Milnesium reductum, Tumanov, Denis V., 2006

Tumanov, Denis V., 2006, Five new species of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae), Zootaxa 1122, pp. 1-23 : 15-18

Milnesium reductum sp. nov. ( Figs. 6, 7 , 30–36 , Table 5 )

Type Material. Holotype: sex indeterminate, slide number 192(1). Collected by Dr. I. G. Danylov (Zoological Institute of the Russian Academy of Sciences, St. Petersburg) 20.06.1998, Kirghizia. Paratypes: slide’s numbers 192(2, 3, 5) from the same locality. Type locality: Kirghizia, Jalal­Abad Area, vicinity of Tashkumyr, Sarakamyshsai, near 2000 m a.s.l., moss from sandstone rock. 10 adult and juvenile specimens were found.

Etymology. This species is named after its typical characters—reduced basal spurs and accessory points on claws.

Description. Body length up to 758.1 µm; colour of living specimens slightly reddish or white, cuticle smooth, eyes present in most specimens (among 6 adult specimens only one lack eyes). Six peribuccal and two lateral papillae present. The mouth with 6 peribuccal lamellae longitudinally striped in their basal portion.

Claws long, slender. Main branch of each claw lacks accessory points. Complex basal claw+secondary branch with a rounded basal thickening. Outer claws on all legs lacks basal spurs. First three pairs of legs with elongated cuticular thickening near the claw bases. All dimensions are given in Table 5 .

No eggs and mature males were found.

Remarks. In one specimen the abnormal development of claws was found. It has an additional branching of the main branch of one claw on the leg of the 3rd pair ( Fig. 35 ) and a small lateral spine on the base of one claw on the leg of the 4th pair, which is possibly the rudimentary basal spur ( Fig. 36 ).

Differential Diagnosis. Milnesium reductum sp. nov. differs from M. reticulatum by having smooth cuticle without gibbosities, larger body length of adult specimens (578– 758 µm in M. reductum sp. nov. and 270–405 µm in M. reticulatum ), longer buccal tube (42.2–43.7 µm in M. reductum sp. nov. and 25.0–38.8 µm in M. reticulatum ) and longer claws without accessory points (pt value of the length of main branches of the claws of the IV pair of legs is 59.3–70.7 in M. reductum sp. nov. and 41.7–44.3 in M. reticulatum ).

Milnesium reductum sp. nov. differs from M. katarzynae by having smooth cuticle, more cephalic position of the insertion point of the stylet supports (pt value 65.3–69.3 in M. reductum sp. nov. and 73.3–78.3 in M. katarzynae ) and longer claws without accessory points and with basal spurs on the inner claws of all legs (pt value of the length of main branches of the claws of the IV pair of legs is 59.3–70.7 in M. reductum sp. nov. and 43.5– 43.8 in M. reticulatum ).

Milnesium reductum sp. nov. differs from M. dujiangensis by having main claw branches on all legs.

Milnesium reductum sp. nov. differs from M. tardigradum by having more slender claws, larger pt ratio of the claws of the IV pair of legs and reduced accessory points on all claws and basal spurs on the outer claws (for comparison see Tables 1 and 5 ).

Milnesium reductum sp. nov. differs from M. almatyense sp. nov. by having slightly longer buccal tube, completely reduced accessory points on all claws and reduced basal spurs on outer claws only (for comparison see Tables 3 and 5 ).

Milnesium reductum sp. nov. differs from M. antarcticum sp. nov. by having larger pt ratio of the length of the claws of the IV pair of legs, smaller buccal tube dimensions, more cephalic position of the insertion point of the stylet supports and more slender claws with reduced accessory points on all claws and basal spurs on outer claws (for comparison see Tables 2 and 5 ).

Milnesium reductum sp. nov. differs from M. asiaticum sp. nov. by having shorter buccal tube, shorter claws (especially on the IV pair of legs), reduced accessory points on all claws and basal spurs on outer claws (for comparison see Tables 4 and 5 ).

Milnesium reductum sp. nov. differs from M. tetralamellatum by having 6 peribuccal lamellae, smaller buccal tube dimensions, more caudal position of the insertion point of the stylet supports (pt value 65.3–69.3 in M. reductum sp. nov. and 63.9 in M. tetralamellatum ), reduced accessory points on all claws and larger pt ratio of the length of the main branch of the IV pair of legs (59.3–70.7 in M. reductum sp. nov. and 54.7 in M. tetralamellatum ).

