Macrobiotus

Bertolani R, Guidetti R, Rebecchi L. 1994. Ulteriore contributo alla conoscenza dei tardigradi delle Marche e dell'Umbria. Atti della Società toscana di Scienze Naturali Memorie, Serie B. 101: 21-34.

Class : Eutardigrada

Order : Macrobiotoidea

Family : Macrobiotidea

Genus : Macrobiotus

Genus 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 double claw characterized by the presence of a peculiar stalk (peduncle) with cylindrical or laminar shape; 10 peribuccal lamellae or papulae; buccal tube strengthened by a ventral lamina. Eggs laid freely and always surrounded by an ornamented shell.”

Macrobiotidae from Thulin 1928: “Fam. Macrobiotidae zeichnet sich dadurch aus, dass Sinnesanhänge am Kopfe fehlen. Die Krallen sind zweihakig. Die hintere an jeder Extremität kann mehr oder weniger vollständig in Basal- und Terminal-kralle aufgeteilt sein, die vordere ist dagegen niemals in dieser Weise differenziert. Die Länge und Weite der Mundröhre variiert erheblich innerhalb dieser Familie, ebenso die Form des Schlundkopfes. Die Mundöffnung ist nicht durch Klappen verschliessbar, aber bisweilen (bei vielen Macrobiotus-Arten) von einem Lamellenkranz umgeben. Die Stilette sind mehr oder weniger stark bogenförmig gekrümmt, mit der Konvexität des Bogens medialwärts gewendet, und kräftiger als bei den übrigen Tardigraden.”

Translation: Fam. Macrobiotidae is characterized by the fact that sensory appendages are missing on the head. The claws are double-hooked. The posterior of each claw may be more or less completely divided into basal and terminal [secondary] claws, whereas the anterior [primary branch] is never differentiated in this way. The length and width of the mouth tube varies considerably within this family, as does the shape of the pharynx. The mouth opening is not closed by flaps, but sometimes (in many Macrobiotus species) surrounded by a lamellae. The stylets are more or less curved, with the convexity of the arch turned towards the medial direction, and stronger than in other tardigrades.

Macrobiotidae from Guidetti et al. 2005: “Parachela with double-claws of each leg similar in shape and size and symmetrical with respect to the median plane of the leg (sequence 2112). Y-shaped claws, with claw branches fused over a tract of variable length (common tract). Ten peribuccal structures (lamellae or papulae) present. Epicuticular layer compact and uniform, without pillar-like structures.”

Macrobiotidae from Bertolani et al. 2014: “Double claws Y-shaped, with the two branches forming an evident common basal tract of variable length. Buccal tube completely rigid, or caudally annulated.”

Genus description from Schultze 1834: “Corpus elongatum, depresso-cylindricum, in decem segmenta distinctum. Pedes octo, alternis segmentis a quarto ad decimum affixi. Caput antennis destitutum, oculi duo.”

Translated: The body is an elongated, flattened cylinder in ten segments. Eight feet on alternate segments from the fourth to the tenth. No antennae on head, two eyes.

Genus description from Schuster et al. 1980: “Ten buccal lamellae present; without peribuccal papulae. Buccal tube short, rigid, without spiraled thickenings. Buccal mucrones and interior buccal baffles present. Pharynx contains apophyses, macroplacoids, or macro- and microplacoids, but no septulum. Cuticle with pores of various sizes, number, and distribution. Two double claws of each leg of similar size and shape; lunulae present; claws not connected; sequence 2,1,1,2. Eggs with protruding processes are laid freely.”

