Although appendicularians are relevant primary consumers and are part of every zooplankton community, there is a lack of information on the species present in different ocean regions. Thus, regional identification guides are useful to develop datasets with high taxonomic resolution. Appendicularian species were identified in 33 epipelagic samples of zooplankton collected in several locations of Costarican waters. Eighteen appendicularian species were identified, of which 15 were found in the Pacific and only three in the Caribbean. Seven species are new records for Costa Rican Pacific waters (Appendicularia sicula, Fritillaria charybdae, F. cf. pacifica, F. tenella, F. pellucida f. omani, Oikoipleura fusiformis f. cornutogastra and Pelagopleura verticalis). Data for each species distribution in Costa Rica is presented together with a key for the identification of appendicularian species recorded in the Inter-American seas and the Eastern Tropical Pacific.
Keywords: Pelagic tunicates, Costa Rica, identification key, Caribbean Sea, zooplankton, taxonomy, species list.