Hypechiniscus gladiator, , Robotti, 1972

Gąsiorek, Piotr, Oczkowski, Artur, Blagden, Brian, Kristensen, Reinhardt M., Bartels, Paul J., Nelson, Diane R., Suzuki, Atsushi C. & Michalczyk, Łukasz, 2021, New Asian and Nearctic Hypechiniscus species (Heterotardigrada: Echiniscidae) signalize a pseudocryptic horn of plenty, Zoological Journal of the Linnean Society 192 : -

THE HYPECHINISCUS GLADIATOR GROUP

SPECIES: HYPECHINISCUS DAEDALUS GĄSIOREK, OCZKOWSKI, BARTELS, NELSON, KRISTENSEN & MICHALCZYK, SP. NOV.

Zoobank registration: 99D4BB97-5668-4C96-BBE3- CAB4FB52EA39.

Echiniscus gladiator ; Durham (North Carolina, USA); Higgins (1960)

E. (Hypechiniscus) gladiator ; Giles and Grayson County (Virginia, USA); Riggin (1962)

E. (H.) gladiator ; Roan Mountain (Tennessee, North Carolina, USA); Nelson (1975)

H. gladiator ; Spruce Mountain (West Virginia, USA); Tarter & Nelson (1990)

H. gladiator ; Monongahela National Forest (West Virginia, USA); Tarter & Nelson (1994)

H. gladiator ; Roan Mountain (Tennessee, USA); Guidetti et al. (1999)

H. gladiator ; Great Smoky Mountains (Tennessee, North Carolina, USA); Bartels & Nelson (2007), Nelson & Bartels (2007, 2013), Nelson et al. (2020)

( FIG 3–6, 26C; TABLES 4–5)

Description

Females (i.e. from the third instar onwards; measurements and statistics in Table 4): Body whitish and stout ( Figs 3A, C, 4), with spheroid or ovoid black eyes, persisting also after mounting. Elongated, dactyloid cephalic papillae (secondary clavae) and (primary) clavae ( Figs 3A, C, 5A, B); peribuccal cirri without cirrophores ( Fig. 5B). Cirrus A short, with cirrophore ( Figs 3A, 5A). Long cirrus dorsalis with a triangular base inserted posterior to median plate 2 ( Figs 3A, C, 4), the flagellum occasionally subdivided into two cirri.

Dorsal plates poorly sclerotized, with the Pseudechiniscus - type sculpturing, that is endocuticular pillars protruding through the epicuticle and visible as densely packed dark dots in PCM ( Fig. 3A), bumps in NCM ( Fig.3C) or weakly elevated protrusions (granules) in SEM ( Fig. 26C). Epicuticular ornamentation in the form of ridges visible in LCM and SEM ( Figs 3A, C, 4, 26C). Generally, the sculpture is well-developed and evident in LCM. The cephalic plate is large and pentapartite, with two small anterior portions, a central keel-like portion and two larger trapezoid portions ( Figs 3A, 4A, 5A). The cervical (neck) plate is not visible in LCM, indistinctly merged with the anterior margin of the scapular plate in SEM ( Fig. 5A). The scapular plate falsely divided in two parts by a central longitudinal suture and by numerous epicuticular ridges ( Figs 3A, 4A, 5A, 6A). Three median plates, all pseudobipartite, falsely subdivided by transverse sutures ( Fig. 6A) and with six pairs of lateral intersegmental platelets flanking their borders ( Figs 3A, 4A, 6A). Two pairs of large segmental plates without marginal incisions, but with a complicated system of epicuticular ornamentation giving an impression of false subdivisions ( Figs 3A, 6A). Caudal (terminal) plate large, with long incisions ( Figs 3A, 4A, 6A).

Ventral cuticle with a clear species-specific pattern of ornamentation reaching the lateroventral sides of the body ( Figs 3A, 4B). Ornamentation composed of epicuticular thickenings and endocuticular pillars of variable sizes, which are tightly arranged and closely adjacent to each other ( Figs 4B, 6B). The largest and most evident pillars occur between legs II and legs III, and in the gonoporal zone, where pillars are densely aggregated and form pseudoplates. Subcephalic zone with a pair of large pseudoplates, and the subcervical area with a slender columnar or pedestal shaped aggregation or plate ( Fig. 6B). Sexpartite gonopore placed between legs III and legs IV and a trilobed anus between legs IV.

Pedal plates and dentate collar IV absent, instead large belts of pillars are present on the outer central part of each leg ( Fig. 5D). Weak pulvini present on all legs. Markedly sclerotized areas present at the inner side of each leg below the claws ( Fig. 3C). A small papilla on leg I present and visible in SEM ( Fig. 5A); a papilla on leg IV present ( Fig. 4A). Claws I–IV of equal heights. External claws on all legs smooth ( Fig. 5C–D). Internal claws with massive spurs positioned at c. one-quarter of the claw height and strongly bent downwards. Fragments of upwardly bent epicuticle formed as pseudoaccessory points on all claws (visible only in SEM; Fig. 5C, arrowheads).

Males (i. e. from the second instar onwards; measurements and statistics in Table 5): Except for the circular gonopore, no sexual dimorphism was observed (compare Fig. 3B with Figs 3A, C). The bs ratios for males and females largely overlap (0.35–0.43 in N = 8 ♂♂ vs. 0.38–0.43 in N = 6 ♀♀).

Juveniles (i.e. the second instar, sexually immature females): No qualitative differences with respect to adults, except for lack of the gonopore. Shorter than adults (165 Μm in length, scapular plate length 20.7 Μm). Lengths of cephalic appendages: cirrus internus 12.1 Μm, cirrus externus 16.2 Μm, cirrus A 21.4 Μm. Cirrus dorsalis length: 65.9 Μm. Claw heights: 9.0–9.2 Μm.

