Epiphytic microorganisms on duckweed roots.


image       I have been keeping a sample of common duckweed which I obtained from a freshwater fountain you can see in the next image.


Whenever my duties allow me, I run and grab  my foldscope and inmensely enjoy watching the microcosmos under it. Refering to this plant (it is frequently mistaken as an algae), I have recently read  that   duckweed  (Lemna spp)  absorbs water and nutrients  mostly through the lower surface of the leaves, not the roots. The only root they  exhibit per leaf  slows the plant’s movement in a windy day or in turbulent waters because roots entangle  easily. This fact is clear in the photograph above.

The more I watch under the foldscope, the more I firmly believe  every living creature, no matter its size, is an exhibition of wonders. I will explain myself. When observing Lemna’s root, I    realized not only sessile rotifers attached to it, but some other epiphytic organisms (living  more or less permanently on top of) which I could not recognise. Take a look.



After gathering information from the Internet and from books, I came to the conclusion they are diatoms. Diatoms have been a subject of many posts in this web. You might know then that they are algae that make a silica microscopic “box” inside which they live. Each cell builds two parts that fit together like a box and lid. The silica deposit is irregular and results in an amazing and beautiful variety of patterns. If I am not mistaken, the algae in the images belongs to genus  Gomphonema.  Amazingly, it also builds a mucilaginous stalk that attaches an individual or some of them (a colony) to Lemna’s root.

There are many species of Gomphonema and differ in shape. Many of them show a more or less triangular lateral view, so I thought it is how it is seen in the video. Here is a drawing to explain myself.


Sure there are more epiphytic diatoms in the former video. Some look like needles, others form chains of cells. I suppose they are difficult to identify, but what makes me wonder is why do they prefer living attatched, ….constant light? Staying above the water column? Saving energy as they are dragged? And furthermore, does Lemna receive anything in exchange?

Next microorganism I found is a complete mystery. Are those pseudopods?

To finish with, here is a general view (excuse me for moving fast).  There is a rotifer in the end,  a dexterous swimmer with a keel on its back, although it’s not moving much now.

Cristina Bosch


6 Comments Add yours

  1. Manu Prakash says:

    What a wonderful post @Christina. I realized we have @Jen ( a diatom expert in our community); let’s see what she has to say about these diatoms.

    Your thoughts on connectedness of organisms at the smallest scales really resonated with me. I want to think about a formal framework to compare how large animal ecosystems interact vs small ones. @Laks – this would be a great question to pursue. We will title this “the Wild West of microscopic world”..


  2. Matthew Rossi says:

    I love the illustration you provided with this! Learning how to actually draw the things we see is a great way to further interact with them. Note to self: must take some sketch classes.

  3. laksiyer says:

    Wow. Just loved the post.. That mysterious one looked like a pseudopod, but it seemed to be encased, which is interesting. We have our diatom expert to identify it, but I am sure you hit the nail. Now if we can only catch them dividing. Need to look at it a few times. @Manu,

    I wonder if we can get some kind of an association network. You remember that mystery organism with the synchronous disaggregation. That too was on a duckweed. That sample of mine is still running fine after almost 4-5 months!!

  4. laksiyer says:

    Sorry above, mysterious one seemed to have a pseudopod

  5. Cristina says:

    Thanks so much for your comments! The truth is that every post is the result of the most enjoyable of assignments and I suppose every foldscope user undergoes the enchantment and amazement this tool brings to our lives. You also feel you can be creative and have special feeling knowing so many people can read and share your experience . On the other hand, and to be honest, they do take its time ( observing once, twice,…many prepared samples, making photos or videos, editing and uploading every media you select, gathering information, organising ideas,….. All in English (I’m Spanish),… So your enthusiasm is the best award and completely contagious. Thank you!

  6. jlpappas says:

    Hi Cristina,

    Sorry I’ve been away for awhile and could not respond to your post until now. You have some wonderful images, and yes, many different kinds of diatoms! Your identification of Gomphonema for the wedge-shaped diatoms might be correct. Keep in mind that there are many other diatoms that have this shape such as Gomphoneis and Didymosphenia. You have many chains of diatoms present as well as the attached forms. Chain formation occurs in taxa that are free floating. The chains may be Aulacoseira granulata and fragilarioid forms. The attached forms do so using a mucilage pad or stalk that anchors them in place to be able to collect nutrients from the water without being swept away. The needle-like shapes may be Synedra or related taxa. There might also be some attached cymbelloid taxa as well; these are more banana-shaped.

    You have a gold mine here of diatoms and other epiphytes!

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