Macrobiotus horningi, Kaczmarek & Michalczyk, 2017

Kaczmarek, Łukasz & Michalczyk, Łukasz, 2017, A description of Macrobiotus horningi sp. nov. and redescriptions of M. maculatus comb. nov. Iharos, 1973 and M. rawsoni Horning et al., 1978 (Tardigrada: Eutardigrada: Macrobiotidae: hufelandi group), Zootaxa 4363 (1), pp. 79-100 : 81-86

Macrobiotus horningi sp. nov.

( Tables 1, 4, Figs 1–4 )

Macrobiotus anderssoni Richters, 1907 ( Horning et al. 1978)

Material examined ( Fig. 1 ). Eight animals and one egg (holotype and 8 paratypes) on nine slides designated as: 1) Macrobiotus anderssoni Richters , 605, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 154, Museum of New Zealand (adult, now designated as a holotype of Macrobiotus horningi sp. nov.); 2) Macrobiotus anderssoni? Richters , egg, proc 14x, Pegleg Flat, Arthur’s Pass Nat. Park, SI, New Zealand, V-18-1970, D.S. Horning, NZ 154, Museum of New Zealand (egg, at present designated as a paratype of Macrobiotus horningi sp. nov.); 3) Macrobiotus anderssoni Richters , 300, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 152, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 4) Macrobiotus anderssoni Richters , 570, Pegleg Flat, Arthur’s Pass Nat. Park., SI, New Zealand, V-18-1970, D.S. Horning, NZ 154, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 5) Macrobiotus anderssoni Richters , 370, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 152, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 6) Macrobiotus anderssoni Richters , 435, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 166, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); Macrobiotus anderssoni Richters , 435, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 152, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 7) Macrobiotus anderssoni Richters, Pegleg Flat , Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 152, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 8) Macrobiotus anderssoni Richters, Pegleg Flat , Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 152, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.); 9) Macrobiotus anderssoni Richters , 220, Pegleg Flat, Arthur’s Pass Nat. Pk., SI, New Zealand, V-18-70, D.S. Horning, NZ 157, Museum of New Zealand (adult, now designated as a paratype of Macrobiotus horningi sp. nov.).

We also examined 32 other animals identified as M. anderssoni , collected from a number of localities in New Zealand (i.e. Mount Egmont National Park, Mountain House Road ; Arthur’s Pass National Park , Halpin Creek and Kellys Creek ; Abel Tasman National Park, Canaan Road terminus; Mount Aspiring National Park , Haast Pass ; Broken Hill ; Tongariro National Park , Ohakune Road ; Eglington River ; Norsewood ; Lake Manapouri ; Rangatira Island , Triangulation Station ; Coopers Knob ; Lewis Pass ; Wainaua Gorge ). However , as none of these specimens were accompanied by eggs, we did not include them in the type series (see also below).

Type locality. 42°54'S, 171°34'E, ca. 850 m asl: New Zealand, South Island , Arthur’s Pass National Park, Pegleg Flat, under shrubs, liverwort ( Porella elegantula ) from rocks.

Description (measurements and statistics in Tables 1, 4). Animals: Body colour unknown, eyes absent ( Fig. 2A ) (but these character may have been affected by the slide mounting media). Entire cuticle covered with round and oval pores not arranged in bands ( Fig. 2B ). Poorly visible granulation present only on legs IV. Buccopharyngeal apparatus of the Macrobiotus type, with the ventral lamina and ten peribuccal lamellae ( Fig. 3A–C ). Mouth antero-ventral. The oral cavity armature of the patagonicus type (see, Kaczmarek & Michalczyk 2017 for details), with only the second and the third band visible under LM ( Fig. 3B–C ). The second band of teeth composed of small granules just above the third band of teeth. The third band of teeth composed of three dorsal and three ventral teeth in the shape of transverse ridges. Pharyngeal bulb spherical with triangular apophyses, two rodshaped macroplacoids and a thin microplacoid. Macroplacoid length configuration 2<1. The first macroplacoid with a central constriction. The second macroplacoid without constrictions, but with latero-terminal globular projections ( Fig. 3A ). Claws of the hufelandi type, stout ( Fig. 3D ). Primary branches with distinct accessory points. All lunules smooth. Thin paired bars under claws I–III present. Other cuticular thickenings on legs absent.

