We examined the spatial and temporal variations of coastal and oceanic epipelagic copepods (rainy–dry seasons of 2009) in a tropical area of the south-west Atlantic. Zooplankton samples were obtained at 48 stations along six transects perpendicular to the coast, in the subsurface water between the 25 and 3000 m isobaths, by horizontal hauls using a Multinet. Abundance (42–64,753 ind. m−3), biomass (0.08–113 mg C m−3) and daily copepod production (0.17–163.20 mg C m−3 d−1) showed longitudinal and latitudinal variability. The highest values were observed over the southern continental shelf during the dry season. Temoridae, Undinula vulgaris and Paracalanus quasimodo dominated the biomass and daily copepod production during the rainy season; while Calanoides carinatus, Calanopia americana, Clausocalanidae, Temoridae, Paracalanidae and Subeucalanidae dominated during the dry season. The copepod assemblages formed four different groups: rainy season–continental shelf (1), dry season–continental shelf (2), rainy season–continental slope (3) and dry season–continental slope (4). Temperature, salinity, chlorophyll-a and suspended particulate matter explained 45% of the productivity distribution of the dominant copepod species. This study is the first attempt to examine the biomass and daily copepod production in oceanic waters in the south-west Atlantic Ocean, and it showed that copepod biomass and production in a tropical region can be relatively high compared with other regions of the world's oceans.

Temporal variations in the taxonomic relatedness of periphytic ciliate microfauna during colonization periods were studied in coastal waters of the Yellow Sea, northern China, from May to June 2010. Samples were collected at two depths of 1 and 3 m, using glass slides as artificial substrates. The colonization dynamics of ciliate microfauna on the slides revealed similar patterns in species composition at both depths. In the immature communities (1–7 days), the taxonomic patterns showed high variability compared to those in the mature ones (10 days and more). However, taxonomic relatedness parameters at the two depths differed during early stages of colonization (e.g. 1–3 days). Taxonomic diversity (Δ) was subject to high variability (coefficients of variation >10%) in both immature and mature communities, whereas taxonomic distinctness (Δ*), average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+) showed high stability (coefficients of variation <10%) during the colonization times of 3–21 days. These findings suggest that 3–21-day exposure times are sufficient to detect the taxonomic distinctness of periphytic ciliate microfauna at water depths of 1–3 m for the purposes of ecological research and monitoring of marine ecosystems.

Based on material collected during oceanographic campaigns in the western Atlantic from 1958 to 2011, two species of primnoid octocorals belonging to the genus Callogorgia were identified: Callogorgia americana and Callogorgia arawak sp. nov. These species are described and illustrated herein and their geographic and bathymetric are given. This is the first record of the genus in the south-western Atlantic. Additionally, the elevation of C. americana americana and C. a. delta to species level is proposed, keeping Callogorgia gilberti, C. delta and C. americana as separate species.

Oersted in 1843 gave a brief description of Dodecaceria concharum collected from the Kattegat. This was inadequate for identifying the species. Caullery and Mesnil in 1898 described three forms of Dodecaceria (A, B and C) but they were uncertain which form Oersted described. Dehorne in 1933 described D caulleryi (now D. fimbriata), which reproduce asexually, and Form B of Caullery and Mesnil. By default Form B became D. concharum the parthenogenetic species Form A of Caullery and Mesnil. Gibson and Heppell in 1995 in an attempt to consolidate these names deposited new types for the two species at the Cambers Street Museum in Edinburgh.

Carnivorous sponges (Porifera: Cladorhizidae) are a particularly interesting group of species typically occurring in deep-sea habitats. In this study a new species, Chondrocladia (Chondrocladia) robertballardi sp. nov., is described from specimens collected on two large north-east Atlantic seamounts – the Gorringe and Galicia Banks – located off the Iberian Peninsula. The holotype, collected on the Gorringe Bank by ROV, is a large, dichotomously branched and stalked sponge with translucent spheres in the middle of secondary axes and a rhizoid basal fixation system. Direct observations on the habit of the new species were made from the ROV. The paratypes, collected on the Galicia Bank by dredge and trawling, are fragments of different sizes. The skeleton is composed of a single class of styles and isochelae. All specimens were collected at similar depths (1400–1738 m) within the upper bathyal, and at the same longitude but separated by 670 km. A synthesis of the geographic as well as bathymetric distribution of this genus is presented. The species is compared with all known species of this genus worldwide.

