Platicrista nivea Gąsiorek, 2024

Gąsiorek, Piotr, Blagden, Brian, Morek, Witold & Michalczyk, Łukasz, 2024, What is a ‘ strong’ synapomorphy? Redescriptions of Murray’s type species and descriptions of new taxa challenge the systematics of Hypsibiidae (Eutardigrada: Parachela), Zoological Journal of the Linnean Society 202 (1), pp. 1-63 : 32-33

Platicrista nivea Gąsiorek sp. nov.

ZooBank registration: urn:lsid:zoobank.org:act:3988853F-DDB5-4217-8293-701E05D226BD

Material examined: Four individuals in total (for details, see Supporting Information, Table S1 ).

Type material: Holotype (slide TW.006.07) from Taiwan, Snow Mountain (Xueshan), East Peak (24°23 ʹ 18″N, 121°15 ʹ 39″E; 3200 m a.s.l.), moss from rock in alpine grassland, 10 February 2020, Dreyer coll., and two paratypes (slides TW.008.14 and TW.008.15 ) from Taiwan, Snow Mountain (Xueshan), North Peak (24°23 ʹ 51″N, 121°14 ʹ 04″E; 3700 m a.s.l.), moss from rock in alpine grassland, 10 February 2020, Dreyer coll., are deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków.

Description: Body massive ( Table 10 ), white and elongated, with blunt cephalic part ( Fig. 28 ). Cuticle without pores, but with both irregular wrinkling and distinct, minute granulation in the caudal body part ( Fig. 29 ). Cribriform areas identifiable under PCM ( Fig. 29A ). Legs short and plump; legs IV poorly delimited from the trunk ( Fig. 28 ). Eyes absent in unmounted animals. Buccopharyngeal apparatus of the Platicrista type ( Fig. 30A ): OCA not visible under PCM; annulation of the pharyngeal tube simple (single bifurcations visible) and comprising tightly merged annuli; stylet supports embedded at the border between buccal and pharyngeal tube; furcae of the Platicrista type; pharyngeal apophyses absent; pharynx oval, with two bar-like macroplacoids: the first much shorter than the second one (1 <2).

Claws of the Hypsibius type, large and slender ( Figs 28 , 30B ). Accessory points divergent from all claw branches. Indentation of claw bases absent. Septa between claw parts absent. Pseudolunulae present, but clearly discernible only under anterior claws ( Fig. 28 ). Cuticular bars absent.

Etymology: From the Latin niveus = snowy, referring to the type locality in Snow Mountain (Taiwan). An adjective in nominative singular.

Differential diagnosis: There are two congeneric species with strong dorsal sculpturing: P. brunsoni and P. cheleusis . Platicrista nivea can be differentiated from them based on differences in the type of sculpturing (minute granules restricted to the caudal part in P. nivea vs. polygonal tubercles covering the entire dorsum in both species) and:

• for P. brunsoni , the presence of internal bars II–III (absent in P. nivea vs. present in P. brunsoni );

• for P. cheleusis , the presence of internal and median bars I–III and posterior bars (absent in P. nivea vs. present in P. cheleusis ).

Platicrista angustata and P. carpathica have a similar-looking dorsocaudal cuticle; see above for differentiation.

Figures

Figure 28. General morphology of Platicrista nivea sp. nov. (holotype in ventral view, PCM). Scale bar is in micrometres.

Figure 29. Caudal sculpturing of Platicrista nivea sp. nov. (paratypes, PCM). Scale bars: 20 μm.

Figure 30. Detailed morphology of Platicrista nivea sp. nov. (PCM): A, buccopharyngeal apparatus in toto (paratype); B, claws II (holotype). Scale bars are in micrometres.