The appendicularians are planktonic tunicates exclusively marine, characterized by the presence of the notochord in the adult stage and the lack of the peribranchial cavity and cloacae. The body is transparent and divided into two regions: a trunk, exceptionally exceeding 5 mm, and a tail which is generally several times longer than the trunk. These organisms, with exception of Oikopleura dioica, are hermaphroditic protandric, and release their gametes directly to the water column. They have both very high fecundity and growth rate. The primarily food item of appendicularians is pico-nannoplankton, virus, bacteria and mucoid substances. They feed by means of a complex mucous structure, the "house" which is secreted by the trunk and used as tangential flow filter to concentrate ambient food particles prior to their collection by the pharyngeal filter. The appendicularians are important food item of others components of the zooplankton, including larval and adult fish. On the other hand, the marine snow produced by them contribute substantially to the carbon turn over time. The sinking rates of their faecal pellets and discharged houses can reach deep waters and their repackaging activity may play a significant role in channeling short lived carbon toward sequestration. The Appendicularians are conspicuous members of marine zooplankton, occurring in both neritic and oceanic regions of all oceans. High number of species is epipelagic, being most abundant around 100-200 m. However, some species inhabit the meso-and bathypelagic regions. The highest diversity of Appendicularians has been reported from warmest waters. At the moment 82 species belonging to the Oikopleuridae, Fritillariidae and Kowalesvkiidae families were identified, and from these, 43 species have been recorded in South Atlantic and 29 species in Brazilian waters. In São Paulo State twenty species were found along the coastal waters.
appendicularia; biodiversity of the State of São Paulo; BIOTA/FAPESP Program