On the permeability of cestodes to colloids: an evaluation of the transmembranosis hypothesis

Abstract

SUMMARY: Adult Hymenolepis diminuta were tested for their ability to transport colloids under in vitro and in vivo conditions. The tracers employed included colloidal thorium dioxide (Thorotrast), carbon (Pelikan Ink), ferritin and the ¹⁴C-labelled protein fraction from Chlorella vulgaris. Though certain of these tracers were adsorbed to the external surface of the tegument plasmalemma, no evidence for the assimilation of any of these colloids was obtained in the present study. Further, significant differences in size and structure between the granular inclusions reported earlier by Rothman (1967) as assimilated colloids and the particles present in the respective colloidal suspensions were noted. Results of this investigation are interpreted as rendering untenable previous conclusions concerning transmembranosis of colloids by tapeworms.