Hormogaster regina sp. n. (Annelida: Clitellata: Hormogastridae): A giant earthworm from Spanish Catalonia, described from morphological and molecular evidence

An in-depth re-evaluation of hormogastrid earthworms inhabiting the Rio Ter Basin near Girona, northeastern Spain, previously assigned to the Hormogaster pretiosa Michaelsen, 1899 complex, resulted in new morpho-anatomical and genetic evidence supporting their recognition as a separate new species. Hormogaster regina sp. n., the largest-bodied species in the Hormogastridae, differs from the type material of H. pretiosa (whose precise locality in Sardinia is unknown) and from most of H. pretiosa-like forms in the authors' collection by having: clitellum and clitellar bands longer, a higher folding of the typhlosole, and different location of thickened and displaced septa. In all these traits, the new species closely resembles a population from the southernmost tip of Sardinia (Cape Teulada). A phylogenetic analysis of mitochondrial markers (COI and 16S-tRNAs) supports such close relationship, yet gives evidence for their status as distinct species. Molecular data, like fine morphology, also shows an unexpected phylogenetic divergence between H. regina sp. n. and its formerly putative relative H. pretiosa hispanica Michaelsen, 1925 from Catalonia, as the latter is recovered in a totally separate and distant cluster. This confirms once again the frequent lack of correlation between genetic and geographic distances in the Hormogastridae, and calls for accurate comparative examinations, with attention to traits of life history and forgotten anatomical details (e.g., the peculiar pattern of anterior septa was illustrated by Daniele Rosa in his first description of Hormogaster), for correct species delimitation and estimations of their relationships.