Larvae (i.e. the first instar): Dorsal sculpturing weakly developed, but epicuticular ornamentation present. Gonopore and anus absent. Shorter than juveniles and adults, body 122 Μm in length, scapular plate length 10.9 Μm. Lengths of cephalic appendages: cirrus internus 4.3 Μm, cephalic papilla 3.7 Μm, cirrus externus 7.8 Μm, clava 4.0 Μm, cirrus A 9.4 Μm. Cirrus dorsalis length: 24.4 Μm. Claw heights: 5.9–7.1 Μm.

Eggs: One or two round, white eggs per exuvia were found.

Genetic markers: 18S rRNA was characterized by two haplotypes with minor differences between them (p -distance = 0.2%). One haplotype was detected in the 28S rRNA and three in the ITS1 (0.1–0.2%); see Table 3 for details.

Type material: Holotype (adult female, slide US.041.02), allotype (adult male, slide US.041.02) and 16 paratypes (8♀♀, 6♂♂, 1 juvenile, 1 larva). Slides US.041.01–2 (3♀♀, 2♂♂, 1 larva) deposited in UJ, slide US.041.05 deposited in NHMD (3♀♀, 2♂♂), slide US.036.18 deposited in NMS (1♀, 2♂♂) and slides US.036.19–20 (2♀♀, 1♂, 1 juvenile) deposited in CU.

Type locality: 35°35’13”N, 83°04’31”W, 1514 m a.s.l.: USA, North Carolina, Purchase Knob (see Supporting Information, Fig. S1); deciduous forest; moss from tree trunk. The species was accompanied by other echiniscids: Claxtonia mauccii ( Ramazzotti, 1956) , Echiniscus virginicus Riggin, 1962 and Pseudechiniscus brevimontanus Kendall-Fite & Nelson, 1996 .

Additional locality: 36°07’17”N, 82°05’37”W, 1239 m a.s.l.: USA, Tennessee, Roan Mountain , (see Supporting Information, Fig. S2); deciduous forest; moss from beech tree ( Fagus grandifolia Ehrh. ) bark .

Etymology: From Latin daedalus = artfully, subtly formed. The name refers to the sophisticated ventral pattern in the new species. An adjective in the nominative singular.

Phenotypic differential diagnosis: The species is separated from the exarmatus group by having a cirrus dorsalis and it differs from the remaining members of the gladiator group:

• H. fengi by the presence of papilla IV, identifiable in LCM (papilla IV not observable in LCM in H. fengi ).

• H. geminus by having median plates 1–2 falsely subdivided into anterior and posterior portions by sutures (clearly unipartite median plates in H. geminus ; compare Fig. 6A with Fig. 10A).

• H. gladiator by both clear epicuticular ridges and endocuticular pillars visible in LCM (only endocuticular pillars visible in LCM in H. gladiator ; compare Fig. 3 with Fig. 11).

• H. papillifer by having smooth external claws (claws with secondary spurs directed upwards in H. papillifer ) and lacking papillae on legs II–III.

G e n e t i c d i f f e r e n t i a l d i a g n o s i s: U n c o r r e c t e d p -distances between H. daedalus and other species are as follows:

• 18S rRNA: from 0.2% ( H. gladiator, MT 809194) to 4.1% ( H. flavus, HM 193377).

• 28S rRNA: from 0.5% ( H. gladiator, MT 809202–3) to 5.0% ( H. cataractus, MT 809195–8).

• ITS1: from 2.4% ( H. gladiator, MT 809192, MT 809194 ) to 18.2% ( H. cataractus, MT 809184) .

Genetically verified geographic distribution: Nearctic: USA.

SPECIES: HYPECHINISCUS FENGI SUN & LI, 2013

Shortened and corrected version of the original description

Females (i.e. from the third instar onwards): Body 171–222 Μm in length, colourless or very light yellow. Eyespots almost invisible. Cephalic appendages lengths: cirrus internus 10.4–13.0 Μm, cephalic papilla 5.7–7.5 Μm, cirrus externus 12.1–21.6 Μm, clava 5.1–6.8 Μm, and cirrus A 19.7–25.8 Μm. Cirrus dorsalis 25.8–30.0 Μm long, arising posteriorly to m2. Dorsal plates poorly sclerotized, sometimes indistinct, with the Pseudechiniscus - type sculpturing, i.e. fine endocuticular pillars protruding through the epicuticle and visible as densely packed dark dots in PCM. Dorsal armour consists of pentapartite cephalic plate, narrow cervical (neck plate), scapular plate, median plates m1–3 (false divisions of m2–3 into two parts resulting from the presence of longitudinal sutures) and caudal (terminal) plate with incisions. Lateral intersegmental platelets present laterally to m1 and m2. Ventral sculpturing pattern unknown. Pedal (leg) plates, patches of granulation and papillae absent or not visible under LCM on all legs. Claws 9.6–12.4 Μm long. Robust spurs pointed downwards present on internal claws; small, sharp spurs usually present at bases of external claws IV. Sexpartite rosette gonopore.

Males (i.e. from the second instar onwards): Sexual dimorphism not specified, but evidenced by the smaller body size (133–180 Μm). Cephalic appendages lengths: cirrus internus 4.6–13.7 Μm, cephalic papilla 5.1–8.7 Μm, cirrus externus 12.1–20.6 Μm, clava 5.8–8.2 Μm and cirrus A 18.1–24.4 Μm. Cirrus dorsalis 16.2–32.2 Μm long. Claws 8.2–12.1 Μm long. Circular gonopore.