Milnesium longiungue, Tumanov, Denis V., 2006

Tumanov, Denis V., 2006, Five new species of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae), Zootaxa 1122, pp. 1-23 : 18-21

Milnesium longiungue sp. nov. ( Figs. 12–14 , 37–42 , Table 6 )

Type Material. Holotype: sex indeterminate, slide number 214(1). Collected by Dr. P. I. Krylov (Zoological Institute of the Russian Academy of Sciences, St. Petersburg) 30.09.1995, India. Paratypes: slide’s numbers 214(2, 3, 4, 5, 6) from the same locality. Type locality: India, Hymalaia, Lahaul, road between Keylong and Kardang, 3600–3700 m a.s.l, moss and lichen on rock. 11 adult and juvenile specimens were found.

Etymology. This species is named after its typical character—long claws.

Description. Body length up to 944.3 µm; colour of living specimens white, cuticle smooth, eyes present in most specimens (among 8 adult specimens 3 lack eyes). Six peribuccal and two lateral papillae present. Mouth with 6 peribuccal lamellae longitudinally striped in their basal portion.

Claws very long, slender. Main branch of each claw lacks accessory points. Basal spur of each claw (especially on the IV pair of legs) strongly reduced. Length of the complex basal claw+secondary branch 3–3.5 times exceed length of the basal spur. Complex basal claw+secondary branch with a rounded basal thickening. First three pairs of legs with elongated cuticular thickening near the claw bases. All dimensions are given in Table 6 .

Remarks. One adult specimen has strongly modificated claws on legs I. Each leg bears a pair of short claws in the form of a simple hook with basal protrusion ( Fig. 14 ), which seems to derivate from the complex basal claw+secondary branch, while the main branches are completely reduced. This configuration of the claws is similar to those found in Milnesium tardigradum (personal observations) and Milnesium tetralamellatum ( Pilato & Binda 1991) males, but in later two species main branches of claws are present. Although it is not proved by the direct observations of the gonad, it is highly possible that this specimen is also the male.

Milnesium longiungue sp. nov. differs from M. reticulatum by having smooth cuticle without gibbosities, more cephalic position of the insertion point of the stylet supports (pt value 59.1–66.7 in M. longiungue sp. nov. and 68.5–69.8 in M. reticulatum ) and longer claws with developed basal spurs on the outer claws and without accessory points (pt value of the length of main branches of the claws of the IV pair of legs is 81.8–92.4 in M. longiungue sp. nov. and 41.7–44.3 in M. reticulatum ).

Milnesium longiungue sp. nov. differs from M. katarzynae by having smooth cuticle, more cephalic position of the insertion point of the stylet supports (pt value 59.1–66.7 in M. longiungue sp. nov. and 73.3–78.3 in M. katarzynae ) and longer claws with developed basal spurs on all claws and without accessory points (pt value of the length of main branches of the claws of the IV pair of legs is 81.8–92.4 in M. longiungue sp. nov. and 43.5–43.8 in M. katarzynae ).

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

Milnesium longiungue sp. nov. differs from M. tardigradum by having longer and more slender claws, larger pt ratio of the claws, reduced accessory points and shorter basal spur (for comparison see Tables 1 and 6 ).

Milnesium longiungue 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, more slender claws with reduced accessory points and shorter basal spur (for comparison see Tables 2 and 6 ).

Milnesium longiungue sp. nov. differs from M. asiaticum sp. nov. by having larger pt ratio of the length of the claws of the IV pair of legs, reduced accessory points and shorter basal spur (for comparison see Tables 4 and 6 ).

Milnesium longiungue sp. nov. differs from M. almaaatensis sp. nov. by having larger pt ratio of the length of the claws of the IV pair of legs, more cephalic position of the insertion point of the stylet supports, reduced accessory points and developed basal spurs on all claws (for comparison see Tables 3 and 6 ).

Milnesium longiungue sp. nov. differs from M. reductum sp. nov. by having larger buccal tube dimensions, longer claws (especially on legs IV), larger pt ratio of the length of the claws of the IV pair of legs and developed basal spurs on the outer claws (for comparison see Tables 5 and 6 ).

