Pseudechiniscus ( Meridioniscus ) rosinae, Fassina & Brotto-Guidetti & Garraffoni & Santos & Mioduchowska & Warguła & Kaczmarek, 2025

Fassina, Paola Visnardi, Brotto-Guidetti, Emiliana, Garraffoni, André Rinaldo Senna, Santos, Danilo De Castro, Mioduchowska, Monika, Warguła, Jędrzej & Kaczmarek, Łukasz, 2025, Integrative description of Pseudechiniscus (Meridioniscus) rosinae sp. nov. (Echiniscidae) with a discussion on Pseudechiniscus in Brazil (South America), Zootaxa 5686 (4), pp. 555-571 : 558-566

publication ID

https://doi.org/10.11646/zootaxa.5686.4.6

publication LSID

lsid:zoobank.org:pub:56301480-231D-4C18-8912-59FEE43229ED

persistent identifier

https://treatment.plazi.org/id/03F387F5-AB3F-FFDF-FF0D-60E2A291340B

treatment provided by

Plazi

scientific name

Pseudechiniscus ( Meridioniscus ) rosinae
status

sp. nov.

Pseudechiniscus ( Meridioniscus) rosinae sp. nov. Fassina, Mioduchowska, Wargula, Kaczmarek urn:lsid:zoobank.org:act:

( Figures 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; Tables 1–3)

Syn: Pseudechiniscus novaezeelandiae marinae Bartoš, 1934 sensu de Barros (1942a) , Pseudechiniscus novaezeelandiae marinae Bartoš, 1934 sensu du Bois-Reymond Marcus (1944)

Material examined: Twenty seven animals: holotype (undetermined sex), 19 paratypes ( 2 females, 1 male and 16 specimens with undetermined sex) mounted on microscope slides in Fluoromont’s or polyvinyl lactophenol medium, 4 animals prepared for SEM and 3 prepared for molecular sequencing .

Type locality: Brazil, Campos do Jordão , Crioulos Cave, 22°42’47.8”S, 45°35’24.2”W, 1,705m asl, moss from trees, 1.0 m above the ground level, 23 April 2018, leg. Paola V. Fassina and Ariane Campos GoogleMaps .

Additional localities in Brazil: Cities of Campos do Jordão ( 22°44′S, 45°35′W), Santos ( 23°57′S, 46°19′W) and Eldorado ( 24°30′S, 48°05′W) ( de Barros, 1942a; du Bois-Reymond Marcus, 1944, respectively) GoogleMaps .

Description. Animals (for measurements and statistics see Tables 1–2).

Body orange in colour in living specimens with round black eyespots. Internal and external peribuccal cirrus and cirrus A present; cephalic papilla is finger-like shaped. All other lateral and dorsal filaments absent ( Figs 1A–D View FIGURE 1 , 2 View FIGURE 2 ).

Cephalic plate with a W-shaped pattern. Neck plate weakly sclerotised. Scapular plate divided by a transverse ridge. The posterior portion is divided into four parts by three short longitudinal ridges.

A transverse fold divides median plate 1. The anterior portion is small and rectangular shaped ( Fig 1A View FIGURE 1 ). The posterior part is triangular and bigger. Median plate 2 has the anterior portion triangular shaped and the posterior portion pentagonal, the anterior is shorter than the posterior. Medium plate 3 is undivided and diamond-shaped with the anterior portion narrower when compared to the posterior. A longitudinal crest divides paired plates 1 and 2. Pseudosegmental plate IV’ without a median longitudinal crest and with two short triangular dorsal teeth/spines (7.1–8.3 µm in length) on the posterior margin ( Figs 1A, C, D View FIGURE 1 , 2A View FIGURE 2 ). Terminal plate with two longitudinal ridges with Y-shaped bifurcation ( Figs 1B–D View FIGURE 1 ).

Dorsal plates with small hemispherical granules/upper ends of cuticular pillars (dots in LM, 0.5–1.1 µm in diameter) joined by striae that are also present on the cuticle between and around the plates and on the base of the legs, but in a smaller size ( Fig 2 View FIGURE 2 ).

Ventral patterns are present and composed by six sets of convex elevations and transverse folds with four smaller elevations on each segment (visible in SEM) ( Fig. 1B View FIGURE 1 ) separated by patches of fine granulation with configuration PG:I-III-IV-V-VI-VII-VIIIg ( Fig. 5 View FIGURE 5 ). Females show granulations all around the gonopore, and males in two patches, one on each side of the gonopore. Females have a gonopore with the typical six-petal rosette shape ( Figs 1B View FIGURE 1 , 5 View FIGURE 5 ), and males with a small protruding tubular gonopore.

Internal claws with a small spur oriented towards the claw base ( Figs 3A–C View FIGURE 3 , 4B–C View FIGURE 4 ). Small and round papilla on hind legs present; dentate collar absent ( Figs 3C–D View FIGURE 3 , 4C–D View FIGURE 4 ).

