A new family, of apseudomorphan Tanaidacea, Sphaeromapseudidae, is discovered and described from the Caribbean Sea. Sphaeromapseudidae is tentatively placed between the Metapseudidae and Tanzanapseudidae. A new genus Sphaeromapseudes and species, S. plumosetosa, associated with intertidal coral rubble, are described.

The Macaronesian Islands in the mid-Atlantic pose a number of questions relating to their colonization by littoral tanaidaceans, as these taxa have no obligate dispersive phase. Recent surveys of the four main archipelagos discovered twelve species of tanaidacean, four of which are new to science, in seven genera (one new to science). In addition, some taxa described by Vanhöffen at the beginning of the last century were rediscovered. All the taxa are described, and their zoogeography, likely origin, and possible means of colonization are discussed.

Upwelling can determine important changes in community structure on rocky shores. However, studies on the meiofauna in areas of upwelling are scarce and do not include analysis on the species level for Copepoda Harpacticoida. The present study aimed to describe the Harpacticoida community in a region under the influence of coastal upwelling (Arraial do Cabo, Rio de Janeiro, Brazil). The hypothesis tested was that temporal differences in the fauna would be greater at the rocky shore more affected by upwelling. Samples were collected from the sublittoral of two rocky shores: Sonar, which is more exposed to upwelling, in January and June 2004; and Pedra Vermelha, which is a sheltered shore, in March and September 2002. Each sample consisted of four replicates collected by scraping epilithic algae along with the associated sediment. Weekly data on surface water temperature and nitrate content denoted stronger upwelling in 2002 compared to 2004. Nine genera of Copepoda Harpacticoida are reported for the first time for the Brazilian coast. Univariate indices identified no differences between rocky shores or seasons, whereas multivariate analysis indicated significant differences in assemblages between shores and between seasons. The strong variation in physicochemical conditions associated with upwelling favoured the dominance of opportunistic species, such as Parastenhelia spinosa. At the Sonar rocky shore, temporal differences were significantly stronger than at Pedra Vermelha, thereby confirming the initial hypothesis. These results indicated that the occurrence of upwelling had a very important role structuring the Harpacticoida assemblage at the species level.

‘Pliocardia' krylovata, sp. nov. (Bivalvia: Vesicomyidae: Pliocardiinae) is described from cold seeps off the coast of the Nicoya Peninsula, Costa Rica (700–1000 m depth). The phylogenetic position of ‘P.' krylovata was assessed by both morphological comparisons as well as nucleotide data from the cytochrome c oxidase I gene. Within the vesicomyids, ‘P.' krylovata belongs to the Pliocardiinae and its closest relative is ‘Calyptogena' ponderosa, which also bears some morphological resemblance to the genus Pliocardia, perhaps suggesting a need for reanalysis of not only its generic designation, but also the entire Pliocardiinae subfamily. ‘P.' krylovata has morphological similarities to ‘Pliocardia' bowdeniana and ‘Vesicomya' crenulomarginata, recently reassigned to the genus Pliocardia, including a thick shell, obvious rostrum, pointed posterior end, and a sculptured shell with concentric ribs on the outer surface, to name a few. It is morphologically distinguished, however, by having a complex pallial sinus and remarkably deep escutcheon.

New arcid species belonging to the genera Paranadara gen. nov., Acar and Asperarca (new record) are described for the western Atlantic Ocean based on shell morphology. Paranadara taludae sp. nov., Acar naturezae sp nov., Acar oliveirae sp. nov. and Asperarca tarcylae sp. nov. were collected off north-eastern Brazil between depths of 70 and 690 m, whereas Acar lepidoformis sp. nov. was dredged off the State of Rio Grande do Sul (southern Brazil) at a depth of 141 m. There are no species along the Brazilian coast that are morphologically similar to Paranadara taludae sp. nov. Acar naturezae sp. nov., Acar lepidoformis and Acar Acar oliveirae sp. nov. are similar to this genus due to shape, ligament, presence of concentric lamellae cut by radial threads, a broad dorsal area and a markedly narrowed anterior region in comparison to the posterior region, which is strongly expanded. Asperarca tarcylae sp. nov. is similar to this genus due to the presence of a small edentulous region below the umbo and smooth inner margin.

The original description of Tegula ignota was based on three shells found on the coast of Totoralillo Sur, northern Chile. Until now, there are no reports of living specimens of the species. The present study redescribes this snail based on shell, radula, epipodium and mantle characteristics observed in living specimens collected from the subtidal zone of La Boca, central Chile. Additionally, we extend the distribution of T. ignota more than 700 km to the south-eastern Pacific with additional material. Molecular analyses based on the 16S ribosomal DNA mitochondrial gene show that T. ignota is most closely related to Tegula atra than other Chilean species of Tegula. Voucher specimens of T. ignota were deposited in the Museo Nacional de Historia Natural de Chile.

Morphological examination of several specimens of aeolid nudibranchs collected from the Ross Sea, Antarctica, revealed an unexpectedly high number of species. Based on the collected material the following species are re-described and for the first time their colour, reproductive anatomy and radula are illustrated together: Eubranchus glacialis, Cuthona modesta, Cuthona crinita, Cuthona elioti and Guyvalvoria paradoxa. Additionally, a new species of Cuthona is described from this area. The new species differs from other Antarctic and sub-Antarctic species of Cuthona in its external appearance, radular morphology and reproductive anatomy. Information on the egg mass and embryonic development of several species is provided.

