Polychaetes (Annelida: Polychaeta) of Cocos Island National Park, Pacific Costa Rica

An extensive collecting effort resulted in identification of 106 species of polychaetes from the intertidal and shallow subtidal of Isla del Coco, Costa Rica. One hundred and three of the species reported here are new records. Only two species had not been previously collected from the Pacific coastline between Mexico and Chile. Transport of polychaetes to the island either as larvae, adults, or by rafting is discussed. Comparisons are made with the less well-analyzed polychaete fauna of the Galápagos Islands, with lower species richness on the smaller and ecologically less variable Isla del Coco. Relative lack of isolation between the polychaetes of Isla del Coco and the mainland is discussed.