Milnesium bohleberi, Bartels, Paul J., Nelson, Diane R., Kaczmarek, Łukasz & Michalczyk, Łukasz, 2014

Bartels, Paul J., Nelson, Diane R., Kaczmarek, Łukasz & Michalczyk, Łukasz, 2014, The genus Milnesium (Tardigrada: Eutardigrada: Milnesiidae) in the Great Smoky Mountains National Park (North Carolina and Tennessee, USA), with the description of Milnesium bohleberi sp. nov., Zootaxa 3826 (2), pp. 356-368 : 358-361

Milnesium bohleberi sp. nov.

( Figs 2–6 , Table 1 )

Material examined. Seventy-two adult specimens, all from Great Smoky Mountains National Park, USA, lichen samples and moss samples from trees, coll. P.J. Bartels: holotype and 56 paratypes: 35°35.1089'N, 83°4.4843'W, 1,515 m asl (Purchase Knob, North Carolina, 16.07.2001, 15.09.2001, and 15.07.2003); 1 specimen: 35°33.7598'N, 83°32.9547'W, 1,685 m asl (Double Springs, Tennessee, 04.11.2003);, 2 specimens: 35°36.6566'N 83°26.5986'W, 1,667 m asl (Indian Gap, Tennessee, 20.07.2001); 7 specimens: 35°36.6845'N 83°32.5209'W, 919 m asl (Goshen Prong, Tennessee, 10.06.2002); 3 specimens: 35°42.3971'N, 83°20.5718'W, 935 m asl (Ramsey Cascade, Tennessee 16.05.2003, 29.06.2003); 2 specimens: 35°40.3098'N, 83°26.0193'W, 1,429 m asl (Trillium Gap, Tennessee, 20.09.2002).

Diagnosis. Adults (morphometrics in Table 1 ): Body white before fixation and transparent afterwards, eyes present. Cuticle smooth, without granulation, pseudopores, pores, reticulations, or gibbosities. Six peribuccal papillae (ventral papilla smallest) and six peribuccal lamellae (of equal size) around the mouth opening, present. Two cephalic papillae positioned laterally ( Fig. 2 ).

Buccal apparatus of the Milnesium type ( Figs 3–4 ). Buccal tube wide and short (standard width on average 59% of the length), and funnel-shaped, wider anteriorly (posterior diameter on average 84% of the anterior diameter). Pharyngeal bulb elongated, pear-shaped and without placoids or septulum.

Claws of the Milnesium type, slender ( Fig. 5 ). Primary branches on all legs with small, but distinct accessory points detaching from the branch at its greatest curvature. Secondary branches with rounded basal thickenings. All secondary branches on all legs with three points (claw configuration: [3-3]-[3-3]). Single, long transverse, cuticular bars under claws I–III present ( Fig. 5 ).

Eggs: Oval, smooth and deposited in exuvium as in all other known Milnesium species. No males were found among a total of 72 specimens.

Description of the holotype (for all measurements in µm and pt ratios, see Table 1 ). Adult 858 µm in length. Cuticle smooth. Pharyngeal bulb elongated, with no placoids. Buccal tube obviously funnel shaped; length 62.7 µm, anterior width 45.3 µm [72.2], posterior width 38.9 µm [62.0], standard width 39.8 µm [63.5], stylet insertion point 41.4 µm [66.0], standard width/length ratio 63%, posterior/anterior width ratio 86%. Claws I–III have similar lengths of primary (24.2–27.1 µm) and secondary branches, but anterior and posterior claws IV have longer primary branches (30.2-30.6 Μm) ( Table 1 ). Transverse cuticular bar present at base of claws I–III.

Locus typicus. USA, North Carolina, Great Smoky Mountains National Park, Purchase Knob; 35°35.1089'N, 83°4.4843'W, 1,515 m asl.

Etymology. This species is named after Steve Bohleber, J.D., who is a long-time supporter of the Great Smoky Mountain National Park and the ATBI, and an accomplished nature photographer.

Type depositories. The holotype and 35 paratypes are preserved in the collection of D. Nelson, Department of Biological Sciences, East Tennessee State University, 10 paratypes are deposited in the Department of Animal Taxonomy and Ecology, A. Mickiewicz University, Poznań, Poland, and 10 paratypes are preserved in the Department of Entomology, Jagiellonian University, Kraków, Poland. All additional specimens are preserved in the collection of D. Nelson, Department of Biological Sciences, East Tennessee State University.

