Three in one: molecular phylogeny of the genus Helodrilus (Crassiclitellata: Lumbricidae) with a description of two new genera and two new species

The earthworm genus Helodrilus comprises about 20 species with distributions ranging from the Iberian Peninsula to the Caucasus, through Central Europe, the Balkans, Anatolia and the Levant. The species prefer moist habitats and are often found in the mud of river banks, in swamps or in caves. Although a high degree of morphological variability is observed in the taxonomic characters, the genus shares a common feature: the absence of nephridial bladders. In this study, we clarify the phylogeny and taxonomy of the genus Helodrilus using an integrated approach including a multilocus molecular phylogenetic analysis and thorough morphological examination of several species across the putative Helodrilus area of distribution. The findings of this study have led to the genus Helodrilus being split and to the description of two new genera and two new species: Coventina Szederjesi, Sarbu & Csuzdi gen. nov. and Imetescolex movilensis Szederjesi, Sarbu & Csuzdi gen. & sp. nov. The highly homoplasic nature of the absence of nephridial bladders was also revealed.