Tardigrades, also known as water bears or moss piglets, are microscopic invertebrates, typically 0.1 to 1.5 millimeters long, known for their extraordinary capabilities. Found across the planet, their widespread presence is a testament to their remarkable resilience in diverse environments.
Ubiquitous Microscopic Habitats
Tardigrades commonly inhabit damp, terrestrial environments. They thrive in the thin film of water surrounding mosses and lichens on rocks, trees, and rooftops. These plants retain moisture, creating suitable micro-ecosystems where tardigrades actively feed and move. Densities can be high, with some moss samples yielding over two million individuals per square meter.
Beyond mosses and lichens, tardigrades are abundant in leaf litter and soil, especially in damp or wet conditions. These habitats provide essential moisture and a rich supply of food sources like bacteria, algae, and decaying organic matter. In freshwater settings, they are found in the sediments of ponds, lakes, and rivers, and among aquatic vegetation. Tardigrades require a surrounding film of water for gas exchange and to prevent desiccation, making moist environments suitable for their active life.
Extreme Environments
The adaptability of tardigrades extends to Earth’s most challenging environments. They have been discovered in the deep sea, surviving pressures six times greater than those in the deepest ocean trenches. High mountain peaks, including the Himalayas, and polar regions like Antarctica host various tardigrade species, enduring freezing temperatures and limited resources.
Tardigrades can be found in deserts, within cryptobiotic soil crusts, and near volcanic vents. Their ability to survive harsh conditions stems from cryptobiosis, a unique state where they suspend their metabolism. In this state, they tolerate extreme temperatures, from nearly absolute zero (-272°C) to well above boiling (149°C), high radiation, and the vacuum of space. Tardigrades can persist for years, reanimating when favorable conditions return.
Collecting and Observing
For observing tardigrades, collecting samples from common habitats is a practical first step. Moss and lichen scraped from tree bark, rocks, or rooftops are excellent sources. Leaf litter or sediment from a pond bottom can also yield specimens. Place collected samples in a container, ideally a paper bag or envelope to prevent mold, allowing them to dry slightly before rehydration.
To encourage tardigrades to emerge, soak dried moss, lichen, or leaf litter in non-tap water (distilled or rainwater) for several hours or overnight. After soaking, gently squeeze or shake the sample over a clean dish to collect the water, which will contain reanimated tardigrades. Allow the water to settle, then use a pipette or dropper to transfer a small amount from the dish bottom onto a microscope slide. A basic compound microscope with at least 40x magnification (400x is ideal for detailed viewing) is sufficient for observation. Patience is helpful, as some tardigrades may take time to become active after rehydration.