Diphascon greveni Dastych, 1984

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 : 5

publication ID	https://doi.org/10.1093/zoolinnean/zlad151
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DOI	https://doi.org/10.5281/zenodo.14536911
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scientific name	Diphascon greveni Dastych, 1984
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Diphascon greveni Dastych, 1984 View in CoL

Hypsibius (D.) scoticus ; South Georgia, South Orkney Islands, South Shetland Islands, Marguerite Bay, Alexander Island; Jennings (1976a, b).

Diphascon greveni View in CoL ; King George Island; Dastych (1984).

Diphascon greveni ; King George Island; Tumanov and Tsvetkova (2023).

Material examined: 128 individuals in total (for details, see Supporting Information, Table S1 View Table 1 ).

Amended description: Large, body can exceed 500 μm ( Table 1 View Table 1 ), with a poorly demarcated, blunt cephalic region and a large interval between legs III and IV ( Fig. 5A View Figure 5 ). Lacking a DABT ( Figs 5B View Figure 5 , 6A View Figure 6 ). The pharyngeal annulation simple in both PCM ( Fig. 5B View Figure 5 ) and SEM ( Fig. 6A, D, E View Figure 6 ), but occasional annular bifurcations present ( Fig. 6D, E View Figure 6 ). One band of teeth in the OCA ( Fig. 6B View Figure 6 ), not detectable in PCM ( Fig. 5B View Figure 5 ). Lateral porous areas in the walls of the buccal crown reduced and partly hidden under the apophyses for the insertion of stylet muscles (AISMs) ( Fig. 6C View Figure 6 ). Furca of the Hypsibius type ( Fig. 6F View Figure 6 ). Large pharyngeal apophyses. Three bar-shaped macroplacoids occasionally merged, but microplacoid and septulum always separate ( Fig. 6G View Figure 6 ). Claws of the Hypsibius type. Claw morphology ( Figs 7 View Figure 7 , 8 View Figure 8 ) largely conforming to that described by Dastych (1984), but in rare cases the posterior claw bases were not broadened (almost all occurring asymmetrically on one leg, Fig. 7D View Figure 7 ) with respect to external claws I–III ( Fig. 7A–C View Figure 7 ). Some posterior claw bases so enlarged as to take almost a conical shape ( Fig. 7E View Figure 7 ). Claws of juveniles (probably hatchlings) delicate and with less well-developed indentation ( Fig. 7F View Figure 7 ). Rarely, this indentation may also be developed on the internal claw bases ( Fig. 8B View Figure 8 ). Internal bars visible under SEM as longitudinal thickenings adjacent to the internal claw bases ( Fig. 8A View Figure 8 ). Accessory points on claws IV more conspicuous and more widely divergent from the primary branches than on claws I–III (compare Fig. 8A, B View Figure 8 with C, D).

References

Dastych H. The Tardigrada from Antarctica with descriptions of several new species. Acta Zoologica Cracoviensia 1984; 27: 377 - 436.

Jennings PG. Tardigrada from the Antarctic Peninsula and Scotia Ridge region. British Antarctic Survey Bulletin 1976 a; 44: 77 - 95.

Tumanov DV, Tsvetkova AY. Some have drops and some do not, but can we rely on that? Re-investigation of Diphascon tenue (Tardigrada: Eutardigrada) with discussion of the phylogeny and taxonomy of the superfamily Hypsibioidea. Zoosystematica Rossica 2023; 32: 50 - 74. https: // doi. org / 10.31610 / zsr / 2023.32.1.50

Figures

Figure 5. General morphology of Diphascon greveni Dastych, 1984 (PCM, topotypes): A, specimen in toto (ventral view); B, buccopharyngeal apparatus in toto. Scale bars are in micrometres.

Figure 6. Detailed morphology of buccopharyngeal apparatus of Diphascon greveni (SEM, topotypes): A, in toto; B, OCA; C, AISM in lateral view; D, annulation of pharyngeal tube; E, annuli in close-up; F, furca; G, pharynx. Scale bars are in micrometres.

Figure 7. Claws of Diphascon greveni (PCM, topotypes): A, claws I; B, claws II; C, claws III; D, E, claws IV; F, claws III of a juvenile. Black arrowheads indicate internal bars. Scale bars: 10 μm.

Figure 8. Claws of Diphascon greveni (SEM, topotypes):A, claws I; B, claws III; C, D, claws IV. Black arrowheads indicate internal bars; white asterisks indicate internal pulvini. Scale bars: 10 μm.