Genus description from Pilato & Binda 2010: “Claws of the hufelandi type. Bucco-pharyngeal apparatus of the Macrobiotus type, Macrobiotus variant. Pharyngeal apophyses and placoids present. Stylet furcae typically shaped. Lunules present in the known species. Eggs laid freely in the known species; egg shell with processes (only two exceptions are known).”

hufelandi group (according to Ram & Maucci 1983 + additions) (biserov 1990: egg projections are inverted cups): hibiscus, hufelandi, humilis, lissostomus, marlenae, persimilis, pseudohufelandi (now Xerobiotus?), rawsoni, martini, diversus, hyperboreus, personatus, seychellensis

hufelandi group revised by Kaczmarek & Michalczyk 2017: porous cuticle, two macroplacoids and a microplacoid in the pharynx, and eggs, in the majority of species ornamented with inverted goblet-shaped processes

polyopus group (defn’d Pilato 2006, acc. to Pilato & Kaczmarek, 2007): polyopus, alvaroi, mandalaae, insularis, ocotensis

ariekammensis group (Tumanov 2005) (poorly differentiated main and secondary branches diverge from very short and wide common tract) ariekammensis, kirghizicus

Key from degma michalczyk kaczmarek 2008 for both Paramacrobiotus and Macrobiotus having 3-0-?:
1. Cuticle with pores ………………………………………………………………………………………………………………………2
– Cuticle without pores ………………………………………………………………………………………………………………….3
2(1)The first macroplacoid is the shortest, eggs with processes in the shape of long narrow spines very distant from each other, egg shell covered with dark granules …………………………………………………… M. komareki
– The second macroplacoid is the shortest and almost in contact with the first, extremely small microplacoid sometimes present, eggs with conical ribbed processes close to each other and without areolation ……….. …………………………………………………………………………………………………………………………………..M. tonollii NOW Paramacrobiotus
3(1)Lunulae at least on hind legs indented …………………………………………………………………………………………..4
– All lunulae smooth……………………………………………………………………………………………………………………..6
4(3)Lunulae on hind legs indented at least occasionally, smooth on other legs, eyes present ……………………..5
– Lunulae on all legs indented, eyes absent, eggs with high conical processes simply tipped, areolation present……………………………………………………………………………………………………………………….M. crenatus
5(4)Ventro-lateral tooth in the oral cavity undivided, hind lunulae well indented; eggs with bulbous or conical processes, often with bi-, tri-, or multi-furcated ends, areolation present ……………………………..M. walteri
– Ventro-lateral tooth in the oral cavity often broken into a transversal series of distinct teeth, indentation of hind lunulae, if present, weakly developed (= lunulae slightly crenate); eggs with conical processes with single tips, areolation present ……………………………………………………………………………………… M. areolatus
6(3)The second macroplacoid is the shortest ……………………………………………………………………………………….7
– All macroplacoids of about equal lengths, a small microplacoid can be present, wide buccal tube, eggs with hemispherical processes surrounded by a row of pores …………………………………………..M. montanus
7(6)The third macroplacoid is not evidently the longest one (approximately as long as the first one), both inter-placoid distances approximately same or the second macroplacoid situated closer to the first than to the third macroplacoid, eggs with or without areolation ………………………………………………………………….8
– The third macroplacoid is evidently the longest one, both inter-placoid distances approximately same, eggs without areolation……………………………………………………………………………………………………………..11
8(7)Eyes present, the second macroplacoid almost touching the first one, egg processes in the shape of rigid spines terminated in a point or bifurcated, the egg shell with irregular polygonal plates slightly furrowed ………………………………………………………………………………………………………………………………… M. psephus
– Eyes present or absent, egg processes conical, eggs with areolation ………………………………………………….9
9(8)Eyes present, areolation of the huziori type (a crown of small, branched areolae separates adjacent egg processes, the space between neighboring areolae usually broader than their width) …………………………10
– Eyes absent, the second macroplacoid placed closer to the first than to the third macroplacoid, a crown of smooth large and unbranched areolae separates adjacent conical egg processes, the space between neighboring areolae usually smaller than their width ……………………………………………………………M. centesimus
10(9)A row of larger teeth and a posterior band of small granules/conical teeth present in the second band of teeth in the oral cavity, the second macroplacoid situated closer to the first than to the third macroplacoid, accessory points extremely well developed, protruding high above the primary branch, diameter of bases of egg processes greater than their height, 12–16 processes on egg circumference ……. M. derkai sp. nov.
– Only a row of larger teeth present in the second band in the oral cavity, the distances between all macroplacoids are approximately the same, accessory points well developed but not protruding high above the primary branch, diameter of bases of egg processes approximately same or a bit smaller than their height, 9–11 processes on egg circumference ……………………………………………………………………………..M. huziori
11(7)Eyes absent, pt of buccal tube width up to 14%, the third macroplacoid with a subterminal constriction; eggs with small widely spaced and irregularly distributed processes, surface between processes coarsely and densely granulated …………………………………………………………………………………………………M .carsicus
– Eyes present, pt of buccal tube width higher than 15%, eggs with hemispherical processes positioned very close to each other and covered with a hyaline layer, which is concave between the processes, the shell surface finely granulated and with a reticular design ……………………………………………………..M. csotiensis

