The yolk of teleost eggs becomes covered with a syncytial periblast during embryonic development. Nutrients must be transported through the periblast before they are available to the embryo. Tranmission electron micrographs of thin sections and of freeze-fractured replicas show a number of features at the yolk-periblast junction which may be correlated with yolk transport. These features include vesicle formation and exchange, channelization and interdigitation.
Bailey, Claudia F.
"Yolk-Periblast Junction in Fundulus heteroclitus,"
Journal of the Arkansas Academy of Science: Vol. 31
, Article 7.
Available at: http://scholarworks.uark.edu/jaas/vol31/iss1/7