Acrochordonoposthia conica Reisinger 1924

Acrochordonoposthia conica Reisinger, 1924

(Figs 2C–D; 3A–G)

Known literature. Acrochordonoposthia conica Reisinger (1924a): 75–77; Steinböck & Reisinger (1931): 22, 33; Steinböck (1932): 312; Papi (1952): 2, 8; Reisinger (1954): 118, 123; An der Lan (1958): 161; Papi (1959): 4–6, figs 5–8; An der Lan (1963): 229, 231; Luther (1963): 17, figs 3 A–B, D–E; Kolasa (1971): 745; Kolasa (1973): 238, 243, figs 10A–D.

New localities. Kreuzberg, Weyer, Austria (47°51’24”N; 14°39’14”E), two specimens in moss growing on dead tree trunk (29 August 2011) (TYPE LOCALITY); Hohe Rannach, Graz, Austria (47°09’53”N; 15°24’50”E), in humus of a beech forest (26 August 2011); Oberau, Bavaria, Germany (47°33’33”N; 11°06’57”E), three specimens in forest litter (13 July 2011); Agoralaan, Diepenbeek, Belgium (50°55’37”N; 05°23’09”E), one specimen in moss growing on a concrete bridge (22 May 2012); Nuropstraat, Voeren, Belgium (50°45’38”N; 05°52’21”E), in moss growing on a tree (2 March 2009).

Known distribution. Widespread in Europe: Austria (Reisinger 1924a; Reisinger 1954 and An der Lan 1963 for detailed locations); humus in the botanical gardens of Pisa, Italy (Papi 1952); Iceland (Reisinger 1954); Långskär and Tvärminne, Finland, in moss (Luther 1963); Pontivy, Bretagne, France and several locations in Germany (Reisinger 1954 and An der Lan 1963); Poznań, Poland, fallen wet leaves (Kolasa 1971); Belsele, East Flanders, Belgium (Van Steenkiste et al. 2013); Godhavn, Greenland, in moss (Steinböck & Reisinger 1931; Steinböck 1932).

Material. Several specimens studied alive. One whole-mounted specimen designated neotype (SMNH Type- 8569). One other whole-mounted specimen from type locality (HU no. VI.2.42), one whole-mounted specimen from Hohe Rannach (HU no. VI.2.43), one sagitally-sectioned specimen from Oberau (HU no. VI.2.44) and two sagitally-sectioned specimens from Voeren (HU nos VI.2.45–VI.2.46).

Remarks. Our observations are in accordance with the data given in the literature cited above (see Known distribution). Animals 0.8–1 mm long. The copulatory organ is 40–52 µm long (average 46 µm; measured on two specimens) and is provided with a conical pouch. This is within the range observed by different authors (Reisinger 1924a: 40–44 µm; Papi 1959: 55 µm; Kolasa 1973: 51–58 µm). Three pairs of large, eosinophilic, coarse-grained prostate glands enter the proximal part of the cirrus. The newly-collected material did not preserve well enough to allow us to measure the length of the cirrus accurately, which probably explains why it is never mentioned in literature. The cirrus shows two bends and its distal two-thirds is covered with small sclerotized warts. A large, slightly sclerotized, sac-shaped bursa containing many vacuoles is connected to the genital atrium by a short duct. The oviduct forms a seminal receptacle. Animals clearly feed on rotifers, as we observed mastaxes in the gut of several specimens.

The specimens from Voeren differ from the above description in that they lack a seminal receptacle, and by the fact that the entire cirrus is covered with spines, instead of only the distal two thirds. These specimens are provisionally identified as A. conica, but might represent a new species.