Bryodelphax australasiaticus Gasiorek , Voncina , Degma & Michalczyk, 2020

Gasiorek, Piotr, Voncina, Katarzyna, Degma, Peter & Michalczyk, Lukasz, 2020, Small is beautiful: the first phylogenetic analysis of Bryodelphax Thulin, 1928 (Heterotardigrada, Echiniscidae), Zoosystematics and Evolution 96 (1), pp. 217-236 : 217

publication ID	https://dx.doi.org/10.3897/zse.96.50821
publication LSID	lsid:zoobank.org:pub:0B80FF1B-5ED7-430B-A471-A5DE02E8E6D3
persistent identifier	https://treatment.plazi.org/id/BE521B67-6769-4EF5-B3C9-56EB43BF2DFE
taxon LSID	lsid:zoobank.org:act:BE521B67-6769-4EF5-B3C9-56EB43BF2DFE
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Bryodelphax australasiaticus Gasiorek , Voncina , Degma & Michalczyk
status	sp. nov.

Treatment

Bryodelphax australasiaticus Gasiorek, Voncina, Degma & Michalczyk sp. nov. Figures 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 12 View Figure 12 , Table 3

B. australis sp. n. in Claxton (2004)

Locus typicus and type material.

5°27'05"N, 100°11'00"E, 4 m a.s.l.; Pantai Keracut, Pulau Penang, Malaysia. Holotype (adult female; slide MY.240.01) and seven paratypes (5 females, 2 juveniles; slides MY.240.01-04) deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University; two paratypes (2 females; slide MY.240.05) deposited in the Department of Zoology, Comenius University in Bratislava; one paratype (1 female; slide MY.240.06) deposited in the Natural History Museum of Denmark, University of Copenhagen; two paratypes (2 females; slide MY.240.07) deposited in the Department of Animal Biology, University of Catania; three paratypes (2 females, one larva; slides MY.241.02, MY.242.02) deposited in the Raffles Museum of Biodiversity Research, National University of Singapore.

Etymology.

The name refers to the currently identified geographic range of the new species that encompasses Asia and Australia. Adjective in the nominative singular.

Adults.

Body pink, pearly opalescent; eyes absent or not visible after mounting in Hoyer’s medium. Primary and secondary clavae small and conical. Cirri interni and externi with poorly-developed cirrophores. Cirri A of typical length for Bryodelphax , i.e. reaching around 25% of the total body length. All dorsal plates with barely-discernible intra-cuticular pillars (better visible under a 1000 × magnification), the centro-posterior portion of the caudal (terminal) plate has evident, largest pillars (Fig. 2A View Figure 2 ). Dark epicuticular granules absent (Figs 3 View Figure 3 ; 4A, B View Figure 4 ), but lateral margins of all dorsal plates and internal margins of facets constituting the scapular plate distinctly thicker and, consequently, darker (Fig. 2A View Figure 2 ). Pores large and easily detectable (Figs 2A View Figure 2 , 3A, B View Figure 3 , 4A, B View Figure 4 ). Pores distributed unevenly, with the largest number present on the antero-central portion of the scapular plate (17-40 pores/100 μm 2, x̅ = 29, N = 16, Fig. 4A View Figure 4 ) and the central portion of the caudal plate (7-43 pores/100 μm 2, x̅ = 31, N = 16, Fig. 4B View Figure 4 ); other plates more variable in terms of pore density, which is always lower than in the aforementioned elements of the armour (0-26 pores/100 μm 2, x̅ = 14, N = 16, Fig. 2A View Figure 2 ). Scapular plate gently faceted by transverse cuticular extensions (Figs 3A View Figure 3 , 4A View Figure 4 ), with deep sutures separating lateral portions from the central faceted part, extending from the base of cirrophore A to the posterior margin of the plate (Fig. 2A View Figure 2 ). Paired plates divided into two roughly equal anterior and posterior parts by a transverse stripe (Figs 2A View Figure 2 , 3A, B View Figure 3 ). Caudal (terminal) plate with poorly developed sutures, not visible under PCM (Fig. 2A View Figure 2 ), but present and visible under SEM (Figs 3A, B View Figure 3 , 4B View Figure 4 ). Median plate 1 subdivided into anterior narrow portion with dark posterior edge and posterior pentagonal portion with transverse suture (Figs 2A View Figure 2 , 3A View Figure 3 ). Median plate 2 is the largest amongst median plates, with well-developed anterior pentagonal portion and poorly sclerotised posterior portion (Figs 2A View Figure 2 , 3A View Figure 3 ). Median plate 3 with only the anterior portion fully developed, the posterior portion triangular and rounded (Figs 2A View Figure 2 , 3A View Figure 3 ). Supplementary lateral platelets present at the level of median plates (three pairs of platelets on each body side: a pair between the scapular plate and the first pair of the segmental plates, a pair between the paired plates and a pair between the second pair of segmental plates and the caudal plate; Fig. 2A View Figure 2 ).

