This study aimed to determine the potential impact of an oil spill on intertidal meiofauna at a clean, sandy beach in Korea. This objective was accomplished by examining changes in the structure of meiofaunal assemblages after a controlled oil spill of different concentrations on the beach. The concentration of total petroleum hydrocabon (TPH) in the experimental plots after oil application was expectedly higher for the first 4 d compared to before oil application. The TPH concentrations decreased at a faster rate in the first 4 d, and then progressively. The sharp decline in meiofaunal density in the experimental plots during the first 4 d after the spill might be attributed to the short-term toxic effects of the oil. This suggestion is supported by a significant negative interaction of the TPH on meiofaunal density during the study period. The period of low density of meiofauna also coincided with the maximum concentration of TPH in the sediment. The multivariate indices proved to be highly efficient, showing that samples contaminated with oil had high TPH concentrations, and were partially separated in terms of meiofaunal communities from samples before oil application or samples with low TPH concentrations. The structure of the meiofaunal communities in the experimental plots was similar before and 1 month after oil application. However, the density of meiofauna sharply decreased immediately after oil application in the experiment plots. Furthermore, the meiofaunal density recovered slowly as time passed.

This study evaluated the decomposition process of leaf litter from the main Brazilian mangrove species Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle. Senescent leaves were collected, dried and placed in nylon bags with different mesh sizes (fine: 2 × 2 mm and coarse: 8 × 8 mm). The bags were distributed over the sediment, and replicates of each species and mesh size were collected periodically over 4 months. In the laboratory, the dry weight of the samples was measured, and the decomposition coefficient (k) for each species and mesh size was obtained over time. All species showed a rapid decomposition rate at the beginning of the experiment, followed by a slower but steady rate of decomposition over time. The rate of leaf litter decomposition was highest in A. schaueriana, intermediate in L. racemosa and lowest in R. mangle. The difference was mainly linked to the activity and abundance of detritivores, together with the different litter quality of the species, which determined their palatability and probably influenced the decomposition process.

Epifaunal invertebrates are sensitive to changes in the identity of the dominant host plant, so assessing differences in the structure of epifaunal assemblages is particularly pertinent in areas where seagrasses have been replaced by alternative vegetation (e.g. green seaweeds). In this study, we aimed to compare the diversity, abundance and structure of epifaunal assemblages, particularly amphipods, between meadows dominated by the seagrass Cymodocea nodosa and the green rhizophytic algae Caulerpa prolifera on shallow soft bottoms of Gran Canaria Island, determining whether patterns were temporally consistent between two times. The epifaunal assemblage structure (abundance and composition) consistently differed between both plants, those assemblages associated with C. prolifera-dominated beds being more diverse and abundant relative to C. nodosa meadows. Amphipods constituted ~70% of total crustaceans for the overall study, including 37 species belonging to 16 families. The amphipod abundance was ~3 times larger in C. prolifera-dominated beds than in C. nodosa meadows. We detected species-specific affinities; for example, Microdeutopus stationis, Dexamine spinosa, Aora spinicornis, Ischyrocerus inexpectatus and Apherusa bispinosa were more abundant in C. prolifera-dominated beds; while the caprellid Mantacaprella macaronensis dominated in C. nodosa meadows. However, some species, such as Pseudoprotella phasma and Ampithoe ramondi, were found in both habitats with varying abundances between times.

Exploration of continental shelves may produce unexpected faunal records. In shelf waters of La Guajira peninsula, Colombia, in the northern tip of South America, southern Caribbean Sea, we found a new species of Rhaphidhistia (Demospongiae, Hadromerida, Trachycladidae) a genus previously thought to be restricted to the Indo-Pacific Ocean. Rhaphidhistia guajiraensis sp. nov. is thickly encrusting, agglutinating bottom debris; it possesses asymmetric oxea as megascleres (465–757 μm by 6.3–17.5 μm) and spiraster-like spinispirae (15–37 μm by 2–5 μm). It is closely similar to the type species of the genus, R. spectabilis Carter, 1879, both standing apart from a third species, R. mirabilis (Dendy, 1924), thus conforming a natural group whose taxonomic placement needs to be reassessed. There are numerous cases of sponge genera with sister species in the Indo-Pacific and the Atlantic Oceans, possibly split since the Tethys Sea breakup; owing to their restricted or deep distribution, they are just starting to be discovered.

