………………………….. 7
6. *Check zsalakoae also* Outer claws without basal spurs; length ratio between complex base+secondary branch and basal spur of inner claws do not exceed 2.5 …………………………………………. ……………………………………………………………………………… Milnesium reductum sp. nov.
– All claws with basal spurs; length ratio between complex base+secondary branch and basal spur not lesser then 3 …………………………………… Milnesium longiungue sp. nov.
7. Short claws; pt value for main claw branches in legs IV lesser then 40, pt value for complex base+secondary branch in legs IV lesser then 30…… Milnesium brachyungue
– Longer claws; pt value for main claw branches in legs IV larger then 40; pt value for complex base+secondary branch in legs IV larger then 30……………………………………. 8
8. Longer, more subtile claws; pt value for main claw branches in legs IV larger then 60 …………………………………………………………………………………………………………………….. 9
– Shorter, more massive claws; pt value for main claw branches in legs IV lesser then 60 ………………………………………………………………………………………………………………….. 10
9. *Check jacobi also* Buccal tube length exceed 50 µm; length of the main claw branches in legs IV exceed 30 µm; with basal spurs on all claws ………………………….Milnesium asiaticum sp. nov.
– Buccal tube length not exceed 42 µm (usually lesser then 40 µm); length of the main claw branches in legs IV not exceed 30 µm; outer claws on legs I–III and both claws on hind legs lacks basal spur …………………………………. Milnesium almatyense sp. nov.
10. Ptss value more then 70 (70.7–75.9); with basal spurs on all claws ………………………… …………………………………………………………………………. Milnesium antarcticum sp. nov.
– Ptss value lesser then 70 (usually 63–66); basal spurs of outer claws could be reduced ………………………………………………………………………………………………………………….. 11
11. Four peribuccal lamellae; ptss value 61.98–64.37 (according to Pilato & Binda 1991); in the complex base+secondary branch apical points are almost equal in size…………… ………………………………………………………………………………….Milnesium tetralamellatum
– Six peribuccal lamellae; ptss value 62.7–67.7; in the complex base+secondary branch point a is distinctly smaller then point b …………………………….. Milnesium tardigradum

Key from Michalczyk Enicz Frohme Kaczmarek 2012, adult females
missing lagniappe, swolenskyi (fossil)
1. Dorsal cuticle smooth…………………………………………………………………………………………………..2 (tardigradum group)
-. Dorsal cuticle sculptured……………………………………………………………………………………………..14 (granulatum group)

The tardigradum group:
2(1). Three spines present on dorso-caudal cuticle………………………………………………………….M. tardigradum trispinosa
-. Dorso-caudal cuticle without spines………………………………………………………………………………………………………….3
3(2).Primary branches on all legs absent……………………………………………………………………………………. M. dujiangensis
-. Primary branches on all legs present……………………………………………………………………………………………………….. 4
4(3). Four peribuccal lamellae present…………………………………………………………………………………….M. tetralamellatum
-. Six peribuccal lamellae present………………………………………………………………………………………………………………..5
5(4). Accessory points on primary branches absent ………………………………………………………………………………………….. 6
-. Accessory points on primary branches present …………………………………………………………………………………………..8
6(5). Secondary branches of external claws I-III and of posterior claws IV with two points…………………….M. reductum
-. Secondary branches of external claws I-III and of posterior claws IV with three points…………………………………. 7
7(6). Pt of the primary branch IV length lower than 93% …………………………………………………………………M. longiungue
-. Pt of the primary branch IV length equal or higher than 94% ……………………………………………………. M. zsalakoae
8(5). Secondary branches of external claws I-III with two points………………………………………………………………………… 9
-. Secondary branches of external claws I-III with three points…………………………………………………………………….. 11
9(8). Secondary branches of anterior claws IV with two points…………………………………………………………M. almatyense
-. Secondary branches of anterior claws IV with three points………………………………………………………………………..10
10(9). Secondary branches of posterior claws IV with two points………………………………………………..M. tardigradum s. s.
-. Secondary branches of posterior claws IV with three points……………………………………………………………. M. jacobi
11(8). Buccal tube short and wide (buccal tube external width at the stylet support insertion point equal or greater than the level of the stylet support insertion point)…………………………………………………………………………M. eurystomum
-. Buccal tube long and narrow (buccal tube external width at the stylet support insertion point less than the level of the stylet support insertion point)…………………………………………………………………………………………………………… 12
12(11). Claws short and robust (pt of the primary branch IV length equal or lower than 35%, pt of the basal claw IV + secondary branch complex length equal or less than 25%)……………………………………………………. M. brachyungue
-. Claws long and slender (pt of the primary branch IV length higher than 36%, pt of the basal claw IV + secondary branch complex length more than 26%)…………………………………………………………………………………………………..13
13(12). Buccal tube longer than 65 µm and wider than 26 µm, pt of the stylet supports insertion point equal or higher than 70%, pt of the primary branches of claws IV lower than 58%…………………………………………………..M. antarcticum
-. Buccal tube shorter than 60 µm and narrower than 25 µm, pt of the stylet supports insertion point lower than 68%, pt of the primary branches of claws IV higher than 62%…………………………………………………………….M. asiaticum

The granulatum group:
14(1).Gibbosities on the dorsal cuticle present, four peribuccal lamellae…………………………………………….M. reticulatum
-.Gibbosities on the dorsal cuticle absent, six peribuccal lamellae CHECK lagniappe……………………………………………………15
15(14).Accessory points on primary branches absent………………………………………………………………………….. M. alabamae
-.Accessory points on primary branches present………………………………………………………………………………………….16
16(15).Secondary branches of external claws I-III and of posterior claws IV with three points……………….M. granulatum
-.Secondary branches of external claws I-III and of posterior claws IV with two points…………………………………..17
17(16).Secondary branches of internal claws I-III and of anterior claws IV with two points……………………M. katarzynae
-.Secondary branches of internal claws I-III and of anterior claws IV with three points……………………. M. krzysztofi


Image modified from Doyère LMF. 1840. Mémoire sur les tardigrades. Annales des Sciences Naturelles, 2me series. 14: 269-362.

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.

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?

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.

(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, choose “Unclear” to ignore this character!


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?

Images from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335