Pristina osborni (Walton, 1906)

Schenková, Jana, Pařil, Petr, Petřivalská, Karla & Bojková, Jindřiška, 2010, Aquatic oligochaetes (Annelida: Clitellata) of the Czech Republic: check-list, new records, and ecological remarks, Zootaxa 2676, pp. 29-44 : 38-39

Pristina osborni (Walton, 1906)

Synonyms: Naidium osborni Walton, 1906 ; Naidium minutum Stephenson, 1914 ; Pristinella osborni (Walton, 1906) ; Pristina minuta (Stephenson, 1914)

Records. Labe (Elbe) River, Dĕčín 50°42'34"N / 14°11'44"E, lgt. JK, det. PP (2008); all specimens were immature.

Characteristics of site. The species was found in a single site, in the Labe (Elbe) River approximately 20 km far from the Czech/ German boundary near Dečín (Tetschen). This river is the largest in the Czech Republic (8th Strahler order) and it is extensively used for shipping to the German port of Hamburg. The mean depth of this reach of the river was 2.4 m, the bottom substrate was predominantly sand (45%) and gravel (55%) and water quality is classified according to BOD (biochemical oxygen demand) in the betamesosaprobity ( Table 3 ).

Ecology. Pristina osborni inhabits freshwaters including hyporheic waters and caves ( Giani et al. 2001) and wet soil ( Stout 1958). Its ability to inhabit also semi-terrestrial environments enhances the opportunity for freshwater populations of this species to persist in intermittent wetlands ( Montalto & Marchese 2005). In tropical regions, P. osborni prefers areas with higher calcium content ( Alves et al. 2008). Asexual reproduction occurs most commonly via paratomy (Timm & Veldhijzen van Zanten 2002). The species is not usually abundant within the oligochaete community ( Giani et al. 2001; Alves et al. 2008).

Morphology. The species can be distinguished by the typical shape of its dorsal bifid chaetae, with the teeth diverting in a wide angle and the presence of only one needle and one smooth hair seta in the dorsal bundles. The budding zone begins from XII, and the stomach dilatation begins abruptly in segments VII–VIII. The morphology of the genital organs was described in detail by Erséus and Grimm (1998).

Distribution. Pristina osborni has a cosmopolitan distribution (Timm & Veldhijzen van Zanten 2002), and is absent only in the eastern Palaearctic region ( Timm & Giani 2004). European records are limited to southern and western countries ( Portugal, Spain, Italy, France, The Netherlands, and Germany; Timm & Giani 2004). The Labe (Elbe) River, which flows through north-eastern Germany to the Baltic Sea, likely serving as a migration corridor for this species—from its original distribution area in western Europe (as well as it was documented for aliens) into the Czech Republic. P. osborni could spread into this reach of the river, probably from a lower part of the watershed via upstream migration or dissemination by shipping. However, downstream dissemination into the Labe River—proven to be an alternative pathway of spreading of epipotamal species ( Pařil et al. 2008)—is rather improbable for P. osborni .

Pristina osborni , Rhyacodrilus subterraneus , Aulodrilus limnobius and A. pigueti sites in the Czech Republic.