Milnesium longiungue sp. nov. differs from M. tetralamellatum by having 6 peribuccal lamellae, longer main branches of all claws (pt value of the length of main branches of the claws of the IV pair of legs is 81.8–92.4 in M. longiungue sp. nov. and 54.7 in M. tetralamellatum ), developed basal spurs on the outer claws and reduced accessory points on all claws.

Milnesium longiungue sp. nov. differs from M. brachyungue by having larger pt ratio of the claws of legs IV (pt value of the length of main branches of the claws of the IV pair of legs is 81.8–92.4 in M. longiungue sp. nov. and 33.1 in M. brachyungue ) and longer claws.

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

Figures

FIGURES 10 – 14. Milnesium asiaticum sp. nov. 10 — claws of the I pair of legs, 11 — claws of the IV pair of legs. Milnesium longiungue sp. nov. 12 — claws of the I pair of legs, 13 — claws of the IV pair of legs, 14 — abnormal claws of the I pair of legs (presumable male) (12, 13 — holotype; 10, 11 — paratype).

FIGURES 37 – 42. Milnesium longiungue sp. nov. 37 — habitus, 38 — bucco­pharyngeal apparatus, 39 — claws of the III pair of legs, 40 — claws of the I pair of legs, 41 — claws of the IV pair of legs, 42 — main branch of the claw of the IV pair of legs (phase contrast; 37 ­ 41 — holotype, 42, — paratype).

Tables

TABLE 6. Summary of morphometric data for Milnesium longiungue sp. nov. (n = 8).

Character	Holotype	Smallest specimen	Largest specimen	Mean (Range) Standard error
body length (µm)	897.8	598.5	944.3	825.4 (598.5–944.3) 38.09
buccal tube length (µm)	57.0	43.7	53.3	50.6 (43.7–57.0) 1.83
Ss (µm)	35.5	27.8	35.5	32.4 (27.8–35.5) 1.19
pt ss	62.3	63.6	66.7	64.1 (59.1–66.7) 0.97
outer buccal tube width (µm)	22.9	14.8	28.9	22.1 (14.8–28.9) 1.99
Pt of outer buccal tube width	40.3	33.9	54.2	43.6 (33.8–59.1) 3.55
claw main branch length, leg I (µm)	33.3	20.7	30.3	27.4 (20.7–33.3) 1.34
Pt of claw main branch length, leg I	58.4	47.5	56.9	54.1 (47.5–58.4) 1.50
claw base+sec. branch length, leg I (µm)	20.0	14.8	19.2	17.9 (14.8–20.0) 0.68
Pt of claw base+sec. branch length, leg I	35.1	33.9	36.1	35.4 (31.2–39.4) 0.86
claw basal branch length, leg I (µm)	7.4	0.0	8.1	7.4 (6.7–8.1) 0.18
bb, leg I	2.7	0.0	2.4	2.5 (2.3–2.7) 0.07
claw main branch length, leg III (µm)	35.5	25.9	36.6	33.0 (25.9–36.6) 1.35
Pt of claw main branch length, leg III	62.3	59.3	68.8	65.4 (57.1–73.5) 1.93
claw base+sec. branch length, leg III (µm)	22.2	15.5	19.2	19.4 (15.5–22.2) 0.81
Pt of claw base+sec. branch length, leg III	39.0	35.6	36.1	38.3 (33.8–42.6) 1.07
claw basal branch length, leg III (µm)	8.1	6.3	9.6	8.0 (6.3–9.6) 0.40
bb, leg III	2.7	2.5	2.0	2.4 (2.0–2.7) 0.09
claw main branch length, leg IV (µm)	47.4	36.6	46.6	44.2 (36.6–47.4) 1.48
Pt of claw main branch length, leg IV	83.1	83.9	87.5	87.5 (81.8–92.4) 1.48
claw base+sec. branch length, leg IV (µm)	27.4	21.5	25.5	25.3 (21.5–27.4) 0.87
Pt of claw base+sec. branch length, leg IV	48.1	49.2	47.9	50.1 (47.9–54.5) 0.85
claw basal branch length, leg IV (µm)	7.4	5.9	7.4	7.3 (5.9–8.1) 0.26
bb, leg IV	3.7	2.5	2.0	3.4 (3.1–3.7) 0.09