Five new species of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae)
Tumanov, Denis V.
Zootaxa
2006
1122
1
23
[264,548,1518,1544]
Polychaeta
Aphroditidae
Milnesium
Animalia
Phyllodocida
1
2
Annelida
species
antarcticum
sp. nov.
Typematerial. Holotype: sex indeterminate, slide number 89(22). Collected by Dr. P. I. Krylov (Zoological Institute of the Russian Academy of Sciences, St. Petersburg) 15.12.1985, King George Island, Antarctica. Paratypes: slide’s numbers 89(1, 5, 17, 18, 19, 23) from the same locality. Typelocality: Antarctica, King George Island, vicinity of Henryka Arctowskiego Polish polar station, moss in a little stream from under snowfield. 27 adultand juvenile specimens and 1 exuvium with three eggs were found.
Etymology.This species is named after the region of its typelocality, Antarctica.
Description.Large animals, exact body length could not be measured, because of the strong constriction during fixation (even in constricted condition it exceed 800 µm), colour of the fixed specimens reddishbrown; cuticle smooth; eyes present. Six peribuccal and two lateral papillae present. Mouth with 6 peribuccal lamellae longitudinally striped in their basal portion. Buccal tube wide and long. Claws large, massive. Main branch of each claw with two well developed accessory points. Complex basal claw+secondary branch with well developed rounded basal thickening. First three pairs of legs with elongated cuticular thickening near the claw bases. All dimensions are given in Table 2. Smooth eggs (white in incident light, colourless in preparation) deposited within exuviae. TABLE 1.Summary of morphometric data for Milnesium tardigradum(European populations) (n=6). Character body length (µm) buccal tube length (µm) Smallest specimen 598.5 48.8 Largest specimen 704.9 46.6 Mean (Range) Standard error 652.8 (598.5–704.9) 18.68 49.4 (46.6–53.3) 1.22 ss (µm) ptss (%) 32.6 66.7 30.3 65.1 31.9 (30.3–33.3) 0.54 64.6 (62.5–66.7) 0.67 outer buccal tube width (µm) ptof outer buccal tube width claw main branch length, leg I (µm) 18.5 37.9? 20.7 44.4 17.0 19.7 (13.3–22.2) 1.40 39.9 (28.6–46.2) 2.56 16.1 (14.8–17.0) 0.46 ptof claw main branch length, leg I claw base+sec. branch length, leg I (µm) ? 12.6 36.5 14.1 32.6 (28.7–36.5) 1.64 13.1 (11.8–14.4) 0.40 ptof claw base+sec. branch length, leg I claw basal branch length, leg I (µm) bb, leg I 25.8 5.2 2.4 30.2 6.7 2.1 26.6 (24.6–30.2) 0.83 6.1 (4.4–7.4) 0.47 2.2 (1.8–2.7) 0.12 claw main branch length, leg III (µm) ptof claw main branch length, leg III 16.3 33.3 19.6 42.1 17 (14.8–19.6) 0.72 34.6 (30.1–42.1) 2.04 claw base+sec. branch length, leg III (µm) ptof claw base+sec. branch length, leg III claw basal branch length, leg III (µm) 12.6 25.8 5.2 14.1 30.2 5.6 13.4 (12.6–14.1) 0.23 27.3 (25–30.2) 0.78 5.3 (5.0–5.6) 0.09 bb, leg III claw main branch length, leg IV (µm) 2.4 21.5 2.5 25.2 2.5 (2.4–2.6) 0.04 22.7 (21.5–25.2) 0.59 ptof claw main branch length, leg IV claw base+sec. branch length, leg IV (µm) ptof claw base+sec. branch length, leg IV 43.9 15.5 31.8 54.0 17.0 36.5 46.2 (41.7–54.0) 2.06 16.2 (15.5–17.0) 0.23 32.8 (30.6–36.5) 0.98 claw basal branch length, leg IV (µm) bb, leg IV 7.0 2.4 8.1 2.5 7.6 (6.7–8.1) 0.27 2.1 (2.02.4) 0.07 TABLE 2.Summary of morphometric data for Milnesium antarcticum sp. nov.