Differential diagnosis. The new species with three points on the secondary branches of all claws (claw configuration: [3-3]-[3-3]), a smooth cuticle, six peribuccal lamellae and a funnel-shaped buccal tube is most similar to M. eurystomum Maucci, 1991 but differs from it morphometrically. The 10 animals indicated in Table 1 have a body length range from 620–880 µm, and we compare those with the two M. eurystomum reported in Michalczyk et al. (2012a). The body size of those M. eurystomum specimens was 823–847 µm. M. bohleberi sp. nov. differs from M. eurystomum by: a slightly shorter buccal tube (52.3–67.3 µm in the new species and 70.8–77.5 µm in M. eurystomum of similar body size), a higher pt of the stylet support insertion point (66.0– 70.8 in the new species and ca. 60.0 in M. eurystomum ), a less conical buccal tube (posterior/anterior width ratio 80–88% in the new species and 61–76% in M. eurystomum ), a slightly narrower buccal tube: (a) anterior width (33.8–48.1 µm [63.4–74.7] in the new species and 53.7–55.9 µm [72.1–75.8] in M. eurystomum ) and (b) standard width (28.5–43.1 µm [54.5–64.0] in the new species and 45.9–47.9 µm [61.8–64.8] in M. eurystomum ), and by generally shorter claws (in the new species the primary branches of claws slightly exceed 30 µm only on legs IV in the largest specimens whereas in M. eurystomum almost all primary branches of claws exceed 30 µm (for more details, see Table 1 herein and Table 2 in Michalczyk et al. 2012a,b).

Other known Milnesium species with a smooth cuticle, accessory points on primary branches of claws, and the [3-3]-[3-3] claw configuration, i.e. M. antarcticum , M. asiaticum , M. brachyungue , M. longiungue and M. zsalakoae , have a lower standard buccal tube width ( M. bohleberi sp. nov. = 28.5–43.1, other species collectively = 10.3–31.8) and a lower buccal tube width to length ratio ( M. bohleberi sp. nov. = 0.54–0.64, other species collectively = 0.31–0.51).

Remarks. All Milnesium specimens were found in either mosses or lichens from trees. They have not been found from soil or other habitats sampled in the GSMNP. In the GSMNP tardigrade database, M. bohleberi sp. nov. occurs in six of the 19 ATBI plots and makes up only 0.5% of terrestrial tardigrade individuals (see Bartels & Nelson 2012 and the Lucid key to “Smoky Bears” for details).

Figures

FIGURE 2. Milnesium bohleberi sp. nov. — habitus (holotype). Scale bar units are micrometres.

FIGURES 3 – 4. Milnesium bohleberi sp. nov. 3 — buccal apparatus, 4 — buccal tube (both ventral views, holotype). Scale bars in micrometres.

FIGURES 5 – 6. Milnesium bohleberi sp. nov. 5 — claw III; 6 — claws IV (both holotype). Scale on 6 same as in 5. Scale bar in micrometres.

Tables

TABLE 1. Measurements (in µm), pt values, and size normalised values (a * = intercept of log Y * vs. BTL) of selected morphological structures of 10 specimens of Milnesium bohleberi sp. nov. mounted in Hoyer’s medium. Note that sample size for specific traits varied since not all traits were measureable on all individuals.? = trait oriented unsuitably for measurement.

