A description of a new species of Magelona, M. parochilis sp. nov. is presented, based on material collected from the Yellow Sea, China. The new species belongs to the ‘Magelona mirabilis group’ of magelonids, possessing a rounded prostomium, lacking prostomial horns and specialized chaetae on chaetiger 9. Paired anteriorly open pouches are present between chaetigers 11–12 and 14–15 (occasionally between chaetigers 17–18). Magelona parochilis sp. nov. inhabits intertidal zones and shallow subtidal waters characterized by sandy mud.

Nectonema species are parasites of decapod crustaceans and the only known representatives of the otherwise freshwater/terrestrial taxon Nematomorpha. We report the American lobster, Homarus americanus, as a new host for Nectonema agile, a first record among astacidean decapods. A female, about 590 mm long, was found in the body cavity of one female lobster specimen. We assume lobster to be a very rare host for Nectonema.

The seasonal growth pattern and size composition of the European anchovy, Engraulis encrasicolus caught by mid-water trawl and purse seine was studied in the southern Black Sea between October 2010 and April 2011. Total length (TL) and size distribution of females caught by purse seine was higher than males and females obtained from mid-water trawl (P < 0.05). The seasonal von Bertalanffy growth parameters, computed from monthly length–frequency distributions, were estimated as asymptotic length to which the fish grow (L∞) = 13.01 cm TL, growth-rate parameter (K) = 0.993 year−1, amplitude of the sinusoidal growth oscillations (C) = 0.800, and the time of the year when the growth rate is slowest, the winter period (WP) = 0.298 for males and as L∞ = 13.69 cm TL, K = 1.249 year−1, C = 0.950, and WP = 0.151 for females caught by mid-water trawl. The seasonal von Bertalanffy growth parameters for anchovy obtained from purse seine fishing in the Rize region were estimated as L∞ = 14.00 cm TL, K = 0.800 year−1, C = 0.980, and WP = 0.212 for males and as L∞ = 13.93 cm TL, K = 0.994 year−1, C = 0.725, and WP = 0.319 for females. The period of slowest growth for males and females estimated between February and April, which is the period with a relatively low water temperature and consequently anchovy in the southern Black Sea have a seasonal growth pattern.

Colonization dynamics of periphytic ciliate communities were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using an artificial substratum. Samples were collected at two depths of 1 and 3 m. The temporal patterns of ciliate colonization had similar dynamics and were fitted to the MacArthur–Wilson and logistic models in colonization and growth curves at both depths, respectively. The ciliate communities reached equilibrium in species composition within at least 10-days exposure time. However, they differed in both structural and functional parameters between the two layers, despite similar species composition. The species diversity, evenness, the colonization rate (G) and maximum abundance (Amax) were distinctly higher, but the time for reaching 90% equilibrium species number (T90%) was shorter at the depth of 1 m than those at a deeper layer. Results suggest that it is an optimal strategy to collect the ciliate communities within shorter exposure time at 1 m for ecological research and a monitoring programme in marine ecosystems.

Virus-like particles were observed in thin sections of partially bleaching colonies of the scleractinian Acropora cytherea, collected in the Hon Mun Marine Protected Area (Vietnam). The most common particles were found in the cytoplasm of epidermal cells, exhibiting icosahedral symmetry and measuring 90–140 nm in diameter. Some had a tail-like structure resembling that of certain Hepadnaviridae such as the hepatitis B virus. Some others were tailless with a virion size. Overall, less than 10% of the cells showed obvious signs of infection. Images of virally-parasitized tissues of A. cytherea provide further evidence that corals are a target for viral infection. However, more research is required into their pathogenicity and involvement in bleaching events.

