Hypechiniscus, DECIPHERED

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 : -

HYPECHINISCUS DECIPHERED 817

dimorphism is rudimentary, as even clavae are of similar lengths in both sexes (size differences in clavae are typically indicative of sexual dimorphism in echiniscids). Cephalic papillae broader in ♂♂ ( Fig. 11C). Of the standardly measured traits, ♂♂ differ significantly from ♀♀ only in body size, estimated both as mean body length ± SD: 200 ± 19 Μm vs. 246 ± 25 Μm (one-tailed Welch’s t -test due to unequal variances, with N ♀♀ = 30 and N ♂♂ = 30: t 55 =8.06; P <0.001) and as average scapular plate length: 21.4 ± 1.8 Μm vs. 25.4 ± 2.6 Μm (t 52 = 6.90; P <0.001). The bs ratio ranges, which are usually clearly separate for each sex, also overlap (0.34–0.41 in N = 11 ♂♂ vs. 0.37–0.47 in N = 10 ♀♀).

Juveniles (i.e. the second instar, sexually immature females): Except for the lack of the gonopore, no qualitative differences with respect to adult females were observed. Shorter than adult females.

Larvae (i.e. the first instar; measurements and statistics in Table 10): Dorsal sculpturing weakly developed. Gonopore and anus absent. Shorter than juveniles.

Eggs: One to four round, white eggs per exuvia were found.

Genetic markers: 18S rRNA was characterized by three haplotypes with minor differences between them (p -distances = 0.1–0.3%), but one haplotype was detected for 28S rRNA, and four in ITS1 (0.3–1.6%); see Table 3 for details.

Neotype material: Neotype (adult female, slide GB.058.12), 105 individuals (25♀♀, 28♂♂, 11 juveniles, and one larva on slides GB.033.16–51; 19♀♀, 14♂♂, 4 juveniles on slides GB.058.11–17), including the form bigladii, and four exuvia. Slides GB.033.16–46 (22♀♀, 22♂♂, 8 juveniles, 1 larva, 2 exuvia) + GB.058.11–12 (5♀♀, 4♂♂, 1 juvenile) deposited in UJ, slide GB.058.13 deposited in NHMD (3♀♀, 3♂♂), slide GB.058.14 deposited in NMS (2♀♀, 3♂♂, 1 juvenile), and slides GB.033.47–51 (3♀♀, 6♂♂, 3 juveniles, 2 exuvia) + GB.058.15–17 (10♀♀, 4♂♂, 2 juveniles) deposited in CU .

New type (neotype) locality: 56° 57’ 33.03’’N, 4°34’04.5’’W, 624 m a.s.l.: Scotland, Creag Meagaidh, Lochan a’ Choire; mountain grassland; moss from rock. The species was accompanied by other echiniscids: Bryodelphax parvulus Thulin, 1928 , Diploechiniscus oihonnae ( Richters, 1903) and Echiniscus merokensis Richters, 1904 .

Additional locality: 57°08’49’’N, 4°40’42’’W, 20 m a.s.l.: Scotland, Loch Ness, Fort Augustus; moss from rock off the lake shore. The species was accompanied by other echiniscids: B. parvulus , D. oihonnae and E. merokensis .

Etymology: The name most likely refers to the presence of the cirrus dorsalis , which resembles a whip that gladiators (lorarii) in the Roman Empire used to goad animals and humans into fighting at arenas. A noun in the nominative singular standing in apposition.

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

• H. daedalus and H. geminus by only endocuticular pillars visible in LCM (clear epicuticular ridges visible in LCM as grey elements overlapping with pillars in the two new species; compare Figs 3, 8 and 11), the epicuticular portion of the sculpture is similar in all three species under SEM ( Fig. 26B, C, E).

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. gladiator and other species are as follows:

• 18S rRNA: from 0.2% ( H. daedalus, MT 809237) to 4.3% ( H. flavus, HM 193377).

• 28S rRNA: from 0.5% ( H. daedalus, MT 809199, MT 809200 ) to 4.5% ( H. cataractus, MT 809195–8) .

• ITS1: from 2.4% ( H. daedalus, MT 809187, MT 809189 ) to 18.2% ( H. cataractus, MT 809184) .

Genetically verified geographic distribution: Western Palaearctic: Iceland, Scotland.

Remarks: Animals found in Italy and the Swedish Öland constitute the first records of this rare species for both countries ( Maucci, 1986; Guidetti et al., 2015). Both the forms fissigladii and bigladii [described by Iharos (1973); see Fig. 15; recorded as subspecies in Degma et al. (2009– 20)] are herein suppressed, because: (1) they fall within the genetic variability of the morphotype of H. gladiator with a single cirrus dorsalis and (2) similar morphological variability with regard to the cirrus dorsalis occurs in the new species of the gladiator group (described above). However, the status of the form spinulosa ( Fig. 15A) is unclear. Originally it was used to separate individuals of ‘ H. gladiator ’ (see the section ‘Biogeography’) having three projections in the median line and at the posterior edges of the scapular and segmental plates, together with two anterior projections of the caudal plate, from ‘typical’ individuals with continuous, smooth plate margins ( Iharos, 1973). However, as the dorsal armour is thin and easily deformable in the entire genus, it is feasible that such projections could be formed as artefacts resulting from incomplete relaxation of an individual during mounting (the examination of the syntypes deposited in the Hungarian Natural History Museum in Budapest revealed that such projections are absent). Therefore, this form possesses no reliable character, which would substantiate its distinctiveness. The form spinulosa should, therefore, be recognized as invalid until Hypechiniscus specimens originating from the Korean Peninsula are examined.

SPECIES: HYPECHINISCUS PAPILLIFER ( ROBOTTI, 1972)

Shortened and corrected version of the original description: Sex not specified: Body 196–227 Μm in length, almost translucent. Eyespots black. Cirrus dorsalis 52.0–59.0 Μm long. Dorsal plates with the fine Pseudechiniscus - type sculpturing. Ventral sculpturing pattern unknown. Papillae present on legs II–IV. Internal claws with robust spurs directed downwards, and external claws with minute, needle-like spurs at their bases, directed upwards.

Phenotypic differential diagnosis: This is the only Hypechiniscus species with papillae on legs II–III.