Ciliates are a primary component of the periphyton microfauna and play a crucial role in the functioning of microbial food webs. Seasonal variation in community structures of periphytic ciliate communities was studied, using glass slides as an artificial substratum, during a 1-year cycle (August 2011–July 2012) in coastal waters of the Yellow Sea, northern China. Samples were collected monthly at a depth of 1 m from four sampling stations. A total of 144 ciliate species representing 78 genera, 43 families, 17 orders and eight classes were recorded. Among these species, 31 distributed in all four seasons, while 11, 11, 13 and two forms occurred only in spring, summer, autumn and winter season, respectively. The species number and total abundance peaked in spring and autumn, with minimum values in winter. Ciliate community structures differed significantly between seasons, and were significantly correlated with the changes in environmental variables, especially temperature, pH, dissolved oxygen (DO) and the nutrients. Of 36 dominant species (top 15 ranked contributors in each season), nine (e.g. Pseudovorticella paracratera, Trochilia minuta and Zoothamnium sp.) were significantly correlated with pH, DO or nutrients. Species richness, evenness and diversity measures were significantly correlated with temperature, pH, DO or soluble reactive phosphates. Results demonstrated that periphytic ciliates exhibited a clear seasonal variation in community structures in response to environmental conditions and potentially might be used as a robust bioindicator for assessing environmental quality status in coastal waters.

In the fourth paper about Ampharetidae from Japan, we describe 12 species in seven genera. The genus Orochi gen. nov. and the eight species Amage ehlersi sp. nov., A. longitorus sp. nov., Glyphanostomum hesslei sp. nov., Lysippe nipponica sp. nov., Melinnopsis augeneri sp. nov., M. mcintoshi sp. nov., Orochi palacephalus gen. et sp. nov., and Samytha annenkovae sp. nov. are newly described. Orochi gen. nov. is characterized by the shovel-like prostomium, the high membrane, from which all four pairs of branchiae emerge and the presence of neuropodia of the abdominal type in the last thoracic unciniger. In the discussions of the remaining genera, we comment on the taxonomic changes suggested by Jirkov (2011). Furthermore, we provide a list of all Ampharetidae species that have been recorded from Japan.

The structure of the microbial food web was studied in six estuary areas along the eastern Adriatic coast during March, July and October 2012. Limitation by phosphorus, not nitrogen, was a common feature for all studied estuaries. Heterotrophic bacteria and autotrophic picoplankton (APP) (particularly picoeukaryotes and Synechococcus) can reach notable abundances and biomasses, suggesting potential importance of the picoplankton community in P-limited estuarine environments. The main features of the microbial community structure in these environments included: (1) higher heterotrophic biomass in comparison to autotrophic biomass within the picoplankton community; (2) general domination of picoeukaryotes within the APP community, and increase of absolute and relative biomass of prokaryotic autotrophs (Prochlorococcus and Synechococcus) in the total APP in P-limited conditions; (3) domination of Synechococcus over Prochlorococcus biomass in all studied conditions, and common spatial distribution of these two groups of cyanobacteria, which was mostly determined by concentration of phosphorus; (4) relatively high contribution (about 50%) of LNA bacteria in the total bacterial abundance; and (5) relatively high contribution (about 33%) of heterotrophic pico-flagellates in the total flagellate abundance.

