Paramacrobiotus marchelmoni sp. nov.

urn:lsid:zoobank.org:act: C91427F4-F50C-4A1F-A475-825777258AE5

Figs 9–11

Diagnosis

Paramacrobiotus without eyespots. Cuticle with fine dorsal granulation visible only in SEM, and medium-coarse granulation surrounding the claws of the legs I–IV visible with DIC and SEM. OCA with three bands of teeth: first composed of numerous small granules, second of a single row of vertical ridges, and third of three ventral and three dorsal transverse crests. Three rod-like macroplacoids and a distant microplacoid present. Claws of hufelandi - type with smooth lunulae. Freely laid eggs with sculptured areolae of richtersi - type; 10–12 reticulated processes around the circumference, conical with a mostly smooth apex.

Etymology

The species is proudly in dedication to Marc “Marchelmon” Hulterström, brother of the first author.

Material examined

A total of 38 animals and 24 eggs observed, including: 16 animals and 15 eggs mounted in Hoyer’s fluid, 10 animals and 5 eggs fixed for SEM, and 11 animals and 4 eggs used for DNA analysis.

Type material

Holotype

SWEDEN • Skåne, Sånnarna; 55°55′41.6″ N, 14°15′11.1″ E; 8 m a.s.l.; 22 Mar. 2021; S. Atherton, R. Guidetti and K.I. Jönsson leg.; moss on calcareous-rich sand and rock; SMNH, slide SMNH-Type-10017.

Paratypes

SWEDEN · 23 specs, 15 eggs; same collection data as for holotype; SMNH, slides SMNH-Type-10018 to SMNH-Type-10029, SEM stub SMNH-Type-10030 • 3 specs, 5 eggs; same collection data as for holotype; GenBank nos: PX093656 to PX093658 (COI), PX093645, PX093646 (ITS), PX093665 (18S), PX093651 (28S); MUSN, slides 22-030, 22-037 and 22-103 .

Description

Morphometric measurements and statistics given in Tables 1 and 2 (raw morphometric data is given in Supp. file 11).

Paramacrobiotus with body length 238–710 µm (Fig. 9A). Eyespots absent. Cuticle transparent in live animals and after fixation in Hoyer’s fluid. Dorsal body cuticle with even and very fine granulation, visible only with SEM (Fig. 10A–B). A patch of larger granulation lateral to the claws on legs I–III and coarse granulation fully surrounding the claws on legs IV visible with DIC and SEM (Figs 9F, 10B–D). Cuticular pores, gibbosities, and papillae absent.

Mouth antero-ventral; ten peribuccal lamellae present. Buccal apparatus with a rigid tube of Macrobiotus - type (Pilato & Binda 2010) with ventral lamina. OCA comprising three bands of teeth (Fig. 9C–D). First band a field of small granular teeth situated closely behind the peribuccal lamellae. Second band one row of vertical ridges, uniform in shape on both ventral and dorsal side. Third band situated close to the second, with three ventral and three dorsal teeth, with the lateral teeth wider (larger along the left/right axis) and shorter (smaller along the anterior/posterior axis) than the median tooth for each side. Ventral teeth thinner (smaller along the left/right axis) than dorsal teeth (Fig. 9C). Latero-dorsal teeth triangular, narrowing away from the median tooth (Fig. 9D). No additional granular teeth observed between the second and third band of OCA. Globular pharyngeal bulb with triangular pharyngeal apophyses, three rod-shaped macroplacoids with length sequence 2<1 <3, and a microplacoid (Fig. 9B). First macroplacoid drop-like. Second macroplacoid oval. Third macroplacoid with a subterminal constriction, ending in posterior bulbs. Microplacoid heart-shaped, with antero-lateral wings, and situated distant from the third macroplacoid, further than its length.

Double-claws of hufelandi - type (Bertolani & Pilato 1988). Main claw branches with evident accessory points. Smooth lunulae on all claws (Figs 9E, 10B–D). Paired muscle attachments below claw present. Cuticular bars absent.

Gonochoristic. Males with sperm filled testis observed, as well as females with eggs.

