Minibiotus dispositus Rocha, Doma, Camarda, Ostertag, Meier, Frigieri, Cesari & Lisi, 2024, sp. nov.

Minibiotus dispositus sp. nov. urn:lsid:zoobank.org:act: 780E50E1-48E8-474C-8935-070FCD6B09AE Figs 1–8; Tables 2–6; Supp. files 1–3 Diagnosis Minibiotus with smooth cuticle but with cuticular pores variously sized (0.9–3.1 µm) and shaped; under SEM, most pores are polygonal or multilobate (3–5 angles/lobes/arms); under PCM, pentagonal pores often appear round, and 5-lobate are rarely observable, only caudal or on legs. Dorsal pores arranged in a group of very cephalic and a group of very caudal pores, with in between a series of transverse bands; young specimens with 8 bands of 1–2 rows; senior specimens with 7 bands of about 2–5 less regular rows (band 8 joined to the very caudal pores). Ventral pores arranged in 7 transverse bands, starting posterior to legs I, of a single row each, but partially duplicated medially in senior specimens. Bucco-pharyngeal apparatus typical for the genus; oral cavity armature with three bands of teeth, better visible under SEM, with band I reduced; three macroplacoids (length sequence 3≤ 2<1) and an evident microplacoid in the pharynx. Robust double claws with short, robust accessory points and small, smooth lunules. Faint leg ‘cuticular bars’, divided on legs I–III, undivided on legs IV; no leg granulation, pulvini present on legs I–III. Moderate allometry regarding buccal tube width, macroplacoid and claw length. Etymology From the Latin word ‘ dispositus ’ = ‘ordered’, in the meaning of ‘with a pattern’, referred to the cuticular pores forming a pattern. Material examined In total, 51 animals (undetermined sex; 31 senior and 20 young specimens) and 6 eggs mounted on microscope slides in Polivinil lactophenol medium; 10 additional specimens mounted on SEM stubs; one specimen (voucher) used for DNA analysis. Holotype ARGENTINA • senior spec.; Salta Province, Salta City; 24°47′18″ S, 65°24′38″ W; 1150 m a.s.l.; 2 May 2014; Rocha and Doma leg.; moss and lichen growing on Handroanthus Mattos; UNLPam 1088(3). Paratypes ARGENTINA • 2 senior specs; same data as for holotype; 2 May 2014; MCNS Tar. 000026(1), Tar. 000026(4) • 1 egg; same data as for holotype; 2 May 2014; MCNS Tar. 000027(1) • 2 senior specs; same data as for holotype; 5 Jun. 2022; UNICT 6010, 6011 • 1 young spec.; same data as for holotype; 2 May 2014; UNICT 6012 • 1 egg; same data as for holotype; 2 May 2014; UNICT 6013 • 26 senior specs; same data as for holotype; 2 May 2014; UNLPam 643(3), 654(1), 655(1), 655(2), 656(1), 659(1), 659(2), 1037(4), 1038(2), 1042(2), 1049(1) to 1049(3), 1050(2), 1050(3), 1056(2) to 1056(4), 1085(1), 1085(3), 1085(4), 1087(3), 1088(4), 1089(3), 1090(1), 1090(2) • 19 young specs; same data as for holotype; 2 May 2014; UNLPam 1033(1), 1034(4), 1035(1), 1035(2), 1036(2), 1038(4), 1040(3), 1041(1), 1041(3), 1044(3), 1046(1) to 1046(4), 1047(1) to 1047(3), 1062(2), 1063(4) • 4 eggs; same data as for holotype; 2 May 2014; UNLPam 348(1), 348(2), 644(1), 1222(3). General morphological description of the animals Body length 97–342 µm (Fig. 1; Tables 3, 5), yellowish before mounting, transparent after mounting. Eyespots, small and very caudal, present (Fig. 1B). Smooth cuticle with pores of different shapes. Under PCM, apparently, the smaller pores (around 1 µm) are usually roundish (though often with irregular margins), or few elliptical, while the larger typically triangular, quadrangular, trilobate or quadrilobate (Fig. 2); the pore size is 0.9–3.1 µm on the dorsum (with the biggest on the head, on the mid-dorsal line along the body, and on the caudal extremity), 1.3–3.4 µm on the legs, 1.0–1.8 µm on the ventral cuticle. Coherently, dorsal pores, on average bigger, appear more often non-roundish, while the ventral ones on average smaller, appear more often roundish. Exceptionally, some caudal or leg pore may appear pentagonal- or, extremely rarely, star-shaped (with five lobes/arms; Fig. 2) under PCM, but this occurs only in few specimens and in only 1–2 pores in each of these few specimens. SEM reveals that pores are actually never perfectly rounded; instead, few small pores are truly elliptical, a minority (of any size) is irregular, while the rest are all (both dorsal and ventral, smaller and larger) polygonal or multilobate, from three to five angles/lobes/arms (Fig. 2); pores in an unsuitable position, and/or too small, may give the false impression to be irregularly roundish under SEM also, and, obviously, the lower magnification of PCM gives the impression of seeing a more common shape, especially where pores are smaller. There is no clear distinction between polygonal and multilobate pores, since there are many intermediate shapes (e.g., between triangular and three-lobated/armed, or between quadrangular and four-lobated/ armed), and, very probably, each pore may partially appear more polygonal or multilobate depending on the cuticle distention or contraction. Pentagonal pores are less common but more easily detectable under SEM