Minibiotus pseudostellarus, Roszkowska, Milena, Stec, Daniel, Ciobanu, Daniel Adrian & Kaczmarek, Łukasz, 2016

Roszkowska, Milena, Stec, Daniel, Ciobanu, Daniel Adrian & Kaczmarek, Łukasz, 2016, Tardigrades from Nahuel Huapi National Park (Argentina, South America) with descriptions of two new Macrobiotidae species, Zootaxa 4105 (3), pp. 243-260 : 254-257

Minibiotus pseudostellarus sp. nov.

( Table 3 , Figs 12–21 )

http://www.tardigrada.net/register/0023.htm

Localities and number of specimens. VI (1), XIV (1), XXI (7 and 1 exuvium), XXV (5 and 1 exuvium)

Material examined. Holotype (slide: 2306/3), 13 paratypes (slides: 1437/1, 1462/7, 1472/2 and 2306/2), two exuviae (slides: 1437/1 and 2306/3).

Description (measurements and statistics in Table 3 ). Animals: Body length 241–320 µm ( Fig. 12 ), white/ transparent after fixation. Eyes present in all specimens before and after fixation in Hoyer’s medium. Cuticle smooth with pores distributed randomly and not forming any specific design ( Fig. 14 ). Generally two types of pores are present over the entire cuticle: round-shaped (0.3–0.9 µm in diameter) and in the shape of ‘pseudo-stars’ (i.e. not fully developed ‘stars’ but with 3–4 irregular ‘arms’ and poorly visible incisions) (0.6–2.5 µm distance from the farthest points of arms) ( Fig. 14 ). Moreover, large star-shaped pores (with 5–6 ‘arms’) are present on legs (a single pore on leg I–III and two pores above legs IV ( Figs 18–21 ). Pores around mouth absent.

Bucco-pharyngeal apparatus of the Minibiotus type, with the ventral lamina and ten peribuccal papulae. Oral cavity armature absent or not visible under PCM. Pharyngeal bulb oval, with triangular apophyses (very near to first macroplacoid and ca. same size), three macroplacoids and small microplacoid. Macroplacoid length sequence 1≤2<3 ( Fig. 13 ).

Claws short and robust with obvious accessory points ( Figs 15–17 ). Fine granulation only present on legs IV ( Figs 16, 17 ). Cuticular bars under claws I–III present. Other cuticular thickenings on legs absent. Lunules under claws with smooth margins ( Fig. 16 ).

Eggs: Not found.

Etymology. The new species is named after the characteristic pores on the cuticle—simulating (pseudo) stars (stellarum).

Type locality. 41°12’S, 71°51’W, ca. 1,200 m asl: Río Negro, Nahuel Huapi National Park, Bariloche, at the foot of the Tronador volcano, Garganta del Diablo waterfall, moss from rock, 17.01.2012, coll. Dawid Diduszko.

Type depositories. Holotype, 12 paratypes and two exuviae are deposited at the Department of Animal Taxonomy and Ecology, Institute of Environmental Biology, Adam Mickiewicz University in Poznań, Umultowska 89, 61–614 Poznań ( Poland) and one paratype (slide 1472/2) is deposited at the Department of Entomology Institute of Zoology Jagiellonian University, Gronostajowa 9, 30–387, Kraków, Poland.

Differential diagnosis. By the presence of star-like pores in the cuticle (on the legs), the new species is most similar to Min. constellatus Michalczyk & Kaczmarek 2003b, Min. eichhorni Michalczyk & Kaczmarek 2004, Min. sidereus Pilato et al. 2003 and Min. vinciguerrae Binda & Pilato 1992, but it differs from all of them by the presence of ‘pseudo-stars’ instead of fully developed stars on dorsal and ventral cuticle. Additionally, new species differs specifically from:

Minibiotus constellatus , only recorded from Peru ( Michalczyk & Kaczmarek 2003b), by absence of pores around the mouth, different arrangement of pores on the dorsal side of the body (randomly arranged pores in Min. pseudostellarus sp. nov. vs. two rows of pores along the main axis of the body in Min. constellatus ), the presence of eyes, absence of granulation on legs I–III (granulation present on all legs in Min. constellatus ), different macroplacoid sequence (1≤2<3 in Min. pseudostellarus sp. nov. vs. 3<2<1 in Min. constellatus ), longer third macroplacoid (2.4 – 3.6 µm in Min. pseudostellarus sp. nov. vs. 1.4 – 1.9 µm in Min. constellatus ), slightly longer macroplacoid row with higher pt (8.7 – 11.0 µm [35.5–38.9] in Min. pseudostellarus sp. nov. vs. 6.7 – 8.6 µm [25.0–35.4] in Min. constellatus ).

