Submitted to: Journal of Reproduction and Fertility
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/1996
Publication Date: N/A
Citation: Interpretive Summary: Embryo mortality is a significant problem in the turkey industry. Our initial approach to finding solutions to this problem is to gain a better understanding of the development of the oocyte prior to the accumulation of yolk. Using light and electron microscopy, the early developmental changes of these oocytes were evaluated and categorized into 5 stages. These stages reflected changes in the size of the oocyte and the appearanc and distribution of structures within the oocyte and consequently provides predictable, standardized stages of turkey oocyte development. This information is important for scientists investigating the mechanisms controlling oocyte development and the contribution of the ovum to early embryonic development.
Technical Abstract: Primary oocytes from turkeys in egg production were examined by light and transmission electron microscopy in order to elucidate the morphological changes associated with early primary oocyte development. Five stages were identified. In Stage I oocytes (less than 80 um in diameter), no Balbiani body was observed. However, pleomorphic mitochondria were observed around the germinal vesicle (GV) and nascent yolk spheres and multivesicular bodies were scattered in the ooplasm. In Stage II oocytes (80-150 um in diameter), the Balbiani body, which consisted of a dense array of pleomorphic mitochondria and branching smooth endoplasmic reticulum (SER), had formed and was adjacent to the GV. Lipid droplets were predominantly distributed in the periphery of the oocyte. Stage III oocytes (150-350 um in diameter) were characterized by the dispersal of the Balbiani body and a redistribution of Golgi bodies and SER to the periphery of the oocyte. In Stage IV oocytes (351-500 um in diameter), the GV was more centrally located and the mitochondria were redistributed to the periphery of the oocyte. In Stage V oocytes (500-800 um in diameter), zonation was clear in the distribution of the organelles and inclusions with the mitochondria immediately subjacent to the oolemma and the lipid droplets subjacent to the mitochondria. We suggest that organelle redistribution and pleomorphism was reflective of the increasing metabolic and transport requirements of the developing primary oocyte.