Helical structures in the cytoplasm of the male germ cells of the desert locust.

A helical structure which had previously been reported in the cytoplasm of many cell types in the desert locust, Schistocerca gregaria, was found in large quantities in the developing male germ cells. The helices were isolated from these cells and negatively stained. The helices, which lie free in the cytoplasm of spermatogonia, primary spermatocytes and secondary spermatocytes (sometimes associated with a second type of helix, a double helix), closely invest the outer surface of the Nebenkern membrane in spermatids. As the Nebenkern elongates, the helices gradually disappear and are replaced by microtubules. The mitochondrial derivatives of the Nebenkern, which form part of the sperm tail, are in late spermatids completely surrounded by a sheath of parallel microtubules.