Echiniscus tantulus, Bochnak & Vončina & Kristensen & Gąsiorek, 2020

Bochnak, Marcin, Vončina, Katarzyna, Kristensen, Reinhardt M. & Gąsiorek, Piotr, 2020, Fig. 18 in Paralbunea dayriti, Zoological Studies (Zool. Stud.) 59 (18), pp. 1-13 : 4-6

publication ID	https://doi.org/ 10.6620/ZS.2020.59-18
persistent identifier	https://treatment.plazi.org/id/F93F87C8-FFCE-FF9E-25FA-FE08FC937DF6
treatment provided by	Felipe
scientific name	Echiniscus tantulus
status

Treatment

Phylum Tardigrada Doyère, 1840 View in CoL Class Heterotardigrada Marcus, 1927 Order Echiniscoidea Richters, 1926 Family Echiniscidae Thulin, 1928 Genus Echiniscus C.A.S. Schultze, 1840

Echiniscus tantulus sp. nov. Gąsiorek, Bochnak, Vončina & Kristensen ( Figs. 2–5 View Fig View Fig View Fig View Fig , Tables 2–3) urn:lsid:zoobank.org:act:4CB6B6FC-A376-4464-8338-B434C82FD8D5

Description: Females (i.e., from the third instar onwards; measurements and statistics in table 2): Body orange with minute red eyes present in live specimens; colours disappearing soon after mounting. Cylindrical, Echiniscus - type cephalic papillae (secondary clavae) and (primary) clavae; cirri growing out from bulbous cirrophores ( Figs. 2A–B View Fig , 3B View Fig , 4A View Fig , 5A View Fig ). The body appendage configuration is A-C-Cd- Dd- E, with trunk appendages formed as: spines (Cd, Dd) or spicules (C, E). Spicules formed precisely at the posterior edges of segmental plates, usually as a prolongation of the cuticular margin. All trunk appendages smooth ( Figs. 2A–B View Fig , 3 View Fig , 4A View Fig ). Single cases of asymmetry in all positions (e.g., Fig. 3A View Fig ).

Dorsal plates with the spinulosus type of sculpturing (see Gąsiorek et al. 2019a), that can be easily subdivided into (I) typical pores present in the majority of plates, (II) more densely arranged pores at the anterior portions of the segmental plates and median plate 2, and the entirety of median plate 3 that are clearly seen under SEM and as darker areas under PCM ( Figs. 2A–B View Fig , 3 View Fig , 4 View Fig ), (III) very fine epicuticular wrinkling present on bands dividing the segmental plates and median plate 2, and the posteriormost part of median plate 3, which are visible only in SEM ( Fig. 3B View Fig ). Pores are smaller and more sparsely distributed in the lateral portions of all plates. Pores without endocuticular rings ( Figs. 3 View Fig , 4B–C View Fig ). The cephalic plate with typical pores, divided into halves ( Figs. 2A View Fig , 5A View Fig ). The cervical (neck) plate poorly delineated from the scapular plate, formed as thin grey belt without pores ( Figs. 2A View Fig , 3A View Fig , 4A View Fig ). The scapular plate large, with poorly marked lateral sutures separating narrow rectangular lateral portions without pores ( Figs. 2A–B View Fig , 3A View Fig , 4 View Fig ). Paired segmental plates divided into a smaller, much narrower anterior and a prominent posterior part by a light nonporous, transverse band (wrinkled in SEM, Figs. 2A–B View Fig , 3 View Fig , 4A View Fig ). Posterior parts heterogenic, with the anteriormost margins adjacent to the belts being identical to the anterior parts of the plate ( Fig. 3 View Fig ). The caudal (terminal) plate with short incisions and horizontal and vertical epicuticular ridges, forming a cross, i.e., dividing the plate into four facets ( Figs. 2A–B View Fig , 3 View Fig , 4C View Fig ). Median plates 1 and 3 unipartite, whereas median plate II divided into a very narrow anterior and wide posterior portion ( Fig. 3 View Fig ). Ventral cuticle with minute endocuticular pillars distributed evenly throughout the entire venter ( Fig. 5B View Fig ), with rudimentary subcephalic plates in the form of convex swellings ( Figs. 4A View Fig , 5A View Fig ). Sexpartite gonopore between genital plates, and a trilobed anus between legs IV.

Pedal plates seen as dark areas on the central leg portions under PCM, without pores; plate IV with a typical dentate collar composed of short teeth ( Figs. 2A– B View Fig , 4A View Fig , 5D View Fig ). Distinct pulvini on all legs ( Figs. 2A View Fig , 4A View Fig ). A small spine on leg I and a papilla on leg IV present ( Figs. 2A–B View Fig , 4A View Fig ). External claws on all legs smooth. Internal claws with large, acute spurs positioned at ca. 1/4–1/3 of the claw height and bent downwards ( Fig. 5B–D View Fig ).

