Cornechiniscus mystacinus, Gąsiorek, 2022

Gąsiorek, Piotr, 2022, Water bear with barbels of a catfish: A new Asian Cornechiniscus (Heterotardigrada: Echiniscidae) illuminates evolution of the genus, Zoologischer Anzeiger 300, pp. 47-64 : 50-55

publication ID	https://doi.org/ 10.1016/j.jcz.2022.06.007
publication LSID	lsid:zoobank.org:pub:858824D0-75BB-4CE7-8C77-6B0284CCD94B
DOI	https://doi.org/10.5281/zenodo.8171144
persistent identifier	https://treatment.plazi.org/id/DBAFC029-7656-44AD-8611-D6B52D8E8A46
taxon LSID	lsid:zoobank.org:act:DBAFC029-7656-44AD-8611-D6B52D8E8A46
treatment provided by	Felipe
scientific name	Cornechiniscus mystacinus
status	sp. nov.

Treatment

3.3. Description of Cornechiniscus mystacinus View in CoL sp. nov.

urn:lsid:zoobank.org:act:DBAFC029-7656-44AD-8611-D6B52D8E8A46

Figs. 2–7C View Fig View Fig View Fig View Fig View Fig View Fig , 8–11 View Fig View Fig View Fig View Fig , Tables 3–5. View Table 3 View Table 4

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 View Table 3 )

Body massive and plump ( Fig. 2A, C View Fig , 3A, C–D View Fig ), yellow to dark orange in live specimens ( Fig. 2A–B View Fig ). Large, round, black crystalline eyes ( Fig. 2A–C View Fig , 7A, C View Fig ). Mouth cone retractable, with a ring of granulation surrounding the peribuccal fissure ( Fig. 7B View Fig ). Cephalic appendages fully developed; cirri interni and externi with reduced cirrophores ( Fig. 2A–C View Fig , 7A–C View Fig , 8 View Fig ), being swollen extensions of extremely elongated flagellum with tufted tips ( Fig. 7A–C View Fig ). Aberrant processes growing out of cirrophores may be present ( Fig. 7C View Fig ). Cephalic papillae (secondary clavae) dome-shaped ( Fig. 2A, C View Fig , 7A–C View Fig ), with a peripapillary granulation ( Fig. 7A–C View Fig ); papillae imperceptible in SEM ( Fig. 8A View Fig ). Appendages A well-developed, with clearly delimited cirrophore ( Figs. 5A View Fig , 7C View Fig and 8 View Fig , 9A–C View Fig ). Outer sheath of appendages A thick and distinct from lumen; the inner striation visible in PCM at 1000× magnification ( Fig. 9A and B View Fig ). Aberrant additional, miniaturised processes may develop on cirrophores A ( Fig. 9B and C View Fig ). Primary clavae conical ( Figs. 5A View Fig and 8A View Fig ), clearly separated from cirrophores A and encompassed by granulation ( Fig. 9A and B View Fig ). Body appendage configuration A-(C)-(D)-(ps)-(E). All appendages in the form of short spines ( Fig. 2A, C View Fig , 9D, F View Fig ), only rarely some appendages may be formed as lobes ( Fig. 9E View Fig ). Asymmetry in appendage development frequent in all trunk positions, spines C and ps frequently absent ( Fig. 3A, C–D View Fig ).

Sculpture covering densely the entire dorsal armour ( Fig. 2A, C View Fig , 3A, C–D View Fig , 5 View Fig , 10A–C View Fig ), comprising numerous endocuticular pillars protruding as polygonal/roundish granules on the epicuticle ( Fig. 10A–C View Fig ). Granules differentiated in size, with a strong tendency towards merging in the posterior portions of plates ( Figs. 3A View Fig , 5B–C View Fig , 10A–B View Fig ). Striae present only in some plate portions, typically clustered and densely arranged (e.g. cephalic plate – Figs. 5A View Fig , 7C View Fig and 9B View Fig ; lateralmost portions of intersegmental and paired segmental plates – Fig. 9E View Fig ). Cephalic plate well-developed, tripartite: two anterior halves demarcated from the posterior portion by a strongly convex ridge ( Fig. 2A–C View Fig , 3A View Fig , 5A View Fig , 7C View Fig , 8B View Fig ). Cervical (neck) plate well-developed too, visible in PCM as a rectangular, sculptured belt preceding the scapular plate ( Fig. 5A View Fig ), poorly discernible from the latter in SEM ( Fig. 8B View Fig ). Scapular plate broad, with a weak W-suture ( Figs. 2A View Fig , 3A View Fig , 5A–B View Fig , 8B View Fig , 10A View Fig ) that may be absent ( Fig. 2C View Fig ). Pseudosegmental plate I ′ narrower than the scapular plate, merged with the scapular plate in lateralmost portions ( Fig. 2A, C View Fig , 3C–D View Fig , 5B View Fig ). Median plates 1–2 bipartite, m1 with slightly larger posterior portion ( Fig. 10A View Fig ), whereas m2 with much larger anterior portion containing central epicuticular extension ( Fig. 10B View Fig ); m1 flanked by the first pair of weakly sclerotized, supplementary lateral plates ( Figs. 2C View Fig , 3C–D View Fig , 10A View Fig ). 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 View Fig , 3A View Fig and 10B View Fig ). The second pair of supplementary lateral plates flanking the most distal margins of m2 ( Figs. 2C View Fig , 3C–D View Fig , 5C View Fig , 10B View Fig ). Second paired segmental plate and pseudosegmental plate III ′ arranged similarly to the first pair on the dorsum ( Figs. 2C View Fig and 3A View Fig ). Median plate 3 undivided and triangular ( Figs. 2C View Fig , 3A View Fig and 10C View Fig ). Pseudosegmental plate IV’ centrally divided, often with a smooth posterior margin that is never lobated ( Figs. 2C View Fig and 3A, C–D View Fig , 10C View Fig ). Caudal (terminal) plate with deep incisions, continuous with base of spine E ( Fig. 2A, C View Fig , 3A, C–D View Fig , 10C View Fig ).

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 View Fig ). Legs broad and short ( Fig. 2A, C View Fig , 3C–D View Fig ). Pedal (leg) plates I–IV present and densely encrusted with minute endocuticular pillars ( Fig. 2A–C View Fig , 11A–B View Fig ). Spine I short and robust ( Fig. 2A–C View Fig , 10D View Fig , 11A View Fig ). Minute papilla on legs IV present ( Fig. 2A, C View Fig , 3C–D View Fig ). Large tooth on legs IV present ( Figs. 2A View Fig and 3D View Fig ), sometimes formed only as a sclerotised triangular ridge. Two teeth present only in the holotype ( Fig. 2C View Fig ). Claws strongly heteronych, spurless ( Fig. 10D–F View Fig , 11 View Fig ). Gonopore hexapartite.

3.3.4. Adult males (measurements and statistics in Table 4 View 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 View Fig and 3B View Fig ), 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 View Fig and 6C View Fig ). Epicuticular granules widely spaced ( Fig. 6 View Fig ), with striae developed in few plate portions (e.g. central part of the caudal plate – Fig. 6C View Fig ). 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 View Table 2 ).

3.3.8. Differential diagnosis

Cornechiniscus mystacinus View in CoL 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 View Fig ) 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) View in CoL 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 View in CoL sp. nov. on the basis of:

• the shape and length of peribuccal cirri (filamentous and longer than appendages A in C. mystacinus View in CoL sp. nov. vs bulbous and shorter than appendages A in C. tibetanus View in CoL );

• 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.