Richtersius nicolai Vecchi, Godziek, Kristensen, Piemontese, Calhim & Stec, 2025, sp. nov.
Creators: name: Vecchi, Matteo
name: Godziek, Jakub
name: Kristensen, Reinhardt M.
name: Piemontese, Lucia
name: Calhim, Sara
name: Stec, Daniel
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Tardigrada
Eutardigrada
Parachela
Macrobiotidae
Richtersius
Richtersius nicolai

description: Richtersius nicolai sp. nov.
urn:lsid:zoobank.org:act: 1BC3E5B8-7DB4-4BC0-BBD9-820FD28BFECD
Figs 2–7; Tables 3–5
Richtersius coronifer – Guidetti et al. 2005.
Richtersius Northern Italy 1 – Guidetti et al. 2016: fig. 1.
Richtersius sp. 5 – Stec et al. 2020b.
Richtersius aff. coronifer – Zawierucha et al. 2023.
Etymology
This species is named after Nicola Piemontese, a naturalist and expert of the flora and fauna of the Gargano Peninsula.
Type material
Holotype
ITALY • Monte Sant’Angelo; 41°42′19.5″ N, 15°57′29.5″ E; 790 m a.s.l.; Jul. 2023; M. Vecchi and L. Piemontese leg.; moss on rock; ISEA-PAS, slide IT.137.4.
Paratypes
ITALY • 60 specs; same data as for holotype; ISEA PAS, slides IT.137.1 to IT.137.6 and slides IT.137.10 to IT.137.13, SEM stubs TAR.2.03, TAR.2.04 • 12 eggs; same data as for holotype; ISEA PAS, slide IT.137.8, SEM stub TAR.2.05 • 5 specs; same data as for holotype; MUC, slide NHMD-1732285 • 6 eggs; same data as for holotype; MUC, slide NHMD-1732286.
Description
Animals (measurements in Tables 3–4; Supp. files 1, 2) Body is bright yellow; all specimens became transparent after the fixation in Hoyers’s medium (Fig. 2). Eyes were visible in 64% of animals (excluding hatchlings) mounted in Hoyers’s medium. Body and leg cuticle is without granulation in all life stages and with pores present only in hatchlings (Fig. 3). Hatchlings are similar in appearance to adults, except for a smaller body size and roundish pores (Fig. 3) (1.14–2.10 µm in diameter) with sometimes jagged edges, faintly visible under PCM, scattered randomly throughout the body cuticle, with a mean pore density of 10 (range 9–11) per 2500 µm 2 of the dorsal cuticle.
Claws are slender, primary branches with distinct accessory points (Fig. 4) and an internal system of septa as described for Richtersius coronifer s. lat. by Lisi et al. (2020). The claw common tract index has an average value between 56% and 58% across all four leg pairs, meaning that the basal portion of the claw is usually longer than half the total length of the primary branch. Lunulae are large, with a crown of long, numerous and densely arranged spikes (Fig. 4). All the lunulae are trapezoidal (Fig. 4). Double muscle attachments in legs I–III and horseshoe structures in legs IV are visible in PCM, whereas cuticular bars are absent (Fig. 4).
Mouth is antero-ventral. The buccal apparatus is of the Richtersius type (Fig. 5). The oral cavity is followed by a system of large apophyses that form a buccal crown (Fig. 5A–B). Anteriorly, the system consists of dorso-lateral and ventro-lateral triangular apophyses (Fig. 5A). The dorsal and ventral apophyses are composed of anteriorly positioned large cuticular hooks, followed by longitudinal crests (Fig. 5B). The hook in the ventral apophyses is smaller than the dorsal hook (Fig. 5B). The wall of the buccal tube exhibits a variable thickness (Fig. 5A), but the internal diameter of the buccal tube is almost uniformly narrow (Fig. 5A). From the mouth opening to the stylet support insertion point, the thickness of the buccal tube wall increases only slightly, while below this point the evident posterior thickness is clearly visible (Fig. 5A). The pharynx is spherical, with bilobed apophyses, three anterior cuticular spikes (typically only two are visible in any given plane) and two granular macroplacoids (2<1). The first and second macroplacoids have a faint constriction positioned centrally and subterminally, respectively (Fig. 5C). The oral cavity armature is faintly visible under PCM, with only the second band of teeth visible mainly in the larger specimens (Fig. 5B). Under PCM, the second band of teeth is visible as several irregular rows of densely packed and faint dark dots (Fig. 5B). The discontinuous third band of teeth is situated between the second band of teeth and the opening of the buccal tube and is divided into a dorsal and a ventral portion, both in the form of a single large tooth resembling a beak.
