Olisthanellinella rotundula Reisinger, 1924

Houben, Albrecht M., Monnens, Marlies, Proesmans, Willem & Artois, Tom J., 2022, Limnoterrestrial ‘ Typhloplanidae’ (Rhabdocoela, Platyhelminthes), with the description of four new species and a new genus, European Journal of Taxonomy 798, pp. 70-102 : 94

Olisthanellinella rotundula Reisinger, 1924

Fig. 9

Material examined

AUSTRIA • 3 specs, studied alive, one of which sagittally sectioned and one of which horizontally sectioned; Graz, Kanzelkügel ; 47°06′49″ N, 15°23′11″ E; 26 Aug. 2011; A.M. Houben and W. Proesmans leg.; forest soil; XIV.2.49–XIV.2.50; HU.

Description and discussion

The body length of the studied specimens is about 0.8 mm. Habitus and internal organisation correspond to the original description ( Reisinger 1924). The most typical characteristics of this monospecific genus are: adenal rhabdites ( Fig. 9A : ar) occurring only in rostral tracks; dermal rhabdites absent; a bipartite bursa ( Fig. 9A–D : bu) with a muscular, sclerotised stalk ( Fig. 9B, D : bs) and a thin-walled proximal part; and the copulatory organ ( Fig. 9A : co) with a muscular ejaculatory duct ( Fig. 9B, D : de) and a large seminal receptacle ( Fig. 9C : rs) that opens into the oviduct ( Fig. 9C : od). The opening of the vitelloduct was never clearly observed. Neither of our sectioned specimens clearly show both male and female reproductive structures. Therefore, and because of (for now) intraspecific differences (see below), we refrain from designating a neotype.

Specimens described by Luther (1963) seem to be somewhat different from those described by Reisinger (1924) since they possess an egg-shaped bursa instead of a bipartite bursa and their oviduct functions as the seminal receptacle. Moreover, the specimens collected by Armonies (1987) were identified based on Luther’s (1963) description.As probably is the case for all protoplanellins, a thorough molecular analysis would help to solve which features are apomorphic/diagnostic for the taxon and help identification and delimitation of species. Therefore, we provisionally keep all within Olisthanellinella rotundula.

Previously known distribution

In the vicinity of Graz, Austria in moist forest soils ( Reisinger 1924); North-East Alps, Austria in moist forest soil ( An der Lan & Franz 1954); Oldenburg, Germany in humus of oak leaves (Reisinger in Luther 1963); Helsingfors, Finland in moss ( Luther 1963); Sylt, Germany, in salt meadows ( Armonies 1987).

Figures

Fig. 9. Olisthanellinella rotundula Reisinger, 1924. A. Internal organisation of a live specimen. B. Organisation of the genital system of a live specimen. C. Reconstruction of female reproductive organs based on horizontal sections. D. Reconstruction of male reproductive organs based on sagittal sections.