Milnesium reductum sp. nov. differs from M. brachyungue by having larger pt ratio of the length of the claws of the IV pair of legs (pt value of the length of main branches of the claws of the IV pair of legs is 59.3–70.7 in M. reductum sp. nov. and 33.1 in M. brachyungue ) and longer claws.

Milnesium reductum sp. nov. differs from M. eurystomum by having typical configuration of buccal apparatus.

Figures

FIGURES 2 – 9. Milnesium tardigradum 2 — claws of the III pair of legs, 3 — claws of the IV pair of legs. Milnesium antarcticum sp. nov. 4 — claws of the III pair of legs, 5 — claws of the IV pair of legs. Milnesium reductum sp. nov. 6 — claws of the I pair of legs, 7 — claws of the IV pair of legs. Milnesium almatyense sp. nov. 8 — claws of the II pair of legs, 9 — claws of the IV pair of legs (9 — holotype; 4 ­ 8 — paratypes.

FIGURES 30 – 36. Milnesium reductum sp. nov. 30 — habitus, 31 — bucco­pharyngeal apparatus, 32 — claws of the III pair of legs, 33 — claws of the IV pair of legs, 34 — main branch of the claw of the IV pair of legs, 35 — abnormal claws of the III pair of legs (arrow points to the additional branch), 36 — abnormal claws of the IV pair of legs (arrow points to the rudimentary spine) (phase contrast; 30 ­ 34 — holotype, 35, 36, — paratype).

Tables

TABLE 5. Summary of morphometric data for Milnesium reductum sp. nov. (n = 6).

Character	Holotype	Smallest specimen	Largest specimen	Mean (Range) Standard error
body length (µm)	665	578.6	758.1	665.0 (578.6–758.1) 25.87
buccal tube length (µm)	42.9	42.2	42.9	43.2 (42.2–43.7) 0.25
ss (µm)	29.6	29.2	28.1	29.0 (28.1–29.6) 0.25
Pt ss	69.0	69.3	65.5	67.2 (65.3–69.3) 0.72
outer buccal tube width (µm)	15.9	15.9	13.7	16.5 (13.3–20.7) 1.21
pt of outer buccal tube width	37.1	37.7	31.9	38.1 (30.5–47.5) 2.71
Claw main branch length, leg I (µm)	21.1	19.6	22.9	21.2 (19.6–22.9) 0.59
pt of claw main branch length, leg I	49.1	46.5	53.4	49.1 (45.8–53.4) 1.31
Claw base+sec. branch length, leg I (µm)	14.1	12.6	16.3	13.9 (12.6–16.3) 0.55
pt of claw base+sec. branch length, leg I	32.8	29.8	37.9	32.3 (28.8–37.9) 1.29
Claw basal branch length, leg I (µm)	5.6	7.0	7.0	6.5 (5.6–7.0) 0.26
bb, leg I	2.5	1.8	2.3	2.1 (1.8–2.5) 0.10
Claw main branch length, leg III (µm)	25.2	23.7	25.9	24.5 (22.9–25.9) 0.44
pt of claw main branch length, leg III	58.6	56.1	60.3	56.9 (52.5–60.3) 1.09
Claw base+sec. branch length, leg III (µm)	15.2	14.8	15.5	14.9 (13.3–15.5) 0.34
pt of claw base+sec. branch length, leg III	35.3	35.1	36.2	34.4 (30.5–36.2) 0.85
Claw basal branch length, leg III (µm)	6.7	0.0	7.8	7.0 (5.9–7.8) 0.33
bb, leg III	2.3	0.0	2.0	2.1 (2.0–2.3) 0.06
Claw main branch length, leg IV (µm)	28.9	26.3	30.3	27.9 (25.9–30.3) 0.67
pt of claw main branch length, leg IV	67.2	62.3	70.7	64.7 (59.3–70.7) 1.60
Claw base+sec. branch length, leg IV (µm)	18.5	0.0	18.5	17.2 (15.5–18.5) 0.59
pt of claw base+sec. branch length, leg IV	43.1	0.0	43.1	39.8 (35.6–43.1) 1.51
Claw basal branch length, leg IV (µm)	8.1	0.0	8.1	7.7 (7.0­8.1) 0.28
bb, leg IV	2.3	0.0	2.0	2.2 (2.2­2.3) 0.02