There are ‘water bears’ all around us

Imagine a bear a few millimetres long, having eight legs, tiny mouth and no snout, swimming in water. Sounds weird? Well, that is a tardigrade for you! Also called ‘water bears’ or ‘moss piglets’, based on their looks, these microscopic organisms are unlike any other. First described in 1773 by the German zoologist Johann August Ephraim Goeze, today we know of about 1,300 species of tardigrades that live in the world.

Tardigrades are found everywhere on the planet—from the hot springs in the lofty Himalayas to the Mariana Trench, the deepest ocean trench. They are also found in mud volcanoes, tropical rain forests and even in the ice sheets of Antarctica! But you don't have to go to such extreme environments to look for them—you can spot them in the nearest pond, meadow or the roof! Wherever there is a trace of moisture, you can find them feeding on tiny bacteria or plants or sometimes, on smaller tardigrades.

Scientists are mesmerised by tardigrades because they can survive in the most hostile environments where no other organism can. They can endure temperatures as cold as absolute zero (−272 °C) or as hot as 150 °C. They tolerate extreme pressure, environmental toxins, dehydration and starvation. They are also not harmed by powerful radiations like Gamma rays. In a recent study, scientists from the Indian Institute of Science, Bengaluru, showed that tardigrades survive Ultraviolet (UV) rays by exhibiting fluorescence, where they absorb UV rays and reflect light that we can see. They are the first known animals to have survived the vacuum of outer space when they were launched into low-Earth orbit in 2007.

Tardigrades are of particular interest in science because they act as ‘pioneer species’, inhabiting new environments and thus attracting other organisms, like their predators, to these environments. Scientists are now learning about what makes these little ‘water bears’ so hardy. In 2019, it was reported that a capsule containing frozen tardigrades might have remained on the Moon after a mission carrying it crashed there. Who knows, the next Astronauts landing on the Moon may bump into these little creatures who may have already made the Moon their home!