The ovarian follicle of the marine teleost, the red sea bream Pagrus major, was investigated ultrastructurally and histochemically, during vitellogenesis and oocyte maturation. Processes from the granulosa cells and from the oocyte grow and make contact with each other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radiata becomes more compact and devoid of pore canals during oocyte maturation. During vitellogenesis the special thecal cells possess organelles characteristic of steroid-producing cells, namely, mitochondria with tubular cristae and smooth endoplasmic reticulum, but the granulosa cells contain organelles typical of protein-secreting cells. Marked ultrastructural changes occur in the granulosa cells during nuclear migration. This involves a dilation of the rough endoplasmic reticulum. Histochemical reactions for Δ5-3β-hydroxysteroid dehydrogenase activity are negative in both granulosa and thecal cells during vitellogenesis and oocyte maturation. Possible cellular sites for ovarian steroid hormone synthesis in this species are discussed and a comparison is made with data derived from other teleosts.
All Science Journal Classification (ASJC) codes
- Aquatic Science