Pseudechiniscus (Pseudechiniscus) formosus, Gąsiorek & Vončina & Kristensen & Michalczyk, 2021

Gąsiorek, Piotr, Vončina, Katarzyna, Kristensen, Reinhardt Møbjerg & Michalczyk, Łukasz, 2021, Fig. 7 in Fig. 4. A in Saphonecrus globosus Schweger and Tang 2015, Zoological Studies (Zool. Stud.) 60 (70), pp. 1-45 : 25-33

Pseudechiniscus (Pseudechiniscus) formosus

sp. nov. ( Figs. 26–27 ) urn:lsid:zoobank.org:act:7FDACA7F-5E5F-4220-A668-DD8179BD04A6

Tardigrada Register: http://www.tardigrada.net/ register/0113.htm

Description: Female (i.e., the third instar): Large (187 μm, sc = 24.9 μm) Pseudechiniscus with cylindrical body ( Fig. 26A ); pale yellow with black crystalline eyes, body colour disappears, but eyes persist after mounting in Hoyer’s medium. Pseudohemispherical cephalic papillae (3.9 μm) and elongated (primary) clavae (4.0 μm, Fig. 27); cirrophores of peribuccal cirri (cirrus internus 9.3 μm, cirrus externus 16.6 μm) weakly outlined, cirrophore A tubular and distinct ( Fig. 26A ). Cirrus A short (32.1 μm).

Dorsal plate sculpturing of the Pseudechiniscus type, with large and hemispherical capituli of endocuticular pillars ( Fig. 26B ) not joined by striae. Pillars heterogeneous in size, their largest capituli present in centromedian plate portions of the scapular, paired segmental and pseudosegmental IV’ plates ( Fig. 26B ). Cephalic plate pentapartite, lacking cervical plate ( Fig. 26A ). Scapular plate comprising the dominant anterior portion and four narrow posterior portions demarcated by weak sutures ( Fig. 26A–B ). All median plates large: m1–2 bipartite, with reduced posterior portions, m3 rhomboidal and unipartite. Four pairs of lateral intersegmental plates flanking boarders of m1–2. Large paired segmental plates I–II and uniform pseudosegmental plate IV’ with a sinusoidal posterior margin ( Fig. 26B ). Short and gently curved incisions on the caudal plate ( Fig. 26A ).

Ventral sculpturing faint and poorly developed ( Figs. 26C , 27), with larger accumulations of pillars only in the subcephalic and genital areas, and at the level of legs I–III. Sexpartite gonopore placed anteriorly to legs IV, and a trilobed anus between legs IV. Pedal plates formed as belts of large pillars in central portions of legs ( Fig. 26A ). Pulvini absent. Papillae or spines on legs I absent. Papilla IV present (3.8 μm). Claws minute (7.9–8.4 μm) and isonych; internal claws with robust primary spurs (2.0–2.4 μm) positioned at ca. 25% of the branch height and divergent from it.

Males, juveniles, larvae and eggs: Not found.

Molecular markers and phylogenetic position: Two gene fragments were sequenced: 28S rRNA (OK048634) and ITS-1 (OK048647). In the updated phylogeny from Gąsiorek et al. (2021c), P. formosus sp. nov. is embedded in the subgenus Pseudechiniscus and it is sister to a subclade comprising six species,

Diploechiniscus oihonnae Legend

Echiniscus testudo Oriental

Nebularmis cirinoi

Nebularmis indicus Afrotropical + Oriental Nebularmis burmensis

Nebularmis re ti culatus Palaearc�c

Nebularmis crebraclava Nebularmis auratus + PalaOriental earc�c

including P. (P.) asper , P. (P.) shintai , and P. (P.) totoro sp. nov. ( Fig. 30 ).

Type material: Holotype (adult female on slide TW.007.01) deposited in the Jagiellonian University. One specimen used for DNA sequencing.

Type locality: 24°23'51"N, 121°14'04"E, 3 700 m asl: Taiwan, Snow Mountain (Xueshan), North Peak. Mosses from rocks exposed to sun.

