Pinnularia are motile diatoms that possess a raphe which is an elongated slit along the diatom‘s shell that secretes an adhesive mucilage that enables these glass made organisms to glide on a surface. Diatoms are unicellular microalgae encased in a self-assembled porous silica shell named frustule. They’re basically made of glass, since silica is the main component of glass! They’re found all over the world in freshwater, marine and terrestrial habitats. They are a highly diverse group and can be found floating around or attached to various animals such as ciliates, Copepods, Daphnias, barnacles, hydroids, krill and even on whales!