Hunting the Tardigrade: A Milestone in Sequencing Earth’s DNA
Hunting the tardigrade – At the Wellcome Sanger Institute in Cambridgeshire, Witek Morek is meticulously examining a weathered brick-and-flint wall. “We’ll employ a remarkable tool—the human hand—to gather some moss and seal it in an envelope,” he explains. This seemingly simple task marks the beginning of a colossal scientific initiative: to catalog the complete genetic blueprint of every organism on Earth. Accompanied by Prof Mark Blaxter, the leader of the institute’s Tree of Life project, Morek collects lichen from a walnut tree on the verdant campus before heading back to the lab. His mission is to study microscopic tardigrades, creatures that have become a symbol of resilience and scientific fascination.
The Genesis of a Global Project
The quest to sequence all life began with a tiny nematode worm in 1998, which became the first animal to have its entire genome mapped. Just five years later, the human genome was completed, though its full complexity wasn’t finalized until 2021. A genome, Morek notes, is the genetic recipe for an organism, encoded in DNA. But genomics extends beyond individual genes to encompass all the genetic material between them, offering insights into evolutionary pathways and biological functions.
“Sequencing genomes used to take years,” says Blaxter. “Now, we’re able to process 48 species each week thanks to technological leaps.”
By 2026, the Tree of Life programme has already amassed over 2,600 reference genomes, spanning diverse life forms from whales to fungi. Most of these focus on species native to Britain and Ireland, but the team is now turning its attention to tardigrades, which won last year’s Guardian Invertebrate of the Year contest. These tiny organisms, numbering around 1,500 species globally, are renowned for their extraordinary survival abilities. They can endure extreme conditions, from searing heat to freezing cold, and even thrive in the vacuum of space.
The Science Behind Super Survival
Morek’s work highlights the unique biology of tardigrades. “Their secret lies in a state called cryptobiosis,” he explains. When deprived of water, these creatures shrink and enter a dormant phase, effectively halting all metabolic activity. This adaptation allows them to survive for years in harsh environments. But the process of reviving them is both delicate and fascinating. By placing collected moss and lichen in water, Morek waits for the tardigrades to rehydrate and become active, a process that takes roughly half an hour.
Once alive, the tardigrades are examined under a microscope. Morek identifies one specimen, a translucent creature about 350 micrometres long—roughly the size of a grain of sand. Its gut contents are visible, indicating recent feeding. To confirm the species, he prepares a temporary slide, ensuring the water doesn’t evaporate too quickly. The tardigrade is then transferred to a barcoded plastic tube and stored in lab freezers set at -71°C, preserving it for later analysis.
Overcoming Genetic Challenges
Sequencing tardigrade DNA presents unique hurdles. These microscopic organisms contain only a small amount of genetic material, ranging from 200 to 500 picograms—far less than other species. In the past, researchers had to pool thousands of tardigrades to extract enough DNA, a laborious process that limited progress. Morek now uses a cutting-edge method: picogram input multimodal sequencing. This technique allows for precise analysis of even minuscule genetic samples, making it possible to sequence individual specimens.
“We can manually disrupt the tardigrade with a scalpel or use a block of ice to mash it while frozen,” Morek explains. “This ensures we get sufficient DNA without losing the sample’s integrity.”
The approach also enables the study of tardigrade reproduction. Some species lay smooth eggs, while others produce irregularly shaped ones, such as mushrooms or needles. Morek highlights the surprising complexity of their life cycle: a mother may shed her cuticle to release eggs, yet retain the skin on her legs until the offspring hatch. This behavior underscores the evolutionary sophistication of these ancient invertebrates, which have existed for over 500 million years.
A Vision for the Future
The Tree of Life project’s progress reflects a broader shift in genomics. By 2026, four high-quality tardigrade genomes are already available in public databases, with another 14 under active investigation. Around 50 species remain in the lab’s freezer, awaiting their turn to be decoded. This effort isn’t just about cataloging life—it’s about unlocking potential. Reference genomes, Morek emphasizes, provide critical tools for understanding how organisms adapt to their environments and for discovering new medicines or biochemical compounds.
As sequencing technology evolves, the pace of discovery accelerates. What once required decades of work can now be achieved in weeks, transforming the study of biodiversity. For Morek, the challenge is twofold: to sequence the DNA of every tardigrade species and to reveal the hidden secrets of their biology. “We’re only just beginning to grasp their full potential,” he says. “These creatures could hold the key to understanding life’s resilience in the face of planetary change.”
The Wellcome Sanger Institute’s work on tardigrades exemplifies the intersection of ancient survival and modern science. By combining traditional methods—such as hand-collected samples—with cutting-edge genomics, researchers are bridging the gap between the microscopic and the macroscopic. This collaboration between human ingenuity and the tenacity of tardigrades may one day revolutionize how we study life on Earth and beyond. As Morek continues his hunt, the next step is clear: to turn these tiny, unassuming creatures into a gateway for unlocking the planet’s genetic legacy.