Here we describe habitat use and the grazing effects of the sea urchin Tetrapygus niger and the gastropod Tegula atra in the low intertidal zone of a rocky shore in central Peru (Ancón bay: 11°46′S 77°12′W), where these two species were documented as coexisting with no evidence of habitat segregation between them. Gut content and isotopic analyses revealed differences between their diets: T. atra consumes mainly microalgae while Tetrapygus niger consumed also benthic macroalgae. Individual grazing effects were evaluated with inclusion/exclusion experiments. Tetrapygus niger prevented the colonization of the substrate by sessile organisms, including the dominant mussel Semimytilus algosus, while Tegula atra reduced the abundance of microalgae and green ephemeral macroalgae during early succession, but these effects were overwhelmed by the rapid increase in cover of S. algosus. We suggest that Tetrapygus niger plays a key role in this low intertidal community. Through directly limiting mussels to monopolize the substratum, T. niger can reduce the diversity of mussel associated species; conversely, through controlling primary space holders, T. niger can also benefit other grazers that live on bare substrate by maintaining a suitable area for feeding or living.

The morphogenesis and morphology of the marine benthic ciliate Certesia quadrinucleata collected from seawater in Nagasaki Mie Port, Japan, were investigated using microscopic observation of live and protargol-stained specimens. In terms of its morphology, the current isolate possesses diagnostic features of the genus and the species: a row of left marginal cirri, a prominent paroral membrane, 11 frontoventral cirri scattered in frontoventral area, five highly developed transverse cirri, four macronuclear nodules, five dorsal kineties and a caudally located contractile vacuole. Its morphogenesis belongs to the ‘Certesia’ subtype, and main events can be summarized as follow: (1) the oral primordium in the opisthe develops de novo in a subcortical pouch; (2) the old paroral membrane is completely replaced by the new one in the proter, but the parental adoral zone of membranelles is wholly inherited; (3) five streaks of cirral anlagen are formed in a primary mode for the proter and the opisthe, which gives rise to cirri in the pattern of 3:3:3:3:3 from left to right; (4) the leftmost frontoventral cirrus develops de novo on the cell surface in both dividers, and has no connection with the undulating membrane anlage; and (5) the anlagen for marginal cirri and dorsal kineties occur intrakinetally. Current observations confirm the separation of Certesiidae from other euplotids at the familial level.

The new species Echinofabricia rousei is described for the Mediterranean Sea based on specimens collected along the Sardinia Coast (Porto Conte). The genus Echinofabricia is reported for the first time in the Mediterranean area. At present three species are described within the genus: E. goodhartzorum, described from the Caribbean, E. dubia, described from the East Pacific (Hawaii) and E. alata from Australia.

Chub mackerel, Scomber colias, is widely distributed in the warm waters of the Atlantic Ocean including the Mediterranean and Adriatic Seas. This medium-sized pelagic fish species occurs in deeper waters during the colder part of the year and schools are found in coastal waters during the warmer parts of the year, where they spawn and feed. Atlantic chub mackerel is one of the most important commercial fish throughout its habitat and as a consequence of its wide distribution and broad commercial exploitation, biological information on the growth and mortality is required for stock assessment and management. Despite the abundance and economic importance of S. colias in the Adriatic Sea, knowledge about its biology and population dynamics is still limited. Studies of the age, growth, mortality and exploitation rates of S. colias have not been undertaken previously in the Adriatic Sea. Therefore, the exploitation status of this species' stock in the Adriatic Sea is unknown. The purpose of this study was to provide information on the age, growth and length–weight relationship as well as estimates of mortality and exploitation rate in order to define the present state of the population in the Adriatic Sea.

