Echiniscus clevelandi Beasley, 1999

Gąsiorek, Piotr, Vončina, Katarzyna, Kristensen, Reinhardt Møbjerg & Michalczyk, Łukasz, 2021, Fig. 7 in Fig. 4. A in Saphonecrus globosus Schweger and Tang 2015, Zoological Studies (Zool. Stud.) 60 (70), pp. 1-45 : 5-9

Echiniscus clevelandi Beasley, 1999 ( Figs. 2–9 , Tables 2–4)

Material examined: 23 adult females, 15 adult males, and three juveniles on slides TW.005.06–7, TW.006.06, TW.007.19, TW.008.02–7, 12. Four specimens on SEM stub 21.07. Four specimens from the sample TW.008 were used for DNA sequencing, including two retrieved as hologenophores.

Amended description: Females (i.e., from the third instar onwards; measurements and statistics in Table 2): Body cylindrical to plump ( Figs. 2 , 4 ), orange to red with dark red eyes; body colour and eyes disappear soon after mounting in Hoyer’s medium. Echiniscus - type cephalic papillae (secondary clavae) and (primary) clavae; cirri growing out from bulbous cirrophores ( Fig. 8D ). The body appendage configuration is A-B- C-D-E, with all trunk appendages formed as short and relatively thick, smooth cirri. Instances of asymmetry in chaetotaxy frequent ( Fig. 2B ), but only rarely are more than one appendage absent.

Dorsal plates with the mixed type of sculpturing typical for the Echiniscus virginicus complex, comprising an evident layer of large polygonal endocuticular pillars visible as black dots under PCM ( Figs. 2 , 6), and a layer of dark uniform epicuticular matrix ( Figs. 2A–B , 6A) pierced with large, often irregularly shaped pores ( Figs. 2 , 6). Epicuticle and pores are typically well-developed and identifiable in SEM ( Figs. 4 , 8A–C ). Rarely, the pores are small and scarce ( Figs. 2C , 5A , 6B, 8C ). The cephalic plate is narrow and separated from the cervical (neck) plate by smooth cuticle. The cervical plate visible as a dark belt of minute pillars clearly distinct from the scapular plate. The scapular plate clearly smaller than the caudal (terminal) plate, with additional lateral sutures separating narrow trapezoidal lateral portions devoid of pores ( Figs. 2 , 6). Paired segmental plates divided into a smaller, much narrower anterior and a dominant posterior part by a smooth transverse stripe. Epicuticular ornamentation better developed in the central plate portions compared to the lateral parts. The caudal plate with short incisions and fully developed epicuticle. Median plates 1, 3 unipartite, whereas median plate 2 bipartite, its anterior portion is narrow, but with identical sculpturing as the posterior part. Ventral cuticle with minute endocuticular pillars covering the entire venter; a pair of subcephalic swellings (likely rudimentary plates, Fig. 8D ) and a pair of rectangular genital plates present. Sexpartite gonopore placed between genital plates, and a trilobed anus between legs IV.

Pedal plates I–III extremely reduced and only rarely identifiable as aggregations of pillars in central leg portions ( Fig. 6B), pedal plate IV developed as a sculptured cushion bearing a dentate collar with numerous teeth ( Figs. 4 , 6A, 8F ). Pulvini present, but weakly visible ( Fig. 2B ). A small spine on leg I ( Fig. 6) and a papilla on leg IV. Internal claws with identical large spurs on all legs ( Figs. 8E–F , 9 ). Claws IV clearly higher than claws I–III ( Table 2).

Buccal apparatus short, with a rigid, stout tube and a spherical pharynx. Stylet supports absent.

Males (i.e., from the third instar onwards; measurements and statistics in table 3): Sexual dimorphism poorly marked. Circular gonopore. Fully falling in the range of morphometric variability of females. Usually slightly slimmer than females ( Fig. 3 ) and with fewer epicuticular pores ( Figs. 3B , 5B , 7 ).

