Food partitioning among coexisting species is often considered advantageous to minimize niche overlap and avoid inter-specific competition. Congeneric fish species such as the mullets Mugil curema and Mugil liza, which co-occur across marine and estuarine habitats, are good models to evaluate resource use and niche overlap or partitioning. We used stomach contents (SCA) and stable isotope analysis (SIA) to assess potential trophic shifts and changes in niche overlap associated with the mullets transitioning from marine to estuarine habitats. SIA included different fractions of organic matter in suspension and in the sediment to estimate the contribution of micro, nano and pico-organisms to the mullets’ diets. We hypothesized higher resource partitioning in the less resource-diverse system (marine surf-zone) than in the more diverse one (estuary). SCA showed diet differences between M. curema and M. liza according to the habitat. They showed distinct diets in the marine area (P < 0.001), but similar diets in the estuary (P = 0.226). A lower niche breadth was observed for both species in the marine area (M. curema = 0.03, M. liza = 0.06) compared with the estuary (M. curema = 0.14, M. liza = 0.16). Isotopic niches of both species were higher in the estuary (64.7%) compared with the marine area (0.7%). These findings corroborated our hypothesis of higher food partitioning in the marine surf-zone. We also demonstrated using SIA the shift from planktonic to benthic feeding following the recruitment of the mullets from the surf-zone into the estuary.

Always to be found in Drake's Island Tank.* Very abundant during the summer, but diminishing innumber during the winter months. It has been described by O. MÜller (22), Ehrenberg (6), Stein (31), Dujardin (5), Claparede and Lachmann (3), under various names, but their descriptions may be regarded as only of historic interest. The later observations of Gruber (13), Cohn (4), and Entz (8) aremore detailed, and Lebedew (17) has given the fullest account of the animal. Kent (16), Biitschli (1), and SchewiakofE (27) have only short notices.

The growth of certain unicellular marine algae has been shown to occur in culture solutions whose total ionic content and chemical composition departs markedly from that of natural sea water. In fact, some of these algae apparently grow more rapidly in half-strength sea water media than in a medium of salinity equal to 35‰. This ability, on the part of the algae, to grow at widely different salinities suggests that the algal cells are able to maintain an internal ionic composition despite wide variation in the external composition of the surrounding culture medium in which they are growing. Droop (1958) has shown that the major cations present in sea water can be varied within wide limits and it was decided to concentrate on the cations, sodium, potassium, calcium and magnesium. A series of analyses of Phaeodactylum tricornutum has been carried out to determine the concentrations of the four cations present in the cells and also to determine whether these concentrations vary during the growth of cells in culture over a period of time. In addition the analyses have been carried out on cells which have been grown at two different salinities, to compare internal cellular concentrations at different salinity levels of the media.

In attributing variations in growth and metabolism within a population to environmental fluctuations, and in interpreting the biological response to environmental fluctuations, it is important to recognize the variations that are intrinsic to the population or species. Consequently, it is common practice in studies on the growth and metabolism of calanoid copepods to separate instars and, in the case of adults, males and females when analysing measurements. Although studies on calanoids, in particular species of Calanus and Euchaeta, have demonstrated the existence of pronounced sexual differences in parameters such as dry weight, biochemical composition and respiration rate (e.g. Comita, Marshall & Orr, 1966; Marshall, 1973; Bamstedt, 1975, 1979; Gatten et al. 1979, 1980), the possibility that similar differences might occur in pre-adult instars has not been examined, this despite the fact that in many species in this group it is possible to distinguish the sex of copepodites IV and V, the two instars preceding the adult.

The feeding habits of the apron ray, Discopyge tschudii, were investigated, off Uruguay and northern Argentina, and we tested the hypothesis that the diet changes with increasing body size, between sexes and seasons using a multiple-hypothesis modelling approach. Discopyge tschudii preys mainly on polychaetes (88.77% index of relative importance (IRI)) followed by siphons of the clam Amiantis purpurata (8.13% IRI) and amphipods (3.08% IRI). Ontogenetic, sexual and seasonal changes were found. Larger individuals of D. tschudii consumed buried polychaetes more often. The consumption of errant polychaetes was higher in males and in the cold season. Also, amphipods were preyed on more heavily by females and the number of siphons of A. purpurata consumed was higher in the cold season.

