Carcharodopharynx schlitzensis Houben, Schwank and Artois

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 : 88-90

Carcharodopharynx schlitzensis Houben, Schwank and Artois n. sp.

( Figs. 2 D–G)

Carcharodopharynx arcanus in Schwank (1981)

Locality. Schlitz, Hessen, Germany (18 & 23 May 1973), in beech litter near helocrene springs ( Schwank 1981). Material. Fifteen photographs (18 May 1978), five of which show the habitus, seven show the male copulatory organ and three show the pharynx. One photograph designated holotype (SMNH no. 8761) One whole mount, from Eisenbach, Schlitz, Hessen, Germany (23 May 1979).

A B vg cir ga

gp

t vde gg gp

gd

C ocm olm icm m pc ss lm gg

cr cir

rs vi t Etymology. The epithet refers to the German city Schlitz, where this species was collected.

Description. The material on which this description is based was already studied and commented upon by Schwank (1981), however, at that time identified as C. arcanus . Animals about 0.8 mm long. Head provided with four strong sensory cilia and two ciliated pits ( Fig. 2 D: cp). Pharynx ( Figs. 2 D–F: ph) and protonephridiopores ( Fig. 2 D: pp) as in C. arcanus (for a description see Reisinger 1924).

The gonopore ( Fig. 2 D: gp) is situated ventrally at ±50 % of the body. A single genital atrium was observed, which shows an evaginated part at one side: the crypt ( Fig. 2 D: cr).

The testes ( Fig. 2 D, 2F: t) lie caudally and ventrally to the vitellaria ( Fig. 2 D: vi). The paired vasa deferentia ( Fig. 2 D, 2G: vde) enter the copulatory organ separately. This 140-µm-long, slightly S-shaped organ is surrounded by weak muscles and is filled with secretion from extracapsular prostate glands ( Fig. 2 D, 2G: gg). Proximally it contains a 65-µm-long seminal vesicle. The spiny cirrus ( Figs 2 D, 2G: cir) is situated in the distal part of the copulatory organ and is 75 µm long. Proximally it has a very thick, oblique rim, which is 26 µm wide. After ± 20 µm it starts to curve and narrows to 11 µm. Distally from this point, it narrows evenly towards the distal tip, which is only 7 µm broad.

The paired, strongly-developed vitellaria run from just behind the pharynx to just behind the gonopore.

Diagnosis. Species of Carcharodopharynx Poche, 1926 with ciliated pits and a 75-µm-long spiny cirrus.

Discussion. As to habitus and general morphology, C. schlitzensis n. sp. is almost identical to C. arcanus . Typical of both species is the aberrant morphology of the pharynx rosulatus, which has a distal elongated part provided with small spines. Such a construction is unique within Rhabdocoela , and hence Bresslau (1933) erected a new family to accommodate C. arcanus . The most recent phylogenetic analysis of Dalytyphloplanida ( Van Steenkiste et al. 2013), however, shows that Carcharodopharynx is deeply embedded within a clade consisting of freshwater and limnoterrestrial Typhloplanidae , and hence Carcharodopharynx was assigned to Typhloplanidae . Carcharodopharynx schlitzensis can easily be distinguished from C. arcanus by the morphology of the cirrus, which is armed with spines in C. schlitzensis , and by the presence of anterior ciliated pits, which are lacking in C. arcanus . We also found many juvenile specimens of a species of Carcharodopharynx at several other localities: Kordel, Germany (49°49’24”N; 6°38’06”E), one specimen in mosses growing on a wall (24 July 2011), in the vicinity of Graz, Austria (26 August 2011): one specimen in humus of a beech forest on the Hohe Rannach (47°09’53”N; 15°24’50”E) and two specimens in humus at the Rohrerberg (47°07’44”N; 15°24’53”E), Diepenbeek, Belgium (50°55’37”N; 5°23’09”E), one juvenile specimen in moss growing on a concrete bridge (22 May 2012). As anterior ciliated pits are not present, it is improbable that these specimens are C. schlitzensis . However, to make a positive identification, the reproductive organs should be studied, as the possibility exists that still other undescribed species occur in the Palearctic.

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).