Known as water bears, a Tardigrade can survive freezing temperatures, radiation, even a trip to outer space. It’s the most resilient animal on Earth.

These water-dwelling creatures are eight-legged microscopic animals. They have been found everywhere. Starting from mountaintops to the deep sea mud volcanoes, and from tropical rain forests to the Antarctic. Pick up a piece of moss, and you’ll find tardigrades. In the soil, the ocean: Tardigrade. They live on every continent, in every climate, and in every latitude. Their extreme resilience has allowed them to conquer the entire planet.

Humans have known about tardigrades since the dawn of the microscope. However, scientists are just starting to understand how these striking organisms are able to survive everywhere.

Scientists initially thought tardigrades were surviving dehydration by using a sugar called trehalose. In bacteria and fungi, trehalose can turn the inside of cells to a glass-like matrix that keeps proteins from being damaged in super dry conditions. Scientists call this process vitrification. It allows dried-up organisms to hold proteins and molecules together until the organism rehydrates and can get back to business.

Discovery and naming

Tardigrades were first described by Johann August Ephraim Goeze in 1773, and dubbed Kleiner Wasserbär, meaning “little water bear.” The Italian scientist, Spallanzani, named it Tardigrada, which means “slow walker.” However, it may be that Anton van Leeuwenhoek was actually the first to see tardigrades. On September 3, 1702, he performed an experiment using dried dust from the gutter on the roof of his house. Leeuwenhoek added boiled water to this dust and when the living organisms came into being, it blew his mind.


Tardigrades are oviparous (animals that lay eggs, with little or no other embryonic development within the mother). So, fertilization is usually external. Mating occurs during the molt with the eggs being laid inside the shed cuticle of the female and then covered with sperm. A few species have internal fertilization with mating occurring before the female fully sheds her cuticle. In most cases, the eggs are left inside the shed cuticle to develop, but some species attach them to a nearby substrate.

The eggs hatch after no more than 14 days, with the young already possessing their full complement of adult cells. Growth to the adult size therefore occurs by enlargement of the individual cells (hypertrophy), rather than by cell division. Tardigrades may molt up to 12 times.

And yeah, they are CUTE.

Tardigrades get up to 17.5 percent of their genes from unrelated organisms. (STEVE GSCHMEISSNER/Science Photo Library/Corbis)