Water bears, also known as tardigrades or moss piglets, are captivating microscopic creatures. These tiny invertebrates are recognized for their distinctive appearance and unusual capabilities. Their presence in diverse environments highlights their remarkable biological design. Their surprising resilience often fascinates.
Observing Water Bears
Water bears are not visible to the unaided human eye. Most species are about 0.5 millimeters (0.02 inches) long, roughly the size of a period. Even larger individuals, up to 2 millimeters, are difficult to spot due to their translucent bodies. A microscope is necessary to observe their intricate details, such as segmented bodies, eight stubby legs, and slow movement. Magnification levels from 40x to 100x are typically required for study.
Under a microscope, water bears exhibit a distinctive barrel-shaped body and eight clawed legs, contributing to their “water bear” moniker. They move with a characteristic slow, ambling gait. Researchers often use basic brightfield microscopy, though advanced techniques like darkfield or phase contrast enhance visibility of internal structures. Even at lower magnifications, their unique morphology and movement patterns become apparent.
Where to Find Water Bears
Water bears are remarkably widespread, inhabiting nearly every environment on Earth where a thin film of water can persist. They are considered aquatic animals, as they require this moisture for active life processes like gas exchange. Common terrestrial habitats include damp mosses, lichens, and leaf litter, which provide both a humid microenvironment and a food source. They can also be found in garden soil, freshwater ponds, and even the powdery lichen growing on rocks and walls.
To find water bears, collect samples of damp moss or lichen and soak them in non-tap water for several hours. After soaking, squeeze the water into a shallow, transparent dish. Water bears, being slow crawlers, will settle at the bottom, making them easier to locate under a microscope. Patience is helpful during the initial search, as they may take time to emerge from dormancy.
The Remarkable Abilities of Water Bears
Water bears are known for their extraordinary resilience, enduring conditions lethal to most other life forms. This survival mechanism is attributed to cryptobiosis, a state of suspended animation. During cryptobiosis, their metabolism slows to less than 0.01% of its normal rate, allowing them to withstand extreme environmental challenges. This dormant state enables survival in extreme temperatures, high radiation, and even the vacuum of space.
One specific form of cryptobiosis, anhydrobiosis, allows water bears to survive severe dehydration. When water is scarce, they curl into a compact, dried-up ball known as a “tun.” In this tun state, a sugar called trehalose replaces water within their cells, preserving cellular structures until conditions improve. Water bears in this state can endure temperatures from -270°C to 150°C and revive within hours or days once rehydrated, even after decades of dormancy.