- Taxonomist Jini Jacob received the Ocean Census Awards 2024 for her work documenting over 60 novel nematode species.
- Nematodes or roundworms make up a majority of the marine meiofauna — minute invertebrates that reside at the bottom of a body of water, marine or freshwater.
- Only 658 species of free-living marine nematodes have been recorded so far from India.
Jini Jacob has always been fond of Lilliputian life. During her school days, ants and other small insects were the subjects of her curious exploration through a hand lens. Zoology was the obvious choice in college, where powerful laboratory microscopes replaced the magnifying lens. After completing her M.Sc. in marine biology from the Cochin University of Science and Technology (CUSAT), Jacob joined a research project at the university on benthic (bottom-living) fauna in the Indian Ocean. During the research, she got enraptured by the “very nice to look at” nematodes, which constitute a large share of marine meiofauna. So, when the time came to pick a topic for her Ph.D. at CUSAT, Jacob chose to study the marine free-living variety of nematodes. “When I look at them under the microscope, I am just fascinated by their appearance,” she says.
Meiofauna or meiobenthos are minute invertebrates that reside at the bottom of a body of water, marine or freshwater. They are defined primarily by size and are distinguished from macrofauna by their smaller size (‘meio’ means ‘smaller’ in the Greek language), ranging from 44 to 500 µm (micrometre).
All about nematodes
Nematodes are ubiquitous organisms found in both terrestrial and aquatic environments. There are two types of nematodes: parasitic and free-living. In the ocean, free-living nematodes dominate a large share of meiobenthos.
Abundant in sediments as smaller-sized infaunal (aquatic animals that live in the sediment at the bottom of a body of water, such as an ocean or river) feeders, free-living nematodes contribute significantly to nutrient recycling in benthic ecosystems. They coexist with other larger infaunal feeders (> 500μm) like polychaetes, molluscs, and crustaceans, which also feed on sediment-dwelling nematodes and organic matter, further enhancing the “benthic-pelagic coupling”. Benthic-pelagic coupling refers to the interaction between the benthic zone (the bottom of aquatic ecosystems, such as oceans, rivers, or lakes) and the pelagic zone (the open water column above the benthic zone). The coupling involves the flow of nutrients and energy between these two zones.
These interactions support the aquatic food web, with nematodes and other benthic organisms forming a crucial link by serving as a protein-rich food source for fish larvae, juveniles, and adults, ultimately contributing to fish biomass. At the same time, parasitic nematodes can infect fish and reduce their reproductive capacity.
So far, 658 free-living marine nematodes have been recorded in India. Jacob is among the few taxonomists studying nematodes and other meiofauna in the country. Currently pursuing her postdoctoral studies at Kerala University, Jacob was one of the taxonomists selected worldwide for the prestigious Ocean Census Awards in 2024. A global alliance dedicated to enhancing ocean life discovery worldwide, Ocean Census aims to create a global repository of marine species that reflects the actual diversity of our oceans.
Jacob’s research “fills a crucial gap by documenting around 60 new nematode species across diverse habitats, creating essential baseline data for understanding species diversity, ecological roles, and ecosystem health”, it says on the Ocean Census Awards page. The taxonomist from Alleppey district in Kerala, blends “traditional taxonomy with molecular methods like barcoding to discover new species.”
A taxing field of research
Even though Jacob has documented more than 60 new nematode species, she has formally described only four. There are seven more under review and many more in between process levels, says Jacob.
According to the Ocean Census, the average time it takes to describe a new species from the ocean is 10 to 12 years. The alliance is hoping to improve species description by providing financial support to marine taxonomists worldwide through the Ocean Census Awards. Jacob’s taxonomy journey affirms the same. “It may be true in my case as well. I (first) noticed these species in 2015, and I’m only trying to describe them now,” she says.
After completing her master’s in marine biology from CUSAT, Jacob couldn’t find any relevant opportunities in marine research. She stuck around doing the odd sorting and identification job at the university, and it eventually paid off when she got to be part of a pioneering deep-sea research project in the Indian Ocean. The research project on meiofauna led to her PhD in nematode ecology, during which she came across several rare and potentially novel nematode species. But with the focus of her studies on the ecology of nematodes, Jacob had to set aside her taxonomy ambitions.
“Very few were working in benthos taxonomy itself, and there was no support for taxonomy in general,” says Jacob. Even then, with limited resources and time, over the course of her Ph.D., Jacob described four novel nematode species — Paramicrolaimus damodarani, Scaptrella filicaudata, Psammonema kuriani, and Spinonema gracilispocula. Describing a new species is tough, time-consuming work, says Jacob. “We have to compare all the existing species with the type specimen. Make every measurement, be precise with every morphology, and perform molecular DNA extraction and identification if possible.”
“We follow taxonomic papers, journals, and online sites like the World Register of Marine Species (WoRMS) and crosscheck with them. When doubts arise, we contact and discuss with researchers who are working in a nearby genus or family. Sometimes, we do the drawings straight away, collate the data, and approach a journal for publication and review,” shares Jacob.
After her Ph.D., Jacob did not work for a few years due to other commitments. In 2023, she came across the call for proposals for the Ocean Census Awards, which then lent a new lease of life to her taxonomic research. The dearth of taxonomic studies in the Indian Ocean is what gave her proposal merit, believes Jacob. “My taxonomic work at a publication level was limited. Only because the Indian Ocean is so understudied; except for my work, there was nothing from the deep sea area (from India). That really counted (in her favour),” she says.
Bioindicators of ecosystem health
For her postdoctoral studies, Jacob is exploring the potential for leveraging nematode assemblages as an ecosystem assessment model. “We can predict the conditions and health of an ecosystem, coastal area or deep sea, simply by focusing on the community of nematodes,” explains Jacob. “Whatever conditions in that environment, whatever stress in that environment, it will affect nematode growth and population dynamics.”
Jacob is studying mangrove sites across Kerala with varying pollution levels to understand how nematode communities react to pollutants. “Tolerant communities flourish while sensitive assemblages disappear. So just by assessing the nematode communities, we can predict the ecosystem health,” she says.
Jacob continues to discover new meiofauna species as she explores newer geographies and locations. “Be it samples from coastal areas or mangroves or deep sea, we come across new species regularly,” says Jacob. “From the current study, we have noticed some species as new, but I am now focusing only on previously discovered species. “Species-level data is sorely lacking. So, we must generate more data about free-living nematodes, especially from the northern Indian Ocean,” she sums up.
Future of meiofauna taxonomy
Jacob hopes to formally describe all 60 nematode species by 2026. “The funding means we have the financial support to conduct taxonomic research using molecular methods or otherwise. It is motivating us to do more towards taxonomy,” says Jacob.
Jacob also hopes that the funding will provide more recognition to deep-sea benthic studies in the Indian Ocean and broaden the mapping of marine life in the region. Researchers have generally stayed away from studying meiofauna in the country, and she hopes this too will change. “Studying benthos is not easy. People do not have the patience to work so many hours with the microscope. As of now, not many are coming to (study) the meiofauna group,” she shares.
When asked why she decided to commit her research life to studying nematodes, Jacob says, “I feel I am giving an opportunity to these smaller animals to come into the world. I want to describe all the species in the group!”
Without question, India will need more people like Jini Jacob to guide future generations of research and preservation of marine life.
Read more: The fish that skips and crawls on land
Banner image: Taxonomist Jini Jacob observes a sample in a lab. She received the Ocean Census Awards 2024 for her work in documenting over 60 nematode species, four of which she has formally described. Image courtesy of Jini Jacob.
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