Carcharodopharynx arcanus (Reisinger, 1924) Poche, 1926

(Figs. 2 A–C)

Syn. Acanthopharynx arcanus Reisinger, 1924

New localities. Oberau, Bavaria, Germany (47°33’33”N; 11°06’57”E) in forest litter (13 July 2011). Kreuzberg, Weyer, Austria (47°51’36”N; 14°39’09”E) in humid mosses and leafy humus (29 August 2011).

Known distribution. Graz, Austria, widespread in forest soils (Reisinger, 1924); Pallanza, Italy in forest soils (Steinböck 1951); Tvärminne, Finland in mosses (Luther 1963); Sierra de Carzola and Finca Caleron, Spain (An der Lan 1963); Schlitz, Germany, in beech litter near helocrene springs (Schwank 1981); Carpathians, Poland (Kolasa in Schwank 1981)

Material. Three adult specimens studied alive. One sagittally-sectioned specimen from Oberau, Bavaria, Germany designated neotype (SMNH, no. 8760).

Descriptive notes. Animals about 0.8–1.5 mm long and usually very dark because of gut contents. The body shape is rounded anteriorly and ends in a small tail with small eosinophilic tail glands. Small, closely-packedtogether dermal rhabdites are present all over the epidermis, adenal rhabdites are lacking. Two separate protonephridiopores (Fig. 2 A: pp) open ventrally at ±35 % of the body. The mouth (Fig. 2 A, 2C: m) has a subterminal position and opens into the prepharyngeal cavity, which is surrounded with longitudinal muscles and is lined with a very thin epithelium. The 75-µm-long pharynx (Fig. 2 C) is situated at ±25 % and is directed forwards. It is divided into an anterior and a posterior part. The anterior part protrudes into the prepharyngeal cavity and contains many longitudinal muscles (Fig. 2 C: lm). The distal wall of this anterior part is provided with many small spines (Fig. 2 C: ss), while its proximal wall is lined by a thin epithelium. The posterior part is a typical pharynx rosulatus, with the musculature consisting of outer circular muscles (Fig. 2 C: ocm), which also are found in the anterior part, outer longitudinal muscles (Fig. 2 C: olm), radial muscles (Fig. 2 C: rm), inner circular muscles (Fig. 2 C: icm) and inner longitudinal muscles (Fig. 2 C: ilm). The pharyngeal glands (Fig. 2 C: pg) have intra- as well as extracapsular cell bodies. Live animals often retract and protrude the spiny anterior part, so that the shape of this part can vary from a short and broad trunk to a very elongate and narrow channel.

The gonopore (Fig. 2 A, 2B: gp) is situated at ±50 % of the body and is connected with the common genital atrium by means of a long gonoduct (Fig. 2 B: gd). Both are surrounded by circular muscles, which increase in strength towards the genital atrium. The genital atrium is lined with a high eosinophilic epithelium.

The small, round testes (Fig. 2 A: t) lie at ±60 % of the body and are situated ventrally from the vitellaria (Fig. 2 A: vi). The paired vasa deferentia (Fig. 2 B: vde) enter the copulatory organ separately at its proximal end. Two inner spiral muscle layers and an outer longitudinal layer surround this 57-µm-long, oval copulatory bulb, which is filled with prostate secretion produced by large, eosinophilic, extracapsular prostate glands (Fig. 2 B: gg). It contains a large seminal vesicle (Fig. 2 B: vs) in its proximal part. The unarmed cirrus (Fig. 2 B: cir) is found in the distal third of the copulatory organ. The male duct (Fig. 2 B: md) is surrounded by circular muscles and is lined by a low epithelium.

Paired vitellaria (Fig. 2 A: vi) extend from the posterior end to ±40 % of the body. They are located dorsally, but extend to the ventral side at their anterior end. Paired vitelloducts unite to form a single vitelloduct (Fig. 2 B: vd), which fuses with a short oviduct (Fig. 2 B: od) to form the female duct (Fig. 2 B: fd). The latter narrows distally and its surrounding circular muscles increase in strength towards the genital atrium.

Discussion. See the discussion following the descriptive notes and remarks on C. arcanus .