Ornamented eggs laid freely, richtersi - type (Kaczmarek et al. 2017; Fig. 11A–B), diameter without processes 67.0–92.4 µm. Processes conical, short (10–16.5 µm) and wide (21.3–30.0 µm), with a smooth rounded apex (Fig. 11A–E). 10–12 processes on the circumference (Fig. 11B). Processes smooth in SEM (Fig. 11A) but labyrinthine layer visible in DIC as a reticular pattern of small, evenly distributed meshes (Fig. 11C). Processes surrounded by a single ring of 12 areolae (Fig. 11A, G). Areolae with sculpturing comprising dotlike indentations, faintly visible fixed in Hoyer’s with DIC and clearly visible with SEM (Fig. 11F).

DNA sequences

Sequences for P. marchelmoni sp. nov. were attained for all four molecular markers using 11 animals and four eggs. 18S and 28S were represented by one haplotype; ITS2 was represented by two haplotypes (uncorrected p-distances between haplotypes 0.81%), and COI was represented by three haplotypes (uncorrected p-distances between haplotypes 0.16–0.31%):

– 18S: specimens 22-004, 22-006, 22-007, 22-019, 22-034, 22-110, 22-113; 1302 bp, GenBank accession number PX093665;

– 28S: specimens 22-004, 22-019, 22-029, 22-110, 23-015; 921 bp, GenBank accession number PX093651;

– COI haplotype 1: specimens 22-004, 22-006, 22-007, 22-019, 22-026, 22-029, 22-034, 22-102, 22-108; 636 bp, GenBank accession number PX093656;

– COI haplotype 2: specimens 22-106, 22-110, 22-113, 23-041; 636 bp, GenBank accession number PX093657;

– COI haplotype 3: specimen 23-015, 636 bp, GenBank accession number PX093658;

– ITS2 haplotype 1: specimens 22-029, 22-102; 370 bp; GenBank accession number PX093645;

– ITS2 haplotype 2: specimens 22-004, 22-006, 22-007, 22-019, 22-034, 22-110, 22-113; 370 bp, GenBank accession number PX093646.

Morphological differential diagnosis

Based on the presence of a microplacoid, P. marchelmoni sp. nov. is a member of the richtersi morphogroup (Kaczmarek et al. 2017). Species of this morphogroup may be difficult or sometimes impossible to distinguish morphologically, with distinguishing features frequently limited to a few differences in egg shell morphologies or reproductive biology (Guidetti et al. 2019a). Indeed, P. marchelmoni is very similar to ten species of this group by the following criteria: richtersi - type of egg, with areolae with sculpturing (Kaczmarek et al. 2017), and egg processes with a blunt apex without a cap-like structure. However, P. marchelmoni can be differentiated from each by the following:

Paramacrobiotus arduus Guidetti, Cesari, Bertolani, Altiero & Rebecchi, 2019 – the animals of P. marchelmoni sp. nov. lack cuticular bars below the claws of the first three pairs of legs. The eggs of the new species are larger (diameter without processes 67.0–92.4 µm compared to 55.3–62.3 µm in P. arduus), with processes that are surrounded by more areolae (12 compared with 5 “double” areolae in P. arduus) and that are much wider at the base (diameter 21.3–30.0 µm compared to 10.4–16.3 µm in P. arduus) with a more rounded and less narrow apex than those of P. arduus .

Paramacrobiotus celsus Guidetti, Cesari, Bertolani, Altiero & Rebecchi, 2019 – the animals of P. marchelmoni sp. nov. lack cuticular bars below the claws of the first three pairs of legs, and the microplacoid has a different shape (heart-shaped with antero-lateral wings compared to drop-shaped in P. celsus). Additionally, the eggs of P. marchelmoni have processes with wider bases (diameter 21.3– 30.0 µm compared to 14.3–18.2 µm in P. celsus).

Paramacrobiotus depressus Guidetti, Cesari, Bertolani, Altiero & Rebecchi, 2019 – the animals of P. marchelmoni sp. nov. have much more evident granulation on all legs compared with P. depressus and lack cuticular bars below the claws of the first three pairs of legs. The microplacoid has a different shape (heart-shaped with antero-lateral wings compared to comma-shaped in P. depressus). The eggs are larger in P. marchelmoni (diameter without processes 67.0–92.4 µm compared to 56.2–66.2 µm in P. depressus) with much wider (21.3–30.0 µm compared to 12.4–15.2 µm in P. depressus) egg processes.

