Rhyacodrilinae

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 : 39-40

Subfamily: Rhyacodrilinae

Rhyacodrilus subterraneus Hrab ĕ, 1963

Records. Robečský Brook, Česká Lípa, 50°40'05"N / 14°30'27"E, lgt. IS, det. JS/PP (2007), immature specimens; Svitava River, Brno, 49°08'43"N / 16°37'48"E, lgt. PH, det. PP (2006); one mature specimen.

Characteristics of sites. Although most published records refer to groundwater and hyporheic habitats ( Erséus et al. 1999; Wetzel & Taylor 2001), we found R. subterraneus in surface waters. These surface habitats, however, likely receive groundwater influences. The Robečský Brook is situated in the north-western part of the Czech Republic in semi-natural landscape with numerous wetlands and fishponds. The sample was taken downstream of the Peklo Natural Reserve, where a brook flows through a narrow sandstone gorge with substrate formed of mud (40%), sand (30%) and gravel (30%). On the contrary, the second sampling site is situated downstream of Brno, the second largest city in the country, in the straightened and dyked Svitava River stretch (substrate: 20% mud, 20% sand, 30% gravel and 30% stones), which also serves as a recipient of sewage water from urban settlements.

Ecology. Rhyacodrilus subterraneus occurs in fresh and brackish water ( Erséus et al. 1999); in reference to its name, especially in interstitial hyporheic zones and wet soil. Many records were reported from deeper hyporheic habitats ( Strayer 2001) and caves ( Wetzel & Taylor 2001; Ferreira et al. 2007); nevertheless, it was also found in species-rich oligochaete assemblages in eutrophic streams ( Timm et al. 1997). Reproduction in this species is sexual (Timm & Veldhijzen van Zanten 2002), but in some regions ( United States) only immature specimens have been found ( Wetzel & Taylor 2001).

Morphology. Rhyacodrilus subterraneus can be distinguished from its congeners by straighter and two times longer upper tooth of anterior dorsal chaetae with intermediate teeth, and two times longer upper tooth in anterior ventral chaetae. Penial chaetae near male pores in XI segment of mature specimens are only single with a simple curved tip ( Timm & Giani 2004).

Distribution. Prior to records collected during this present study, this rare Holarctic species had been found only in western European countries ( France, Germany, Norway, Sweden, Spain, and The Netherlands; Timm & Giani 2004), and in the eastern and Midwestern United States (Strayer & Bannon - O'Donnell 1988; Strayer 2001; Wetzel & Taylor 2001; Kathman & Brinkhurst 1998).