Water currents in the microcosmos

Mar 20, 2020 • 3:28 AM UTC

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Microorganisms

TCIS Outreach

We are a group of students, volunteers and staff working with TIFR Hyderabad's Science Education and Outreach program: http://www.tifrh.res.in/~outreach/

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Watching different water samples under the Foldscope, I was fascinated by the variety of constantly active minute organisms, each with their unique ways of capturing food. Their feeding process, driven by tiny cilia, creates competing water currents on a single glass slide. Each minute animal makes its own whirlpool to suck food into its mouth groove. This activity continues non-stop right till the last drop of water remains under the coverslip.
Now I have a new source of microorganisms: the natural fertiliser that I make for the potted plants on my balcony. This time I tried a variation of the Korean Cho Han-Kyu method , popularly depicted in Telugu videos as the ‘Chouhan-Q’ method! I made a juice out of peels of pomegranate, banana, watermelon and jaggery, put the mixture in a plastic cover and sealed it. After ten days I opened the cover and added a few drops of the juice to a bucketful of water. After watering my plants I kept the leftover liquid in a separate vessel. Within a week there was a dramatic change in my plants: new branches and flowers too! Amazing!! What magic was it in that dark fluid?

Out of curiosity I took a drop of the leftover fluid on a slide, put a coverslip and focused the sample under the Foldscope. Wow!! It was a teeming ciliate culture! Just watch the water flows from the ciliary movements of the Colpoda sp.!

Next, me and Chandrika collected a water sample from one of the pedestal ponds in our housing complex ‘Aparna Sarovar’ , mainly to observe some clusters of worms that we found there (just wait for the next post , on those worms)! In this sample we saw the rapid ciliary movement near the mouth of a Euplote. Watch how strong are the currents that they produce: an unsuspecting baby rotifer gets swept up against the Euplote, giving it quite a hard knock!

In the same water sample I saw a Bdelloid rotifer, with its two crowns of swiftly whirling cilia, rapidly drawing in currents of water and food. Watch how it extends its corona outwards and then retracts it quickly at the end of the feeding session. A large Annelid glides by, rubbing its chetae against the rotifer, but the rotifer continues its feeding unperturbed. A couple of green leaf-like Phacuses tumble by, narrowly escaping the rotifer’s vortices.
Another time I saw water currents, and thought they may be made by a Euplote or rotifer, but I was surprised to find a large copepod (i.e. small crustacean!) there!! A copepod creating water currents?? How odd!! Focusing on its abdomen I saw the movement of its digestive organs. But what were those movements outside the body?

Then I remembered the Vorticella that Akshatha had observed on a mosquito larva and those that I once saw on the legs and gills of a mayfly larva . Sure enough, on the body of the copepod were a few sessile Vorticella sp. creating strong whirlpools in the water.
What a coordination, what unison in movement of cilia to catch their food! And what energy they have!! After 24 hours, if the water drop is not yet dried up, with the same energy they struggle for existence. What an inspiring experience!!!
Cheers,
Ashalatha
with Jayashree