The Salty Microcosmos – 1


About a month ago had visited a beach at Juhu, Mumbai. The reason was a talk at Prithvi theatre – Chai and Why? I hope most of the Mumbai-residents here might know about it. So after the talk, went to Juhu beach and collected some sea water. It was wonderful to have seen such a clean beach.

The sea water was collected in a plastic bag (superuser Mitali might know….) and is being stored in a plastic bottle. Initially I withdrew some sample directly from the bottle and observed. All I got to see were some sand grains. 

Quite interesting shapes and patterns they have on them, don’t they? I wonder how and why they have these.

My initial expectations were to get to see some protozoans. However found no sign of any living organisms in the initial mounts. Later took some of the sea water into a tray and using the magnifier began looking for any sign of movement. That’s when  I came across these creatures referred to as zooplanktons…


The water was full of krills as was observed!

It was fun to keep watching those tiny little krills swimming around. I used mobile flashlight to be able to observe them. To observe better, I placed the light source below and lo! All the krills were getting attracted to the light source and swimming around it. There there, I got a way to be able to pick them up easily from the water. I placed some on a watch glass and attempted to keep light source away from the water. Found them to try and jump out of the water in watch glass.

Finally after some playtime, I observed one of these under foldscope. It did not show any movement whilst on the glass slide.

While experimenting with light, I found another creature that preferred to stay at bottom. In the video, it may look like an omlette with a black centre.

Very carefully picked it up using a Pasteur pipette and prepared a mount on PVC slide. This one chose not to stay still.

A little while later when I observed it I found that it shed its exoskeleton. It seems as if this is a larva of some organism. Please let me know the identity if anyone can identify it.

Some more time later, it became totally stationary, except for its arms (arms or whatever it is called, please let me know) which revealed to have several rows of cilia on them. Notice how it creates a water current. Definitely this is how it feeds itself.


Keep foldscoping and more!


2 Comments Add yours

  1. Manu Prakash says:

    Dear @Ronak,

    You post absolutely phenomenal data – but this single post is my favouirate for many reasons. Here are ideas, theories, resources and hints towards next steps..

    1) many of your “sand grains” look to be either “foraminiferans” and others are fish scales. This by itself is very cool; and we are just atvthe very first few pictures you posted. Do image the spiral looking grains; foraminiferans are fascinating – they are planktonic Protists and most likely you just have the shell (which is called “ test” for some reason). Look for Discorbis as a family for starting point.

    2) for the fast swimming zooplankton; they are copepods – and since so many species exist – they are almost impossible to identify. They swim and “jump” in water; and are difficult to image live – but really fun when you get them to behave.

    3) the last sample is the most intriguing. From your videos – it’s very clear that it’s completlely ciliates; which makes for a fascinating behavior. The two possibilities are either a “planula” larvae of a Cnidaria. The second possibility is that it’s a kind of flat worm. The two little “hands” makes me believe that it’s a planula larvae – and it’s now transitioning from planuala to the next stage.

    4) for the last video; it’s very clear that a flow structure exists at the arms. This has reminiscence to flow structures we have been studying for star fish larvae. We just realeased an open source program (flowtrace); you can put some particles (soot or little bit of milk in water) to visualize the flow and pr Cesar those movies with “flowtrace” using it as a module under “imageJ” – and you will get some incredible quantitative data through the same. See this website:

    5) for marine invertebrate larvae and protist – my first step identification key is this book: A guide to marine coastal and plankton and marine invertebrate larvae; by DeBoyd Smith and Kevin Johnson. See if you can get it from the library.

    You should collect more data on this – this might turn out to be an important observation; and if you have more samples alive now – would be wonderful to document this carefully. I am puzzled you just picked up all this on the beach – not even being on a boat. Tells us how much of microscopic mysteries are just accessible right under our feet.

    Ronak: it’s absolutely brilliant to see your work. I am so proud of having met you via the foldscope community.

    Keep exploring.

    1. Ronak Hati says:

      Unfortunately none of those creatures are alive in the sea water sample. The videos are a month old. However some other things have grown in the water (this would be for another post).
      Thanks for identifying those as copepods. And for the last sample even I think that is a planula larva.
      Flowtrace is amazing to look at. Would like to use it next time when I collect a sample.

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