A product of the fusion of the mitochondria during spermatogenesis. After the completion of meiosis the mitochondria of the spermatid collect along side the nucleus and fuse into two masses; these wrap around each other to produce the spherical Nebenkern. During flagellum elongation the Nebenkern unfolds and the two derivatives (major and minor mitochondrial derivatives) elongate down the axoneme.
Nebenkern