with respect to PCM (several of them can be seen on each specimen), while properly star-shaped (with five arms/lobes) are quite rare: some of the specimens mounted for SEM apparently lack them, while the others may show one or few of them (Fig. 2). Pores are arranged in transverse bands made of one or more transverse rows (more regular in young specimens). The cuticle along the body, as visible in most eutardigrades, forms transverse folds marking the division into the five body segments (head plus four segments of the trunk), and, additionally, each segment is subdivided into 2 ‘subsegments’, one more anterior, and one more posterior, by an additional transverse cuticular fold. In this way, there are ten cuticular subsegments of the body clearly followed by the dorsal (Tables 2, 4), and partially ventral, pore arrangement. Smaller (97–156 µm, called young) and larger (180–342 µm, called senior) specimens show differences in the pore number and arrangement on each subsegment, but we concluded they must belong to the same species (additionally to having been found in the same sample, first sampling) for the following reasons: 1) only one egg type was found; 2) most morphological characters were the same; 3) regarding the more detailed characters for which they differed, the two groups had clear body size distinction (97–156 µm vs 180–342 µm) with no exceptions; 4) the main difference regarded the pore number and pattern, but this was consistent with ontogenetic changes documented in other species (e.g., Minibiotus pentannulatus Londoño, Daza, Lisi & Quiroga, 2017), and the pattern of the bigger specimens was still perfectly comparable with that of the smaller, just more complicated due to the appearance of more pores; 5) the other differences were metric, but they all appeared consistent with allometric growing (buccal tube becoming wider, and placoids and claws becoming longer) already known in eutardigrades, especially macrobiotids. Besides, specimens from resampling (only large individuals) matched perfectly the morphology and the morphometry of the large animals obtained from the first sampling. As already mentioned, noticeable differences in the pore number and arrangement on each subsegment can be seen between young and senior specimens; for this reason, their pattern is indicated separately in the subsequent paragraphs with the pertinent tables and illustrations. It must be stressed that the determination of bands, rows and pore number and shape, was obtained through the observation of all specimens of each group (i.e., young and senior specimens); the bands of pores and the average pattern were always recognisable, but the precise number, disposition and shape of the pores composing the rows, or other patterns, had some degree of variability (especially in senior specimens); for this reason, descriptions and illustrations (Figs 6–7) are partially schematic trying to take into account the average situation of most specimens and have to be intended more as a tendency than an exact, constant reality. Mouth antero-ventral; peribuccal papulae present (Fig. 3C–E, SEM), very probably corresponding to reduced lamellae (see Stec et al. 2020a). Oral cavity armature (Fig. 3) with three bands of teeth. The first band, very reduced and visible only under SEM, is located at the basal zone of peribuccal papulae and composed of a single row of small cone-shaped teeth fused to form a continuous ring ridge around the oral cavity (Fig. 3D). The second band of teeth comprises one row of rather large, globular-shaped, separate teeth (Fig. 3D), partially visible under light microscopy (Fig. 3A–B PCM and DIC), depending on the animal size and quality of the preparation: it may be also invisible or appearing as an irregular line since teeth are not distinguishable from one another; this second band of teeth is instead very obvious under SEM (Fig. 3D–E). Third band of teeth (buccal crests) difficult to see under light microscopy; under SEM, in our specimens it was possible to see only the dorsal portion, made of three little-protruding ridges, with two lateral, and one medial bearing two sharpened teeth (Fig. 3D–E); ventral portion not visible under SEM in our specimens, but supposedly more developed than the dorsal one, since slightly better visible under DIC, showing two lateral crests and a median tooth (Fig. 3B). Bucco-pharyngeal apparatus of the Minibiotus type (Fig. 4A–B). Buccal tube rigid with anterior and posterior dorsal bends; well-developed ventral lamina. Buccal tube wall with cribrous areas, at least anteriorly (Fig. 3E). Pharyngeal bulb oval, with triangular apophyses, three granular macroplacoids and a small microplacoid. The macroplacoid length sequence is 3≤ 2 <1. The first macroplacoid tapering anteriorly (Fig. 4B). All macroplacoids without constrictions. Robust double claws with short and robust accessory points and small, smooth lunules (Figs 4C–E, 5). Faint leg cuticular bars (i.e., muscular attaches), divided on legs I–III, undivided on legs IV, but not