We have found a new species of Autolytinae (Annelida, Syllidae), Proceraea janetae, feeding on the scleractinian coral Montastrea cavernosa in coral reefs surrounding the Grand Cayman Island (Cayman Islands, British West Indies). The new species has a characteristic combination of transversal brown markings on the segmental margins and diffuse white mid-dorsal transverse bars, together with a diffuse white mid-dorsal longitudinal band. Antennae are brown, tentacular cirri are pale, the first dorsal cirri are white with pale base; the second dorsal cirri are pale, and the remaining dorsal cirri are alternately long, bright yellow-orange with brownish tips and short, entirely brown. The trepan has 18 tricuspid teeth in one ring. There are 9 teeth with all cuspids equally long and 9 with a longer median cuspid, arranged in an alternating pattern. We describe and illustrate the feeding behaviour of the new species, which appears to be closer to parasitism rather than to specialized predation. Proceraea janetae sp. nov. is the second polychaete, and the first syllid, known to feed on scleractinian corals.

Due to postglacial isostatic uplift many stratified lakes, at different stages of isolation, are located along the shores of the White Sea. In five lakes, located near the White Sea Biological Station of Moscow State University, salinity, temperature, pH, concentration of dissolved oxygen, redox potential, and illuminance were measured. Distribution of microorganisms and spectral properties of water layers were also studied. All the lakes had a narrow bright coloured layer in the redox zone caused by mass development of phototropic microorganisms. Light absorption and fluorescence spectra indicated algae containing chlorophyll a predominate in the red water layers while the colouration of green and brown layers is caused by green sulphur bacteria with bacteriochlorophylls d and e. Sunlight is completely absorbed in the redox zone because of the high density of algae and/or bacteria, resulting in aphotic conditions below. Coloured layers act as a specific biotope for special communities of microorganisms. Eukaryotes identified by the 18S rRNA gene included different species of mixotrophic algae and ciliates resistant to anoxia. The water layer colour and spectral characteristics (i.e. light absorption and fluorescence) of water in the redox zone can be considered indicators of the stage of lake isolation from the sea, with the red colour caused by cryptophyte alga Rhodomonas sp. bloom found in earlier stages and brown and green colours caused by green sulphur bacteria in later stages.

Genus Onyx Cobb, 1891 has been reviewed and 19 valid species including two new species have been reported in the world. Two new species, Onyx rizhaoensis sp. nov. and Onyx minor sp. nov. from the Yellow Sea coast are described and illustrated. In addition to the genus characters Onyx rizhaoensis sp. nov. has relatively long cephalic setae; a single loop-shaped amphidial fovea; 12 S-shaped tubular precloacal supplements in 10 + 2 arrangement, posterior 10 closely spaced, anterior two set apart; female vulva situated at almost midpoint of the body. Onyx minor sp. nov. is characterized by a relatively small body for the genus (body length usually shorter than 800 μm); gubernaculum slender parallel to spicules and with a hooked dorsal apophysis; 12 S-shaped tubular precloacal supplements fairly evenly spaced; female vulva situated at about midbody. At the same time, a dichotomous key for Onyx males is proposed.

An overview is proposed of the hexactinellid sponge fauna of the Mediterranean Sea, including the description of a new species of Sympagella, S. delauzei sp. nov., collected by ROV during the exploration of deep-sea canyons of the NW Mediterranean and of deep banks and seamounts of the Alboran Sea. The type species of Sympagella, S. nux, is redescribed from specimens from the type locality. An 18S rDNA sequence of the new species was obtained and included in a phylogenetic tree of related hexactinellids. Some modifications to the classification of Rossellidae are proposed according to the new morphological and molecular data obtained during this study: the genera Caulophacus, and Caulophacella are accordingly moved from Rossellinae to Lanuginellinae.

Identification of marine invertebrate larvae using morphological characters is laborious and complicated by phenotypic plasticity. Balanus amphitrite is a dominant barnacle, important in the context of intertidal ecology and biofouling of manmade structures. Morphological identification of barnacle larval forms in a mixed population is difficult because of their intricacy and similarity in size, shape and developmental stages. We report the development and application of a nucleic acid-based Polymerase Chain Reaction (PCR) method for the specific identification of the barnacle, B. amphitrite, from the heterogeneous zooplankton sample. This method is reliable and accurate thereby overcoming taxonomic ambiguity. Sequence alignment of the 18S rRNA gene region of selected species of barnacles allowed the design of B. amphitrite-specific PCR primers. Assay specificity was evaluated by screening DNA obtained from selected species of barnacles. The oligonucleotide primers used in the study flanked a 1600 bp region within the 18S rRNA gene. The primer is specific and can detect as few as 10 individuals of B. amphitrite larvae spiked in a background of ~186 mg of zooplankton. This technique facilitates accurate identification and the primer can be used as a marker for enumeration of B. amphitrite larvae in the plankton.

