Appendicularia

Larvaceans, copelates or appendicularians, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. While larvaceans are filter feeders like most other tunicates, they keep their tadpole-like shape as adults, with the notochord running through the tail. They can be found in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, usually ranging from to in body length including the tail, although giant larvaceans can reach up to in length.

Larvaceans are known for the large houses they build around their bodies to assist in filter-feeding. Secreted from mucus and cellulose, these structures often comprise several layers of filters and can reach up to ten times their body length. In some genera like Oikopleura, houses are built and discarded every few hours, with sinking houses playing a key role in the oceanic carbon cycle.