Cornechiniscus mystacinus Gąsiorek 2022, sp. nov.

3.3. Description of Cornechiniscus mystacinus sp. nov. urn:lsid:zoobank.org:act: DBAFC029-7656-44AD-8611- D6B52D8E8A46 Figs. 2–7C, 8–11, Tables 3–5. 3.3.1. Type locality and type series ca. 41 Ǫ 22 ′ 31 ′′ N, 72 Ǫ 15 ′ 21 ′′ E, 1046 m asl: Kyrgyzstan, Jalalabat Region, Tashk¨omür. Holotype (adult female, slide KG.030.01) and allotype (adult male, slide KG.029.12), and 28 paratypes: 15 adult females, eight adult males, five juveniles on slides KG.028.01, KG.029.01–15, KG.030.02–03. Five paratypes on SEM stub no. 22.05. Three hologenophores preserved on slide KG.029.17. All deposited in the Department of Invertebrate Evolution of the Jagiellonian University, with the exception of the following slides: KG.028.01 (male), deposited in Comenius University in Bratislava, Slovakia; KG.030.02 (female), deposited in University of Modena and Reggio Emilia, Italy; KG.030.03 (juvenile), deposited in University of Catania, Italy. 3.3.2. Etymology From Latin mystax =moustache. The name alludes to the significant prolongation of peribuccal cirri, especially of external ones, that calls to mind barbels of a catfish. An adjective in the nominative singular. 3.3.3. Adult females (i.e. from the third instar onwards; measurements and statistics in Table 3) Body massive and plump (Fig. 2A, C, 3A, C–D), yellow to dark orange in live specimens (Fig. 2A–B). Large, round, black crystalline eyes (Fig. 2A–C, 7A, C). Mouth cone retractable, with a ring of granulation surrounding the peribuccal fissure (Fig. 7B). Cephalic appendages fully developed; cirri interni and externi with reduced cirrophores (Fig. 2A–C, 7A–C, 8), being swollen extensions of extremely elongated flagellum with tufted tips (Fig. 7A–C). Aberrant processes growing out of cirrophores may be present (Fig. 7C). Cephalic papillae (secondary clavae) dome-shaped (Fig. 2A, C, 7A–C), with a peripapillary granulation (Fig. 7A–C); papillae imperceptible in SEM (Fig. 8A). Appendages A well-developed, with clearly delimited cirrophore (Figs. 5A, 7C and 8, 9A–C). Outer sheath of appendages A thick and distinct from lumen; the inner striation visible in PCM at 1000× magnification (Fig. 9A and B). Aberrant additional, miniaturised processes may develop on cirrophores A (Fig. 9B and C). Primary clavae conical (Figs. 5A and 8A), clearly separated from cirrophores A and encompassed by granulation (Fig. 9A and B). Body appendage configuration A-(C)-(D)-(ps)-(E). All appendages in the form of short spines (Fig. 2A, C, 9D, F), only rarely some appendages may be formed as lobes (Fig. 9E). Asymmetry in appendage development frequent in all trunk positions, spines C and ps frequently absent (Fig. 3A, C–D). Sculpture covering densely the entire dorsal armour (Fig. 2A, C, 3A, C–D, 5, 10A–C), comprising numerous endocuticular pillars protruding as polygonal/roundish granules on the epicuticle (Fig. 10A–C). Granules differentiated in size, with a strong tendency towards merging in the posterior portions of plates (Figs. 3A, 5B–C, 10A–B). Striae present only in some plate portions, typically clustered and densely arranged (e.g. cephalic plate – Figs. 5A, 7C and 9B; lateralmost portions of intersegmental and paired segmental plates – Fig. 9E). Cephalic plate well-developed, tripartite: two anterior halves demarcated from the posterior portion by a strongly convex ridge (Fig. 2A–C, 3A, 5A, 7C, 8B). Cervical (neck) plate well-developed too, visible in PCM as a rectangular, sculptured belt preceding the scapular plate (Fig. 5A), poorly discernible from the latter in SEM (Fig. 8B). Scapular plate broad, with a weak W-suture (Figs. 2A, 3A, 5A–B, 8B, 10A) that may be absent (Fig. 2C). Pseudosegmental plate I ′ narrower than the scapular plate, merged with the scapular plate in lateralmost portions (Fig. 2A, C, 3C–D, 5B). Median plates 1–2 bipartite, m1 with slightly larger posterior portion (Fig. 10A), whereas m2 with much larger anterior portion containing central epicuticular extension (Fig. 10B); m1 flanked by the first pair of weakly sclerotized, supplementary lateral plates (Figs. 2C, 3C–D, 10A). First paired segmental plate tightly joined with the pseudosegmental plate II ′, separated by epicuticular extension devoid of