Carrier Mediated Membrane Transport. Transmission electron microscopy reveals docking of epididymosomes on the sperm plasma membrane to allow delivery of GPI-linked proteins to the sperm surface via hydrophobic interactions.23 On the smaller epididymosome SPAM1 which is immunogold- labeled is seen in the process of being transferred to the sperm membrane, while the contact of the larger epididymosomes appears to involve membrane fusion. Taken from Mol Reprod Dev 2008; 75: 1627–36.23. Epididymosomes: transfer of fertility-modulating proteins to the sperm surface. Martin-DeLeon PA - Asian journal of andrology (2015). Not Altered. CC.