Selective transport of coelomic fluid protein into oocytes of a tubicolous polychaete,Pseudopotamilla occelata

Summary Coelomic fluid proteins, which are expected to include vitellogenin and putative yolk proteins isolated from the oocytes, were found to be transported selectively into the oocytes of specific stages ranging from 70–140 μm in diameter; whereas bovine serum albumin, a nonspecific protein, was not incorporated into the oocytes of any size class. Furthermore, removal of the oocyte membrane proteins with trypsin effectively retarded the transport of the coelomic fluid proteins and yolk proteins. Carbohydrate residues of the membrane proteins appear to play a significant role in transferring vitellogenin into oocytes since the transport of the coelomic fluid proteins and yolk proteins was completely blocked by saturating with Concanavalin A or by digesting with endoglycosidase F. The observations strongly suggest that the selective transport of the coelomic fluid proteins into the oocytes of specific stages is mediated by the membrane proteins, which appear to be receptors.