Tuesday, May 10, 2011

Life in a Few Drops of Water: Diatoms

A few days ago, when we were out walking in Weardale, I collected a small sample of water from a pond in a disused quarry on the edge of the moors, then spent several hours that same evening exploring just a few drops of the pond water - maybe ten in total - under the microscope. The organisms pictures in this post are all diatoms - minute photosynthetic organisms encased in a shell of pure silica that often bears the most intricate pattern on its surface. This one, caught in the act of dividing, is Pinnularia.


Some are long and thin (this is Nitzchia sigmoidea), while.....

....others are joined together in chains.

Navicula? When diatoms die their silica shell remains, almost indestructible, and in that transparent state, with no contents, the full beauty of the sculpturing on their shells can be appreciated.

The pattern of fine ridges on Cymbella tests the ability of microscope lenses to resolve such fine detail.

Diatoms generally move in a gliding motion through the water but sometimes they can be attached to a substrate via mucilaginous stalks.....

... seen here at higher magnification.

Most of these organisms are less than one twentieth of a millimetre long.

Coming next: Desmids....mirror-images in miniature


  1. Phil, if your goal is to get me to run out and find stuff to put under my microscope, it's working! I've got some water barrels that are itching to be scrutinized now...

  2. Awesome pictures! (also enjoyed your previously posted Actinophryid with a testate amoeba – so cool! I always end up squashing my actinophryids, buggers are too big...)

    Just curious, have you ever tried floating coverslips on a jar of pondwater/mud/rotting leaves/whatever? It's a cool trick where you can basically get a bunch of stuff growing right on your slide, and a bunch of benthic+gliding protists crawling all over it after a day or two. You just pick up the coverslip and trasnfer to slide. And all the cool stuff is right under the coverslip, meaning you get the best image quality too since you don't have to worry about thick slides – awesome for DIC...

    Sorry if this is common sense to people, but it's a pretty cool trick to getting not-so-planktonic biota... I'm still amused by it.

  3. Hi Alan, When I investigated the slimy stuff around the edge of my water butt it turned out to be a beautiful 'golden alga' - Dinobryon....... well worth exploring!

  4. Thanks for the tip Psi Wavefunction - I'll try it right away. I'm still a novice explorer in Protist World (defector from crop botany) so haven't picked up many 'tricks of the trade'. I read about a similar technique, using vertically immersed slides in Betsy Dexter Dryer's Field Guide to Bacteria, for culturing bacteria and archaea....... but never got around to trying it. I only had a bog-standard teaching microscope to hand when I looked at these specimens but I can imagine the combination of your coverslip cultures and DIC would produce vastly superior results. Kind regards (I'm a great fan of your blog - I'm learning a lot from it) - Phil

  5. Stunning images of organic "glass";)

  6. P.S. Just followed. Enjoyed rounding up the number;)

  7. Thanks for visiting, Antares Cryptos


Note: Only a member of this blog may post a comment.