Moss in rainwater

Jul 06, 2018 • 2:21 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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After a few monsoon showers, the water in the large rainwater pool looked quite clear, showing no obvious sign of life, even under the foldscope. But standing in a bottle over 18 days, it got steadily cloudier.
Our first surprise came when, at the foldscope workshop , teachers from TSWREIS Chilkur school put a drop of the turbid rainwater under a foldscope, and found it crawling with amoebae and microarthropods!
Trying to introduce some (visible!) plant life into this water, we scraped off a bit of moss from the base of a nearby small concrete water tank, soaked it in some of this rainwater, and kept it aside in a vial.

Moss ecosystem: (Top left) Rainwater pool; (Bottom left) Moss on concrete tank, (Right) Moss and rainwater mixed in a vial Our little ecosystem in a vial remained undisturbed for nine days. Then we watched a bit of the moss through a foldscope, and got another surprise! It was a worm with a segmented body and bristles along its length, which caught the light as the worm turned. Since it had no head and tail appendages we decided it was not an insect larva.

Oligochaete on moss
The transparent body showing the digestive system made us think it must be an oligochaete. Since the ‘setae’ or bristles were on one side only, it is likely to be a member of the Chaetogaster genus. Here is a link to an image showing a typical chaetogaster. Our conclusion — Family: Naididae, Order: Oligochaeta, Genus: Chaetogaster, Species: unknown.
Around this worm were other organisms. In the next video we see an oval-shaped organism which starts from the centre of the screen and moves left. From its rotating motion we think it may be Chlamydomonas. The small shining cylindrical organisms are most probably diatoms.

Oligochaeta (Chaetogaster sp.), Chlamydomonas and diatoms?

Oligochaeta (Chaetogaster sp.), Chlamydomonas and diatoms? In the next video a rotifer swims in from the left and exits the lower end of the screen. A closer, slow-motion view of the rotifer helped us spot the “crown of cilia” projecting at the front end, the cilia moving in and out rhythmically in a way characteristic of rotifers.

Oligochaete and Rotifer (Lepadella sp.) Looking the oval shape and a pointed tail and referring to this paper on freshwater rotifers we decided that this rotifer belonged to the Class: Monogonanta and Genus: Lepadella. Here is an image of a typical Lepadella .
Finally through the 10X objective of a compound microscope we saw this curious organism with a tube-like body with tapering ends, thrashing wildly in one place.

The scene looks very much like this video of three tube-like nematodes which are stuck at one end and making whipping movements . In our video it seems like just one nematode has got stuck in some biomass and is trying to free itself. Is it also feeding at the same time? Let us know what you think.
Bhavya , Udit , Debashree and Jayashree