The near-cosmopolitan genus Clytia is abundantly found in coastal waters, but difficulties of identification in this genus make nearly all species records of medusae suspect. Complex life histories, ambiguous taxonomic characters, and phenotypic plasticity pose serious problems for accurate species-level identifications and future revisions of Clytia species. In the present study, morphological investigations and molecular analyses of Clytia specimens from the coastal waters of the East China Sea revealed Clytia gulangensis sp. nov. as a new species. DNA barcoding based on the mitochondrial cytochrome oxidase I (COI) gene supported the new species as a separate species within Clytia, and phylogenetic analyses based on mitochondrial 16S rDNA and nuclear 18S rDNA further confirmed this new species to be a distinct lineage. Moreover, detailed observation of medusae and polyps of this species showed sufficient morphological differences from other Clytia species for a diagnosis. Our results indicated that life cycle and DNA-based studies should be a standard approach in future biodiversity investigations of Clytia species.

We resolve taxonomic confusion regarding brooding sea anemones in the genus Epiactis Verrill 1869a in the North Pacific Ocean based on newly collected material from Hokkaido (Japan), Haida Gwaii (British Columbia, Canada), and Kodiak and Adak Islands (Alaska, USA), and museum specimens collected from the Kurile Islands (Russia), Alaska, British Columbia, Oregon (USA), and California (USA). We find that the internally brooding individuals identified by Hand & Dunn (1974) as Cnidopus ritteri (Torrey, 1902) and placed in the genus Epiactis by Fautin & Chia (1986) belong to a new species which we describe and name Epiactis handi sp. nov. Epiactis handi and E. ritteri can be differentiated by morphological and behavioural features including ornamentation and structure of the column and mode of brooding offspring. To highlight and clarify these differences, we redescribe E. ritteri based on specimens from Alaska. We provide the first account of external brooding in E. ritteri, which necessitates a clarification of the differences between E. ritteri and another externally brooding species from the North Pacific, E. japonica Verrill, 1869b. Epiactis ritteri and E. japonica differ in sex allocation, ornamentation of the column and details of external brooding: members of E. ritteri are gonochoric with a smooth column and brood groove which tightly closes, whereas those of E. japonica are hermaphroditic and have mid-column spherules.

Clownfish and their associated sea anemones are icons of tropical and subtropical coastal ecosystems, but bleaching and collecting for the aquarium trade has reduced their population densities in several Indo-Pacific locations. We surveyed four Entacmaea quadricolor populations and their associated clownfish Amphiprion clarkii in Hong Kong. These assemblages represented a combination of exposed and sheltered, flat bottomed and sloped conditions. Different from tropical areas, where E. quadricolor is usually found in sheltered shallow waters, the four populations in Hong Kong were distributed in 4–10 m depths, being densest on a 40 × 80 m slope of volcanic rocks (34.2–76.6% substrate cover and 48.7–102.1 ind  m−2) at an exposed site. This distribution pattern could be explained by the high turbidities associated with river discharge and sedimentation rates in local waters, which discourage the establishment of E. quadricolor populations in sheltered bays; shallow habitats might not be suitable for E. quadricolor in Hong Kong due to strong wave actions generated by typhoons. Amphiprion clarkii was present at low densities (0.07–0.26 fish m−2) across the sites. Our data provide a baseline for monitoring the changes of these conspicuous members of shallow water communities in Hong Kong.