Key from Ramazzotti & Maucci (1983):
1. The cuticle is at least partially granulated, dotted, or has gibbosities, or is provided with more or less soft thorny appendages or small papillae . . . . . . . . . . . . . . . . . . . . 2
The cuticle is smooth or provided with “pearl like” pores more or less large . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2 (1). The cuticle shows only a more or less diffuse granulation, without appendages or gibbosities . . . . . . . . . . . . . . . . . . . 3
The cuticle has papillae, gibbosities, or appendages . . . . . . . . . . . . . . . . . . . 5
3 (2). There exists a zone of fine granulation, only along the flanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. hibernicus NOW Murrayon
There is a fine diffuse granulation on the whole dorsal side . . . . . . . . . . . . . 4
4 (3). The sculpturing is an indistinct and irregular granulation; 2 macroplacoids and microplacoid . . . . . . . . . M. ovovillosus
The sculpturing consists of small stellate structures; 3 macroplacoids; microplacoid absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. dianeae NOW Murrayon
5 (2). The cuticle shows small tubercles on all, or part, of the dorsal surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
The cuticle has gibbosities, plates, papillae, or thorns . . . . . . . . . . . . . . . . . . 8
6 (5). There are tubercles sparsely covering the whole body, each having a central point . . . . . . . . . . . . . . . . . . M. topali
The tubercles are restricted to the extreme caudal region . . . . . . . . . . . . . . 7
7 (6). “Pearl like” pores are present in addition to the tubercles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granatai NOW Minibiotus?
There pores are not present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. arguei
8 (5). The sculpturing consists of plates ………………………….. 9
The sculpturing consists of gibbosities, thorns, or papillae …………. 10
9 (8). The plates are of a brown lenticular form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. hufelandi maculatus
The plates form pointed pyramids with polygonal bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. primitivae
lO(8). The whole body covered with gibbosities . . . . . . . . . . . . . . . . . . . . . . M. rollei
Papillae or appendages are present on the dorsal surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ll(10). There are club-shaped papillae in a pleated cuticle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. papillosus
The appendages are spine-like . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
12(11). The appendages of the cuticle spine-like, with bulbous bases, and arranged in 2 longitudinal lines along dorsal surface . . . . . . . . . . . . . . . . . . . . . . . . . . . M. julietae NOW Minibiotus?
The appendages are of a conical shape . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
13(12). There exists 3 pairs of spines . . . . . . . . . . . . . . . . . . . . . . . . . . M. aculeatus NOW Minibiotus?
There is a single pair of spines, near the posterior end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. subjulietae NOW Minibiotus aculeatus
14(1). The cuticle has pores in the form of dimples which are very dense and/or large . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
The cuticle is smooth, or has small sparse “pearl-like” pores . . . . . . . . . . . . 23
15(14). There are 2 macroplacoids ……………………………… 16
There are 3 macroplacoids ……………………………… 17
16(S). Microplacoid present, lunules dentate ………………… M. dentatus NOW crenulatus
Microplacoid absent, lunules smooth ………………… M. gemmatus
17(B). Macroplacoids rod-shaped, the third the longest; microplacoid present . . . . . . . . . . . . . . . . . . . . . . . . M. terricola
Macroplacoids are equal sized granules . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
lB(17). The line of the placoids is short, not passing the middle of the pharynx . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
The line of placoids passes the middle of the pharynx . . . . . . . . . . . . . . . . 20
19(B). The pores are small and circular, laid in transverse bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. striatus
The pores are sub-circular or polygonal, increasing in size from mid-dorsal to the rostral and caudal zones where they may be 6-7µm in diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. pustulatus NOW Minibiotus?
20(18). Mouth without lamellae ……………………………….. 21
Mouth surrounded by lamellae …………………………… 22
21(20). Colorless; eggs having projections like the “head of a screw” enclosed in a transparent capsule . . . . . M. intermedius NOW Minibiotus?
Yellowish; eggs with small, dense, soft spines . . . . . . . . . . . . . . . M. furcatus NOW EITHER furciger or Minibiotus
22(20). Pores circular or triangular (trilobed triangles), with a regular diameter of l.8µm . . . . . . . . . . . . . . . . . M. pseudofurcatus
Pores irregular polygons, with diameters of 2-2.2µm . . . . . . . . . . M. spallanzanii NOW lazzaroi
23(14). There are 2 macroplacoids ……………………………… 24
There are 3 macroplacoids ……………………………… 49
24(23). Microplacoid absent ………………………………….. 25
Microplacoid present …………………………………. 33
25(24). First macroplacoid clearly constricted in the middle . . . . . . . . . . . . . . . . . . 26
First macroplacoid not constricted, or the constriction is very slight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
26(25). Moss dweller; there are many small dense “pearl-like” pores; buccal lamellae absent . . . . . . . . . . . . M. occidentalis
Aquatic; buccal lamellae present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