Male measurements: Body length: 108.0 µm, Claw I, II, III, IV heights: 5.3 µm, 6.0 µm, 6.6 µm, 5.2 µm, respectively.

Remarks: Due to the not well-prepared material, most of the examined specimens had undetermined sex because gonopores were not visible. However, taking into consideration visible smaller size of the male found in studied population and, in general, small number of males (or even absent) in Pseudechiniscus populations (e.g. Roszkowska et al. 2020), it should be considered that most of measured specimens with undetermined sex were females. For this reason we used them in differential diagnosis.

DNA sequences :

We obtained sequences for the applied molecular markers:

• 18S rRNA (GenBank: PP693724): 642 bp long;

• 28S rRNA (GenBank: PP693725): 644 bp long;

• COI (GenBank: PP693143): 529 bp long.

Type depositories: Holotype (lam 78 ind 5— ZUEC TAR 33 ) and 18 paratypes ( ZUEC TAR 34 View Materials to ZUEC TAR 45 View Materials and ZUEC PIC 1110 to 1115 View Materials ) were deposited at the Museum of Biological Diversity , Institute of Biology , University of Campinas, Campinas, Brazil.

Etymology: Dedicated to Rosina de Barros who, due to her effort and perseverance, laid the cornerstone of Brazilian tardigradology. Morphological differential diagnosis Pseudechiniscus ( Meridioniscus) rosinae sp. nov. by the presence of small double teeth/spines on pseudosegmental plate and absence of lateral spines/teeth is similar to Pse. ( Mer.) bartkei Węglarska, 1962 , Pse. ( Mer.) celebesiensis Gąsiorek and Michalczyk , 2025, Pse. ( Mer.) mascarenensis Kiosya, Vončina & Gąsiorek, 2021,

Pse. ( Mer.) novaezeelandiae ( Richters, 1908) , Pse. ( Mer.) saltensis Rocha, Doma, Gonzales Reyes and Lisi, 2020, Pse. ( Mer.) santomensis Fontoura, Pilato and Lisi, 2010 , Pse. ( Mer.) spinerectus Pilato, Binda, Napolitano and Moncada, 2001 , Pse. ( Mer.) titianae Vecchi, Cesari, Bertolani, Jönsson, Rebecchi and Guidetti, 2016 and Pse. ( Mer.) yunnanensis Wang, 2009 but it differs from:

1. Pseudechiniscus ( Mer.) bartkei , known from Argentina and Vietnam ( type locality— Węglarska 1962, Claps & Rossi 1984, Rossi & Claps 1989) by: smaller distances between hemispherical granules on the dorsal side of the body (distances smaller than the diameter of granules itself ( Fig. 1C View FIGURE 1 ) in Pse. ( Mer.) rosinae sp. nov. vs distances clearly larger than the diameter of granules itself ( Fig. 6 View FIGURE 6 ) in Pse. ( Mer.) bartkei ), shorter cirrus A (13.7–21.0 µm [ sp=60.4-89.4] in Pse. ( Mer.) rosinae sp. nov. vs 26.5–39.4 µm [ sp=94.0-116.9] in Pse. ( Mer.) bartkei ) and lower cirrus A /body length ratio (9–14% in Pse. ( Mer.) rosinae sp. nov. vs 17–22% in Pse. ( Mer.) bartkei ). Measurements and photographs of Pseudechiniscus ( Mer.) bartkei based on type material of the species and personal communication from Łukasz Michalczyk .

2. Pseudechiniscus ( Mer.) celebesiensis, known only from type locality on Celebes ( Indonesia) ( Gąsiorek and Michalczyk 2025) by: pillars jointed by well visible striae (striae poorly visible between random pillars in Pse. ( Mer.) celebesiensis), distribution of endocuticular pillars on dorsal plates (uniformly distributed in Pse. ( Mer.) rosinae sp. nov. vs arranged in belts in Pse. ( Mer.) celebesiensis), different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Fig. 20 for Pse. ( Mer.) celebesiensis in Gąsiorek & Michalczyk (2025)), presence of spurs on internal claws, lower sp value of cirrus A ( sp= 60.4–89.4 in Pse. ( Mer.) rosinae sp. nov. vs sp= 95.6–114.5 in Pse. ( Mer.) celebesiensis) and lower percentage value of the cirrus A /body length ratio (9%–14% in Pse. ( Mer.) rosinae sp. nov. vs 16%–20% in Pse. ( Mer.) celebesiensis).

3. Pseudechiniscus ( Mer.) mascarenensis known only from type locality on Mauritius (Mascarene Archipelago) ( Kiosya et al. 2021) by: well visible teeth/spines on the posterior margin of pseudosegmental plate (the posterior margin of the pseudosegmental plate sinusoid) and different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Figs 13 and 14 for Pse. ( Mer.) mascarenensis in Kiosya et al (2021)).

4. Pseudechiniscus ( Mer.) novaezeelandiae , known from various places on New Zealand ( Horning et al. 1978) and later reported from many localities, however all of them are doubtful ( Michalczyk et al. 2022) by: shorter dorsal teeth/spines on the posterior margin of pseudosegmental plate (compare with fig. 11B in Pilato et. al. 2005, and fig. 1C in Gąsiorek et al. 2021a).