Nassarius nitidus is a marine snail species with a widespread distribution along European shorelines from the North Sea to the Mediterranean and Black Seas. Despite its widespread distribution, N. nitidus has been largely neglected due to taxonomic confusion with the congeneric Nassarius reticulatus. Discrimination between these two Nassarius is particularly challenging in areas where their ranges overlap: the European Atlantic and western Mediterranean. Here, we propose the use of the mtDNA gene cytochrome c oxidase subunit I (COI) to discriminate between these two morphologically similar congeneric species. A numerically comprehensive sampling of the areas of overlap reveals strong population-level differentiation in N. nitidus, particularly between the Mediterranean and the Atlantic. Despite this strong population structure, we found a wide (9.6 ± 1.6% mean K2P corrected sequence distance) barcoding gap with N. reticulatus that guarantees that COI barcodes may serve as a reliable diagnostic tool. A protocol using species-specific restriction patterns was developed to allow a quick and accurate discrimination between these two cryptic species.

The genus Kolga has been revised. Kolga nana (Théel, 1879) is re-established and a new species, Kolga kamchatica sp. nov., is described. The new species was found in the Kurile–Kamchatka Trench at 6225–6236 m water depth. The three species of Kolga, K. hyalina, K. nana and K. kamchatica, differ mainly in morphology of tube feet ossicles. For the first time, swimming activity is reported in K. nana.

For the first time, brittle stars were collected on two seamounts in the Andaman Back-arc Basin. Of the six species, two were new to science and are described herein as Ophioleuce longispinum sp. nov. and Ophiophyllum minimum sp. nov., in the family Ophiuridae, subfamilies Ophioleucinae and Ophiurinae, respectively. Skeletal details were studied and documented by scanning electron microscopy. Morphological similarities between related species are discussed in detail. Ophioleuce longispinum sp. nov. is particularly interesting, because it combines characters typical for its genus with those otherwise only known from Ophiophyllum, such as a limpet-like disc, a fringe of marginal disc papillae or spines, and a paddle-like modified lower arm spine. The remaining species, Astrophiura cf. tiki, Ophiactis perplexa, Ophiolimna antarctica and an unidentified Ophiura, are new records for the Andaman Sea.

Of three intertidal fish species collected on the east coast of South Africa, 67% (127/190) had haemogregarine infections. Horned rockskippers, Antennablennius bifilum Günther, 1861, demonstrated 77% parasite prevalence, maned blennies, Scartella emarginata Günther, 1861, 53% prevalence, and a single specimen of the hotlips triplefin, Helcogramma obtusirostre Klunzinger, 1871, was also parasitized. Less than 1% of A. bifilum and S. emarginata erythrocytes were infected, but ~2% of those of H. obtusirostre. Haemogregarines in A. bifilum and S. emarginata were morphologically similar to H. bigemina Laveran & Mesnil, 1901, but uncharacteristic clusters of four merozoites were observed in S. emarginata and paired gamonts were smaller overall than those of the type species, although close in size to H. bigemina reported elsewhere. Intraerythrocytic gamonts in H. obtusirostre, occurred mainly in fours, a characteristic of the European species originally named H. quadrigemina Brumpt & Lebailly, 1904. Additionally however, this South African species infrequently demonstrated eight intraerythrocytic gamonts and host cells commonly had spiny perimeters and were de-haemoglobulinized. Owing to the differences observed, this species is described as new to science and named Haemogregarina kunegemina sp. nov. Possible haemogregarine developmental stages were found in first and second stage pranizae of the gnathiid isopod, Gnathia pilosus Hadfield, Smit & Avenant-Oldewage, 2008, that had fed on the three fish hosts. These are the first reports of haemogregarines from teleosts of the subtropical east coast of South Africa.

The spatial patterns of distribution of five species of the Gerreidae (Diapterus rhombeus, Eucinostomus argenteus, Eucinostomus gula, Eucinostomus melanopterus and Eugerres brasilianus) in Mambucaba estuary, south-eastern Brazil, were determined to assess habitat partitioning of the estuarine reaches. Sampling was conducted between October 2007 and August 2008. Diapterus rhombeus and E. gula were exclusively found in the lower estuary, whereas E. melanopterus and E. brasilianus were exclusively found from the middle estuary. Eucinostomus argenteus was common in the two estuarine zones. Total length and total weight data showed that the smallest individuals of D. rhombeus and E. gula were found near to the estuarine mouth compared with deeper areas of high salinity and lesser influence of the estuarine plume. The smallest individuals of E. argenteus, E. brasilianus and E. melanopterus were found in a protected estuarine lagoon connected to the main estuarine channel, and the largest in the other sites in the main channel of the middle estuary. Spatial partition seems to be the strategy developed by the 5 members of the Gerreidae family to coexist in the Mambucaba estuary, which may be attributed to competition in the past between the species of Gerreidae or to differentiated tolerance to environmental constraints