The saga of the Sompura green worm began one day during the summer break of 2017. Biology students Shivani and Deepak set out on a short field trip to a water body in Sompura, a locality on the outskirts of Bengaluru, near Azim Premji University’s then-temporary campus. Intending to collect tiny crustaceans called Daphnia from the rain-replenished pond, the duo happened to find a bunch of green worms in their sample. Something about their accidental catch reminded them of Planaria, the free-living flatworms they had heard about from Sravanti Uppaluri, a BSc Biology faculty member at Azim Premji University. 

At first sight, Sravanti was not sure what to make of the millimetre-long green blobs presented to her. They did not look like any Planaria she had seen documented before, so what on earth were they, she wondered. Only time and further tests would tell.

Unfortunately, before they got the chance to probe, the sampled worms died out. With the ponds drying out in the dry season, and Shivani and Deepak graduating soon, Sravanti wondered when and if she would ever hear of the mystery worms again. 

Unexpected reappearance

A couple of years later, she was back at one of Sompura’s other ponds, this time accompanying students on a drawing workshop. Sravanti joined her students in sampling the pond water. Her sample seemed rather nondescript, nevertheless she took it back to the lab. Nearly a week later, she noticed something. The mud had fully sedimented, and a few familiar green worms were swimming in the container.

This was around the time a final-year student named Anjali Paranjape (BSc Biology, 2017 – 2020) expressed her desire to work with Sravanti on a project. They were about to finalise Planaria as their subject of study when Sravanti brought up the unidentified green worms that had re-appeared in her life. Immediately intrigued, Anjali did not waste much time before heading out in search of these worms herself. 

“That was generally the kind of atmosphere within our batch,” says Anjali, describing how she and her friends often ventured into the nearby forested areas for field trips. Temporary ponds would periodically crop up in the eucalyptus forest in Sompura, either due to human-made excavation activities or land erosion caused by grazing cattle. 

There were at least two such ponds that Anjali knew of; ponds which had provided her peers with plenty of interesting biological creatures to experiment with including planaria, hydra, daphnia, as well as several unidentified ones like the mysterious Sompura green worms. 

Almost five years later, Anjali still remembers what it was like to go sample collecting for the green worms. She would tentatively insert a falcon tube into the pond, watch as pond water as well as some surface soil poured in, and hold her breath as tiny oval creatures streamed out, their dark bodies stark against the orange Karnataka soil. As the water cleared, she would see it, the unmistakable green.

Testing for superpowers

It did not take long for Anjali and Sravanti to gather that the worms were inherently transparent. The source of their colour was a photosynthetic algae that lived under the surface of their skin, perhaps, the surmised, in some kind of symbiotic relationship. 

Naturally, the first thing Anjali thought to do was to try and identify the species. For this, some basic observations would have to be made on the appearance and behaviour of the worms, their lifespan, mode of reproduction, etc. Answering these seemingly simple questions was trickier than expected, primarily because the worms would not stay alive in the lab long enough. 

“Moreover, it was incredibly difficult to observe these processes in real time,” remarked Anjali. ​“At some point, we had to close the lab, and we did not know what was happening at that time.” 

Flatworms like Planaria have a famous capability: they are, as Scottish naturalist John Graham Dalyell put it in 1814, practically ​“immortal under the edge of a knife”. Studies have shown that a Planarian cut up into a fragment as small as ¹⁄₂₇₉^th its original size can regenerate completely within a few weeks! 

Not only is this power just plain fascinating, but it also teases us with some awesome possibilities. If we figure out how the worms can do it, maybe someday we can engineer a way to regenerate our lost tissues. Scientists have been at this for decades.

Did the Sompura green worm have regenerative capabilities, too? ​“We would not know unless we tried. So we tried cutting them and just seeing if they grew back,” says Anjali. This did not happen. Still, there was something curious happening: ​“I noticed that the amputated worms would stay alive for a few weeks, and their movement and feeding continued during that time.” This indicated to Anjali that there was some kind of wound-healing mechanism at play, enabling them to live on for a while. 

