The epidermis of six ectosymbiontic Temnocephala species (T. axenos, T. chilensis, T. digitata, T. microdactyla and T. pignalberiae from freshwater crustaceans and T. iheringi from a mollusc) from Argentina examined using scanning electron microscopy revealed characters indicating their relationships with other members of the Platyhelminthes and with the congeneric Australian and New Zealand species. In all species, the whole surface is covered with microvilli and no locomotory cilia were observed. Aggregates of monociliated receptors are on the tentacles of all species and on the ventral surfaces of three. Furthermore, T. axenos and T. chilensis show other ciliated structures interpreted as collar receptors, such as those described for some turbellarian groups (e.g. Proseriata and Rhabdocoela). Two species (T. digitata and T. iheringi) show structures that are probably related to the duo-gland adhesive system.Facultad de Ciencias Naturales y Museo