Freshwater isopods of the genus Lirceus from caves and springs of the Interior Highlands, USA, with description of three new species (Isopoda: Asellidae)

Eleven species of the freshwater isopod genus Lirceus occur in the Interior Highlands, a region of the south-central United States comprised of the Ozark and Ouachita physiographic provinces. As part of research on the morphology and molecular genetics of eastern North American asellid isopods, three new species of Lirceus were discovered in the Interior Highlands. Lirceus slayorum, n. sp., is described from Greathouse Spring, Washington County, Arkansas and occurs in caves and springs associated with the Ozark Springfield Plateau. Lirceus ozarkensis, n. sp., is described from Maxey Cave, Pulaski County, Missouri and was originally identified in 1949 by Hubricht and Mackin as a subspecies of Lirceus hoppinae. In actuality, L. ozarkensis is quite distinct from L. hoppinae, and occurs allopatrically in caves and springs of the southern Ozark Salem Plateau in southern Missouri. Lirceus robisoni, n. sp., is described from Abernathy Spring, Polk County, Arkansas and is found in only a few springs in a narrow area of the Ouachita Mountains in western Arkansas. Eight other species of Lirceus occur in the Interior Highlands, most of which are confined to springs and caves. New localities are presented and the ranges of the species are established. Illustrations of the genital pleopods demonstrate a common theme across the species of the Interior Highlands, with all possessing a sperm-transfer cannula arising adjacent to a variously papillate or dentate digitiform lateral process, and nestled under a dominant broadly rounded or subtriangular apex. Within this morphological template, some of the Ozark species, like Lirceus bidentatus, are among the most anatomically bizarre in North America.