A new species of leech of the genus (Hirudinida, Glossiphoniidae) from the American alligator () in Mississippi, USA.

To date, the only species of leech reported from the American Alligator, is . Seven specimens of a previously undescribed species of were collected from the feet and lower jaw of a single female alligator from the Pascagoula River Wildlife Management Area, George County, Mississippi. The new species was named Richardson & Moser, , in honor of the contributions of Dr. Mark Siddall to our understanding of the biology of leeches. Richardson & Moser is similar to other papillated members of the genus , but differs from Hughes & Siddall, 2007, (Verrill, 1874), Moore, 1953, and (Verrill, 1872) in coloration, papillation, ventral striping, and in the possession of a relatively large caudal sucker. In addition, molecular comparison of 626 nucleotides of CO-I between the new species and other papillated leeches (, , , , ) revealed interspecific differences of 14.0-18.0% (88-113 nucleotides).