Abstract Mysidopsis gemina n. sp. is described from protected and exposed beach habitats in the provinces of Puntarenas and Guanacaste on the northern Pacific coast of Costa Rica. Morphologically, M. gemina most closely resembles M. furca Bowman, 1957 known from the Atlantic and Gulf Coasts of North America. Both these species are unique within the genus by their distinctively sexually dimorphic telsons. The new Costa Rican species can be distinguished from M. furca and other species of Mysidopsis by a combination of having a male with biarticulated endopods on the first pleopods and pleopods 2-5 with large plate-like pseudopodia (exites). The occurrence of these characters and morphological features within the subfamily Leptomysinae is discussed.

ABSTRACT A survey of the invertebrate fauna of coral reef hard bottom communities in the shallow waters of Isla del Coco yielded a new species of mysid belonging to the genus Heteromysis S. I. Smith, 1873. Heteromysis (Olivemysis) cocoensis, n. sp. was collected from coral rubble at depths of 8 to 34 m. It differs from its congeners by having male pleopods 1, 3, and 4 with modified setae. Within the subgenus Olivemysis Băcescu, 1968, the new species is morphologically most similar to Heteromysis. ekamako Wittmann and Chevaldonne, 2017 from the Pacific, Heteromysis. gomezi Băcescu, 1970, H. mayana Brattegard, 1970, and H. rubrocinta, Băcescu, 1968 from the Western Atlantic, and Heteromysis. dardani Wittmann, 2008, Heteromysis. wirtzi Wittmann, 2008, and Heteromysis. sabelliphila Wittmann and Wirtz, 2017 from the Eastern Atlantic. However, H. cocoensis n. sp. is distinguished from these six apparently closely related species by the following combination of characters: flagellate, modified setae on articles 1 and 3 of the antennular peduncle, and setation of thoracic endopod 3, male pleopods 1, 3 and 4, uropodal endopods, and the apical and lateral margins of the telson. A diagnostic table separating these eight species is given.

El grupo de los cangrejos anomuros es uno de los mejor conocidos de la costa Pacífica de Costa Rica, pero muy poco conocidos de la costa Caribe. En esta recopilación, basada en la literatura y en las colecciones del Museo de Zoología, Escuela de Biología, Universidad de Costa Rica, informamos de la presencia de 114 especies del Infraorden Anomura en Costa Rica, 20 especies del Caribe, 96 especies del Pacífico, y dos especies presentes en ambas costa. Veintinueve especies son informes nuevos para Costa Rica, 15 del Caribe (75% del total de especies informadas para esa costa) y 14 del Pacífica (15% del total de esa costa). La distribución de diez especies es ampliada hasta Costa Rica, siete en el Caribe y tres en el Pacífico. Seis especies son informadas por primera vez para la Isla del Coco, donde además hay cuatro especies endémicas.

Marine biodiversity of Costa Rica: Crustacea: Infraorder Anomura. The anomuran crabs are among the best known crustacean groups from the Pacific coast. However, this group is poorly known from the Caribbean coast of Costa Rica. In this compilation based on the literature and the collection at the Zoology Museum, Biology School, University of Costa Rica, we report the presence of 114 species of the Infraorder Anomura for Costa Rica, 20 species from the Caribbean, 96 species from the Pacific (two are present on both coasts). Twenty-nine species are new reports for Costa Rica, 15 from the Caribbean coast (74% of the total of species from that coast) and 14 from the Pacific (15% of the total from the Pacific). The range of ten species is extended to Costa Rica, siete from the Caribbean and three from the Pacific. Six species are reported for the first time from Cocos Island, where there are also four endemic species. Rev. Biol. Trop. 54(2): 461-488. Epub 2006 Jun 01.

Este estudio proporciona el primer informe taxonómico de los hidroides de los Ordenes Anthoathecatae y Leptothecatae presentes en las colecciones del Museo de Zoología de la Escuela de Biología de la Universidad de Costa Rica. Se informan 16 especies de hidroides: Eudendrium carneum, Pennaria disticha, Acryptolaria longitheca, Plumularia floridana, Halopteris polymorpha, Aglaophenia dubia, Aglaophenia latecarinata, Lytocarpia tridentata, Macrorhynchia phillipina, Macrorhynchia sp., Clytia gracilis, Cnidoscyphus marginatus, Thyroscyphus ramosus, Dynamena disticha, Sertularella diaphana y Tridentata distans. Se presenta una exhaustiva revisión de la sinonimia y una clave taxonómica simple e ilustraciones y descripciones para cada una de las especies

This paper is the first taxonomic account of the hydroid orders Anthoathecatae and Leptothecatae from the Caribbean and Pacific coast of Costa Rica. All specimens are currently stored at the reference collection of the Museo de Zoología, Escuela de Biología, Universidad de Costa Rica. Sixteen hydroid species are recorded: Eudendrium carneum, Pennaria disticha, Acryptolaria longitheca, Plumularia floridana, Halopteris polymorpha, Aglaophenia dubia, Aglaophenia latecarinata, Lytocarpia tridentata, Macrorhynchia phillipina, Macrorhynchia sp., Clytia gracilis, Cnidoscyphus marginatus, Thyroscyphus ramosus, Dynamena disticha, Sertularella diaphana, and Tridentata distans. An extensive synonymy has been given for each species. A simplified taxonomic key is included, and illustrations and descriptions are provided for each species