27(26). Eggs have projections in the form of goblets, heraldic lilies, or similar, which are immersed, totally or partially, in a transparent zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. hastatus NOW Murrayon?
Egg projections are not immersed in a transparent zone . . . . . . . . . . . . . . 28
28(27). Maximum size 250µm; eggs with projections in the form of small, conical, bent spines, in height about 3µm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. nocentiniae NOW Murrayon?
Maximum size 560µm; eggs with projections in the form of small conical or mammary tubercles with spaces between . . . . . . . . . . . . . . . . . . . . . . . . M. pullari NOW Murrayon?
29(25). The 1st macroplacoid is a little longer than the 2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
The 1st macroplacoid is long, about twice the length of the 2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
30(29). Color yellow or orange; cuticle with obvious pores; lunules large, usually dentate or crenate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. islandicus
Colorless; lunules small and smooth . . . . . . . . . . . . . . . . . . . . . . . . M. annae
31(29). Aquatic; no buccal lamellae; placoids are very long and thin . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. longipes
Moss dweller; placoids are short . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
32(31). The 1st macroplacoid has a projection pointing toward the midline; eggs have long spines, ll-20µm, which do not touch at their bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. evelinae
The 1st macroplacoid has no projection; egg projections are large and angular, arising from hexagonal pattern on the shell . . . . . . . . . . . . M. polyopus
33(24). Length of the 1st macroplacoid is 2, or more,timesthatofthe2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Length of the 1st macroplacoid is less than double the 2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
34(33). The 1st macroplacoid is clearly constricted in the middle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
The 1st macroplacoid is not constricted, or it is very slight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
35(34). Red-brown color; lunules small, almost smooth, eggs smooth, deposited in exuvium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .M. rubens
Colorless; lunules large, those of the 4th pair dentate; eggs smooth, deposited in the exuvium . . . . . . . . . . . . . . . . . . . . . . M. hystricogenitus
36(34). The two branches of the claws are joined at mid-length, the main branch does not have an accessory point; lunules large and those of the 4th pair dentate . . . . . . . . . . . . . . . . . . . . . . . .M. ariekammensis
Accessory points are present, the two branches of the claws are joined at the base; lunules very small and incomplete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. polyopus
37(33). The 1st macroplacoid is not constricted, or it is very slight ……………………………….. 38
The 1st macroplacoid is constricted in the middle ………………. 41
38(37). The 1st macroplacoid has a projection pointing toward the midline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
The 1st macroplacoid does not have a projection . . . . . . . . . . . . . . . . . . . . 40
39(38). Eyes anterior ……………………………….. M. spectabilis
Eyes posterior ………………………………… M. grandis
40(38). Aquatic; placoids very long and thin, principal branch of the claws has no accessory points; eggs smooth, deposited in the exuvium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. brevipes
Moss dweller; placoids short; claws have accessory points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. hibiscus
41(37). Buccal lamellae absent; pores numerous and dense; eggs have small, dense, soft spines with small conical bases and strongly bent tips . . . . . . . . M. occidentalis
Buccal lamellae present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
42(41). In the pharynx, between the apophysis and the 1st macroplacoid, there are 2 thin cuticular bars; eggs have conical ornamentation with large bases and strongly tapered tips . . . M. adelges NOW ariekammensis
There are no cuticular bars in the pharynx . . . . . . . . . . . . . . . . . . . . . . . . 43
43(42). Lunules large, those of the 4th pair are crenate or dentate . . . . . . . . . . . . . 44
Lunules normal or small, not dentate, though possibly those of the 4th pair faintly crenate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
44(43). Lunules of the 4th pair are crenate; eggs have truncated cones as ornamentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. tenuis
Lunules of the 4th pair dentate; eggs with conical projections, or bulbous projections with thin tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. echinogenitus
45(43). The eggs have projections in the form of an up-turned egg cup, or they have large conical bases elongated into a cylinder terminating in a small disk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . hufelandi group
Eggs different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
46(45). Length up to 800µm; distance between the stylet supports and end of buccal tube is less than the diameter of the tube; egg ornamentation takes the form of cones with blunt tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. recens
Maximum length 500µm; distance between the stylet supports and end of buccal tube is greater than the tube diameter . . . . . . . . . . . . . . . . . . . . . . . 47
47(46). Eggs have conical projections, and between projections the shell is “tiled” . . . . . . . . . . . . . . . . . . . . . . M. pallarii
