group shot

Description:

Pennate diatoms. The cells are enclosed in siliceous valves. There are typically two valves - a top one and a lower one, and they are joined together with fine bands or girdle strips. With plastids containing chlorophylls a and c (they are stramenopiles after all). Genera and species distinguished largely by the shape of the organism and the pattern of pores and sculptings of the siliceous shell or frustule. 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 benefits diatoms which may move towards the light, recover their location after disturbances by overlying water currents, wave actions, animal burial and so on. Several species illustrated. Phase contrast.