Discovering high species diversity of tapeworms (Cestoda: Proteocephalidae) of watersnakes (Colubridae) in North America.

Tapeworms of the genus La Rue, 1911 parasitize herptiles (= amphibians and 'reptiles') throughout the world, with about 100 species recognised as valid. In the present work, the North American species found in watersnakes (Colubridae) are reviewed. An examination of the holotype of La Rue, 1911, the type species of the genus, and other specimens from (Hallowell) revealed that two species were used for the species description. The 'true' has a small scolex and small, round suckers. This species is redescribed based on new material from Oklahoma, USA. The other species from , n. sp., has a larger scolex and larger, almost triangular suckers. Examination of the types of (Brooks, 1978) from and (Duméril, Bibron et Duméril) from Louisiana, USA has revealed that it is a mixture of two or more species. Because of poor quality of these specimens, it is not possible to adequately characterise , which is considered a . In addition, two new species are described from (Blanchard). n. sp. from Mississippi, USA is characterised by elongate, narrow proglottids, few testes, and a relatively long cirrus sac. n. sp. from Louisiana, USA is characterised by relatively short and wide proglottids, more testes, and an unusual terminal part of the vagina with folds. Morphologically similar tapeworms of , (Förster), (Linnaeus), and (Lacépède) (Viperidae) from Arkansas and Oklahoma, USA, which are genetically nearly identical, are considered to be conspecific with n. sp. The present data suggest a high, previously undescribed species diversity of proteocephalid tapeworms in watersnakes in North America, and generally strict host specificity of these tapeworms.