Identification of a cytoskeletal network adherent to the mitochondria of mammalian spermatozoa.

In this study we identify a reticular network of electron-dense material in the spermatozoan midpiece which is immediately peripheral to the outer dense fiber-axoneme complex and is adherent to the overlying mitochondria. This network, termed the submitochondrial lattice, extends throughout the midpiece and terminates at the midpiece-principal piece junction where it fuses to the annulus. In cross sections this material appears as an approximately 10-14-nm-thick, discontinuous layer adherent to the outer mitochondrial membrane; longitudinal sections reveal that the network is arranged as longitudinally oriented electron-dense bands which branch and anastomose laterally to form a cylinder-shaped reticulum. The potential role of this complex in organizing the mitochondrial helix and in maintaining mitochondrial distribution is discussed.