Adenoplea perigraptopera Reisinger, 1924

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 : 87

Adenoplea perigraptopera Reisinger, 1924

( Fig. 1 C)

New localities. Vyle-et-Tharoul, Liège, Belgium, moss collected along the Rue Pont de Vyle (50°27’06”N; 5°16’46”E) (18 August 2008).

Known distribution. In the vicinity of Graz, Austria, common in forest soil ( Reisinger 1924). Schlitz, Hessen, Germany in moss in helocrene springs ( Schwank 1981)

Material. One horizontally-sectioned specimen from Belgium, designated neotype ( SMNH, no. 8759).

Descriptive notes and remarks. Habitus and internal organization as described by ( Reisinger 1924). As Reisinger (1924) and Schwank (1981) only studied live animals, the study of our sectioned specimens reveals many additional details.

Animal about 2 mm long, slender, 5–6 times as long as wide. Rostrally, two groups of adenal rhabdite glands are present. They extend from just caudally from the brain to the anterior body end. A large, weakly-stained gland is present just behind the brain. The protonephridiopores open in the mouth. The rosulate pharynx lies just behind the centre of the body.

The gonopore ( Fig. 1 C: gp) is situated at about 80 % of the body and is connected to the genital atrium ( Fig. 1 C: ga). This genital atrium is lined with a high, nucleated epithelium and is surrounded by muscles (orientation not clearly observed).

The large, oval testes are situated rostrally from the pharynx. The paired vasa deferentia ( Fig. 1 C: vde) enter the copulatory organ separately, although very close to each other. The 77-µm-long copulatory organ proximally contains a large seminal vesicle ( Fig. 1 C: vs). In its distal part it contains the prostate secretion and a slightlysclerotized ejaculatory duct ( Fig. 1 C: de). The extracapsular prostate glands enter the bulbus laterally and consist of coarse-grained eosinophilic ( Fig. 1 C: gg1) and basophilic ( Fig. 1 C: gg2) glands. A very short male duct connects the copulatory organ with the genital atrium. An elongated, narrow muscular bursa ( Fig. 1 C: bu) is directly connected with the genital atrium. This bursa shows several bends and is surrounded with circular muscles over its distal 90 %. These muscles are extremely thick and almost circular proximally, forming a number of thick sphincters, whereas the proximal 10 % of the bursa is surrounded with much thinner and spirally-running muscles. A loose matrix embeds the entire bursa.

The vitellaria are not entirely developed in the sectioned specimens, and a vitelloduct was not observed. The genital atrium receives a short female duct, which in its turn proximally receives a long oviduct ( Fig. 1 C: od), a seminal receptacle ( Fig. 1 C: rs) and the secretion of the coarse-grained female glands ( Fig. 1 C: fg). Longitudinal muscles surround both oviduct and seminal receptacle.

Discussion. When introducing the genus in order to place five new species, Reisinger (1924) recognized two basic types of copulatory organ within Adenoplea . A copulatory organ with a cirrus divided into two parts, with a separate exit for sperm and prostate secretion, and provided with small sclerotic spines he called the armata-type. Such a copulatory organ is found in A. armata Reisinger, 1924 , A. paraproxenetes Reisinger, 1924 and A. nanus Sayre & Wergin, 1994 . In the inermis-type copulatory organ the prostate secretion and the sperm are drained jointly, and the cirrus does not have spines. Apart from the three species treated in this contribution ( A. reisingeri n.sp., A. meridionalis and A. perigraptopera ), three other species have a copulatory organ of the inermis type: A. inermis Reisinger, 1924 , A. pinguis Reisinger, 1924 and A. weyeri An der Lan, 1955. Only in A. reisingeri and A. inermis is a seminal receptacle lacking. A. reisingeri can easily be distinguished from A. inermis by the fact that it has a large copulatory bursa, which is lacking in A. inermis . Moreover, A. reisingeri differs from all other species with a copulatory organ of the inermis-type by the oval shape of its bursa, whereas it is typically much more elongated in A. perigraptopera and A. weyeri , even longer than the copulatory bulb. Additionally, the bursa of A. weyeri contains many "crypts", which are not found in any other species of Adenoplea (see An der Lan 1955). In A. pinguis the bursa is strongly sclerotized, whereas it is extremely small in A. meridionalis (see Kolasa 1981; Reisinger 1924). These differences make it clear that A. reisingeri n. sp. is indeed best treated as a separate species that is quite distinguishable from A. meridionalis and A. perigraptopera .