Itaquascon serratulum Gąsiorek & Michalczyk, 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 : 22-24

Itaquascon serratulum Gąsiorek & Michalczyk sp. nov.

Itaquascon sp. nov.; Uganda; Gąsiorek and Michalczyk (2020). ZooBank registration: urn:lsid:zoobank.org:act:AD578316-D601-4F5A-B00D-F37B94809FE9

Material examined: 50 individuals in total (for details, see Supporting Information, Table S1 ).

Type material: Holotype and 26 paratypes (slides UG.004.01– 11 ) from Uganda, Kibaale District (0°54 ʹ 55″N, 31°4 ʹ 44″E; 1188 m a.s.l.), moss from tree trunk, 21 October 2014, Przybyłowicz coll., are deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków.

Description: Body medium-sized to large ( Table 5 ), elongate and white, distinctly tapering in its anterior part ( Fig. 15A ). Cuticle smooth,without pores, wrinkling or granulation.Cribriform areas not visible under PCM. Legs very short and plump, legs IV barely distinguishable from the posterior body end ( Fig. 15A ). Eyes absent in live animals. Buccopharyngeal apparatus of the Itaquascon type, short (i.e. the pharynx reaches the level of the first pair of legs, Fig. 15 ). The OCA not visible under PCM ( Fig.15B ). Furcae of the Itaquascon type, with large and divergent apices. Stylet supports S-shaped, large and robust. Buccal-to-buccopharyngeal tube length ratio, pbf = 43–48% (46% on average). Pharyngeal apophyses absent ( Fig. 15B ). Pharynx oval and narrow, devoid of cuticular ridges (i.e. reduced macroplacoids).

Claws of the Hypsibius type, large and robust, with slightly protruding accessory points ( Fig. 16 ). External and posterior claw bases long and rectangular in shape. External claw bases visibly concave. Anterior and posterior claw bases with weak/slight indentation ( Fig. 16B, D ). Secondary claw branches short and bluntly terminated ( Fig. 16 ). Pseudolunulae absent. Internal cuticular bars I–III present, long and thick, with those on the first pair of legs occasionally less evident ( Figs 15A , 16A ).

Remarks: Claw bases with aberrant spines were found in only one specimen ( Fig. 16C, D ). Some itaquasconin taxa were described on the basis of single specimens (e.g. Platicrista itaquasconoide Durante Pasa & Maucci, 1975 ), and the spines on their claw bases were used in delineating them. Therefore, we would like to note that this trait seems vague and might not be an appropriate criterion for species delineation.

Etymology: From the Latin serratum = indented, which highlights the peculiar character of the new species, i.e. claw IV bases with small teeth. An adjective in nominative singular.

Differential diagnosis: The only other species of Itaquascon having indented claw bases is I. mongolicus . However, I. serratulum differs from it in having the indentation only on claw IV bases (all claw bases indented in I. mongolicus ). The general claw morphology is also different (more slender claws in I. serratulum vs. stout, massive claws in I. mongolicus ; compare Fig. 16A, B with Fig. 17A ), and the buccal tube constitutes less than half of the buccopharyngeal apparatus (pbf <50% in I. serratulum vs. pbf> 50% in I. mongolicus ). Following Pilato and Lisi (2009), we use pbf = 50% as the main discriminative criterion in the newly proposed key (see below). Therefore, it is only necessary to compare I. serratulum with the other member of the genus having pbf <50% and cuticular bars on legs I–III, namely Itaquascon biserovi Pilato et al., 1999 . The latter taxon, described from Central Africa, has all claws with smooth bases and S-shaped stylet supports inserted directly at the boundary between the buccal and pharyngeal tubes (pt = 100%), whereas in I. serratulum stylet supports are positioned in a more anterior position, and never on the border between these structures (pt = 89.9–98.0%).

Figures

Figure 15. Itaquascon serratulum sp. nov. (PCM): A, holotype habitus in ventral view; B, buccopharyngeal apparatus in toto (paratype). Scale bars are in micrometres.

Figure 16. Claws of Itaquascon serratulum sp. nov. (paratypes): A, claws II (PCM; black arrowhead indicates an internal bar); B, claws IV (PCM); C, claws II (SEM); D, claws IV (SEM). Note aberrant spurs on the basal portions of external and posterior claws.Scale bars: 10 μm.

Figure 17. Claws of Itaquascon spp. (PCM, paratypes): A, claws IV of Itaquascon mongolicus Kaczmarek et al., 2002 (note serrated margin of the anterior claw basis); B, claws II of Itaquascon placophorum Maucci, 1973 (black arrowhead indicates internal bar). Scale bars: 10 μm.