Minibiotus eichhorni , only recorded from Peru ( Michalczyk & Kaczmarek 2004), by different arrangement of pores on the dorsal side of the body (randomly arranged pores in Min. pseudostellarus sp. nov. vs. pores arranged in six transverse bands in Min. eichhorni ), absence of granulation on legs I–III (granulation present on all legs in Min. eichhorni ), shorter external primary and secondary branches of claws III (5.6 – 7.1 µm and 4.4 – 5.5 µm respectively in Min. pseudostellarus sp. nov. vs. 7.6 – 11.4 µm and 5.7 – 8.6 µm in Min. eichhorni ), higher pt of the buccal tube external width ([10.2–11.6] in Min. pseudostellarus sp. nov. vs. [6.9–9.7] in Min. eichhorni ), a slightly higher pt of the second macroplacoid length ([9.3–11.3] in Min. pseudostellarus sp. nov. vs. [6.9–9.2] in Min. eichhorni ), smaller pt of the external primary branches of claws II ([21.7–25.5] in Min. pseudostellarus sp. nov. vs. [26.9–33.3] in Min. eichhorni ), smaller pt of the external primary branches of claws III ([22.7–26.8] in Min. pseudostellarus sp. nov. vs. [29.4–33.3] in Min. eichhorni ), and smaller pt of anterior primary and secondary branches of claws IV ([26.6–31.7] and [19.1–22.4] in Min. pseudostellarus sp. nov. vs. [34.6–41.7] and [23.1–27.8] in Min. eichhorni , respectively).

Minibiotus sidereus , only recorded from Ecuador ( Pilato et al. 2003), by stylet supports inserted in a more posterior position ([65.6–68.8 in Min. pseudostellarus sp. nov. vs. [58.6–58.9] in Min. sidereus ), a slightly higher pt of the second macroplacoid length ([9.3–11.3] in Min. pseudostellarus sp. nov. vs. [7.9–9.1] in Min. sidereus ), longer macroplacoid row with higher pt (8.7–11.0 µm [35.5–38.9] in Min. pseudostellarus sp. nov. vs. 5.7–7.9 µm [26.6–29.9] in Min. sidereus ) and longer placoid row with higher pt (10.4–13.0 µm [42.2–46.2] in Min. pseudostellarus sp. nov. vs. 6.4–9.6 µm [29.9–36.4] in Min. sidereus ).

Minibiotus vinciguerrae , only recorded from Antarctica ( Binda & Pilato 1992), by the lack of oral cavity armature, absence of granulation on legs I–III, short and robust claws (long and slender in Min. vinciguerrae ), different macroplacoid sequence (1≤2<3 in Min. pseudostellarus sp. nov. vs. 2<3<1 in Min. vinciguerrae ), smaller body size (230–326 µm in Min. pseudostellarus sp. nov. vs. 380–520 µm in Min. vinciguerrae ), shorter buccal tube (23.5–29.3 µm in Min. pseudostellarus sp. nov. vs. 35.1 µm in Min. vinciguerrae (in specimen 520 µm in length)), lower width of the buccal tube (2.5–3.3 µm in Min. pseudostellarus sp. nov. vs. 3.6 µm in Min. vinciguerrae (in specimen 520 µm in length)), smaller first and second macroplacoid (2.2–3.2 µm [8.9–10.9] and 2.3–3.3 µm respectively in Min. pseudostellarus sp. nov. vs. 4.4 µm [12.4] and 3.6 µm respectively in Min. vinciguerrae (in specimen 520 µm in length)), smaller microplacoid (1.1–1.5 µm in Min. pseudostellarus sp. nov. vs. 1.9 µm in Min. vinciguerrae (in specimen 520 in length)), shorter macroplacoid and placoid rows (8.7–11.0 and 10.4–13.0 µm respectively in Min. pseudostellarus sp. nov. vs. 13.1 and 15.39 µm in Min. vinciguerrae (in specimen 520 µm in length)) and smaller length and pt values of the external primary branches of claws II, III, IV (5.7–7.3 µm [21.7–25.5], 5.6–7.1 µm [22.7–26.8] and 6.7–8.9 µm [26.6–31.7] respectively in Min. pseudostellarus sp. nov. vs. (12.34 µm [35.1], 12.63 µm [35.9] and 14.6 µm [41.6] respectively in Min. vinciguerrae (in specimen 520 µm in length)).

Figures

FIGURES 12 – 14. Minibiotus pseudostellarus sp. nov.: 12 — habitus (lateral view, holotype); 13 — buccal apparatus (holotype); 14 — dorsal cuticle with pseudo-stars and round pores (holotype).

