Carcharodopharynx arcanus ( Reisinger, 1924 ) Poche, 1926

Houben, Albrecht M., Schwank, Peter, Proesmans, Willem, Bert, Wim & Artois, Tom J., 2015, Notes on some enigmatic taxa of limnoterrestrial rhabdocoels, with the description of two new species, Zootaxa 4040 (1), pp. 83-92 : 88

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 .

Figures

FIGURE 2. Carcharodopharynx arcanus: (A) Habitus of live animal from Oberau. (B) Reconstruction from sagittal sections of the reproductive organs (SMNH, no. 8760). (C) Reconstruction from sagittal sections of the pharynx (SMNH, no. 8760); C. schlitzensis n. sp.: (D) Habitus of live animal. (E) Free swimming animal. (F) Live animal. (G) Male copulatory organ. D – E, after Schwank (1981).