Fig. 1

Ultrastructure of sea urchin sperm basal bodies and distal centrioles. a Longitudinal section of a sperm head. At the base of the head one can see the basal body—flagellar apparatus, the mitochondrion, and the short distal centriole lying between the mitochondrion and the nucleus. Here, the distal centriole in tangential section appears as an electron-dense patch to the left of the basal body (arrow). Scale bar 1 μm. b Longitudinal section of the head of a sperm treated with gluconate-glycine buffer. The dense cap on the proximal end of the basal body is located where it is mechanically attached to the hof in the base of the nucleus. The mitochondrion has moved to the side of the nucleus along with the distal centriole seen in longitudinal section (arrow). Scale bar 1 μm. c Cross-section of an isolated distal centriole. Scale bar 0.1 μm