is a elongate pennate diatom usually found in sediments. Pennate diatoms are important in intertidal and illuminated subtidal sediments in marine ecosystems and primary producers. Pennate diatoms are capable of movement, relying on the raphe to produce thrust. Movement is needed so that diatoms can move towards the light, recover their location after disturbances by overlying water currents, wave actions, animal burial and so on. Several species illustrated to right. All have a siliceous shell (frustule) and chlorophyll a/c rich plastids. Phase contrast.