Xerobiotus euxinus, Pilato, 2011

Vincenzi, Joel, Cesari, Michele, Kaczmarek, Łukasz, Roszkowska, Milena, Mioduchowska, Monika, Rebecchi, Lorena & Guideưi, Yevgen Kiosya and Roberto, 2024, The xerophilic genera Xerobiotus and Pseudohexapodibius (Macrobiotidae; Tardigrada): biodiversity, biogeography and phylogeny, Zoological Journal of the Linnean Society 200 (1), pp. 111-141 : 130

Xerobiotus euxinus

According to our observations, the following characters not reported in the original description ( Pilato et al. 2011) should be added to the species description: presence of semilunar thickening at the base of the claws of the first three pairs of legs (visible with LM; Fig. 4D–G ); presence of small indentations on the margin of the lunules of the hind legs ( Fig. 4I, J ); a cuticular thickening in the shape of a ring with irregular margins present under the claw base (and connected with it) of the hind legs ( Fig. 4H, I and K ); and presence of very small dorsolateral cuticular pores (visible only with SEM; Fig. 5F ). It is a bisexual species.

Asser the discovery of this species, two other species of the genus were described, and some others are redescribed or described here. Because of this, the description of the species is no longer sufficient to distinguish this species clearly from congenerics. Moreover, the eggs of X. euxinus type population are unknown, and the new characters reported above should be added to the description. For these reasons, we think it is opportune to redescribe this species in the future.

Figures

Figure 4. Xerobiotus euxinus. A, buccal armature (dorsal view) (Northern Apennines population). B, buccal armature (ventral view) (Northern Apennines population).C, anterior portion of the body.D, claw I of the holotype.E, claw III (Northern Apennines population). F, claw II (Northern Apennines population). G, claw II (Georgian population).H, claw IV of holotype. I, claw IV (Ukrainian population).J, claw IV (Northern Apennines population).K, claw IV (Central Apennines population). L, egg processes (Northern Apennines population). M, terminal discs of egg processes (Northern Apennines population). N, gonad with sperm (*) in a male (stained with Orcein) (Georgian population).Key: white indented arrowheads, swellings of the furbelow-like structure; black arrows, semilunar thickenings; black arrowheads, thickenings under claw base; white arrows, lunules. A–K, PhC; L–M, DIC. Scale bars:10 µm in A, B, D–N; 20 µm in C.

Figure 5. Xerobiotus euxinus. A, animal in toto (Georgian population). B, mouth opening (Northern Apennines population). C, leg II, with the swelling of the furbelow-like structure (Northern Apennines population). D, claws II with ventral plate (arrowheads) (Georgian population). E, claws IV (Georgian population). F, posterior portion of the dorsal cuticle, with a pore, microdigitations and small granules (arrowhead) (Georgian population). G, egg surface and processes (Georgian population). A–G, SEM. Scale bars: 10 µm in A, C; 5 µm in B, D, E, G; 3 µm in F.