CHARACTER	N	RANGE (µm)	RANGE (pt)	MEAN	SD Holotype	a*
		min max	min max	µm pt	µm pt µm pt	µm
Body length	9	620 – 880	1159 – 1458	771 1321	99 103 858 1369	774
Peribuccal papillae length	7	15.5 – 20.3	27.2 – 32.3	17.7 30.1	1.9 1.6 19.4 30.9	17.4
Lateral papillae length	6	10.1 – 13.0	17.7 – 22.1	11.8 20.1	1.0 2.0 12.3 19.6	11.9
Buccal tube
Length	10	52.3 – 67.3	–	57.7 –	4.7 – 62.7 –	–
Stylet support insertion point	10	35.9 – 44.9	66.0 – 70.8	39.2 67.9	2.8 1.5 41.4 66.0	39.2
Anterior width	10	33.8 – 48.1	63.4 – 74.7	39.5 68.1	5.1 4.1 45.3 72.2	39.5
Standard width	10	28.5 – 43.1	54.5 – 64.0	34.4 59.5	4.6 3.5 39.8 63.5	34.6
Posterior width	10	27.4 – 41.3	52.4 – 62.0	33.0 56.9	4.6 3.6 38.9 62.0	33.0
Standard width/length ratio	10	54% – 64%	–	59% –	4% – 63% –	60%
Posterior/anterior width ratio	10	80% – 88%	–	84% –	3% – 86% –	84%
Claw 1 lengths
External primary branch	7	21.0 – 26.0	37.2 – 43.0	22.9 39.4	1.7 1.8 24.3 38.8	22.6
External base + secondary branch	7	16.4 – 21.5	28.4 – 34.0	18.7 32.1	1.9 2.0 20.6 32.9	18.5
External spur	6	4.5 – 5.4	7.4 – 10.1	5.0 8.8	0.4 0.9? ?	5.2
Internal primary branch	7	20.0 – 24.2	35.7 – 41.1	22.1 38.0	1.6 1.8 24.2 38.6	22.1
Internal base + secondary branch	7	15.4 – 19.8	26.7 – 32.8	17.5 30.2	1.5 2.4 18.0 28.7	17.5
Internal spur	7	4.0 – 6.0	7.0 – 10.5	5.1 8.7	0.6 1.3 5.3 8.5	5.4
Claw 2 lengths
External primary branch	8	22.3 – 26.5	38.3 – 43.6	24.2 41.2	1.6 1.9 26.5 42.3	23.9
External base + secondary branch	7	18.3 – 23.1	32.1 – 37.0	20.2 35.4	1.7 1.7 23.1 36.8	20.2
External spur	6	4.5 – 6.4	8.3 – 11.2	5.8 10.2	0.7 1.0? ?	6.3
Internal primary branch	8	21.5 – 25.4	36.1 – 40.9	22.9 39.0	1.4 1.9 25.4 40.5	22.7
Internal base + secondary branch	7	16.8 – 21.0	28.4 – 33.5	18.5 32.4	1.6 1.9 21.0 33.5	18.3
Internal spur	6	4.1 – 7.0	7.7 – 11.8	5.5 9.5	1.1 1.6 6.3 10.0	5.7
Claw 3 lengths
External primary branch	6	22.0 – 26.9	40.0 – 44.6	25.3 42.3	1.9 1.8 26.6 42.4	24.9
External base + secondary branch	4	18.3 – 20.3	30.6 – 35.6	19.3 32.4	0.8 2.3 19.2 30.6	19.4
External spur	4	6.0 – 7.3	10.1 – 12.8	6.7 11.3	0.6 1.3 6.5 10.4	6.8
Internal primary branch	5	23.4 – 27.1	37.1 – 43.2	25.1 41.2	1.4 2.7 27.1 43.2	24.9
Internal base + secondary branch	4	18.2 – 21.5	30.7 – 35.8	20.3 34.0	1.5 2.3 21.5 34.3	19.8
Internal spur	3	5.0 – 6.0	8.4 – 10.5	5.6 9.6	0.5 1.1? ?	5.7
Claw 4 lengths
Anterior primary branch	6	23.7 – 30.6	45.3 – 52.3	27.0 47.7	2.8 2.5 30.6 48.8	27.9
Anterior base + secondary branch	6	19.0 – 23.6	35.7 – 41.4	21.2 37.5	2.3 2.1 23.6 37.6	22.0
Anterior spur	5	5.0 – 5.9	9.6 – 10.3	5.4 9.8	0.4 0.3? ?	5.8
Posterior primary branch	6	24.9 – 30.2	45.6 – 50.9	27.1 47.9	2.1 1.9 30.2 48.2	27.6
Posterior base + secondary branch	6	18.2 – 24.0	34.8 – 42.1	21.3 37.7	2.1 2.8 22.1 35.2	22.2
Posterior spur	3	4.5 – 7.0	8.5 – 11.2	5.7 10.0	1.3 1.4 7.0 11.2	6.1