We studied biochemical characteristics and the response to low salinity at short and long-term after feeding of alkaline phosphatase (AP) activity in hepatopancreas of the osmoregulator crab Neohelice granulata from Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina) (37°32′–37°45′S 57°19′–57°26′W). The hepatopancreas exhibited a levamisole-insensitive and a levamisole-sensitive AP activity with distinct characteristics. Levamisole-insensitive activity was similar within the range of pH 7.4–9.0 and exhibited a Michaelis–Menten kinetics. Levamisole-sensitive AP activity appeared to be maximal at pH 8.5 and appeared to exhibit an allosteric kinetics. In crabs acclimated to 10 psu (hyper-regulation conditions) levamisole-insensitive and levamisole-sensitive AP activity increased (about 16-fold) over time from short term (2–4 h) to long term (120 h) after feeding while no changes occurred in crabs acclimated to 35 psu (osmoconforming conditions). The changes of AP activity along with the higher values at 120 h after feeding in 10 psu compared with those in 35 psu, and the concomitant changes in proteolytic activity, suggest a role of AP in digestive and metabolic adjustments at the biochemical level upon hyper-regulatory conditions.

This is the first comprehensive research study on the parasites of Mytilus galloprovincialis collected from the Sinop coasts of the Black Sea and their relationships with several environmental and biotic factors. A total of 1740 mussels were collected monthly at three sampling localities representing different ecosystems in the period between August 2012 and July 2013 and examined for parasites. Identified parasites were Nematopsis legeri, Peniculistoma mytili, Urastoma cyprinae, Parvatrema duboisi and Polydora ciliata. Infection prevalence (%), mean intensity and mean abundance values of each parasite species were calculated according to season, sampling localities and length classes of mussel. Nematopsis legeri was the most prevalent species (32.5%), followed by Pe. mytili (6.70%), U. cyprinae (6.30%), Pa. duboisi (4.50%) and Po. ciliata (2.20%). Nematopsis legeri and Parvatrema duboisi had their highest infection prevalence and intensity values in sampling locality III where secondary hosts present to complete their life cycle and larger sized mussels had higher parasite loads. Statistically significant differences were determined in the prevalence of infection and intensity values among seasons, length classes of mussel and sampling localities of each parasite species. The present study provided valuable information on mussel parasites and their relationships with host length, seasons and ecology.

Amongst the Hexactinellida, Hexasterophora is the most important taxon in terms of number of species as well as concerning the variability in morphological characters. In this study the first comprehensive analysis of phylogenetic relations between hexactinellid families and genera of the subclass Hexasterophora based on morphological features is presented. Therefore, 157 morphological characters of the Hexasterophora were compiled into a matrix by presence/absence data. The resulting phylogenetic trees are compared with conclusions based on molecular data and classical systematics. So far, we find the main hexasterophoran taxa (Hexactinosida, Rossellidae and Euplectellidae) well established as monophyletic and in rather good correspondence with classical systematics and molecular results. Our phylogenetic trees largely support the systematic classification proposed by Schulze (1886) and Mehl (2002). However, some families (e.g. Euretidae) are not corroborated. For others (Euplectellidae), our cladistics approach is at odds with the system proposed by Tabachnick (2002a). Morphological phylogeny becomes problematic for those taxa, in which many of the diagnostic characters are either symplesiomorphic, or multiple homoplastic. Our results indicated the need for revision of the classification features used.

The shallow water sea anemone Phymanthus crucifer exhibits three distinct morphotypes, characterized by the presence or absence of protuberances on the marginal tentacles, as well as intermediate forms. The taxonomic status of the different morphotypes and the diagnostic value of protuberances on the tentacles have been debated for this species and the family Phymanthidae. We analysed the external and internal anatomy, cnidae and three mitochondrial molecular markers for representatives of each of the three morphotypes. In addition, we address the putative monophyly of the family Phymanthidae based on molecular data. With the exception of the protuberances, our morphological and molecular results show no differences among the three morphotypes; thus, we consider this feature to be intraspecific variability within P. crucifer. Furthermore, molecular data reveal that the family Phymanthidae is not monophyletic. In addition, we discuss several diagnostic morphological features of the family Phymanthidae.