[Electron microscopic and morphometric investigations of the integument of Acanthocephala (Aschelminthes) (author's transl)].

The integument of the acanthocephalans Echinorhynchus gadi, Acanthocephalus lucii, Polymorphus minutus and Macracanthorhynchus hirudinaceus have been investigated by stereoscan and transmission electron microscopy. The absorptive surface is considerably increased by invaginations of the outer plasma membrane (pore canals and vesicles). The rate of this enlargement has been calculated using morphometric methods. The values range from 20 to 62. The values are compared to values obtained from other gutless parasitic helminths and from the free-living rotifers which are presumably to be regarded as closely related to the acanthocephalans.