A new species of Geodia is described from the North Pacific, collected in the summer of 2012 in the western Aleutian Islands. Geodia starki sp. nov. differs from all known species of Geodia by the possession of two categories of sterrasters and exceptionally large megascleres. The new species is compared with congeners of the North Pacific Ocean, Bering Sea, Arctic and the North Atlantic Oceans.

Six new species of Hexactinellida are described from hard bottom communities of shelf, canyon and seamounts of the west coast of North America: Washington, British Columbia and Gulf of Alaska. They were collected by a variety of methods, trawl, manned submersible, and robot submersible, and hence vary greatly in condition. The six species comprise additions to five different families of the subclass Hexasterophora, Farreidae (Farrea omniclavata sp. nov. and F. truncata sp. nov.), Euretidae (Chonelasma oreia sp. nov.), Euplectellidae (Amphidiscella lecus sp. nov.), Leucopsacidae (Oopsacas olympicus sp. nov.) and Rossellidae (Acanthascus malacus sp. nov.). These additions represent an increase of 29% to the known species of Hexactinellida in this area. A completely unique form of defended tabulate stalk is described for A. lecus. The species Chauoplectella spinifera is transferred to Oopsacas.

Five new species of Homoscleromorpha (Porifera) of four genera, Oscarella, Plakortis, Plakina and Corticium, are described from vertical walls of reef caves at depths ranging from 23 to 28 m in the Caribbean Sea. Oscarella nathaliae sp. nov. has a leaf-like thinly encrusting, flat body, loosely attached to the substrate and a perforated, not lobate surface. Oscarella nathaliae sp. nov. contains two bacterial morphotypes and is characterized by two mesohylar cell types with inclusions. Plakortis myrae sp. nov. has diods of two categories: abundant large ones (83–119 μm long) and rare small ones (67–71 μm long) with sinuous, S-bent centres; triods Y- or T-shaped (18–5  μm long), and abundant microrhabds (5–12 μm long). Plakortis edwardsi sp. nov. has diods of one category with thick, sinuous, S-bent centres (110 to 128 μm long); triods T-shaped (actines 28–59 μm long). It is the only species of this genus showing small diods (22–31 μm long). Plakortis dariae sp. nov. has diods of two categories: large ones (67–112 μm long) and small, rare, irregular ones, slightly curved, often deformed with one end blunt (30–59 μm long); triods rare and regular (actines 20–44 μm long). Corticium diamantense sp. nov. has oscula situated near its border, regular non-lophose calthrops of one size-class, very rare tetralophose calthrops and candelabra with the fourth actine ramified basally in 4–5 microspined rays. In addition, a re-description of Plakina jamaicensis is based on newly collected material and the type specimen. Plakortis jamaicensis has a convoluted brain-like surface; well developed sub-ectosomal cavities; irregular sinuous diods, triods, calthrops, rare monolophose calthrops, rare dilophose calthrops, rare trilophose calthrops and common tetralophose calthrops. Molecular ‘barcoding’ sequences for mitochondrial cob are given for Plakortis edwardsi sp. nov., P. dariae sp. nov., Plakina jamaicensis and Corticium diamantense sp. nov. An identification key for all western Atlantic Homoscleromorpha is provided.

South Georgia is a remote sub-Antarctic island, considered a marine biodiversity ‘hotspot’ in the Southern Ocean. During a survey along the north coast of South Georgia several marine planarians were found. One of the specimens was a new species of Allogenus (Uteriporidae), which is described here as Allogenus sluysi sp. nov. The new species has the characteristics of the genus and can be distinguished from the type and only known species, Allogenus kerguelensis, by its smaller size, blackish-brown pigmentation, presence of three retinal cells in each eye cup, position of its testes half-way between the ventral and dorsal body surfaces or at a slightly more ventral position, and by having an ejaculatory duct that opens centrally at the tip of the penis papilla. The presently known geographical distribution of Allogenus, the heterogeneous marine planarian species composition in South Georgia, and the distribution of these species in this region are in agreement with a previously proposed vicariance hypothesis, albeit that dispersal cannot be ruled out.