Etymology: The name has a twofold meaning, as in Latin formosus = beautiful, describing the dorsal plate sculpturing, and the former name of Taiwan, derived from Portuguese, was Formosa. Adjective in the nominative singular.

Differential diagnosis: Species representing the subgenus Pseudechiniscus are morphologically more similar to each other than species in the subgenus Meridioniscus ( Gąsiorek et al. 2021c) . There are several species lacking appendages on the posterior margin of the pseudosegmental plate IV’ (several species are considered dubious and/or indistinguishable from other congeners due to scarce descriptions and are therefore excluded from the list below, e.g., P. (P.) clavatus Mihelčič, 1955 and P. (P.) megacephalus Mihelčič, 1951 ; see Roszkowska et al. 2020, Tumanov 2020, and Gąsiorek et al. 2021c for details) that are differentiated from P. formosus sp. nov.:

P. (P.) beasleyi Li et al., 2007 , described from the Qinling Mountains (Shaanxi, continental China), by body colour (pale yellow in P. (P.) formosus sp. nov. vs red in P. (P.) beasleyi ) and shorter claws (7.9–8.4 μm in P. (P.) formosus sp. nov. vs 9.1–13.1 μm in P. (P.) beasleyi ).

P. (P.) chengi Xue et al., 2017 , also described from mainland China, by body colour (pale yellow in P. (P.) formosus sp. nov. vs brown in P. (P.) chengi ) and the epicuticular ornamentation on the dorsum (absent in P. (P.) formosus sp. nov. vs present in P. (P.) chengi ).

P. (P.) ehrenbergi Roszkowska et al., 2020 , by a longer cirrus externus and cirrus A (16.6 μm, 32.1 μm in P. (P.) formosus sp. nov. vs 9.0–11.7 μm, 21.6–26.8 μm

in P. (P.) ehrenbergi ).

P. (P.) lacyformis Roszkowska et al., 2020 , by the epicuticular ornamentation on the dorsum (absent in P. (P.) formosus sp. nov. vs present in P. (P.) lacyformis ) and shorter cirrus internus (9.3 μm in P. (P.) formosus sp. nov. vs 10.6–14.0 μm in P. (P.) lacyformis ).

P. (P.) shintai Vončina et al., 2020 , by body colour (pale yellow in P. (P.) formosus sp. nov. vs orange in P. (P.) shintai ) and the epicuticular ornamentation on the dorsum (absent in P. (P.) formosus sp. nov. vs present in P. (P.) shintai ).

P. (P.) suillus ( Ehrenberg, 1853) , by relative lengths of some cephalic appendages (cirrus internus 37.3, cephalic papilla 15.7, (primary) clava 16.1 in P. (P.) formosus sp. nov. vs cirrus internus 44.0–49.6, cephalic papilla 19.1–24.3, (primary) clava 20.9–26.8 in P. (P.) suillus ).

P. (P.) xiai Wang et al., 2018 , by body colour (pale yellow in P. (P.) formosus sp. nov. vs orange in P. (P.) xiai ) and the epicuticular ornamentation on the dorsum (absent in P. (P.) formosus sp. nov. vs present in P. (P.) xiai ).

Moreover, P. (P.) formosus sp. nov. is also distinguishable from all abovementioned species by the ventral sculpturing pattern.

Figures

Fig. 26. Morphology of Pseudechiniscus (Pseudechiniscus) formosus sp. nov. (PCM): A, holotypic female in dorsal view; B, dorsal sculpturing (arrowheads indicate large capituli of pillars); C, ventral sculpturing. Scale bars in μm.

Fig. 30. Position of the Taiwanese species on the phylogenetic tree of the genus Pseudechiniscus based on the concatenated matrix (18S rRNA+28S rRNA+ITS-1). Values at nodes separated by forward slashes signify Bayesian posterior probability and bootstrap values (ML), respectively. Maximum supports, i.e., 1.00 for BI and 100 for ML, are indicated by asterisks (*), whereas nodes unsupported in either analysis are marked by hashtags (#). The scale refers to the Bayesian consensus tree and represents substitutions per site. Species numbering preserved from Gąsiorek et al. (2021c).