Paramacrobiotus fairbanksi (following the redescription of Guidetti et al. 2019a) – animals of P. marchelmoni sp. nov. differ from animals of P. fairbanksi in the heart-shaped microplacoid (compared to a comma-shape microplacoid in P. fairbanksi), and the new species is gonochoristic (males are presumed absent for P. fairbanski). The eggs of P. marchelmoni have more areolae surrounding each process (12 compared with 5–6 “double” areolae in P. fairbanksi) and processes with wider bases (21.3– 30.0 µm compared to 10.9–20.8 µm in P. fairbanksi) and smoother, more rounded apexes.

Paramacrobiotus gerlachae (Pilato, Binda & Lisi, 2004) – the animals of P. marchelmoni sp. nov. differ from the animals of P. gerlachae by the absence of cuticular bars near the lunules of legs I–III (present in P. gerlachae); by the cuticular granulation on legs I–III (absent in P. gerlachae); and by the more distinct granulation on leg IV (granulation very faint in P. gerlachae). The egg processes are wider in P. marchelmoni (base diameters 21.3–30 µm compared with 16.8–18.7 µm in P. gerlachae).

Paramacrobiotus halei (Bartels, Pilato, Lisi & Nelson, 2009) – animals of P. marchelmoni sp. nov. differ from animals of P. halei by the absence of the cuticular tubercles (present in P. halei); the narrower buccal tube (pt 18.1–23.8 compared with pt 26.5–28.6 in P. halei); and the longer internal claw II (pt 21.4–30.0 compared with pt 20.4–21.1 in P. halei). The eggs of P. marchelmoni are smaller (full diameter 92.5–115.0 µm compared with 117.0–121.0 µm in P. halei) with processes with smoother, more rounded apexes.

Paramacrobiotus pius Lisi, Binda & Pilato, 2016 – animals of P. marchelmoni sp. nov. differ from animals of P. pius in the lack of cuticular bars below the claws on the first three pair of legs (present in P. pius), the longer third macroplacoid (pt 18.3–29.4 compared to 14.2–14.6 in P. pius) and the longer macroplacoid/placoid rows (pt 52.1–75.7/69.5–95.2 compared to pt 41.4–43.1/53.0– 56.2 in P. pius). The eggs of P. marchelmoni have processes with smooth apices (compared to apices with short spines in P. pius) and are surrounded by more numerous areolae (12 compared to 5 “double” areolae in P. pius).

Paramacrobiotus richtersi (Murray, 1911) (following the redescription of Guidetti et al. 2019a) – the animals of P. marchelmoni sp. nov. differ from the animals of P. richtersi in the undivided medioventral crest in the third band of the OCA and the lack of cuticular bars below the claws of the first three pairs of legs (bars present in P. richtersi). The eggs of P. marchelmoni differ in the processes, which are shorter (10.0–16.5 µm compared to 17.1–22.1 µm in P. richtersi) and wider (diameter 21.3–30.0 µm compared to 17.1–21.2 µm in P. richtersi) and thus have a stouter appearance than those of P. richtersi .

Paramacrobiotus sklodowskae (Michalczyk, Kaczmarek & Węglarska, 2006) – the animals of P. marchelmoni sp. nov. differ from the animals of P. sklodowskae by the absence of eyespots (present in P. sklodowskae); by the more anteriorly inserted stylet support (pt 72.3–80.6 compared with pt 81.8– 85.2 in P. sklodowskae); and by the larger third macroplacoid (pt 18.3–29.4 compared to pt 16.7–18.0 in P. sklodowskae). The eggs are differentiated by the process surfaces, which are always smooth in P. marchelmoni (ring folds present in P. sklodowskae).

Paramacrobiotus spatialis Guidetti, Cesari, Bertolani, Altiero & Rebecchi, 2019 – the animals of P. marchelmoni sp. nov. possess an undivided medioventral crest in the third band of the OCA (subdivided into three round teeth in P. spatialis). The eggs of P. marchelmoni have wider processes (21.3–30.0 µm compared to 15.2–20.4 µm in P. spatialis) with smooth apices (compared to apices with tubercles as in P. spatialis).