In recent years the Norwegian Taxonomy Initiative started thorough investigations of poorly known organism groups. In this context, several marine inventories have rendered a number of marine invertebrate species new to science. Within the phylum Nemertea (ribbon worms) a characteristic hoplonemertean was encountered on two different occasions. We describe the new species Amphiporus rectangulus sp. nov. with a combination of histology and DNA data (COI). For the morphological description we use a previously proposed character matrix and, in a context given by the results, also provide a brief discussion on benefits and drawbacks with both methods. We argue that for small animals with soft bodies external characters can be more informative than hitherto expected.

The genus Megasyllis is herein reorganized excluding the size from the diagnosis, since it is not a characteristic of all the species of the genus. We provide here a taxonomic account of all known species and a key to species identification. Seven species are new combinations, and re-descriptions of the four latter are included: Megasyllis nipponica (Imajima, 1966) and M. multiannulata (Aguado, San Martín & Nishi, 2008) from Japan; Megasyllis procera (Hartman, 1965) from the Atlantic; Megasyllis pseudoheterosetosa (Böggemann & Westheide, 2004) from the Indian Ocean. Megasyllis glandulosa (Augener, 1913), from Australia; Megasyllis marquesensis (Monro, 1939) from the Marquesas Islands, Micronesia and Megasyllis subantennata (Hartmann-Schröder, 1984) from Australia. Four new species from the Pacific Ocean namely Megasyllis tigrina sp. nov., Megasyllis mariandreworum sp. nov. (both from Australia), Megasyllis chrissyae sp. nov. (from the Philippines) and Megasyllis eduardoi sp. nov. (from New Zealand) are described.

A new species of Curidia is described based on material collected from Sisal Coral Reef System, south-east Gulf of Mexico, Mexico. It is the eighth species of this genus described worldwide. Curidia nunoi sp. nov. is morphologically similar to C. wakabarae and C. andreae. Curidia nunoi sp. nov., however, differs from these two species by a combination of several characters, including: the posteroventral spine of peduncle articles 1 and 2 of antenna 1, the distoventral spine of peduncle article 4 of antenna 2, the distal margin of coxa of gnathopod 1, the dactylus of gnathopod 2, the inner and outer plates of maxilla 1, and the distal margin of telson. The global geographical distribution of the genus Curidia is mostly from tropical to subtropical seas; five species are documented in the southern hemisphere and three in the northern hemisphere. Only C. debrogania, C. monicae, and C. nunoi sp. nov. are restricted to the Gulf of Mexico and the Caribbean Sea.

Adult specimens of Capitulum mitella were collected in August 2011 in the intertidal zone of Dinghai, Fuzhou, Fujian, China (26°16′N 119°48′E). The morphology of the cypris larva reared under our conditions was determined using scanning electron microscopy (SEM). Special emphasis was given to the carapace, lattice organs, antennules, thoracopods and furcal rami. The whole carapace surface is sculptured by slender ridges demarcating rectangular or irregular polygonal areas with very fine pores. The cyprid possesses five pairs of lattice organs, arranged as two anterior and three posterior pairs. The second segment carries a preaxial seta 2 and a postaxial seta 2. The third segment carries a postaxial seta 3 outside the attachment disc, whereas a postaxial disc seta, an axial disc seta and two radial disc setae are located inside the attachment disc. The attachment disc is somewhat bell shaped. A series of slender cuticular flaps forms a distinct ‘velum’ around the base of the disc. The fourth segment carries four subterminal setae and five terminal setae. The cyprid bears six pairs of biramous natatory thoracopods consisting of a protopod (coxa + basis), a two-segmented exopod and a two-segmented endopod. The cyprid possesses a rudimentary abdomen and an almost completely cleaved telson with a pair of one-segmented furcal rami. The morphology and setation of the antennules of C. mitella resemble those of Balanus amphitrite (=Amphibalanus amphitrite) and Megabalanus rosa, but differ in some morphological details.

A total of 75 specimens belonging to four species of thalassinoids were collected in the intertidal and estuarine zones of two localities along the Pacific coast of Mexico. Callianassa tabogensis is recorded for the first time in Mexico, and is transferred to the genus Neotrypaea. Material of Callichirus is assigned to Callichirus seilacheri with some doubts due to taxonomic problems related to this genus in the eastern Pacific. Neocallichirus cf. grandimana, an amphi-American species described for the western Atlantic and previously reported in Ecuador and along the Pacific coast of Panama and Colombia, is reported for the first time in Mexico. Upogebia dawsoni is recorded for the second time from the coast of Jalisco. An updated list of Axiidea and Gebiidea known from the Mexican Pacific is provided, including 35 species.