The majority of biochemical studies in corals has been focused on the lipidic composition and little attention has been given to the amino acid profile of these invertebrates. The objectives of this work were to investigate, for the first time, the temporal variations in the total amino acid (AA) composition of an octocoral, namely the sea pen Veretillum cynomorium, and to evaluate possible interspecific differences in AA profile between this octocoral and hexacorals. The quantitatively most important AAs in V. cynomorium colonies were: glutamic acid, varying from 3.92 to 5.94% dry weight (dw) and representing around 14–15% of total AA content; aspartic acid (3.34–4.99% dw; 11–12%); and glycine (2.87–4.57% dw; 9–12%). On the other hand, the minor AAs were methionine (0.41–0.73% dw; 1–2%) and histidine (0.54–0.76% dw; 2%). Almost all AAs showed the same significant seasonal variations, with the highest values in February, second highest in October and the lowest in June. Some AAs, namely lysine, phenylalanine and methionine did not follow this trend and showed the major peak in October. Most of the AA variations seemed to be linked to changes in food availability and/or gametogenesis. Principal component analysis clearly separated the octocoral from the group of hexacorals, mainly due to the higher percentages of arginine, tyrosine and glycine in V. cynomorium, and valine, serine, histidine, isoleucine and alanine in hexacorallia species. We speculate that this differentiation possibly derived from physiological differences related to phylogeny, and was not affected by reproductive or environmental seasonality.

Sabellidae is the second most diverse polychaete family in the Adriatic Sea, after Syllidae. Herein we report the updated list of the Sabellidae and Fabriciidae families in the Adriatic Sea deriving both from literature data and presently conducted researches in the northern Adriatic. During these researches polychaetes were sampled from three offshore soft-bottom and three coastal rocky shore stations. Among the analysed material three Sabellidae species are new records for the Adriatic fauna, while four Sabellidae and one Fabriciidae species were recorded for the first time in the northern part. Two new species were found and described: Amphicorina rovignensis spec. nov. and Megalomma pseudogesae spec. nov. These findings increase the number of Sabellidae taxa recorded in the northern Adriatic from 29 to 38. Our results point out the lack of the recent taxonomic studies in the area, but might also indicate the widening of the species areal. Taking into consideration that studies on only six stations raised the number of known sabellid taxa from the area by 31%, our results support the need for the regular taxonomic updating of the polychaete fauna in the northern Adriatic.

The digestive system of sea spiders (Pycnogonida) presents peculiarities that have not been discussed in the context of their ecology or feeding behaviour. We investigated the digestive system of two Mediterranean species, a carnivorous species Ammothella longipes and a detritivorous Endeis spinosa, with special focus on its correlation with behavioural feeding habits. The midgut and hindgut sections did not present significant differences between the two species, but major differences were observed in the foregut, reflecting concordance to their diet and their feeding behaviour. Jaws, setose lips, the structure of the pharyngeal filter and musculature of the proboscis are the main differential elements when comparing feeding habits of A. longipes and E. spinosa. These elements are responsible for the reduction of the food pulp down to subcellular size. The digestion process observed in the species studied agrees with that observed in other pycnogonid lineages, but differs from most marine arthropods mainly because of the absence of midgut gland cells and the presence of a unique multifunctional type of midgut epithelial cell. Epithelial digestive cells are present in a small ‘resting’ form during starvation periods. During digestion, secretion granules possibly containing zymogen move to their apical border to be secreted to the midgut lumen, secondary lysosomes are formed and intracellular digestion occurs within them. Residual bodies are formed within the epithelial cell and released to the midgut lumen to be transported towards the hindgut. The characteristics of the digestive process of the pycnogonids studied seem to reflect a plesiomorphic state in arthropods.

Community parameters of diatoms have been used as useful bioindicators for bioassessment of both lentic and lotic systems. The influence of enumeration time periods on detecting community parameters of periphytic diatom assemblages within different exposure times was studied using an artificial substratum in coastal waters of the Yellow Sea, northern China, during the period May–June 2010. Samples were collected at a depth of 1 m, and were examined with different enumeration time periods. Enumeration time periods represented a significant influence on detecting the community features of periphytic diatoms, although no significant changes occurred in periphytic diatom community structure between two enumeration schemes (within 24 h and 24–48 h). The delayed enumeration (within 24–48 h) may result in the similarity of the communities being reduced 10–29%, and in species numbers decreasing and in abundance increasing with exposure duration, respectively. The diversity (richness, evenness and diversity of species) indices were significantly decreased in almost all samples with >10% standard errors at some exposure times by the delayed enumeration scheme. These results suggest that the delayed enumeration may have resulted in the species richness and individual abundance of periphytic diatoms significantly decreasing and increasing, respectively, and thus significantly affected the analyses of species diversity for assessing water quality in marine ecosystems.

