while studying living cells, locomotion might be detected.
it is thought that contractile fibers just inside the cell membrane produce waves of motion on the cytoplasmic surface that extends through a groove in the cell wall. what is the body form of motile diatoms?
Diatoms inhabit both freshwater and marine environments and belong to both the planktonic and benthic communities. Some planktonic forms can regulate their buoyancy, and many benthic species are able to crawl slowly over the substrate. It is thought that some diatoms secrete a mucus-like substance that aids their locomotion.
Pennate diatoms, which developed later in the earth’s history, are able to locomote in a slow gliding fashion in the direction of the length of the cell. The mechanism for this is still not well understood but it seems that through the slit alongside the cell (the raphe) tiny microfibrils protrude. With these they can move over a surface.