A huge undescribed diversity of the subgenus Hystricochaetonotus (Gastrotricha, Chaetonotidae, Chaetonotus) in Central Europe

The subgenus Hystricochaetonotus Schwank, 1990 is one of the most species-rich subgenera Chaetonotus Ehrenberg, 1830. It has a worldwide distribution and encompasses 37 species predominantly living in benthos periphyton limnetic habitats. We have discovered further nine new running stagnant waters Slovakia (Central Europe): Ch. (H.) arcanus sp. nov., avarus gulosus iratus luxus mirabilis optabilis slavicus superbus nov. Their morphology was studied using differential interference contrast microscopy subsequent morphometric analyses were carried out. In addition, primary secondary structures their 18S, ITS2, 28S rRNA molecules as well barcoding mitochondrial gene encoding for cytochrome c oxidase (COI) analyzed. Species boundaries tested also compensatory base change analysis. could be separated both morphologically molecularly. present revealed that nuclear ITS2 sequences represent powerful DNA barcode addition to COI gene. According multi-gene phylogenetic analyses, lineage leading last common ancestor ‘Hystricochaetonotus’ clade longest internal branch within family Chaetonotidae Gosse, 1864. Since members are highly heterogeneous, parallel evolution Chaetonotus-like and/or Hystricochaetonotus-like characters scales spines occurred during its radiation.