The great majority are benthic sac-like filter feeders in the class Ascidiacea. Most species filter water by a variety of mechanisms to extract fine planktonic food particles. They have a superficial resemblance to the so-called tadpole larvae of benthic ascidians. The tail possesses a notochord and is used for locomotion and for producing water currents that aid feeding. An individual may produce up to 10 or more houses in a single day.
Most larvaceans are hermaphrodites.
With a short generation time and rapid rate of development, larvaceans can form dense blooms over a wide area in a matter of days. The most commonly encountered surface dwelling West Coast larvaceans are several species of Oikopleura . Salps can form massive aggregations of millions of individuals that may play a significant role in marine ecosystems. They exhibit among the fastest growth rates of any multicellular organism. A transparent test encloses the cylindrical body, and may be relatively thick and tough with projections and keels.