Appendicularians (Urochordata) and chaetognaths (Chaetognatha) of Isla del Coco National Park, Costa Rica. Appendicularians and chaetognaths are important members of the zooplancton but little studied in Costa Rica and not at all at Isla del Coco Nacional Park, eastern tropical Pacific. Epipelagic (0-50m) zooplankton samples from the oceanic area off Isla del Coco, were collected in November 2001, and over patch reefs in 2009. We analized the species composition of appendicularians and chaetognaths present in 31 samples. Nine species of appendicularians, and eight species of chaetognaths were identified. Oikopleura longicauda was the most abundant in the surveyed area (217 specimens, 65.56% of total appendicularian numbers), followed by Oikopleura rufescens with 35 (10.57%). All the appendicularian species found in this study are common in warm ocean waters, but six species herein recorded for the first time from waters off Isla del Coco, and two species are new records for Costa Rica. Among the chaetognaths, Flaccisagitta enflata was the commonest species (85 specimens, 50.6% of total numbers) recorded in this study, followed by Serratosagitta pacifica with 38 organisms (20.62%). Zonosagitta bedoti was represented by a single specimen. These species have been recorded from tropical waters of the Eastern Pacific, but six species are new records for Isla del Coco. Data on the distribution and morphology of the species recorded are presented together with keys for the identification of both taxa in the surveyed area. Citation: Castellanos-Osorio, I., R.M. Hernández-Flores, Á. Morales-Ramírez & M. Corrales-Ugalde. 2012. Apendicularias (Urochordata) y quetognatos (Chaetognatha) del Parque Nacional Isla del Coco, Costa Rica. Rev. Biol. Trop. 60 (Suppl. 3): 243-255. Epub 2012 Dec 01.
Keywords: appendicularians, chaetognaths, Isla del Coco, Costa Rica, identification key