Larvaceans: Appendicularia

Larvaceans (lar-VAY-shuns) are small, clear sea animals that make a complex net, or house, of mucus. They live their entire lives as tadpoles, or larvae, even when they are adults and ready to reproduce. Larvae (LAR-vee) are animals in an early stage that change form before becoming adults. The body of larvaceans is made up of a trunk containing most of the internal organs and of a tail with a notochord running down the middle. A notochord (NOH-tuh-koord) is a flexible rod of cells that supports the body of some simple animals. The trunk secretes the mucus house, which encloses the entire animal or only the tail, depending on the species. The body and house are jellylike. The body of larvaceans is 0.04 to 1 inches (1 to 25 millimeters) long. The house is 0.2 inches to 7 feet (4 millimeters to 2 meters) across.

Larvaceans have an amazing filtering mechanism. The wall of the house contains two filters, and a filter in the trunk is connected to the animal's mouth. The filters are made of strands of mucus that allow only the smallest food particles, those less than 0.0004 inches (1 micrometer) in diameter, into the tube leading to the mouth.