Pseudechiniscus shintai, Vončina & Kristensen & Gąsiorek, 2020

Voncina, Katarzyna, Kristensen, Reinhardt M. & Gasiorek, Piotr, 2020, Pseudechiniscus in Japan: re-description of Pseudechiniscus asper Abe et al., 1998 and description of Pseudechiniscus shintai sp. nov., Zoosystematics and Evolution 96 (2), pp. 527-536 : 527

Pseudechiniscus shintai sp. nov. Figures 3 , 4 , 5B , Tables 4, 5

Locus typicus and type material.

ca. 40°54'03.6"N, 140°51'58"E, 30 m a.s.l.; Asamushi-Onsen Forest Park (Aomori, Northern Honshu, Japan); mosses from tree trunks. Collector: R.M. Kristensen. Holotype and allotype: mature female and male on slide JP.013.01. Eight juveniles on the slides JP.012.02-3, JP.013.03-4, JP.014.01-3, JP.015.01. Hologenophores: JP.012.02-3, JP.013.03-4. Holotype, allotype and the majority of paratypes (slides JP.012.02-3, JP.013.01, JP.013.03-4 and JP.015.01) are deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland; other paratypes (slides JP.014.01-3; NHMD-669705-7) are deposited in the Natural History Museum of Denmark, University of Copenhagen, Denmark.

Etymology.

The name is a patronym honouring Shinta Fujimoto, an excellent Japanese tardigradologist specialising in marine Heterotardigrada. Noun in the genitive singular.

Description.

Mature female (i.e. the third or latter instar; measurements in Table 4 ). Body orange, with minute, round black eyes that are absent after mounting (Figs 3A , 4A ). Member of the suillus-facettalis complex: dome-shaped (hemispherical) cephalic papillae (secondary clavae) and minute (primary) clavae; peribuccal cirri with poorly developed cirrophores. Cirrus A short, with cirrophore.

Dorsal plates poorly sclerotised, but clearly demarcated from each other, with the Pseudechiniscus -type sculpturing, i.e. endocuticular pillars protruding through the epicuticle and visible as dark dots in PCM (Fig. 4A ). Striae absent; epicuticular ornamentation visible as darker belts on all dorsal plates. The cephalic plate pentapartite, with the two anterior portions and three posterior portions approximately equal in size (Fig. 4A ). The cervical (neck) plate absent. The scapular plate with sutures, separating a wide anterior portion from the four posterior portions (Fig. 4A ). Three median plates: m1-2 bipartite; m3 unipartite (Figs 3A , 4A ); four pairs of lateral intersegmental platelets flanking the borders of m1-2. Two pairs of large segmental plates. The pseudosegmental plate IV’ divided by a median longitudinal suture; the posterior margin of the plate can be wide (Fig. 4A ), but without lobes or teeth (Fig. 3A ). The caudal (terminal) plate with short sclerotised incisions (Figs 3A , 4A ).

Ventral cuticle with a pronounced species-specific pattern reaching the lateroventral sides of the body (Figs 4B , 5B ), being a typical reticulum composed of large multiangular, longitudinal shapes joined by belts of pillars. The subcephalic zone with a wide belt of pillars. Sexpartite gonopore located anteriorly of legs IV and a trilobed anus between legs IV.

Pedal plates and dentate collar IV absent, instead large patches of pillars are present centrally on each leg (Fig. 3A ). Pulvini indistinct. A papilla on leg I undetectable in PCM and a papilla on leg IV present, but scarcely visible. Claws I-IV of similar heights. External claws on all legs smooth. Internal claws with minuscule, thin spurs positioned at ca. 1/5 of the claw height. (Fig. 3A , insert).

Mature male (i.e. the second or latter instar; measurements in Table 4 ). No significant differences from females (Fig. 3B ). Gonopore circular.

Juveniles (i.e. the second instar; measurements in Table 5 ). A morphometric gap exists between adult females and juveniles. Phenotypically similar to adults. Gonopore absent.

Larvae. Unknown.

Eggs. Unknown.

DNA sequences.

Single haplotypes in 18S rRNA (MT645084, 900 bp), 28S rRNA (MT645082, 754 bp) and ITS-1 (MT645086, 622 bp), but two in COI (MT644270-1, 510 bp) were found.

Phenotypic differential diagnosis.