Juveniles (i.e., the second instar; measurements and statistics in table 4): Gonopore absent. Smaller than sexually mature specimens of both sexes. Morphometric differences evident also in cephalic appendages and claw heights. Body appendage configuration A-C-E. Dorsal cuticle lacks epicuticular ornamentation.

Larvae: Not found.

Eggs: Two to three orange eggs per exuvia were found.

Molecular markers and phylogenetic position: Single haplotype was found in 18S rRNA ( OK 048609– 10), ITS-1 ( OK 048639–40) and COI ( OK 047271–2), but two haplotypes were revealed in 28S rRNA ( OK 048627–8) and ITS-2 ( OK 048620–1), with minor intra-population p -distances (0.1–0.2%). We acquired a set of all five markers (18S rRNA: OK048611, 28S rRNA: OK048629, ITS-1: OK048641, ITS-2: OK048622, COI: OK 047273) also for one specimen of E. hoonsooi Moon & Kim, 1990 , a species of similar phenotype ( Fig. 10 ), previously reported from

Japan ( Abe et al. 2000). The BI tree indicates that E. clevelandi and E. hoonsooi are sister species, and constitute a sister clade to the E. lineatus + E. virginicus Riggin, 1962 clade ( Fig. 11 ; see also Gąsiorek et al. 2020).

Remarks: Taxonomy of the virginicus complex is scrutinised in table 5. The Taiwanese populations greatly broadened the range of intraspecific variability of E. clevelandi presented in the original description. Although Beasley (1999) specified that some type specimens lack dorsal appendages, this variant of chaetotaxy seems to be dominant in Taiwan. Therefore, the body appendage formula for the species is A-B-C- (C d)-D-(D d)-E. Moreover, the porosity of dorsal plates varies greatly between specimens, from highly porous with irregularly shaped pores (see fig. 4 in Beasley 1999 and Figs. 2–8C herein), through moderately porous with mostly round pores ( Figs. 2–8C ) to almost completely smooth plates with few small pores ( Fig. 5A ). If found separately, these morphotypes could be identified as separate taxa, which underlines the importance of integrative analyses carried out on a considerable number of specimens in order to reduce the risk of taxonomic inflation.

Figures

Fig. 2. Habitus of females of Echiniscus clevelandi (PCM): A, fully developed sculpturing and chaetotaxy (dorsal view); B, typical sculpturing and asymmetric lack of spine C (dorsolateral view); C, atypical sculpturing with poorly developed pores and full chaetotaxy (dorsal view). Scale bars in μm.

Fig. 3. Habitus of males of Echiniscus clevelandi (PCM): A, typical sculpturing (dorsolateral view); B, atypical sculpturing with poorly developed pores and asymmetric lack of spine B (dorsolateral view). Scale bars in μm.

Fig. 4. Habitus of females of Echiniscus clevelandi with fully developed sculpturing (dorsal view, SEM). Scale bars in μm.

Fig. 5. Habitus of Echiniscus clevelandi (SEM): A, female with atypical sculpturing (dorsal view); B, male with poorly developed sculpturing (lateral view). Scale bars in μm.

Fig. 8. Morphological details of Echiniscus clevelandi (SEM): A–C, varying levels of the sculpturing development of the scapular plate; D, cephalic region with peribuccal appendages and marked subcephalic swellings; E, claws II; F, claws IV. Scale bars in μm.

Fig. 9. Claws of Echiniscus clevelandi (PCM): A, claws I (female); B, claws III (female). Scale bars in μm.

Fig. 7. Dorsal plate sculpturing of Echiniscus clevelandi (males, PCM). Empty arrowheads indicate pulvini, whereas white arrowheads – pedal plates. Scale bars in μm.

Fig. 10. Habitus of Echiniscus hoonsooi (PCM) from Japan: A, female (dorsolateral view, insert shows claws II); B, dorsal sculpturing in close-up. Scale bars in μm.

Fig. 11. Phylogenetic relationships within the Echiniscus virginicus complex based on concatenated ITS-1, ITS-2 and COI sequences as inferred in the Bayesian approach. Echiniscus succineus was used as an outgroup. Scale bar represents substitutions per site.