Phylogeny and Evolution of the Arhynchobdellida (Annelida: Oligochaeta: Hirudinida). Elizabeth Borda* and Mark E. Siddall. Department of Biology, Graduate School and University Center, City University of New York, NY; Division of Invertebrate Zoology, American Museum of Natural History, New York, NY, USA.

Unlike proboscis-bearing leeches, the Arhynchobdellida are characterized by their possession of muscular "jaws" used for feeding or cutting through skin. Arhynchobdellid leeches are among the most widely recognized and frequently encountered in historical and contemporary medical applications of bloodletting. The phylogenetic relationships, using parsimony analysis, of the Arhynchobdellida, were investigated using a total of 3644 characters, including nuclear 18S and 28S rDNA, mitochondrial 12S rDNA and cytochrome c oxidase subunit I sequence and morphological data. Thirty-nine arhynchobdellid species were chosen to represent the seven currently recognized families. Outgroup taxa included 16 species from the Glossiphoniidae and Piscicolidae. Analysis of all available data resolved one most-parsimonious tree. The cladogram yielded an hypothesis conflicting with most traditional classifications of the Arhynchobdellida. Monophyly of the Erpobdelliformes and Hirudiniformes was supported. However, the families Haemadipsidae, Haemopidae, Hirudinidae, and the genera Hirudo and Aliolimnatis were polyphyletic. An additional 5, 112 and 108 steps, respectively, were required to make the families monophyletic. The results provide insight on the phylogenetic positions for some unusual families (Americobdellidae and Cylicobdellidae), the genera Semiscolex, Patagoniobdella, Mesobdella, Xerobdella, and genera traditionally classified under Hirudinidae. A taxonomic revision of Arhynchobdellida is proposed and evolution of life-history traits is examined.