Tardigrades are microscopic invertebrates measuring between 0.2 mm and 1.1 mm in length. They are close relatives of arthropods (spiders, insects, crustaceans), and can live in a wide variety of environments. Yet little is known about them. Tardigrades are microscopic invertebrates measuring between 0.2 mm and 1.1 mm in length. They are close relatives of arthropods (spiders, insects, crustaceans), and can live in a wide variety of environments. Yet little is known about them. Ecology Cell & Microbiology Phys.org – latest science and technology news stories