(n=15). Character Holotype Mean (Range) Standard error buccal tube length (µm) 74.7 71.4 (67.0–74.7) 0.72 ss (µm) 53.3 51 (47.4–54.0) 0.55 ptss 71.3 71.5 (70.0–73.7) 0.30 outer buccal tube width (µm) 27.4 28.1 (25.9–31.8) 0.41 ptof outer buccal tube width 36.6 39.2 (35.4–43.9) 0.63 claw main branch length, leg I (µm) 26.3 26.5 (23.7–30.3) 0.46 ptof claw main branch length, leg I 35.1 37.2 (34.0–43.2) 0.64 claw base+sec. branch length, leg I (µm) 17.8 18.1 (16.3–20.0) 0.30 ptof claw base+sec. branch length, leg I 23.8 25.4 (22.9–28.4) 0.50 claw basal branch length, leg I (µm) 8.9 8.1 (7.4–8.9) 0.11 bb, leg I 2.0 2.2 (2.0–2.5) 0.05 claw main branch length, leg III (µm) ? 30.0 (25.9–31.8) 0.46 ptof claw main branch length, leg III ? 42.3 (38.5–45.7) 0.65 claw base+sec. branch length, leg III (µm) 18.9 19.8 (18.9–21.1) 0.25 ptof claw base+sec. branch length, leg III 25.2 27.6 (25.2–30.0) 0.46 claw basal branch length, leg III (µm) 8.9 9.2 (8.1–11.1) 0.30 bb, leg III 2.1 2.1 (1.8–2.4) 0.05 claw main branch length, leg IV (µm) 39.2 37.2 (34.0–39.2) 0.36 ptof claw main branch length, leg IV 52.5 52.1 (49.8–55.9) 0.42 claw base+sec. branch length, leg IV (µm) 23.7 22.2 (19.6–25.2) 0.39 ptof claw base+sec. branch length, leg IV 31.7 31.2 (28.0–34.3) 0.49 claw basal branch length, leg IV (µm) 11.8 11.5 (9.3–14.1) 0.30 bb,leg IV 2.0 1.9 (1.6–2.5) 0.06 No mature males were found. Differential Diagnosis. Milnesium antarcticum sp. nov.differs from Milnesium reticulatumby having smooth cuticle without gibbosities, more caudal position of the insertion point of the stylet supports ( ptvalue 70.0– 73.7 in M. antarcticum sp. nov.and 68.5–69.8 in M. reticulatum), claws with developed basal spurs on the outer claws and larger ptratio of the length of main branches of the claws of the IV pair of legs ( 49.8–55.9 in M. antarcticum sp. nov.and 41.7–44.3 in M. reticulatum). Milnesium antarcticum sp. nov.differs from M. katarzynaeby having smooth cuticle, slightly more cephalic position of the insertion point of the stylet supports ( ptvalue 70.0– 73.7 in M. antarcticum sp. nov.and 73.3–78.3 in M. katarzynae), claws with developed basal spurs on all claws and larger ptratio of the length of main branches of the claws of the IV pair of legs ( 49.8–55.9 in M. antarcticum sp. nov.and 43.8– 43.5 in M. katarzynae). FIGURE 1.Schemes of the measurements of Milnesiumclaw structures and buccopharyngeal apparatus. Milnesium antarcticum sp. nov.differs from Milnesium dujiangensisby having main claw branches on all legs. Milnesium antarcticum sp. nov.differs from M. tardigradumby larger buccal tube and claws’ dimensions and more caudal position of the insertion point of the stylet supports (for comparison see Tables 1and 2). Milnesium antarcticum sp. nov.differs from M. tetralamellatumby having 6 peribuccal lamellae, lesser ptratio of the length of the complex basal claw+secondary branch of the IV pair of legs (28.0– 34.3 in M. antarcticum sp. nov.and 46.2 in M. tetralamellatum), larger buccal tube dimensions, more caudal position of the insertion point of the stylet supports ( ptvalue 70.0– 73.7 in M. antarcticum sp. nov.and 63.9 in M. tetralamellatum) and claws with developed basal spurs on the outer claws. Milnesium antarcticum sp. nov.differs from M. brachyungueby having larger ptratio of the length of the claws of the IV pair of legs ( ptvalue of the length of main branches of the claws of the IV pair of legs is 49.8–55.9 in M. antarcticum sp. nov.and 33.1 in M. brachyungue), more caudal position of the insertion point of the stylet supports ( ptvalue 70.0– 73.7 in M. antarcticum sp. nov.and 69.4 in M. brachyungue) and longer claws. Milnesium antarcticum sp. nov.differs from M. eurystomumby having typical configuration of buccal apparatus.