bucky ball is required for Balbiani body assembly. (A, B) 1500x TEM images reveal the Balbiani body (red box) in wild-type (A), but not in buc (B). Mitochondria (yellow arrows) are abundant and clustered within the Balbiani body (C), whereas on the opposite side of the nucleus they are sparse (D, yellow arrows). (E) TEM reveals mitochondria (yellow arrowheads) and associated nuage in the Balbiani body of another wild-type oocyte. Nuage is adjacent to the nucleus and surrounds the wild-type Balbiani body. In buc stage I oocytes, perinuclear nuage is present (F and white arrowhead in panel B). (G) Mitotracker red labels mitochondria in the Balbiani body (Bb) of wild-type stage I oocytes, and (H) reveals abundant mitochondria in buc stage I oocytes, which fail to aggregate into a Bb. (I) Actin localizes to the oocyte nucleus, the somatic cells (FC) and the Bb in wild-type stage I oocytes. (J) In buc mutants, Actin localization is like wild-type except for the lack of a Bb aggregate. Hematoxylin and Eosin stained sections of primary oocytes confirm the presence of a Bb in wild-type (K), but not in buc (L). (C–F) 10,000x TEM; (G–H) 63x confocal images; (I–J) 40x confocal images; (K, L) 40x images. Scale bars are 50 μm for panels G–J.