Some nemerteans of the coast of Guanacaste, North Pacific Costa Rica

Introduction: Nemertea is a phylum of invertebrates commonly found in marine habitats; however, knowledge of the species in the Eastern Tropical Pacific is scarce. The study of their morphological characteristics, such as coloration patterns and head-region structures, together with genetic data, can help to discriminate between species and increase the understanding of regional biodiversity. Objective: The objective of the present study is to create an inventory of nemertean species along the Pacific coast of Área de Conservación Guanacaste, Costa Rica. Methods: Specimens were collected from the intertidal and subtidal zones, mangrove forests, and sediment or rocky substrates using manual techniques or sediment corers and van Veen grabs. The specimens were photographed in vivo. Tissue samples were stored in 95 % ethanol for DNA barcoding using mitochondrial 16S and cytochrome c oxidase I (COI) genes. The specimens were identified using the BLAST, Neighbor-Joining trees, and published descriptions and taxonomic keys. Results: Of the 46 specimens collected at several marine habitats, a total of 26 putative species (Operational Taxonomical Units) were found. Five species correspond to hoplonemerteans, belonging to the genera Tetrastemma, Poseidonemertes, and Nipponnemertes. The other 21 species are heteronemerteans of the families Valenciniidae (two species in the genus Baseodiscus) and Lineidae (19 species in the genera Archimicrura, Cerebratulus, and Notospermus). Of these nemertean records, 17 may represent new species. The other nine records match species from the Pacific of Panama. Conclusions: The present study increases the known biodiversity of Costa Rica and can help future nemertean research in the Eastern Tropical Pacific by providing access to DNA sequences and images of the 26 nemertean species.