Gastrotrichs: Gastrotricha

Gastrotrichs (GAS-truh-tricks) are microscopic water-dwelling worms shaped like straps, bowling pins, or various forms in between. They are 0.002 to 0.1 inch (50 micrometers to 3.5 millimeters) long. The body is flat on the bottom and arched on the top. The body covering is almost see-through, like fogged-up glass. The belly is covered with hairlike fibers. The body is divided into head and trunk regions. The head has a mouth at the tip and sometimes eyes, tentacles, or both. The trunk contains a straight intestine, reproductive organs, at least one pair of simple waste-filtering organs, and an anus (AY-nuhs). Muscles on the trunk run in the circular, lengthwise, and spiral directions. There is no body cavity. Some gastrotrichs have sticky tubes on the head or trunk.