Doing biological experiments at home was all about improvisation. For example, Risha used paper mache to create a makeshift test-tube holder; the plastic tops of drinking water cans doubled up as petri plates. They managed to do a number of experiments in this manner, including some of the amputation tests needed for Anjali to study wound healing in the worms.

While Risha’s parents were used to their home becoming a site of odd science experiments, their conservative grandmother would not approve of the beef liver they needed to store at home to feed the worms. For a while, Risha hid the beef liver in their room, inside iced thermocol boxes. Eventually, seeing how serious the project was to them, their parents allowed Risha to use the freezer. The only rule was to not tell grandma. 

When Risha got back to campus in 2021, they began trials to extract the algae from the worm. They also designed experiments to study how the worms responded to mechanical stimulus and quantified movement. While Risha was not able to complete everything they started, they did manage to spend some time exploring the aspect of the project that fascinated them the most — the ecosystem of Sompura’s ponds. 

“Sometimes, as I looked under the microscope, I wondered why I was studying the worms this way… Rather than looking at them as an object of research, would it not have been cooler if I could just — I do not know — be with them?” they deliberate. And so Risha started spending more time at the ponds, observing the sights and sounds, sometimes for hours at a time. 

Enigmatic ponds of Sompura

One of the ponds they frequented was nestled between trees and alligator weed. Birds like kingfishers were commonplace and Risha even spotted wild rabbits rustling in the thickets a few times. They encountered planaria floating on the surface, red larvae of midge flies, a strange shrimp and a long worm filled with little eggs. ​“Once, I came across a hydra hanging on to a little leaf on the side. After that, all I wanted to do was visit every single pond and look for more of those. There were so many things that I would find and I had no idea what they were,” says Risha.

Many of these ponds would completely dry up in the summers. What was happening to all the living creatures that lived in the water during this time? How were they able to re-appear when the ponds did? Were they going into some kind of hibernation, burrowing themselves in the soil, or forming cysts? The mysteries of the life cycles of these organisms occupied Risha’s mind and she still thinks about them today.

Besides observing the various idiosyncrasies of Sompura’s ponds, the other thing that Risha enjoyed was sharing their experiences. When Aastha Vartak joined Sravanti as a Research Assistant in 2021, it was Risha who guided her to the usual haunts of the green worms. By then Risha had developed a good instinct for where the creatures were likely to exist, based on the microhabitats they had shown to prefer. 

It is not easy for someone new to get used to the Sompura landscape. Being temporary, many of these ponds did not have names and were not marked on online maps. Over the years, Sravanti and the young researchers came up with their own naming convention for them, such as the weaver bird pond and the cattle pond. By the time Risha finished her part in the project, Aastha had a good enough sense of how to find the ponds. The Sompura green worms were in good hands. 

The group had still not managed to establish a lab population of the worms. This meant that when the ponds dried up every year, experiments would have to pause. The researchers were highly insecure about this because they were completely at the mercy of the occasionally erratic monsoons. Moreover, being a peri-urban area, the whole locality was in transition. Any day now, a new apartment complex could be announced, sounding the death knell for the ponds of Sompura and the green worms that inhabit them. 

Struggles, and a new discovery

Even back in 2020, Anjali had seen signs of a declining population and the perils of an unpredictable pond. ​“Sometimes they would be filled with water, sometimes they would dry out. We did not have a way of knowing when what would happen. I was always a bit ready for the fact that these ponds would disappear anytime and the worms with them.” Her dream was to establish their pond within the campus, which could be populated with worms to keep the science going. 

In her quest to find more missing pieces of the puzzle, Aastha continued many of Anjali’s experiments and tried some of her own. She found that besides beef liver, the worms seemed to like egg yolks as well, and they did seem to thrive better in the presence of an external food source. 

A few months in, she shifted her focus to the perfectly symmetrical spheres that could be seen inside some worms clearly, and also at times floating in the pond water. Anjali had already identified that these were the worm’s eggs. 

“We wanted to allow for the eggs to hatch so we could have our own source of worms in the lab,” explains Aastha. She stored the eggs in a range of different temperatures inside an incubator, hoping that one of them would be in the right conditions for hatching. 

One morning, to her delight, Aastha realised that it worked. ​“There were fewer eggs, and we could see that some had hatched. But we could not see the baby worms. We wondered where they could be,” she recollected. Only after a while, when scanning the sample under a microscope, did Aastha find the baby worms. The moment she saw the newborns, she realised that she had found an important piece of the puzzle: the babies were transparent. ​“It meant that the algae was not being transferred to the new generation, it was acquired somewhere along the way.” 

It now became all the more relevant to understand the nature of the relationship between the algae and the worm. The fact that baby worms were born without the algae suggested that they were not a survival necessity — not for hatchlings, at least. But perhaps they were necessary for the worm’s development further in its life cycle.

When Aastha moved the transparent hatchlings into pond water containing algae, she observed that it was only a matter of time before the worms absorbed it and turned green.

Give and take

When she compared the survival of green hatchlings with transparent hatchlings, she did not find a big difference. However, the green worms grew longer, while the colourless ones decreased in length. Aastha also kept some worms in the dark, knowing that the algae would atrophy in the absence of light. Once the algae died, the worms did not live long. All of this was evidence that the algae were indeed beneficial in some way, possibly as a source of nutrition for the worms. 

That is only half of the symbiosis story. Does the algae too have something to gain through this live-in situation? Aastha got an answer to this question when she performed a desiccation experiment on them.

The idea was to mimic the yearly cycle of the pond drying up. It turned out that algae freshly extracted from the worms were able to survive desiccation while free-living algae could not. It is hard to say what exactly is at play, but Aastha suspects that the worms offer some kind of protection to the algae in the dry times.

Before her research stint at the university ended, Aastha also managed to send the worms to InSTEM for RNA sequencing. This technique offers information about the proteins produced in an organism. The results were not conclusive, but they did open the possibility that there is more than a single species of algae that resides in the worm.

Aastha left in 2022 with the hope that investigations into the Sompura green worm would continue. For a while it did, however, in the following monsoon season, the worms could not be located. Anjali found out about this when she bumped into Risha during a visit to Bengaluru in 2023. ​“I was sad to hear that, but ultimately not very surprised,” she said glumly.

The end? Not yet

Flatworms are very understudied in our part of the world, and so it is not at all outlandish to suggest that the Sompura green worms may end up being a brand-new species. Despite fully realising the vulnerability of a peri-urban landscape, Sravanti believes that the worms are unlikely to be extinct. There is no reason for the worms to be restricting themselves to Sompura alone. She advocates for a more extensive search for them in similar ecosystems. After all, there is still so much to learn about the life cycle of these worms.

Whether or not the Sompura green worms are rediscovered, the teacher within Sravanti will always cherish how the tiny creatures managed to bring together so many successive batches of students and researchers. It also led to several spin-off projects, such as the discovery of green hydra, which is now a big part of her lab’s research.

The project turned into a way for students and researchers to keep in touch with each other, even though they have all moved on. Aastha is now pursuing a master’s in neuroscience at the National Brain Research Centre (NBRC), Bengaluru. Risha has just started work at Science Gallery Bengaluru, and Anjali, after completing her master’s, is now pursuing a career in academic publishing.

None of them are likely to forget the green worms any soon, especially Anjali who holds a special place for the creatures in her heart. ​“Since it started with me, it sort of felt like my baby. This was a discovery and I got to be in charge of what to do with them, and finding out what was going on with them. Most importantly,” she added, with a glint in her eye, ​“they are just so incredibly cute!”

About the Author

Nandita Jayaraj is a Science writer and Communications Consultant at Azim Premji University.