The species was compared with the members of the suillus-facettalis complex (with hemispherical cephalic papillae) and other Pseudechiniscus species lacking pseudosegmental projections. P. shintai sp. nov. is differentiated from:

P. angelusalasRoszkowska et al., 2020, described from Madagascar, by the shape of its cephalic papillae (hemispherical in P. shintai sp. nov. vs. dactyloid, elongated in P. angelusalas) and by the presence of striae (striae absent in P. shintai sp. nov. vs. present, but poorly developed in P. angelusalas);

P. beasleyiLi et al., 2007, described from Qinling Mountains (China), by much shorter claws (5.3-9.2 μm in P. shintai sp. nov. vs. 9.1-13.1 μm in P. beasleyi);

P. chengiXue et al., 2017, described from Ningxia (China), by body colour (orange in P. shintai sp. nov. vs. brown in P. chengi) and by the distribution of pillars in the dorsal plates (sparsely distributed in P. shintai sp. nov. vs. densely arranged in P. chengi);

P. dastychiRoszkowska et al., 2020, described from the Argentine Islands (maritime Antarctic), by the shape of the cephalic papillae (hemispherical in P. shintai sp. nov. vs. dactyloid, elongated in P. dastychi) and by the presence of striae (striae absent in P. shintai sp. nov. vs. present in P. dastychi);

P. ehrenbergiRoszkowska et al., 2020, described from Northern Italy and reported from Mongolia (Cesari et al. 2020), by the subdivision of the scapular plate (without the median longitudinal suture in P. shintai sp. nov. vs. with the median longitudinal suture in P. ehrenbergi) and by the presence of a rudimentary papilla I (absent in P. shintai sp. nov. vs. present in P. ehrenbergi);

P. indistinctusRoszkowska et al., 2020, described from Norway, by the shape of its cephalic papillae (hemispherical in P. shintai sp. nov. vs. dactyloid, elongated in P. indistinctus) and by the presence of striae (striae absent in P. shintai sp. nov. vs. present in P. indistinctus);

P. lacyformisRoszkowska et al., 2020, described from Norway, by the length of its cephalic appendages: cirrus internus (5.2-8.9 μm in P. shintai sp. nov. vs. 10.6-14.0 μm in P. lacyformis), cirrus externus (6.1-12.8 μm in P. shintai sp. nov. vs. 14.1-19.4 μm in P. lacyformis) and cirrus A (17.1-26.0 μm in P. shintai sp. nov. vs. 26.5-35.0 μm in P. lacyformis);

P. suillus (Ehrenberg, 1853), reliably recorded only from Italy (Grobys et al. 2020), by the length of cirrus A (17.1-26.0 μm in P. shintai sp. nov. vs. 28.4-34.4 μm in P. suillus) and by the presence of males (present in P. shintai sp. nov. vs. absent in P. suillus);

P. xiaiWang et al., 2018, described from Ningxia (China), by the contrasting dorsal sculpturing (epicuticular ornamentation darker and more pronounced in P. xiai) and by the morphology of the pseudosegmental plate IV’ (paired in P. shintai sp. nov. vs. unpaired in P. xiai).

Moreover, the ventral pattern distinguishes P. shintai sp. nov. from all other species for which this character has been described. We used morphometric differences for comparisons only as a last resort as sample sizes for the majority of the specimens in the type series were small. Importantly, although Roszkowska et al. (2020) included P. angelusalas , P. dastychi and P. indistinctus in the suillus-facettalis complex, such combination is phylogenetically unjustified, as they all exhibit elongated (dactyloid) cephalic papillae, which is a distinguishing trait of P. novaezeelandiae (Richters, 1908) (see Pilato et al. 2005) and of the entire novaezeelandiae lineage ( Cesari et al. 2020).

Genotypic differential diagnosis.

p -distances between the new species and the remaining Pseudechiniscus spp., for which COI sequences are available, ranged between 18.6% ( P. suillus ) and 29.3% ( P. lacyformis ). Intraspecific distance was equal to 0.2%.

Figures

Figure 3. Habitus of Pseudechiniscus shintai sp. nov. (PCM): A - female (holotype); B - male (allotype). Insert shows claws I. Scale bars: in μm.

Figure 4. Sculpturing of Pseudechiniscus shintai sp. nov. (PCM): A - dorsal; B - ventral. Scale bars: in μm.

Figure 5. Schematic drawings of ventral sculpturing patterns: A - Pseudechiniscus asper; B - Pseudechiniscus shintai sp. nov.