Eggs: Spherical, ornamented and laid freely ( Fig. 4A ), with the chorion surface of the hufelandi type (reticulated; Fig. 4B ). The reticulum well defined, with a limited mesh between egg processes. The mesh size almost uniform (1.0–1.8 µm in diameter), but the mesh forming peribasal rings around processes slightly larger than the interbasal mesh. Process trunks mostly sigmoidal, sometimes concave, wide at the base and very narrow just below the disc, occasionally bifurcated, and terminated with a concave disc ( Fig. 4C ). Disc edges indented, with well-developed teeth ( Fig. 4D ).

CHARACTER N RANGE MEAN SD Holotype µm pt µm pt µm pt µm pt Body length 7 214 – 612 – 425 – 150 – 612 – Buccal tube

Length 8 25.0 – 47.7 – 38.2 – 7.6 – 47.7 – Original measurements according to Horning et al. (1978), including the original terminology: Body length (190–605 µm, mean 390 µm); body width (200 µm); mouth tube length (60 µm); mouth tube width (6 µm, and 9 µm at base); stylet supports attached 12 µm from base; apophyses length (5 µm); I macroplacoid length (15 µm); II macroplacoid length (9 µm); microplacoid length (3 µm); claws length (16 µm); lunules (3–5 µm); egg diameter excluding processes (75–80 µm); height of egg processes (14–20 µm).

Etymology. We dedicate this species to Donald S. Horning, the first author of the “Tardigrada of New Zealand ” monograph, who collected the samples containing the species.

Type depositories. Holotype and paratypes are preserved at the Museum of New Zealand Te Papa Tongarewa, Tory Street, PO Box 467, Wellington , New Zealand.

Remarks. Specimens described here as M. horningi sp. nov. were originally classified by Horning et al. (1978) as “ Macrobiotus anderssoni Richters, 1907 ”. This was a clear misidentification that had already been noticed by Ramazzotti & Maucci (1983) (translation Beasley 1995) and again by Pilato et al. (2006), as the specimens collected by Horning et al. (1978) belong to the M. hufelandi group, whereas M. anderssoni is probably a member of the Mesobiotus furciger complex. Similar doubts about the taxonomic status of M. anderssoni were formulated by Roszkowska et al. (2016). Therefore, as M. horningi sp. nov. and M. anderssoni are not similar and even belong to different genera, we decided to not compare them in the differential diagnosis (below). Horning et al. (1978) reported “ M. anderssoni ” in 60 samples collected from 39 New Zealand localities, but “ M. anderssoni ” eggs were reported only from the following five localities: 175 (Arthur’s Pass National Park, Kellys Creek), 382 (Mount Aspiring National Park, Haast Pass), 391 (Banks Peninsula, Otepatotu Bush), 536 (Abel Tasman National Park, Canaan Road terminus), and 746 (Mount Egmont National Park, Mountain Road House). However, when examining Horning’s New Zealand collection, we only found an “ M. anderssoni ” egg in sample 154 (Arthur’s Pass National Park, Pegleg Flat) but no eggs on slides from localities 175, 382, 391, 536 and 746. Thus, although animals from all localities exhibit very similar morphology, we chose to be conservative and have only included in the type series specimens from the locality 154, i.e. the only locality in which, both animals and an egg were present. The eight animals and the egg from the locality 154 correspond perfectly with the description and microphotographs in Horning et al. (1978).

Differential diagnosis. Macrobiotus horningi sp. nov. is characterised by having the oral cavity armature of the patagonicus type and eggs chorion of the hufelandi type (see Kaczmarek & Michalczyk 2017 for details). Thus, it is most similar to the following six species but can be distinguished from:

M. personatus Biserov, 1990 , reported from the type locality in Russia, by: the absence of granulation on legs I–III, the apparent absence of eyes, the presence of teeth on concave terminal discs of the egg processes (terminal discs flat and smooth in M. personatus ), longer egg processes (11.8–20.0 µm in the new species vs. 7.0–10.5 µm in M. personatus ), and a smaller diameter of terminal disc on egg processes (6.0–6.6 µm in the new species vs. 7.0– 9.0 µm in M. personatus ).

