If there was an official fan club for tardigrades, also known as water bears, its president would be Ana Lyons, Ph.D. She first learned about these charismatic microscopic animals on a trip to the library as a teenager, and she’s been a lifelong enthusiast of these creatures that are found in nearly every ecosystem imaginable. “I found it captivating that there is this parallel microscopic world that I could learn about,” said Lyons.
The smallest animal we know of that has both eyes and limbs, at just half a millimeter in length, tardigrades are well known for their hardiness in extreme conditions. We’ve sent them to space and found them among hydrothermal vents on the ocean floor. But Lyons, who as a graduate student studied their thermal tolerance, cautions that their reputation for indestructibility is somewhat misunderstood. “They can go into all of these forms of complex dormancy because they’re so sensitive to environmental stimuli.”
With all their complexity in a tiny transparent package, could tardigrades be a useful organism for neuroscientists to study as they unravel the many mysteries of the brain? In systems neuroscience, animals like Drosophila fruit flies and C. elegans worms are all the rage, each with particular benefits as model systems, but Lyons thinks it’s time tardigrades have their moment.
For tardigrades to be adopted as a model organism in neuroscience, some basic research needs to be done, and Lyons is more than willing to lay the groundwork for this to happen. As a 2024 Grass Fellow, she set out to the Marine Biological Laboratory at Woods Hole, Massachusetts, with two main goals in mind for her go-to tardigrade species, Hypsibius exemplaris: neuronal mapping and introducing an optical sensor into its genome.
Each of the approximately 2,000 tardigrade species has several hundred neurons, but we don’t yet know the exact number any one species has, or if it changes throughout development. At the Grass Lab (and in collaboration with Nipam Patel’s lab) Lyons used RNA tools to place fluorescent probes on biomarkers for different types of neurons, allowing her to count the amounts and types of neurons at different stages of development. Lyons will present these results at the International Tardigrade Symposium in Tsuruoka Japan in June 2025, and in an upcoming preprint.
Another frontier to explore for tardigrades to serve as models for neuroscience research are genetic tools, like genetically encoded calcium indicators (GCaMP). When these genes are successfully incorporated into the genome and expressed, a green fluorescent protein lights up when bound to calcium ions, allowing researchers to watch neural activity in real time with single-cell resolution. Lyons attempted to introduce GCaMP6s into the germline of tardigrades to result in a culture of tardigrades ready for optical neuroscience research. She found partial success on this front, establishing transient expression but not quite germline integration, although the techniques she developed will enable future work in this area.
As someone who is passionate about blazing new trails in neuroscience, Lyons found camaraderie and support during her time at the Grass Lab at the Marine Biological Laboratory, surrounded by passionate and curious scientists who are eager to learn and try new things.
“So many people are working in non-model organisms, that we start to recognize patterns of bottlenecks that we’re having. We see things that we can take from one system to another that I think just wouldn’t typically happen in our day-to-day or in the typical conferences we might go to,” said Lyons. “It’s definitely a bit of a risk and a bold move to try to develop an entirely new system as your life’s work scientifically, so the supportive aspect is so important to me.”
Lyons recently relocated to Japan to work with renowned tardigrade expert Kazuharu Arakawa, where she is currently a postdoctoral researcher at Keio University’s Institute for Advanced Biosciences. She’s laying the groundwork to launch her own lab dedicated to the neurobiology of these tiny, resilient creatures. Lyons plans to be as open as possible in her research practices to welcome more scientists into the tardigrade community, from publishing open source protocols and open source papers to video instructions and other shared resources.
“We’re going to make tardigrades take off!” she said.