pillars (a smooth line in PCM; Figs. 2C, 3A and 10B). The second pair of supplementary lateral plates flanking the most distal margins of m2 (Figs. 2C, 3C–D, 5C, 10B). Second paired segmental plate and pseudosegmental plate III ′ arranged similarly to the first pair on the dorsum (Figs. 2C and 3A). Median plate 3 undivided and triangular (Figs. 2C, 3A and 10C). Pseudosegmental plate IV’ centrally divided, often with a smooth posterior margin that is never lobated (Figs. 2C and 3A, C–D, 10C). Caudal (terminal) plate with deep incisions, continuous with base of spine E (Fig. 2A, C, 3A, C–D, 10C). Venter without grooves typical for Cornechiniscus; aggregations of endocuticular pillars present at the level of legs I–III, fainter and smaller pillars dispersed throughout the remaining parts of venter (Fig. 4B). Legs broad and short (Fig. 2A, C, 3C–D). Pedal (leg) plates I–IV present and densely encrusted with minute endocuticular pillars (Fig. 2A–C, 11A–B). Spine I short and robust (Fig. 2A–C, 10D, 11A). Minute papilla on legs IV present (Fig. 2A, C, 3C–D). Large tooth on legs IV present (Figs. 2A and 3D), sometimes formed only as a sclerotised triangular ridge. Two teeth present only in the holotype (Fig. 2C). Claws strongly heteronych, spurless (Fig. 10D–F, 11). Gonopore hexapartite. 3.3.4. Adult males (measurements and statistics in Table 4; instar unknown since it is difficult to ascertain whether males develop from juveniles or from larvae based on body length ranges) Body more slender than in females (Figs. 2D and 3B), and much smaller on average. Gonopore circular, with an arc-shaped slit. No other qualitative differences between males and females, thus sexual dimorphism is negligible. 3.3.5. Juveniles (i.e. the second instar; measurements and statistics in Table 5) Clear morphometric gap between juveniles and females, but ranges overlap in the case of juveniles and males. Typically all trunk spines present (Figs. 4A and 6C). Epicuticular granules widely spaced (Fig. 6), with striae developed in few plate portions (e.g. central part of the caudal plate – Fig. 6C). Gonopore absent. 3.3.6. Larvae and eggs Not found. 3.3.7. Type sequences Single haplotypes were obtained in all nuclear markers, and two were recovered in COI (Table 2). 3.3.8. Differential diagnosis Cornechiniscus mystacinus sp. nov. is easily distinguishable from all congeners by the combination of the following characters: extreme elongation of peribuccal cirri (cirrus internus slightly longer than appendage A and cirrus externus several times longer than the latter; peribuccal cirri are typically bulbous in the genus, Fig. 7D) with tufted tips, granulation around the mouth cone and cephalic papillae, and the presence of males in populations. The species closest morphologically is C. tibetanus (Maucci, 1979) because of its large body size (adult females 500–600 μm on average), strongly heteronych and smooth claws, and by the development of spines in the lateral positions C–E and at the posterior margin of the pseudosegmental plate IV’. However, it can be separated from C. mystacinus sp. nov. on the basis of: • the shape and length of peribuccal cirri (filamentous and longer than appendages A in C. mystacinus sp. nov. vs bulbous and shorter than appendages A in C. tibetanus); • the mode of reproduction (sexual in C. mystacinus sp. nov. vs parthenogenetic in C. tibetanus). Moreover, C. tibetanus usually exhibits two teeth on leg IV (Biserov (1999) noted a variability in this trait in the Turkmen populations, in which some individuals showed 1–3 teeth per leg, yet stated that the majority had two teeth as described by Maucci (1979)), and C. mystacinus sp. nov. – only one. This criterion can be therefore treated as an additional, auxiliary character in the species identification. 3.3.9. Associated species Four taxa co-occurred in the samples KG.028–30: C. imperfectus, E. testudo, and unidentified Milnesium and Ramazzottius species.Published as part of Gąsiorek, Piotr, 2022, Water bear with barbels of a catfish: A new Asian Cornechiniscus (Heterotardigrada: Echiniscidae) illuminates evolution of the genus, pp. 47-64 in Zoologischer Anzeiger 300 on pages 50-55, DOI: 10.1016/j.jcz.2022.06.007, http://zenodo.org/record/816400