We have compiled available records in the literature for medusozoan cnidarians and ctenophores of South America. New records of species are also included. Each entry (i.e., identified species or still as yet not determined species referred to as "sp." in the literature) includes a synonymy list for South America, taxonomical remarks, notes on habit, and information on geographical occurrence. We have listed 800 unique determined species, in 958 morphotype entries: 5 cubozoans, 905 hydrozoans, 25 scyphozoans, 3 staurozoans, and 20 ctenophores. Concerning nomenclatural and taxonomical decisions, two authors of this census (Miranda, T.P. & Marques, A.C.) propose Podocoryna quitus as a nomen novum for the junior homonym Hydractinia reticulata (Fraser, 1938a); Euphysa monotentaculata Zamponi, 1983b as a new junior synonym of Euphysa aurata Forbes, 1848; and Plumularia spiralis Milstein, 1976 as a new junior synonym of Plumularia setacea (Linnaeus, 1758). Finally, we also reassign Plumularia oligopyxis Kirchenpauer, 1876 as Kirchenpaueria oligopyxis (Kirchenpauer, 1876) and Sertularella margaritacea Allman, 1885 as Symplectoscyphus margaritaceus (Allman, 1885).

The occurrence of ephyrae of the scyphozoan orders Semaeostomeae and Rhizostomeae is reported for the first time for the Brazilian coast. The specimens, caught in plankton tows in the São Sebastião Channel and the Cananéia lagoon estuarine system, are: Chrysaora lactea (Semaeostomeae), Phyllorhiza punctata (Rhizostomeae), and an unidentified species of Pelagia (Semaeostomeae). A table with all species of scyphozoan with the known life cycle is provided.

Brazil has an extensive marine coast of over 9.200 km. However, the taxonomical, biogeographical and ecological knowledge of the organisms present in coastal and neritic waters is scanty. Although the gelatinous plankton constitutes one of the main groups of pelagic predators, is abundant and relatively large, in size, it is usually underestimated in number and importance by the traditional sampling methods. Hydrozoa are one of the most numerous and common groups in this planktonic community. Among the works on hydromedusae, only some included extensive areas of the Brazilian continental shelf, although sampling of oceanographic expeditions, as the ones accomplished by the Instituto Oceanográfico of the Universidade de São Paulo (IO-USP), are available for study. The goal of this study is to survey the hydromedusae species collected by two oceanographic expeditions by the Brazilian vessel carried out by IO-USP along the continental shelf between Cabo Frio (RJ) and Cabo de Santa Marta Grande (SC) (South Brazil Bight-SBB), in 1991 and 2001: Sardinha 1 and PADCT 2. The diversity and geographic distribution of the hydromedusae fauna were analyzed. Data were interpreted trying to infer correlations in the distribution of the species with the characteristic water masses present in the area (Coastal Water-CW; Tropical Water-TW; South Atlantic Central Water-SACW). The distribution data were also used in a Parsimony Analysis of Endemicity (PAE), to verify possible endemic areas of the species. From the 155 samples a total of 51,808 hydromedusae specimens were found, belonging to 20 species/morphotypes: 10 Anthoathecata; 5 Leptothecata; 3 Trachymedusae; 2 Narcomedusae. The diversity and abundance of the species were lower in the samples of PADCT 2 when compared to Sardinha 1. All of the species had already been recorded for the Brazilian coast; however, some had their geographical distributions enlarged. Liriope tetraphylla and Aglaura hemistoma were the most frequent and abundant species in the samples of the Sardinha 1 and PADCT 2, respectively. There are indications that the geographical distributions of some species are associated, as Aglaura hemistoma and Corymorpha gracilis; Solmundella bitentaculata and the pair Aglaura hemistoma-Liriope tetraphylla; Turritopsis nutricula and Proboscidactyla ornata, the last association usually occurring when both species are abundant. The relative low number of hydromedusae species found in SBB can be consequence of the sampling method, which did not aim at the gelatinous plankton. However, among the 20 identified species/morphotypes are the most frequent species already recorded for SBB, as Aglaura hemistoma, Liriope tetraphylla, Rhopalonema velatum, Solmundella bitentaculata and Turritopsis nutricula.. Some species distributions are associated to specific water masses like Turritopsis nutricula, Niobia dendrotentaculata, Proboscidactyla ornata, Solmundella bitentaculata and Corymorpha gracilis in a mixture of SACW and CW. Most individuals of Liriope tetraphylla and Eucheilota duo...

We analysed hydromedusa assemblages of South America (from 22°S to 56°S and from 040°W to 080°W), their association with water masses and the influence of the life cycle on medusa distributions. The geographic distribution of 130 species of hydromedusae was compiled from literature reports (62 publications between 1913 and 2012). Seven areas were defined: Atlantic Magellanic, Argentinean, Pacific intermediate zone, Pacific Magellanic, Peruvian-Chilean, South Brazilian and Oceanic. The variance of the species-environment relationship was explained by depth and temperature. Distribution patterns of Atlantic hydromedusae are associated with neritic water masses, supporting previously proposed biogeographical provinces. Assemblages on the Pacific side of South America are under the influence of the Humboldt Current system, with a break in species distribution around Chiloé Island. Only the oceanic assemblage contained the same species in both the Pacific and Atlantic zones. We found that meroplanktonic medusae contributed more to define the neritic assemblages, while the oceanic assemblage was better defined by holoplanktonic medusae. Therefore, our data suggest that meroplanktonic hydromedusae appeared to be more restricted in distribution than holoplanktonic ones.

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A new species of hydrozoan, assigned here to the genus Hydractinia, is described from the southeastern coast of Brazil (São Paulo state). This new species is distinguished from all known species of the genus Hydractinia by a combination of the following characters: monomorphic colonies, long tentacles of the polyp, production of frustules, and free medusae with branched mouth arms and ocelli.