Gastrotricha
Gastrotricha are microscopic aquatic animals that belong to the phylum Gastrotricha. They are commonly known as hairy bellies due to the presence of cilia on their ventral surface, which they use for locomotion. These tiny creatures, typically measuring between 0.05 and 0.3 millimeters in length, inhabit a wide range of aquatic environments, including freshwater, marine, and brackish waters. They are often found in interstitial spaces of sediments, such as sand and mud, as well as on submerged vegetation.
The body of a gastrotrich is elongated and unsegmented, with a distinct head region and a tail.