On the Early Development of the Protonephridial Systems in Some Species Belonging to the Genera Diphyllobothrium, Triaenophorus and Schistocephalus (Cestoda, Pseudophyllidea)

Malmberg, G. {Department of Zoology, University of Stockholm, Stockholm, Sweden.) On the early development of the protonephridial systems in some species belonging to the genera Diphyllobothrium, Triaenophorus and Schistocephalus {Cestoda, Pseudophyllidea). Zool. Scripta 1 (5): 227–228, 1972.–The protonephridial systems of coracidia (oncospheres) and procercoids of four Diphyllobothrium species, of Triaenophorus nodulosus (Pallas) and of Schistocephalus solidus (Muller) were studied. In the oncospheres of Diphyllobothrium and Schistocephalus the two flame bulbs of the primary protonephridial system were present, but not in the oncospheres of Triaenophorus. In Schistocephalus the two flame bulbs were found to be inactive in the oncosphere (studied inside the coracidium), but very active in the youngest procercoids, which may imply that the primary protonephridial system does not start its function until the oncosphere has entered the copepod body cavity. The primary protonephridial system of the Triaenophorus procercoids was totally (most specimens) or partly reduced. The secondary protonephridial system, however, began developing more or less simultaneously with the integumental hooklets, the cercomer and the first calcareous bodies, which is in accordance with what is described concerning Diphyllobothrium. The ciliated, excretory bladder described by Rosen in 1919 was found to be a posteriorly open invagination, surrounding the “cercomer shaft”. Reverse bends of the posterior main canals of the secondary system are located closely around the wall of, though very likely not emptying into this invagination.