Hypsibius, Ehrenberg, 1848

Zawierucha, Krzysztof, Gąsiorek, Piotr, Buda, Jakub, Uetake, Jun, Janko, Karel & Fontaneto, Diego, 2018, Tardigrada and Rotifera from moss microhabitats on a disappearing Ugandan glacier, with the description of a new species of water bear, Zootaxa 4392 (2), pp. 311-328 : 319-321

Hypsibius sp.

Material. Four individuals (slides number: U/6, U/10, U/11, and U/13) are deposited in the Department of Animal Taxonomy and Ecology at Adam Mickiewicz University, Poznań, Poland.

Locality. Mount Stanley , Rwenzori Mountains (0°22'31''N, 29°52'40''E; 4790 m asl), Uganda.

Diagnosis. Body transparent/white, eyes present in three of the four specimens mounted in Hoyer’s medium ( Fig. 5A ). Dorsal cuticle sculptured: from head to legs II without delicate thickenings, from legs II to the caudal end of the body thickened, with irregular thickenings that form large wrinkles from legs III to the caudal end ( Figs. 5A–C ). Thickenings increasing in size from the anterior to the posterior part of the body, reaching maximum dimensions between legs III and IV ( Figs. 5A–C ). Ventral cuticle smooth. Buccal apparatus short and rigid ( Fig. 5D ). Teeth in the oral cavity armature absent or not visible under PCM. Pharynx with apophyses and with two rodshaped macroplacoids. Macroplacoid length sequence 2<1. Microplacoid and septulum absent ( Fig. 5D ). Claws of the scabropygus - type, internal claws much smaller and of a different shape than the external claws ( Fig. 5E ). All primary branches with accessory points. Smooth, indistinct pseudolunulae under claws more visible on external claws ( Fig. 4E ). Cuticular bars under claws I–III absent but a small bar is present near the posterior claw IV.

Remarks. The potentially new Hypsibius species is similar to H. scabropygus Cuénot, 1929 , H. macrocalcaratus Beasley, 1988 , H. roanensis Nelson & McGlothlin, 1993, and H. stiliferus Abe, 2004 , but it differs from them by the type of cuticular thickenings and folds on the dorsal side. According to the recently suggested optimal sample size for morphometric ranges in taxonomic traits of tardigrades ( Stec et al. 2016), we decided not to formally describe Hypsibius sp. as a new species based on only four individuals. Moreover, establishing Hypsibius sp. as a new species without re-descriptions of the other hypsibiids in the H. scabropygus group (e.g. Zawierucha et al. 2014) would not make much sense. Currently the genus Hypsibius consists of 42 species (Degma et al. 2009–2017), but from a molecular and morphological point of view it appears polyphyletic and with cryptic diversity ( Dastych et al. 2003; Kiehl et al. 2007).

Figures

FIGURE 4. Adropion afroglacialis sp. nov.: A—claws I, paratype (PCM), B—claws II, paratype (SEM), C—claws IV, paratype (PCM), D—claws IV, paratype (SEM), E—claws IV and cloaca, paratype (SEM). Arrowheads indicate poorly visible pseudolunulae. All scale bars in micrometres.

FIGURE 5. Hypsibius sp.: A—habitus, dorso-ventral projection (PCM), B, C—dorso-caudal cuticle with distinct sculpturing formed by folds and thickenings, D—buccal apparatus (PCM), E—claws III, arrowheads indicate poorly visible pseudolunulae (PCM). All scale bars in micrometres.