A new species of Hirsutonuphis (Annelida: Onuphidae) is described from the continental shelf of the Gulf of California, Mexican Pacific. Hirsutonuphis paxtonae sp. nov. is easily distinguished from eight previously described species belonging to this genus, by the bi- and tri-dentate pseudocompound hooded falcigers on the first 5–6 chaetigers, the pectinate chaetae from chaetigers 6–11, the bidentate subacicular hooded hooks from chaetigers 18–21, and its colour pattern: a dark transverse band in the dorsal part of the peristomium and on each chaetiger, which gradually fades from chaetigers 12–27. Most species of Hirsutonuphis have been found in the Pacific Ocean, and more particularly in Australian waters, although this new onuphid is the third species of the genus described from the Mexican Pacific, in the Tropical Eastern Pacific. A taxonomic key is provided for all the species of the genus.

Marine sessile invertebrates with outer skeleton constitute additional substrate for a diverse group of epibiotic organisms. Colonial hydroids are no exception. Large numbers of motile and sessile organisms use hydroid colonies covered with chitinous perisarc for permanent or temporal attachment. Such epibiotic associations between colonial hydroids and microorganisms are poorly studied and mostly known for subtropical regions. There are no data about the development of such epibiotic association and type of its specificity yet. The present paper for the first time describes the epibiotic association of the colonial thecate hydroid Dynamena pumila from the high latitude sea. We reconstruct the spatial and temporal development of such epibiotic community and analyse the organization of the multicomponent biofilm covering the hydroid colony. Comparison of the epibiotic community in different seasons indicates for holding out of the basal features and components of the community during the whole year. Ultrastructural investigations revealed that components of the biofilm affect the outer skeleton of the hydroid colony that results in penetration of the microorganisms into the skeleton and even soft tissues. Our data allow supposing that association of hydroid D. pumila with a microorganism community has features of a symbiotic system.

Near-shore benthic sediment samples collected at low tide from the western Atlantic Ocean (Sable Island, Nova Scotia, Canada) and the eastern Pacific Ocean (Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada) were searched for little-known species of the rhizarian (Cercozoa) genera Pinaciophora, Rabdiaster and other related rotosphaerids. Several representatives with complete investitures of silica-scales (the structure of which is taxonomically diagnostic) were studied by transmission and scanning electron microscopy. The validity of the genus Pinaciophora (sensu Penard, 1904) as defined by a single type of plate-scale only, was strengthened by the discovery of Pinaciophora rubicunda and of another previously undescribed entity, both of which lacked spine-scales. Several earlier reports of loose scales from marine habitats, and erroneously identified as the freshwater P. fluviatilis, might be assigned to P. marina sp. nov. The new genus Thomseniophora was erected to include all ‘Pinaciophora' previously known to produce spine-scales and seven new taxa were described. Six other little-known species of Thomseniophora, Pinaciophora and Rabdiaster were described from the Canadian west coast (Pacific Ocean) including one new species of Pinaciophora. The addition of Thomseniophora brings the number of genera assigned to the Rotosphaerida to six: Pinaciophora, Thomseniophora, Rabdiaster, Rabdiophrys and Pompholyxophrys. The presence of several apparently closely related taxa in the same collection (same location and sampling date) strengthens the conclusion that relatively small differences in the morphology of their siliceous scales were more likely caused by genetic differences than by environmental influences.

This contribution reports the first record of intertidal reefs built by the sabellariid worm Sabellaria nanella in the lower intertidal at Monte Hermoso beach, Argentina (39°S). All previous records of S. nanella in the study area correspond to solitary individuals from shallow subtidal depths in coastal environments, while the present findings refer to well established reefs on stony rocks. Worms sort medium size sand grains to build the reefs, which contain higher amount of organic matter than the surrounding sediments. Size structure of worms shows multiple size cohorts that include recent recruits and mature adults. Many invertebrates, i.e. various annelids, arthropods, molluscs, nemerteans and nematodes, are the frequent organisms living within the reef, some of them already recorded in the area. The presence of intertidal reefs of S. nanella indicates that the species has plasticity to adapt to environments with different physical conditions (subtidal–intertidal areas).