Venter with seven rows of faint, greyish plates (VII:4-4-2-4-2-2-1), of which two plates of the first, subcephalic row are located in a more ventrolateral position (Figs 2B View Figure 2 , 3C, D View Figure 3 , 10 View Figure 10 ). Under SEM, only the central subcephalic and genital plates are visible as true cuticular thickenings, whereas other plates are visible only as darker areas on the cuticular surface (Fig. 3C, D View Figure 3 ). Leg papillae undetectable under LCM (Fig. 2 View Figure 2 ), but papillae IV visible under SEM (Fig. 3B, C View Figure 3 ). Both pulvini and pedal plates present, the former developed as thin rectangular stripes in the proximal leg portions (Figs 2A View Figure 2 , 3C View Figure 3 ) and the latter - as large swellings in the central leg portions (Figs 2A View Figure 2 , 3C View Figure 3 ). Pedal plate IV toothless, but with a distinct dark margin (Fig. 2A View Figure 2 ). External claws spurless, but internal ones with minute spurs positioned close to the claw bases (Figs 2B View Figure 2 [insert], 4C).

Juveniles.

Body 73-101 μm long in the two found juveniles. Dorsal and ventral plates developed similarly to adults. Scapular plate 12-16 μm long. Claws 3.7-4.8 μm long.

Larvae.

Body 80 μm long in a single found two-clawed specimen. Dorsal and ventral plates developed similarly to adults. Scapular plate 12.7 μm long. Claws 4.0-4.4 μm long.

Eggs.

Up to one egg in exuvia was found.

DNA sequences.

Single 18S rRNA haplotype (MT333468), two 28S rRNA haplotypes (MT333460-1) and single ITS-1 haplotype (MT333477).

Phenotypic differential diagnosis.

Within the weglarskae group, only B. decoratus sp. nov., B. sinensis and B. instabilis have seven plate rows, but B. olszanowskii Kaczmarek et al., 2018 exhibits peculiar ventrolateral plates in the subcephalic row and that is why this taxon is also taken into consideration in the differential diagnosis. Adult females of B. australasiaticus sp. nov. are differentiated from:

B. decoratus sp. nov., by the ventral plate formula (VII:4-4-2-4-2-2-1 in the new species vs. VII:4-2- 2-4-2-2-1 in B. decoratus sp. nov.) and by dorsal plate sculpturing (merged epicuticular ridges surrounding the borders of all dorsal plates in the new species vs. large, dark epicuticular granules in B. decoratus sp. nov.);

B. sinensis, known from Caucasus and China (the record from Spitsbergen (Dastych 1985) represents B. parvuspolaris), by the ventral plate formula (VII:4-4-2-4-2-2-1 in the new species vs. VII:2-2-2-2-2-2-1 in B. sinensis) and the caudal (terminal) plate faceting (invisible under LCM in the new species vs. four facets formed by the raised plate areas between two longitudinal and one transversal sutures in B. sinensis);

B. instabilis, currently considered endemic to the Tatras and northern Slovakia, by the ventral plate formula (VII:4-4-2-4-2-2-1 in the new species vs. VII/IX:(2)-(1)-2/4-2-2/4-2-2-2-1 in B. instabilis), the presence of dentate collar IV (absent in the new species vs. present in B. instabilis), the detectability of papilla IV under LCM (undetectable in the new species vs. detectable in B. instabilis) and by the reproductive mode (parthenogenesis in the new species vs. dioecy in B. instabilis);

B. olszanowskii, reported from the Antarctic, by the ventral plate formula (VII:4-4-2-4-2-2-1 in the new species vs. VIII:4-1-1-2-2-2-2-2 in B. olszanowskii), the presence of dark epicuticular granules (ab sent in the new species vs. present and accumulated on ventral plates in B. olszanowskii) and the detectability of papilla IV under LM (absent in the new species vs. present in B. olszanowskii).

Genotypic differential diagnosis: p -distances between the new species and the remaining Bryodelphax spp., for which DNA sequences are available, were as follows:

18S rRNA: from 0.3% (B. decoratus sp. nov., MT333469-70) to 3.4% (B. cf. parvulus, HM193371);

28S rRNA from 0.5% (Bryodelphax sp. nov. from Celebes, MT333467) to 9.3% (B. cf. parvulus, MT333466);

ITS-1: from 2.6% (B. arenosus, MT346599-600) to 3.3% (B. decoratus sp. nov., MT333478).

Remarks.

Two ventrolateral plates were not drawn in Claxton (2004), which is an unpublished PhD dissertation, thus the species described therein are not valid. However, having ascertained that these structures exist in specimens from Australia, the compared populations from both continents appeared identical in terms of morphology.