Coiling of the flagellar shaft in the head region of the mature sperm of Nucella (purpura) lampillus (L.).

The sperm of Nucella are long and threadlike. The fiagellar shaft runs from the acrosome at the front of the head to the tip of the tail. Its anterior portion, the head shaft, is ensheathed by the nucleus. If a suspension of sperm in normal-concentration sea water is observed under phase contrast, and allowed to dry out slowly, the nuclear material of sperm near the edge of the coverglass swells and the head shafts of these sperm are thrown into gentle spirals within the nuclei. In some sperm the nuclear material disperses completely, and the front threequarters of the head shaft springs into a tight right-handed coil of 5-7 turns. Instantaneous coiling of the head shaft may also be induced by treatment of the sperm with x 2 concentrated sea water or o-oi % (w/v) solution of sodium lauryl sulphate in sea water. The enzymes pronase and trypsin at a concentration of 50 /tg/ml in sea water at pH 8-o cause dispersion of the head nucleoprotein and subsequently the head shaft forms a loose coil. The appearance and activity of the sperm do not change perceptibly over a pH range of 5-5—8-5. Sperm spread on a Langmuir trough containing normal concentration sea water were negatively stained with phosphotungstic acid and examined with an electron microscope. After such treatment the nuclei are partially spread and the fibrils of the head shafts appear twisted as the wires of an electrical flex. The twisted flagellar fibrils are seen more clearly in negatively stained head shafts of sperm whose nuclei have been completely dispersed by spreading on a Langmuir trough containing x 2 concentrated sea water. Negatively stained preparations of sperm treated with enzymes show sperm with twisted and coiled head shafts. The nucleoprotein of these sperm is disaggregated into strips or sheets, or may appear as a mass of branching fibres. The flagellar fibres of the enzyme-treated sperm are often bent or broken. Longitudinal sections of mature sperm heads show that in the intact sperm the fibres of the head shaft are not twisted but run straight throughout the length of the head. Sections from the testis and testicular duct show that microtubules are present in sperm in the testis but absent from mature sperm in the testicular duct. It is suggested that the head shaft, as a consequence of some event in spermiogenesis, has an inherent tendency to twist and coil but in the mature sperm it is 'strait-jacketed' by the sperm nucleus.