the paired spermatozoa of the dytiscid beetles dytiscus marginalis and hydaticus seminiger were studied by electron microscopy with the aim of examining whether the regions of the cell membrane in the zones of sperm conjugation might differ from other regions and to explore whether these cells had any other specialized domains of the cell membrane that could be recognized by the freeze-fracturing technique .
C0007634
cells
C0007603
cell membrane