What kind of organisms enter a "tun" state when exposed to unfavorable conditions?

Bonus: Tardigrades are microscopic eight-legged animals that have been to outer space and would likely survive the apocalypse. Bonus: They look like adorable miniature bears.

Around 1,300 species of tardigrades are found worldwide. Considered aquatic because they require a thin layer of water around their bodies to prevent dehydration, they’ve also been observed in all kinds of environments, from the deep sea to sand dunes. Freshwater mosses and lichens are their preferred habitat, hence their nickname, moss piglet.

The most remarkable feature of the tardigrades is their ability to withstand extremely low temperatures and desiccation (extreme drying). Under unfavourable conditions, they go into a state of suspended animation called the “tun” state—in which the body dries out and appears as a lifeless ball (or tun). In this state their metabolism may decline to as little as 0.01 percent of its normal rate. Tardigrades can survive as tuns for years, or even decades, to wait out dry conditions. In addition, specimens kept for eight days in a vacuum, transferred for three days into helium gas at room temperature, and then exposed for several hours to a temperature of −272 °C (−458 °F) came to life again when they were brought to normal room temperature. Sixty percent of specimens kept for 21 months in liquid air at a temperature of −190 °C (−310 °F) also revived. Tardigrades are easily distributed by wind and water while in the tun state.