The Schistosoma mansoni host-interactive tegument forms from vesicle eruptions of a cyton network

During trans-dermal invasion of the vertebrate host, larval schistosomes (c ercariae) transform into schistosomula and become enveloped by a double lip id bilayered, tegumental membrane. The glucose transporter protein SGTP4 is found exclusively in these host-interactive tegumental membranes and in me mbranous vesicles proposed to be their precursor. In this study, we monitor ed the appearance and migration of this tegumental marker protein during la rval transformation to test the current model of tegumental membrane biosyn thesis in parasitic blood flukes. Only minutes after transformation was ini tiated, SCTP4 began accumulating in a previously unrecognized, bilaterally symmetrical, 'cyton network beneath the peripheral muscle. Approximately 30 min after the initiation of transformation the marker protein was seen in tubules connecting the network to the surface and erupting onto the surface in discrete patches. After 1 h the patches were regularly arrayed over the schistosomula body and began to cover the anterior organ, By 3 h the stain ing has largely resolved into a contiguous layer of fluorescence covering m ost of the worm surface. These findings confirm earlier suggestions, based on electron microscopy, that the parasite's surface tegumental membranes ar e derived from the migration of membranous resides produced within cytons a nd reveal a new subtegumental architecture interconnecting the cytons.