pennate frustule

描述：

Diatoms are algae which live in little glass boxes or frustules - rather like little petri dishes. Pennate diatoms are motile, and rely on, we believe, the excretion of mucus through a slit in the wall - the slit is the raphe and runs down the flat faces of the petri dishes (frustules in diatom terminology). The frustule is perforated with tiny holes to allow the diatom to excrete waste products, and pick up nutrients, dissolved gases etc. from the surrounding water. The one is seriously asymmetric. Phase contrast.