The genus Clytia is distributed worldwide, but most accepted species in this genus have been examined either only at the hydroid or medusa stage. The challenge in identifying Clytia species reflects their complex life cycles and phenotypic plasticity. In this study, molecular and morphological investigations of Clytia specimens from the coastal waters of China revealed an as yet unreported species, designated C. xiamenensis sp. nov., that was considered as conspecific to two nearly cosmopolitan species, C. hemisphaerica and C. gracilis. DNA barcoding based on partial mitochondrial cytochrome c oxidase subunit I (COI) and large subunit ribosomal RNA gene (16S) confirmed the highly distinct lineage of C. xiamenensis sp. nov. These results were corroborated by the detailed observations of its mature medusae and its colonies, which showed that C. xiamenensis sp. nov. was morphologically distinct from other species of Clytia. Thus, based on our findings, the nearly cosmopolitan distribution attributed to some species of Clytia might rather be due to the misidentification, and it is necessary to elucidate their whole life cycle in order to establish the systematic validity of all species within the genus Clytia.

Sipunculans represent a discrete component of the coral reef ecosystem, since they live inside the calcareous structure. They are an important component in terms of biomass and number of organisms. The present study describes the diversity of sipunculans living inside massive coral skeletons. A total of 43 blocks of dead coral skeletons from Montastraea cavernosa, Montastraea annularis and Diploria strigosa were collected from nearby coral reef areas off Santa Marta, on the Colombian Caribbean coast. Using hammer and chisel, blocks of approximately 1 dm3 were broken into small pieces, from which the sipunculans were extracted. A total of 381 organisms were obtained from the coral blocks comprising four families and 10 species. All the species found have been widely reported in different studies from the Caribbean region. Aspidosiphon fischeri and Phascolosoma perlucens were the two most abundant species comprising more than 60% of the total organisms with a mean density of 18.52 ± 4.64 organisms dm−3. Dead coral substrate from M. cavernosa had the greatest abundance (N = 148), followed by D. strigosa (N = 121) and M. annularis (N = 112). There were no significant differences in the abundance, richness, and diversity of sipunculans between coral skeletons; and within samples there was high variability suggesting that the skeletal substrates analysed came from coral skeletons of different unknown ages of succession. These results describe the sipunculan community structure that live inside three important massive coral skeletons, and contributes to the knowledge of the cryptobiota diversity of the Santa Marta area of Colombia.

Six new marine species of the silica-scaled heterotrophic genus Thaumatomastix are formally described: two were found in Canadian Atlantic Ocean coastal waters (T. asymmetrica sp. nov. and T. sablensis sp. nov.) and four from Canadian Pacific Ocean coastal waters (T. inornata sp. nov., T. multipora sp. nov., T. gwaii sp. nov. and T. curvata sp. nov.). These discoveries more than double the number of known marine species of this genus from four to ten. The scale structures of all differ significantly from those of previously known species and therefore warrant erection as new species. Amended descriptions of two previously little-known freshwater species (T. triangulata and T. nigeriensis) are provided based on specimens found in freshwater ponds and lakes in Ontario, Lanada, and provide evidence refuting the recent published proposals to transfer T. triangulata back to the photo-autotrophic genus Chrysosphaerella and to transfer T. nigeriensis to the related thaumatomonad genus Reckertia. Until now, all known species of Reckertia (including several taxa previously classified in Thaumatomastix) were marine. This paper describes the first known freshwater species of Reckertia (R. hindoni sp. nov.) found in two separate Ontario ponds. The similarities and differences among many of the marine and freshwater species of Thaumatomastix suggest a common ancestor but significant evolutionary divergence over time and space.