The quest for an ID

So what were these worms? The absence of regeneration seemed to confirm her professor’s hunch that the worm was not a planarian after all. They sought the help of some international flatworm experts, but they too were unable to identify the Sompura green worm. With attempts to identify the worm based on observable characteristics and existing knowledge going nowhere, Sravanti nudged Anjali to look to genetics for some answers. 

DNA sequencing is a sure-shot way of identifying known species, and it is no longer as expensive and time-consuming as it used to be. Anjali had access to kits that would extract DNA from the worms as well as PCR equipment to amplify this DNA. Eventually, the sample was sent for sequencing to the Centre for Cellular and Molecular Platforms (C‑CAMP), Bengaluru. 

“Now, all we had to do was compare our sequence to existing databases of flatworm sequences and wait to find a match,” said Anjali. ​“We did not find a match. That was when we realised this might be a new species.” 

Anjali was unsure what her next options were, but fortunately, she received a useful suggestion from Priya Tamma, a biologist who had just joined the university as faculty. ​“Priya had worked in biogeography and she had worked a lot with phylogenetics. Speaking to her, we realised that the next best thing to do was to run a phylogenetic analysis,” said Anjali. 

A phylogenetic analysis is a technique that uses the same DNA sequence and statistical models to construct an evolutionary tree that depicts possible ancestors as well as closely related species of the sample. Doing this could help narrow down an unidentified species to the closest family or genus. 

The analysis revealed that the worms were closest to a flatworm species called Phaenocora foliacea; though there were no records of P. foliacea containing green algae. Further, Anjali’s analysis showed that despite the similarity, the genetic distance between the Sompura green worm and P. foliacea was large enough to constitute a new species.

It must be said that the group was well aware that there was an obvious drawback to their analysis. ​“The databases we were using were based on research done by scientists who worked on worms all over the world, but there was just one species that was from India,” pointed out Anjali. The Indian worm happened to be from Goa. Curious to see this worm for herself, she snuck in a sampling session while on a Goan holiday with friends that year. Anjali did not manage to find any worms there, but it sunk in her that there were very likely dozens of flatworm species waiting to be discovered in India.

While this was all going on, the world outside Anjali’s microscope was in chaos. Early in 2020, the pandemic struck, and soon, classrooms and labs closed. It was frustrating to have to terminate her experiments and pack up to Pune, her hometown, without any definite idea of when she would be able to return. The silver lining for Anjali was Risha (BSc BEd Biology, 2019 – 2023), her junior at the university.

Risha was just a few months into their first semester when they came upon Anjali’s research. ​“She was presenting a research poster at Undergraduate Science Research Conference (SURC 2019 held at Azim Premji University, Bengaluru campus), which had before-and-after photos of some pond. I could see that it changed so much just over the last year. Anjali also showed me pictures of the worm that she was trying to study,” reminisced Risha. Once they heard about the unidentifiable creatures lurking within these transient ponds, Risha decided that they would have to see this for themselves.

The next few times Anjali visited the ponds of Sompura to collect samples for her research, Risha tagged along. Tantalised as they were by the presence of unidentified creatures in their backyard, it was the broader pond ecosystem that drew Risha in. The idea that a small, dynamic water body could be so rich in terms of species diversity was just too cool for them to ignore. 

Guided by Sravanti, Risha joined Anjali in testing the worms in the lab. They started with a series of survival experiments to figure out what temperatures the worms thrived in, how to maintain the sample, clean the medium… the basics, but extremely useful for the first-year student to get to know the process of working in a lab better. 

Homebound but making it work

Homebound during the pandemic, Anjali and Risha kept the project alive through periodic online brainstorming sessions. They would discuss new research papers and outline plans for experiments they would perform as soon as they were back. But as the lockdown kept getting extended, it became evident that the university would not open any time soon. Anjali’s batch of 2020 graduated, and for a moment it seemed like the end of the road for the Sompura green worm project.

Indeed all the experiments would have come to a screeching halt, if not for the lucky fact that Risha lived in Bengaluru. Around August, they were able to commute to Sompura, drop into the university laboratory to borrow some collection equipment, and find their way to the ponds for some sampling. The university wasn’t officially open, and it was still not safe to travel often, so Risha took the worms home. And so the next phase of research on the Sompura green worms occurred in Risha’s bedroom laboratory.

About the Author

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