Aquí se informan para la costa Caribe de Costa Rica un total de 30 especies de camarones y langostas. Estas se clasifican en el Suborden Dendrobranchiata (Penaeoidea, 6 spp.; Sergestoidea, 2 spp.); y en el Suborden Pleocyemata (Stenopididea, 2 spp.; Caridea, 15 spp.; Thalassinidea, 2 spp. y Palinura, 3 spp.). Del total de especies, 22 son informadas por primera vez para Costa Rica, y adicionalmente una, informada previamente para la costa Pacífica, se informa para el Caribe. Además, se amplia la distribución geográfica de Pontonia domestica, previamente informada de Carolina del Norte, Golfo de México y Bahamas; y Rhynchocinetes rigens, de Florida, Bahamas, islas Vírgenes, Bermuda, Madeira y Azores, a la costa Caribe de Costa Rica. De 218 especies de Penaeoidea, Sergestoidea, Stenopodidea y Caridea mencionadas por Chace (1972) para el Caribe, solo 25 (11.5%) se han encontrado hasta ahora en la costa Caribe de Costa Rica.

A total of 30 species of shrimp and lobster are reported from the Caribbean coast of Costa Rica. They belong to the Suborder Dendrobranchiata: Penaeoidea, 6 spp. and Sergestoidea, 2 spp.; and Suborder Pleocyemata: Stenopodidea, 2 spp.; Caridea, 15 spp.; Thalassinidea, 2 spp.; Palinura, 3 spp. Of these, 22 species are reported for the first time for Costa Rica, and one species previously known from the Pacific coast is informed from the Caribbean coast. Distribution ranges are extended for: Pontonia domestica Gibbes, from North Carolina, Gulf of Mexico and Bahamas; and Rhynchocinetes rigens Gordon, from the northern Caribbean, Bermuda and eastern Atlantic, to the Caribbean coast of Costa Rica. Of 218 species of Penaeoidea, Sergestoidea, Caridea and Stenopodidea mentioned for the Caribbean by <A HREF="#Chace">Chace (1972)</A>, only 25 (11.5%) have been reported from the Caribbean coast of Costa Rica.

En el Pacífico de Costa Rica se ha encontrado 117 especies de camarones y langostas. Estas se ubican en el Suborden Dendrobranchiata (Penaeoidea, 25 spp.; Sergestoidea, 1 sp.); y en el Suborden Pleocyemata (Caridea, 73 spp.; Astacidea, 1 sp; Thalassinidea, 13 spp. y Palinura, 4 spp.). Veintisiete especies (23%) son nuevos infomes para Costa Rica. Cinco informes representan ampliaciones de ámbito, tres de importancia: Pontonia simplex (<A HREF="#Holthuis51">Holthuis, 1951</A>) se extiende la distribución desde la bahía Tenacatitán, México hasta bahía Culebra, Guanacaste; Veleronia serratifrons (<A HREF="#Holthuis51">Holthuis, 1951</A>) se amplia la distribución al norte desde La Libertad, Ecuador hasta Sámara, Guanacaste y Axiopsis serratifrons (A. Milne Edwards, 1873) también al norte desde la isla Gorgona, Colombia hasta bahía Culebra, Guanacaste. Nueve especies fueron descritas con material recolectado en Costa Rica y dos son endémicas. 43% de las especies de camarones del Pacífico este se encuentran en la costa Pacífica de Costa Rica. El total de especies indicado aquí es probablemente una subestimación de la diversidad de estos grupos en el Pacífico de Costa Rica.

A total of 117 species of shrimp and lobster are known from the Pacific coast of Costa Rica. They belong to the Suborders Dendrobranchiata, Superfamily Penaeoidea (26 species) and Pleocyemata, Infraorder Caridea (73), Astacidea (one), Thalassinidea (13), and Palinura (four species). Twenty seven species (23%) are reported for the first time for Costa Rica. The distribution range of five species is extended, three of which are significant: Pontonia simplex (<A HREF="#Holthuis51">Holthuis, 1951</A>) from Tenacatitán Bay, México to Culebra Bay, Guanacaste; Veleronia serratifrons (<A HREF="#Holthuis51">Holthuis, 1951</A>) from La Libertad, Ecuador to Sámara, Guanacaste and Axiopsis serratifrons (A. Milne Edwards, 1873) from Gorgona Island, Colombia to Culebra Bay, Guanacaste. Nine species, two of which are endemic, were described based on specimens collected in Costa Rica. Forty three percent of the tropical eastern Pacific species of shrimps are found on the Pacific coast of Costa Rica.