The taxonomic status of the San Francisco Bay area Leech Helobdella triserialis (SF) (Annelida Hirudinida Glossiphoniidae) with notes on its ecology

Over the past decades, freshwater leeches of the genus Helobdella Blanchard, 1896 (Annel-ida: Hirudinida: Glossiphoniidae) have been used as model organisms for developmental studies. Notably, the species ” Helobdella triserialis US”, discovered during the 1970s in ponds in San Francisco (California , USA) was kept in lab-populations and served as representative of the genus, as documented in numerous publications. Here, I show that this enigmatic “San Francisco Bay area leech” has been misclassified and confused with the South American species H. triserialis (E. Blanchard, 1849), and later with H. papillata (Moore, 1952). Using specimens collected in Matadero Creek, Palo Alto (California , USA), novel morphological, anatomical, behavioral and molecular data (novel mitochondrial 618 bp-COI gene sequence) were generated. Based on these results, it is shown that this taxon represents a new North American species, described here as Helobdella farmeri n. sp. In addition, the occurrence of extant and extinct populations of Helobdella sp. in natural habitats of Northern California is documented over the past three decades.