Abstract
Nematoda is the fourth most diverse animal phylum and is widely distributed. Marine nematodes are generally the most speciose group of meiofauna, yet there are relatively few studies on the taxonomy and biodiversity of free living marine nematodes. Here we present a review of the existing scientific literature and data in international databases on marine nematodes of Costa Rica. Most of the papers currently available mentioned Nematoda as the most abundant phylum in terms of the number of individuals within sand samples, nonetheless, only three publications included taxonomic data such as the description of new species or new records. Most publications are for the Pacific coast and we found only one paper for the Caribbean coast of Costa Rica. Large sections of the coasts and almost all the Exclusive Economic Zone remain unexplored in terms of nematode diversity, abundance and ecological role. Ten species, five free-living and five parasitic species, have been reported from the coasts of Costa Rica. Several reports indicate the presence of nematodes without further identification. More effort should be dedicated to the taxonomic identification of nematodes since, in addition to being the most abundant group, they can also be used as biological indicators.