I recently found these planctonic centric diatoms in a freshwater pond. Interestingly, their long fibrils, which are said to reduce sinking velocity but definitely prevent most predators from eating these diatoms, are not made of silica but of chitin. Is there a diatom expert who can by these pictures tell me whether these specimen belong to the genus Cyclotella or Stephanodiscus?
Images made through a microscope. All subject types.