M. sandrae Bertolani & Rebecchi, 1993 , reported from the type locality in Germany, by: the absence of granulation on legs I–III, the absence of teeth on lunules IV, the apparent absence of eyes, the presence of teeth on terminal discs of egg processes (terminal discs jagged, ragged or almost smooth, but never dentate in M. sandrae ), a lower process base/height ratio (65–69% in the new species vs. 109–111% in M. sandrae ), and higher egg processes (11.8–20.0 µm in the new species vs. 4.3–7.6 µm in M. sandrae ).

M. serratus Bertolani et al., 1996 , recorded from the type locality in Italy, by: the absence of teeth on lunules IV, the apparent absence of eyes, a higher pt of buccal tube width (11.6–15.1 in the new species vs. 7.5–9.9 in M. serratus ), a lower number of processes on the egg circumference (ca. 20 in the new species vs. ca. 29 in M. serratus ), higher egg processes (11.8–20.0 µm in new species vs. 5.5–8.0 µm in M. serratus ), wider egg processes (8.2–8.6 µm in the new species vs. ca. 6.5 µm in M. serratus ), and larger diameter of terminal discs of egg processes (6.0–6.6 µm in the new species vs. ca. 2.5 µm in M. serratus ).

M. sottilei Pilato et al., 2012 , reported from the type locality in Belarus, by: the absence of granulation on legs I–III, the absence of teeth on lunules IV, the apparent absence of eyes, a higher pt of stylet supports (77.0– 80.2 in the new species vs. 75.3–76.6 in M. sottilei ), a lower number of processes on the egg circumference (ca. 20 in the new species vs. ca. 29 in M. sottilei ), a lower process base/height ratio (65–69% in the new species vs. 84–89% in M. sandrae ), higher egg processes (11.8–20.0 µm in the new species vs. 5.4–6.2 µm in M. sottilei ), wider bases of egg processes (8.2–8.6 µm in the new species vs. 4.8–5.2 µm in M. sottilei ), and a larger diameter of terminal discs of egg processes (6.0–6.6 µm in the new species vs. 3.6–4.4 µm in M. sottilei ).

M. terminalis Bertolani & Rebecchi, 1993 , recorded from several localities in Italy, by: the absence of granulation on legs I–III, absence of teeth on lunules IV, the apparent absence of eyes, the presence of teeth on terminal discs of egg processes (terminal discs jagged in M. terminalis ), a lower number of processes on the egg circumference (ca. 20 in the new species vs. ca. 26 in M. terminalis ), a lower process base/height ratio (65–69% in the new species vs. 111–123% in M. terminalis ), longer egg processes (11.8–20.0 µm in the new species vs. 4.6–6.0 µm in M. terminalis ), wider egg processes (8.2–8.6 µm in the new species vs. 5.1–7.4 µm in M. terminalis ), and a larger diameter of terminal discs of egg processes (6.0–6.6 µm in the new species vs. 3.8–4.8 µm in M. terminalis ).

M. vladimiri Bertolani et al., 2011 , reported from the type locality in Italy, by: the absence of granulation on legs I–III, the absence of teeth on lunules IV, the apparent absence of eyes, the presence of teeth on terminal discs of egg processes (terminal discs jagged in M. vladimiri ), a lower process base/height ratio (65–69% in the new species vs. 78–91% in M. vladimiri ), higher egg processes (11.8–20.0 µm in the new species vs. 6.5–8.0 µm in M. vladimiri ), wider bases of egg processes (8.2–8.6 µm in the new species vs. 5.1–7.3 µm in M. vladimiri ), and a larger diameter of terminal discs of egg processes (6.0–6.6 µm in the new species vs. 3.8–4.8 µm in M. vladimiri ).

Figures

FIGURE 1. Macrobiotus horningi sp. nov.—slides constituting the type series.

FIGURE2. Macrobiotushorningi sp. nov. A—habitus (holotype); B—dorsal cuticle with pores (arrowheads; paratype).Scale bars in µm.

FIGURE3. Macrobiotus horningi sp. nov. A—buccal apparatus (holotype); B–C—oral cavity armature (B—dorsal teeth,Cventral teeth; indented arrowhead indicates the second band of teeth whereas the arrow shows the third band; holotype); D— claws IV (holotype).Scale bars in µm.

FIGURE 4. Macrobiotus horningi sp. nov. A—egg; B—chorionic reticulum and two partially connate egg processes; C—egg process with theside view of the terminal disc exhibiting the convex shapeof the disc; D—egg process with thetop view of the terminal disc exhibitingteeth.Scale bars in µm.