On the morphology and biology of Kronborgia spiralis (Baylis, 1949) (Turbellaria, neorhabdocoela), with a note on its systematic position

Abstract A redescription is given of Kronborgia spiralis (Baylis), an endoparasite in the antarctic isopod, Serolis schythei Lutken. The species is shown to be dioecious with a dwarf male. Anatomical changes during development of the female to the mature stage and during spawning are described. The host is not castrated by the parasite, and it is not killed when the parasite emerges to construct its cocoon. The male enters the cocoon to fertilize the eggs of the female. Reasons for moving the species from the genus Fecampia to the genus Kronborgia are given.