Two new species of chemosymbiotic bivalves are described from a poorly localized site in the Hatton–Rockall Basin at 1187–1200 m. The new species Isorropodon mackayi sp. nov. is compared with others of the genus from the North and South Atlantic. A novel anatomical structure, suggested to be a secondary gill, is described. The second bivalve Thyasira scotiae sp. nov. is compared with other species known to inhabit cold seeps in the Atlantic and most resembles Thyasira sarsi. Other than the minor morphological differences, the bathyal range and presence of commensal polychaetes, Antonbrunnia, never reported in T. sarsi support the erection of a new species. In the North Atlantic Isorropodon species and the larger thyasirids, with the exception of T. sarsi, are typically found at hydrocarbon seeps associated with pockmarks and mud volcanoes. If correct, then this is the first indication of active sulphidic seepage in the Hatton–Rockall Basin.

An investigation of ectoparasites of skates caught off the coast of Lesvos Island, north-eastern Aegean, Greece was performed from May 2010 to February 2012. One parasite, identified as the marine leech Pontobdella muricata, was found on the skin of 0.43% of Raja clavata and 3.6% of Dasyatis pastinaca specimens examined during the investigation period. This is the first record of D. pastinaca as being a host to P. muricata. Macroscopic and microscopic observation of the lesions caused by the parasitism, revealed haemorrhages and swelling of the skin of R. clavata, a milder inflammation of the skin of D. pastinaca, congestion, necrosis and liquefaction of the skin at the site of leech attachment and a lesion with disappearance of upper skin layers after the detachment of the leech.

Although many skates possess life history characteristics that may make them vulnerable to exploitation, the detailed biological information needed to enact effective management schemes is lacking for most species. The objectives of this study were to provide age, growth, and maturity estimates for the roughtail skate, Bathyraja trachura, from the eastern Bering Sea. Maximum age was estimated at 36 yr based on band pair counts in vertebral centra. Of the four growth models applied, the logistic model provided the best description of growth (asymptotic total length = 911 mm; growth coefficient = 0.131 yr−1). There was no evidence of difference in growth between males and females. Females attained maturity at larger sizes and older ages than males. The median size-at-maturity was estimated at 741 mm total length (TL) for males and 796 mm TL for females; median age-at-maturity was estimated at 21.1 yr and 24.7 yr for males and females, respectively. The results of this study may indicate a latitudinal pattern in size and growth, with individuals from the eastern Bering Sea growing more slowly and reaching higher maximum ages than previously reported for specimens collected off the western coast of the continental United States.

Benthosema pterotum is a dominant myctophid in the shelf region of the East China Sea (ECS). They are a key species linking secondary producers and upper trophic levels. We examined the reproductive biology of B. pterotum in the ECS, based on 3065 specimens (10.7–54.8 mm standard length (SL)) sampled during cruises in 1999 and 2004–2009 to enable data over a 12 month cycle to be assessed. Between 14 and 30 mm SL, the ratio of females to males was ~1:1; it increased with SL, and all individuals ≥46 mm SL were females. The gonadosomatic index (GSI) at 50% sexual maturity of females and males was 3.91 and 0.24, respectively. Based on this criterion, females and males can mature at sizes larger than 28 mm and 24 mm SL, respectively. Although mature females having GSI ≥3.91 occurred over nine months (May–January), mean GSI of females peaked sharply during August–September, i.e. the primary spawning period. The hepatosomatic index peaked during April–July, and declined during August–September, indicating storage of materials and energy for reproduction. Based on data from seasonal bottom trawl surveys, small individuals of B. pterotum began to occur abundantly in autumn, and modal body lengths increased progressively during spring–summer, corresponding to the above reproductive seasonality. Oocytes at various sizes were found in mature ovaries, indicating that they are multiple spawners. Egg size at hydration ranged from 0.5 to 0.85 mm. Batch fecundity was positively correlated with SL, and ranged from 253 to 1942 eggs in fish from 30.1–54.8 mm SL.