Eggs different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
48(47). Eggs have numerous small (about 4µm) projections in the form of truncated cones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. santoroi
Eggs have projections in the form of elongated cones, the apices of which are subdivided into points or are enlarged into a small notched disk . . . . . . . . . . . . . M. anderssoni
49(23). Macroplacoids in the form of almost isodiametric granules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Macroplacoids, or at least 2 of them, more or less elongated rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
50(49). Microplacoid is absent, or very small, scarcely seen . . . . . . . . . . . . . . . . . . . . . . . . . . . . hufelandioides group NOW just M. artipharyngis
Microplacoid present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . intermedius group NOW just ascensionis
51(49). One of the macroplacoids is a granule, the others are rod-like . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
All the macroplacoids are rod-like . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
52(51). The 2nd macroplacoid is a granule, 1st and 3rd are rod-like . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Thelstand3rdareofgranularshape . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
53(52). Aquatic; claws slender with a robust basal basal part; eggs smooth, deposited in exuvium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. norvegicus
Moss dwelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
54(53). Along the dorsal surface are 3 (or 5) longitudinal bands of brown pigment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. virgatus
Colorless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. potockii
55(52). The 1st macroplacoid is granular ……………………. M. insignis
The 3rd macroplacoid is granular …………………….. M. porteri
56(51). Microplacoid absent or very small …………………………. 57
Microplacoid present …………………………………. 64
57(56). Cavity globules and eggs colored red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. komareki
Colorless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
58(57). Buccal lamellae absent ………………………….. M. carsicus
Buccal lamellae present ……………………………….. 59
59(58). Buccal tube narrow (4µm); pores arranged in transverse bands . . . . . . . . . . . . . . . . . . . . . . . M. bisoctus NOW Minibiotus?
Buccal tube average or very wide (not less than 5µm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
60(59). Tube of average width (5-8µm) ……………………………. 61
Tube much wider (9-12µm or more) ………………………… 62
61(60). Macroplacoids increase in size from 1st to 3rd; eggs have hemispherical projections enveloped in a transparent layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. mahunkai NOW Bertolanius?
The 2nd macroplacoid is the shortest and the 3rd is the longest; shell of egg is “tiled” and the projections conical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. areolatus NOW Paramacrobiotus
62(60). Maximum length is less than 500µm; the 2nd macroplacoid does not touch thelst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. csotiensis NOW Paramacrobiotus
Maximum length is greater than 500µm; the 2nd macroplacoid approaches, and almost touches, the 1st . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
63(62). Maximum length up to 620µm; the 2nd macroplacoid is much shorter than the others (half the length of the 3rd); eggs have a “stellate” appearance . . . . . . . . . . . . . . . . . . . . . . M. tonolli NOW Paramacrobiotus
Length up to 800µm; the 2nd macroplacoid is long, more than half the length of the 3rd; egg shell has polygonal plates whose edges rise up as rigid spines . . . . . . . . . . . . . . . . . . . M. psephus
64(56). Macroplacoids are short rods (3-5µm) ……………………….. 65
Macroplacoids are longer rods (7-10µm) ……………………… 66
65(64). The 2nd macroplacoid almost touches the 1st and is shortest, the 3rd longest; eggs have conical projections . . . . . . . . . . . . . . . . . . . . . . . . . M. ovidii
Macroplacoids increase in length from first to last, projections on eggs are immersed in a hyaline zone . . . . . . . . . . . . . . . . . . . . . . . M. spertii
66(64). Macroplacoids increase in length from 1st to 3rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Macroplacoids about equal length (the second possibly a littler shorter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
67(66). Surface of eggs with reticular design produced by small granular deposits . . . . . . . . . . . . . . . . . . . . M. kolleri
Eggs have hemispherical projections which have funnel-shaped depressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. submorulatus
68(66). Macroplacoids short rods with rounded ends and arranged in a line concave toward the middle; microplacoid large and placed near the 3rd macroplacoid; cuticle without pores . . . . . . . . . . . . . . . . . . . . . . . . harmsworthi group
Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
69(68). Buccal tube average width (7µm); eggs have long cones with strongly tapered tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. willardi
Buccal tube much wider (15µm or more) . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
70(69). Egg projections are truncated cones or almost hemispherical, shell “tiled” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. richtersi NOW Paramacrobiotus
Eggs covered with a hyaline layer, in which are partially immersed the ornaments consisting of spine-like cones interspersed with smaller conical or club-shaped projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. beotiae NOW Paramacrobiotus

