Three New Species of Lagenophryid Peritrichs (Ciliophora) Ectocommensal on Freshwater Decapod Crustaceans from Madagascar1

One species of Lagenophrys and two species of Operculigera are described for the first time. Lagenophrys machaerigera n. sp. was discovered on the freshwater crab Gecarcinautes goudoti and varies between two extreme forms in the structure of its lorica aperture. Operculigera carcini n. sp. was also found on G. goudoti and exhibits several characteristics that set it apart from other members of its genus. Some of these characteristics also suggest a phylogenetic link between O. carcini and the genus Lagenophrys. Operculigera madagascarensis n. sp. was discovered on the parastacid crayfish Astacoides granulimanus. The occurrence of O. madagascarensis on a Madagascan parastacid and other species of Operculigera on Chilean parastacids suggests that parastacids are the oldest hosts of the genus Operculigera. Continental drift is the most likely mechanism by which species of Operculigera and parastacids could have been dispersed to distant parts of the southern hemisphere. The absence of Operculigera on Australian parastacids may be due to its replacement by the genus Setonophrys on those hosts.