Appendicularia (Larvacea)

Article By:

Alldredge, Alice L. Department of Biological Sciences, University of California, Santa Barbara, California.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.044350

A class of marine, planktonic animals in the subphylum Tunicata. The class Appendicularia (alternatively known as Larvacea) is characterized by the persistence of a tail, notochord, gill slits, and dorsal nerve cord throughout life and by a unique feeding structure—the “house.” Appendicularians (larvaceans) are free-swimming, solitary animals that are believed to have evolved through neoteny from the tadpole larvae of a bottom-dwelling, ascidianlike, ancestral tunicate. They resemble a bent tadpole with a flat, muscular tail and a trunk containing all major organs. Appendicularians have a complex digestive system, reproductive organs, two ciliated openings of the gill slits (the spiracles) leading to a mucus-lined pharynx, a mucus-producing gland called the endostyle, and a simple circulatory system with a single, muscular heart (Fig. 1). There are three families: Oikopleuridae, Fritillariidae, and Kowalevskiidae. See also: Chordata; Neoteny; Tunicata (Urochordata)

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