Key to hufelandi group from R&M 1983:
1. Projections of the egg consist of a conical base, surmounted by an extended cylinder that spreads out at the tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Projections are usually in the form of an inverted egg cup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2(1) The cylindrical part is shorter than the conical base; lunules occur onlyinthe4thpairoflegs . . . . . . . . . . . . . . . . . . . M. pseudohufelandi NOW Xerobiotus
The cylindrical extension is longer than the conical base; lunules are present in all the legs . . . . . . . . . . . . . . . . . . . . . . . . M. lissostomus
3(1). Between the egg projections the shell is smooth, without pores . . . . . . . . . . . . . . . . . . . . . . . . . M. persimilis
Egg shell has numerous pores between projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4(3). Projections are very close together; a single line of pores runs between neighboring projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. rawsoni
Projections are further apart, so more lines of pores run between them . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5(4). The terminal disk has an entire or only slightly notched margin . . . . . . . . . . . . . . . . . . . . . . . . . . M. hufelandi
The terminal disk has a markedly notched margin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. hibiscus


Citations :

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

“Parts” 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.

Bertolani R, Guidetti R, Marchioro T, Altiero T, Rebecchi L, Cesari M. 2014. Phylogeny of Eutardigrada: New molecular data and their morphological support lead to the identification of new evolutionary lineages. Molecular Phylogenetics and Evolution. 76: 110-126.

Guidetti R, Gandolfi A, Rossi V, Bertolani R. 2005. Phylogenetic analysis of Macrobiotidae (Eutardigrada, Parachela): a combined morphological and molecular approach. Zoologica Scripta. 34 (3): 235-244.

Marley NJ, McInnes SJ, Sands CJ. 2011. Phylum Tardigrada: A re-evaluation of the Parachela. Zootaxa. 2819: 51-64.

Schultze CAS. 1834. Macrobiotus hufelandii, animal e crustaceorum classe novum, reviviscendi post diuturnam asphyxiam et ariditatem potens. Berolini, Berlin.

Schuster RO, Nelson DR, Grigarick AA, Christenberry D. 1980. Systematic criteria of the Eutardigrada. Transactions of the American Microscopical Society. 99: 284-303.

Thulin G. 1928. Über die phylogenie und das system der tardigraden. Zoologisches Institut, Lund.

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