Scanning Electron Micrograph of a C. elegans Spermatozoon

This is a mature sperm cell, or spermatozoon, from C. elegans . At the right is the pseudopod, which the cell uses for crawling (see the video of a crawling spermatozoon). The pseudopod has knobby projections, called vilipodia, which constantly flow rearward toward the cell body. New vilipodia form at the tip of the pseudopod as the old ones flow back. The vilipodia adhere to the substrate, pulling the sperm in the direction of the pseudopod. This scanning electron micrograph shows the surface features of the cell. To examine the internal structures of the sperm, you can look at a transmission electron micrograph .

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