Adropion afroglacialis Zawierucha & Gąsiorek & Buda & Uetake & Janko & Fontaneto 2018, sp. nov.

Adropion afroglacialis sp. nov. Zawierucha, Gąsiorek & Buda

Material. Holotype (slide U/8) and paratypes including 35 individuals, one simplex and two exuviae (slides numbers: U/2–9, U/12–13, U/15–20) are deposited in the Department of Animal Taxonomy and Ecology at Adam Mickiewicz University, Poznań, Poland. Five paratypes (slides UG.007.01 [U/1] and UG.007.02[U/14], and three paratypes mounted on a SEM stub) are deposited in the Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland.

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

Etymology. The name afroglacialis means “occurring on an African glacier” and refers to the ecosystem where the new species was found.

Description. Body colourless or whitish in vivo as well as in slide mounts (Fig. 2A). Cuticle covered with faint irregular granulation (granules forming small dots), more visible on dorsal side and legs, sometimes poorly visible (Figs. 2B–E), for details see Remarks. Eyes absent in mounted specimens (Figs. 2A, 3A–B). Oral cavity armature not visible under PCM (Figs. 3A–B). Stylet furcae of the Hypsibius - type, unmodified (Figs. 3A–B). Drop-like thickening absent at the junction between the buccal and the pharyngeal tube (Figs. 2A, 3A–B). Annulation of the pharyngeal tube clearly visible in DIC (Fig. 3A) as a single narrow annuli (Fig. 3D). Pharynx with three double rows of macroplacoids, microplacoid and septulum (Figs. 3A–C). The apophyses clearly separated from the 1 st macroplacoids. All macroplacoids clearly separated. Macroplacoid length sequence 2<1<3 (however in five specimens out of twenty four the first macroplacoid is shorter than the second—the difference ranges are 0.1–0.2 µm); macroplacoids bar-shaped, arranged in parallel. All macroplacoids without constrictions (Figs. 3A–C). Microplacoids in the form of small round granules. Elongated septulum present (Figs. 3A–C). Claws of the Hypsibius type, with widened bases and with obvious accessory points on the primary branches (Figs. 4A–E). On the primary branch, at the border between accessory points and primary claw branch, a thick line is visible along entire branch length. Internal and anterior claws usually with two septa dividing the claw into the basal portion, the secondary branch, and the primary branch (Fig. 4C). Claws with poorly visible pseudolunulae (Figs. 4A–D, arrowheads). Bases of all claws smooth. Cuticular bars absent.

......continued on the next page Remarks and differential diagnosis. Granulation is poorly visible or not visible on some individuals, completely undistinguishable in SEM. Granulation is invisible in SEM, but is visible in both PCM and DIC, indicating that it may be comprised of depressions (fossae) covered with cuticle. On the holotype, granulation is visible only in some areas on the dorsal side. Thus, observation of cuticle should be done carefully. In five specimens, the first macroplacoid is shorter than the second; the difference ranges between 0.1–0.2 µm. Currently, the genus Adropion consist of twenty species (Degma et al. 2009–2017), but from a molecular point of view the genus appears polyphyletic and potentially with cryptic diversity (Bertolani et al. 2014). It is first report of the genus Adropion from Uganda (McInnes et al. 2017).

Apart from the peculiar granulation on cuticle, by having three macroplacoids, microplacoid and septulum in the pharynx, the new species is most similar to the following Adropion species: A. gordonense (Pilato, Claxton & Horning, 1991), A. greveni (Dastych, 1984), A. linzhiensis (Li, 2007), and A. onorei (Pilato, Binda, Napolitano & Moncada, 2002), but it specifically differs from:

- A. gordonense by clearly smaller pharyngeal apophyses (compare: Fig. 1b in Pilato et al. 1991), and absence of thickened bars under internal claws I–III.

- A. greveni by absence of long bars under internal claws I–III, the absence of spines under the claws, and much shorter macroplacoid row and all macroplacoids (macroplacoid row length 7.3–11.4 µm in A. afroglacialis sp. nov. vs 18–24 µm in A. greveni).

- A. linzhiensis by having a less elongated body (compare: Figs. 6 –7 in Li (2007)), a different macroplacoid length sequence (2<1<3 in the new species vs. 1<2<3 in A. linzhiensis), relatively shorter macroplacoid row (36.5–50 % in A. afroglacialis sp. nov. vs 50–57.1 % in A. linzhiensis), and relatively shorter claws I–IV (external claw secondary branches 15.0–22.6 %, internal + anterior claw primary branches 11.4–25.7 %, and internal claw secondary branches 11.6–21.4 % in A. afroglacialis sp. nov. vs 25.0–37.5 %, 25.0–37.5 %, and 22.6–37.3 % in A. linzhiensis, respectively).

- A. onorei by absence of bars under internal claws I–III, and absence of spines under posterior claws IV, the stylet supports inserted more anteriorly on the buccal tube (54.5–63.5 % in A. afroglacialis sp. nov. vs 64.2– 65.3 % in A. onorei), much shorter macroplacoid row (7.3–11.4 µm [36.5–50 %] in A. afroglacialis sp. nov. vs 14.9–17.7 µm [78.8–84.3 %] in A. onorei).