Mapping the mind of a water bear

Tardigrades are microscopic, eight-legged invertebrates that live in diverse environments ranging from deep oceans to damp moss. They are widely known for their ability to enter a dormant state called cryptobiosis, allowing them to survive extreme temperatures, high pressure, radiation, and the vacuum of space. Once reintroduced to water, they rehydrate and return to their normal active state.

Tardigrades possess a segmented body plan consisting of a head and four trunk segments, each supporting a pair of legs. Despite having a relatively small number of cells and a simple nervous system with few neurons, they exhibit complex limb coordination and can adjust their walking gaits based on the surface they are traversing. They also feature rudimentary eyespots, known as ocelli, which allow them to detect light.

Over 1,300 species of tardigrade have been described, inhabiting nearly every environment on Earth — from Antarctic ice sheets to tropical rainforests and deep-sea sediments. While many share the hallmark traits of cryptobiosis and radiation resistance, their exact physiological and neurological properties vary considerably across the phylum. Our research focuses on Hypsibius exemplaris, a freshwater species that has become the leading laboratory model for tardigrade biology thanks to its transparency, short generation time, and well-characterised genome.