Buccal apparatus short, with a rigid, stout tube and a roundish pharynx containing serrated, chitinous placoids. Stylet supports absent.

Males: Unknown (likely a parthenogenetic species).

Juveniles (i.e., the second instar, measurements and statistics in Table 3): Clearly smaller than adult females, but with the trunk appendage configuration as in sexually mature individuals. In one individual, spines Cd displaced in the direction of the dorsolateral position ( Fig. 2C View Fig ). Pores fainter than in adult females; the differences in dorsal sculpturing between anterior and posterior portions of segmental plates not apparent. Lacking gonopore. No other significant disparities were found between the juvenile and mature life stages.

Larvae: Unknown.

Eggs: Up to five round, orange eggs per exuvia were found in two exuviae.

Molecular markers and phylogenetic position: All five genetic markers were represented by single haplotypes (GenBank accession numbers: 18S rRNA – MT126785, 28S rRNA – MT126765, COI – MT107427, ITS-1 – MT108138, and ITS-2 – MT108137). Both ITS-1 and ITS-2-based phylogenies reflected the topology of the Echiniscus clades from Gąsiorek et al. (2019a), with the virginicus complex as basal and E. testudo ( Doyère, 1840) as sister to the spinulosus complex, which included E. tantulus sp. nov. According to the ITS-1 tree, E. tantulus sp. nov. is a sister species to the clade E. succineus Gąsiorek & Vončina, 2019 + E. ornamentatus Gąsiorek & Kristensen, 2018 ( Fig. 6 View Fig ). In the ITS-2 tree, E. tantulus sp. nov. is also most closely related to these two taxa, but their relationships are unclear as the tree is inconclusive. The p -distances were calculated for both ITS and COI markers on the dataset of selected sequences (see Table S2).

Type material: Holotype (slide TZ.072.01), and 16 paratypes on slides TZ.072.01–06. Three paratypes mounted on SEM stub no. 19.15. Moreover, two voucher specimens (hologenophores) mounted on the slides TZ.073.01–02. The slides TZ.072.02–03 (5 ññ) deposited in the Natural History Museum of Denmark, University of Copenhagen , Denmark; the slide TZ.072.04 (5 ññ) deposited in the Catania University , Sicily, Italy. All remaining slides deposited in the Institute of Zoology and Biomedical Research , Jagiellonian University , Poland. The present species was found together with abundant populations of E. tristis Gąsiorek & Kristensen, 2018 .

Additional material: Two females mixed with a population of E. tristis in an additional sample collected in the locus typicus (sample reference TZ.069).

Type locality: 7°49'04"S, 36°50'39"E, ca. 2100 m asl; Mwanihana Peak, Udzungwa Mountains, Tanzania; Afromontane rainforest, lichens growing on exposed bedrock.

Etymology: From Latin tantulus = “so small”. The name refers to the microscopic size of the animal. An adjective in the nominative singular.

Differential diagnosis: The stable body appendage configuration A-C-Cd- Dd- E, with the dorsal spines several times longer than short lateral spicules, makes E. tantulus sp. nov. unique among the members of the spinulosus group ( Gąsiorek et al. 2019a), which are typically highly variable in terms of the development of trunk spines and frequent asymmetries (e.g., see Pilato et al. 2008; Meyer 2016). There is only one other species showing a combination of long dorsal spines and short lateral spicules: E. spinulosus ( Doyère, 1840) . Echiniscus canedoi da Cunha & do Nascimento Ribeiro, 1962 also bears some resemblance to E. tantulus sp. nov. due to the dorsal spines Dd two times longer than the longest lateral spines C, yet the new species can be differentiated from:

E. canedoi View in CoL , so far found only in Madeira, based on the trunk appendage configuration (C - Cd - Dd -E in E. tantulus sp. nov. vs C-D-Dd in E. canedoi View in CoL ), and dissimilarities in the dorsal sculpturing (markedly darker anterior portions of segmental plates, with densely arranged pores in E. tantulus sp. nov. vs anterior portions with sparsely arranged pores in E. canedoi View in CoL ); E. spinulosus View in CoL , reliably reported only from numerous locales in Western Palaearctic ( McInnes 1994), by the distinct trunk appendage configuration (C - Cd - Dd -E in E. tantulus sp. nov. vs (B)- C-Cd- D-Dd- E in E. spinulosus View in CoL ), dissimilarities in the dorsal sculpturing (markedly darker anterior portions of segmental plates, with densely arranged pores in E. tantulus sp. nov. vs uniform sculpturing in E. spinulosus View in CoL , see Pilato et al. 2008), the presence of epicuticular ridges on the caudal plate (forming a cross in E. tantulus sp. nov. vs absent in E. spinulosus View in CoL , see Pilato et al. 2008), and the level of development of pedal plates (poorly developed and lacking pores in E. tantulus sp. nov. vs well-developed, with large pores identical to the pores present on the dorsal plates in E. spinulosus View in CoL , see Gąsiorek and Degma 2018).