FIGURES 15 – 17. Minibiotus pseudostellarus sp. nov.: 15 — claws II (holotype); 16 — claws IV (holotype); 17 — claws IV (holotype).

FIGURES 18 – 21. Minibiotus pseudostellarus sp. nov. 18 – 21 — large star-shaped pores present on legs I – IV (holotype).

Tables

TABLE 3. Measurements [in µm] and pt values of selected morphological structures of Minibiotus pseudostellarus sp. nov. mounted in Hoyer’s medium (N—number of specimens / structures measured, RANGE refers to the smallest and the largest structure among all measured specimens; SD—standard deviation).

CHARACTER	N	RANGE	MEAN	SD	Holotype
		µm pt	µm pt	µm pt	µm pt
Body length	14	230 – 326 941 – 1125	261 1016	28 62	233 941
Buccal tube
Length	14	23,5 – 29,3 –	25,7 –	1,6 –	24,8 –
Stylet support insertion point	14	16,1 – 19, 3 65,6 – 68, 8	17,4 67,6	1,0 1,0	16, 8 67,7
External width	14	2,5 – 3,3 10,2 – 11,6	2, 8 11, 1	0,2 0,3	2, 7 10,9
Internal width	14	1,1 – 1,7 4,5 – 6,1	1,3 5,2	0,2 0,5	1,2 4,8
Ventral lamina length	13	13,0 – 16, 2 52,6 – 57, 4	14,2 55,0	1,0 1, 3	13,3 53,6
Placoid lengths
Macroplacoid 1	14	2,2 – 3,2 8,9 – 10,9	2,5 9,6	0,3 0,6	2,3 9,3
Macroplacoid 2	14	2,3 – 3,3 9,3 – 11,3	2,5 9,9	0,3 0,5	2,3 9,3
Macroplacoid 3 14 2,4 – 3,6 9,7 – 12,7	14	2,4 – 3,6 9,7 – 12,7	2, 8 10,8	0,3 0,8	2,4 9,7
Microplacoid	14	1,1 – 1,5 4,5 – 5,7	1,3 5,1	0,1 0,4	1,3 5,2
Macroplacoid row	14	8,7 – 11,0 35,5 – 38,9	9, 5 37,2	0,7 1,0	8, 8 35,5
Placoid row	14	10,4 – 13,0 42,2 – 46, 2	11,3 43,9	0,9 1, 4	10,5 42,3
Claw 1 lengths
External primary branch	10	5,8 – 7,2 22,1 – 26,8	6, 1 23,9	0,5 1,5	6,0 24,2
External secondary branch	8	4,5 – 5,4 18,1 – 19,6	4, 8 18,7	0,3 0,6	4, 5 18,1
Internal primary branch	9	5,6 – 6,9 21,7 – 25,2	5, 9 23,3	0,4 1,1	5,7 23,0
Internal secondary branch	4	4,2 – 5,7 16,9 – 19,5	4, 8 18,4	0,6 1,1	4, 2 16,9
Claw 2 lengths
External primary branch	10	5,7 – 7,3 21,7 – 25,5	6, 1 23,9	0,5 1,3	6,0 24,2
External secondary branch	7	4,5 – 5,9 18,0 – 22,4	5, 1 19,9	0,5 1,6	4, 5 18,1
Internal primary branch	9	5,4 – 6,7 20,6 – 25,5	5,9 23,0	0,4 1,6	5,7 23,0
Internal secondary branch	4	4,0 – 5,0 16,1 – 19,9	4, 6 18,6	0,4 1,7	4,0 16,1
Claw 3 lengths
External primary branch	8	5,6 – 7,1 22,7 – 26,8	6, 3 24,6	0,5 1,2	6,0 24,2
External secondary branch	7	4,4 – 5,5 17,8 – 20,9	5,0 19,3	0,4 1,2	4, 5 18,1
Internal primary branch	9	5,4 – 6,7 21,9 – 25,8	6, 1 23,7	0,5 1,4	5, 6 22,6
Internal secondary branch	7	4,0 – 5,4 16,1 – 20,3	4, 8 18,4	0,5 1,4	4,0 16,1
Claw 4 lengths
Anterior primary branch	12	6,7 – 8,9 26,6 – 31,7	7, 3 28,4	0,7 1,6	6, 8 27,4
Anterior secondary branch	10	4,9 – 6,0 19,1 – 22,4	5, 4 21,2	0,4 1,0	5,0 20,2
Posterior primary branch	11	6,3 – 8,8 27,0 – 32,9	7, 5 29,1	0,7 1,8	7,0 28,2
Posterior secondary branch	7	5,0 – 6,6 20,2 – 24,2	5, 8 22,6	0,5 1,4	5,0 20,2