5. Pseudechiniscus ( Mer.) saltensis, known only from type locality in Argentina ( Rocha et al. 2020) by: different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Fig. 3 View FIGURE 3 for Pse. ( Mer.) saltensis in Rocha et al. (2020)), different configuration of ventral patches of granulation (PG:I-III-IV-V-VI-VII-VIIIg in Pse. ( Mer.) rosinae sp. nov. vs PG:I-II-III-IV-V-VI-VII-VIIIg in Pse. ( Mer.) saltensis).

6. Pseudechiniscus ( Mer.) santomensis , known only from type locality on São Tomé Island ( Democratic Republic of São Tomé and Príncipe) ( Fontoura et al. 2010) by: different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Fig. 1D View FIGURE 1 for Pse. ( Mer.) santomensis in Fontoura et al. (2010)) and longer dorsal teeth/spines on the posterior margin of pseudosegmental plate (7.1–8.3 µm in Pse. ( Mer.) rosinae sp. nov. vs 1.4–6.3 µm in Pse. ( Mer.) santomensis ).

7. Pseudechiniscus ( Mer.) spinerectus , known from Costa Rica and Ecuador ( type locality) ( Pilato et al. 2001, Kaczmarek et al. 2014) by: different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Fig. 1B View FIGURE 1 for Pse. ( Mer.) spinerectus in Pilato et al. (2001)), shorter dorsal teeth/spines on the posterior margin of pseudosegmental plate (7.1–8.3 µm in Pse. ( Mer.) rosinae sp. nov. vs 10.9–11.2 µm in Pse. ( Mer.) spinerectus ), shorter cirrus internus (6.7–9.8 µm in Pse. ( Mer.) rosinae sp. nov. vs 12.1–14.7 µm in Pse. ( Mer.) spinerectus ) and shorter cirrus A (13.7– 21.0 µm in Pse. ( Mer.) rosinae sp. nov. vs 32.2–34.9 µm in Pse. ( Mer.) spinerectus ).

8. Pseudechiniscus ( Mer.) titianae, known only from type locality on Dronning Maud Land ( Antarctica) ( Vecchi et al. 2016) by: different ventral pattern ( Fig. 5 View FIGURE 5 for Pse. ( Mer.) rosinae sp. nov. vs Fig. 6c View FIGURE 6 for Pse. ( Mer.) titianae in Vecchi et al. (2016)), shorter cirrus internus (6.7–9.8 µm in Pse. ( Mer.) rosinae sp. nov. vs 10.5–10.6 µm in Pse. ( Mer.) titianae) and shorter cirrus A (13.7–21.0 µm in Pse. ( Mer.) rosinae sp. nov. vs 64.3–74.1 µm in Pse. ( Mer.) titianae).

9. Pseudechiniscus ( Mer.) yunnanensis, known only from type locality in China ( Wang 2009) by: presence of the ventral pattern and spurs on internal claws, posterior portion of scapular plate divided into four parts by three short longitudinal ridges, smaller diameter of pillars on dorsal plates (0.5–1.1 µm in Pse. ( Mer.) rosinae sp. nov. vs ca. 2.4 µm in Pse. ( Mer.) yunnanensis), slightly shorter dorsal teeth/spines on the posterior margin of pseudosegmental plate (7.1–8.3 µm in Pse. ( Mer.) rosinae sp. nov. vs 8.4–9.1 µm in Pse. ( Mer.) yunnanensis) and shorter cirrus A (13.7–21.0 µm in Pse. ( Mer.) rosinae sp. nov. vs 24.7–32.2 µm in Pse. ( Mer.) yunnanensis).

Genetic differential diagnosis

DNA molecular markers and genetic distances

The ranges of uncorrected genetic p-distances between Pse. ( Mer.) rosinae sp. nov. and other species of the genus Pseudechiniscus are as follows ( Table 3):

• 18S rRNA: only the sequence of Pse. ( Mer.) mascarenensis Kiosya, Vončina & Gąsiorek, 2021 (GenBank: MW031972 View Materials ) was complementary, with a p-distance of 0.5%;

• 28S rRNA: 1.1–7.0% (3.3% on average), with the most similar being Pse. ( Mer.) cf. saltensis (GenBank: MW032010 View Materials ), and the least similar being Pse. ( Mer.) celebesiensis (GenBank: MW032029 View Materials ).

• COI (the translation was successfully carried out with the invertebrate mitochondrial codon table and the -1st reading frame): 21.3–26.8% (23.3% on average), with the most similar being Pse. ( Mer.) dreyeri Gąsiorek, Vončina, Kristensen & Michalczyk , 2021b (GenBank: OK047278 View Materials ), and the least similar being Pse. ( Mer.) indistinctus Roszkowska, Grobys, Bartylak & Kaczmarek, 2020 (GenBank: MN528471 View Materials ).

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Museu de Zoologia da Universidade Estadual de Campinas

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