Contributions to the knowledge of the genus Trichodrilus Claparède (Lumbriculidae, Clitellata) with the description of new groundwater species from Spain

The freshwater genus Trichodrilus Claparède is a common member of the invertebrate stygofauna (obligate groundwater fauna) of central and southern Europe. This study focuses on some of the smallest representatives of Trichodrilus worms from groundwaters (caves, wells and springs) in Spain. Several populations were still impossible to ascribe to a species, due either to scarcity of individuals or to the lack of clear characters. However, two populations from Itxina karst (Basque Country) are well separated and described as T. benati sp. nov. based on distinct characteristics of the male duct. Another population, from the Ereñozar karst (Bizkaia), is described as T. stygodytes sp. nov. Two of the most widely reported species, T. tenuis Hrabě, 1960 and T. moravicus Hrabě, 1937 are difficult to separate morphologically based on the original descriptions, therefore, we have re-examined and measured the type material. Our study reveals a wide distribution of T. tenuis in the Iberian Peninsula, and the absence of T. moravicus. However, study of the type material of the latter showed two different morphospecies, hence, a lectotype from the Říčka R. (Czech Republic) is proposed for T. moravicus, while the population from Cave Býčí Skála (Czech Republic) is here ascribed to T. stygodytes sp. nov.