Five pairs of coelomic pouches form. The posterior pair fuse to form the gonad. The others degenerate and form the buccal apparatus and body muscles. The embryo undergoes direct development. After hatching, growth occurs by increase in cell size, not number.
Hatching is accomplished by the piercing of the egg by the stylets and legs.
Aquatic and semi-aquatic species in marine, freshwater, and damp terrestrial habitats. Typically found as part of interstitial communities, on filamentous algae, or inhabiting the surface films of mosses, lichens, and damp forest litter. Tardigrades feed on the fluids of plant and animal cells. Some tardigrades are entirely carnivorous. Tardigrades are prey for amoebas, nematodes, and other tardigrades.