Eggs (measurements in Table 5; Supp. file 1)
Large, roundish, yellow, laid freely. The surface between processes is smooth but with refracting dots faintly visible only under PCM, but difficult to observe because of the amount of debris that is typically attached to the egg surface (Figs 6–7). Processes in the shape of elongated, thin cones with a ragged surface caused by small granules visible both in LM and SEM (Figs 6, 7B–E). Terminal discs or other structures absent.
Reproduction
The species is gonochoric-amphimictic (Guidetti et al. 2016).
DNA sequences
– 18S: HQ604987 –8 (Bertolani et al. 2014), PP989298 (this study)
– 28S: KT778695 –6 (Guidetti et al. 2016), PP989299 (this study)
– COI: AY598780 –1 (Guidetti et al. 2005), PP986909-11 (this study)
– ITS2: PP989300 (this study)
Distribution
Locus typicus: Monte Sant’Angelo, Puglia, Italy (41°42′19.5″ N, 15°57′29.5″ E; 790 m above sea level (a.s.l.)). Moss on rock (sample IT. 137 in this study).
Monte Sant’Angelo, Puglia, Italy (41°43′29.4″ N, 15°56′40.7″ E; 800 m a.s.l.). Lichen on tree (sample JYU.S 606 in this study).
Pratignano, Emilia Romagna, Italy (4°09′11.8″ N, 10°48′24.9″ E; 1500 m a.s.l.). Moss on rock (Richtersius Northern Italy 1 in Guidetti et al. 2016).
Differential diagnosis
Richtersius nicolai sp. nov. differs from:
Richtersius coronifer by having smaller eggs (bare diameter 118–134 µm in R. nicolai sp. nov. vs 173– 233 µm in R. coronifer) and by having a lower pores density in the newborns (PD 9–11 in R. nicolai vs 60–88 in R. coronifer).
Richtersius ziemowiti by having a lower pores density in the newborns (PD 9–11 in R. nicolai sp. nov. vs 20–24 in R. ziemowiti).
Richtersius mazepi by having bigger eggs (bare diameter 118–137 µm in R. nicolai sp. nov. vs 77–91 µm in R. mazepi), by the absence of a crown of thickenings distributed around the bases of the egg processes (present in R. mazepi), by the different shape of the egg processes (conical spikes in R. nicolai vs wide dome-shaped proximal portion and an elongated slender distal portion in R. mazepi), by having a lower pore density in the newborns (PD 9–11 in R. nicolai vs 26–36 in R. mazepi), and by having a higher claw IV anterior cct (49–63 % in R. nicolai vs 32–44 % in R. mazepi).
Richtersius tertius by having a higher pore density in the newborns (PD 9–11 in R. nicolai sp. nov. vs 3–6 in R. tertius), and by having a smaller first macroplacoid (pt = 10–14 in R. nicolai vs pt = 14–20 in R. tertius).
Richtersius ingemari sp. nov. by having a higher pore density in the newborns (PD 9–11in R.nicolai sp.nov. vs 4–7 in R. ingemari), and by the reproductive mode (gonochorism in R. nicolai vs parthenogenesis in R. ingemari).
description: Published as part of Vecchi, Matteo, Godziek, Jakub, Kristensen, Reinhardt M., Piemontese, Lucia, Calhim, Sara & Stec, Daniel, 2025, Taxonomic reanalysis of the genus Richtersius (Tardigrada; Eutardigrada), with description of two new species from Italy and Sweden, pp. 155-188 in European Journal of Taxonomy 981 on pages 160-170, DOI: 10.5852/ejt.2025.981.2823, http://zenodo.org/record/15023722