Sequences of the ribosomal internal transcribed spacer regions 1 and 2 (ITS-1 and ITS-2) were employed to investigate relationships between putatively very closely related species of marine haplosclerids and to investigate the species status of Haliclona cinerea. Results indicate that intra-genomic and intra-specific levels of diversity are equivalent, and sequences from multiple clones from a number of individuals of a single species could not be separated on phylogenetic trees. As a result, the ITS regions are not suitable markers for population level studies in marine haplosclerids. Sequences of these regions were highly species specific, and large differences were found between species. ITS sequences from three Callyspongia and three Haliclona species could not be aligned successfully and therefore this locus could not be used to investigate relationships between these putative close relatives. However, ITS sequences retrieved from one H. cinerea were very different from sequences generated from other H. cinerea individuals indicating that this species comprises more than one taxon.

The species included in the present report have all, with one exception, been taken since the opening of the Laboratory in June, 1888. Twenty-four genera and thirty-six species will be found recorded, and those afford a considerable addition to the previously known Nudibranchiate Fauna of the Sound.

Here I record the cleaning activity of the occasional cleaner Diplodus argenteus at rocky reefs off southern Brazil. Diplodus argenteus juveniles are referred to as occasional cleaners, but there is no further description of their cleaning activity in the literature. Only two fish species were here recorded as clients, which I hypothesize to be related to a lack of visual attractiveness of D. argenteus cleaning services.

Squids have more than two accessory reproductive glands, namely oviducal and nidamental glands which release gelatinous substances at the time of spawning to produce an egg mass and in some sepiolids and loliginids there also exist accessory nidamental glands (Hamabe, 1962; Boletzky, 1986; Mangold, 1987). An exception are some enoploteuthid squids which lack the nidamental glands but have large oviducal glands (Naef, 1923). Ikeda et al. (1993) showed experimentally that the gelatinous substance from the oviducal gland has the role of generating the elevation of the chorion at fertilization, which causes the formation of the perivitelline space in squid such as Todarodes pacificus; the perivitelline space became larger during embryonic development in the presence of the oviducal gland jelly. Since T. pacificus lacks accessory nidamental glands (Sasaki, 1921), we address the question as to whether the gelatinous substances of nidamental gland origin also induce the formation of perivitelline space, as does the oviducal gland jelly in T. pacificus, based on the observations of artificial insemination.

Knowledge of the population dynamics and productivity of exploited species is essential to achieve the sustainable development of fisheries, and to ensure sustainable, long-term use of these resources. The venerid clam Anomalocardia brasiliana is harvested as a fishery resource from the French West Indies to Brazil. Yet, the exploitation of this species is not backed by management or regulations based on scientific knowledge. This can result in reduced (or even depleted) A. brasiliana density and biomass. Here, we examined the population dynamics of A. brasiliana over the course of 1 year at Cidade Beach, a sheltered sandy beach located in south-eastern Brazil. Sampling was done monthly from March 2007 to February 2008. The sampled population was predominantly juvenile. Growth and recruitment were continuous, indicating no major fluctuation in limiting factors, such as temperature, salinity and food. Nevertheless, the abundance and the turnover rate (P/B ratio) of A. brasiliana at Cidade were much smaller than the values observed in other areas of occurrence. The mortality was more intense in young individuals, and the peak of individual production occurred in individuals with a 25 mm shell length, suggesting that individuals smaller than this size should not be exploited.

The gills of Patella consist of a row of triangular shaped leaflets suspended from the roof of the pallial groove. The surface of each gill is thrown into a series of transverse furrows. Tufts of cilia are irregularly distributed over the surface and generate a current of water which flows in the opposite direction to the flow of blood within. The central part of the gill comprises a large haemocoelic space traversed by trabeculae which contain muscle fibres and suggesting that the flow of blood through the gill may be under nervous control. A blood channel runs around the periphery of the gill.

The epithelial layer bounding the blood space comprises a single layer of columnar epithelial cells. The outer surface is protected by a structured mucopolysaccharide glycocalyx held in place by a dense mat of microvilli. The cells contain clearly defined mitochondria, Golgi complex, lysosomes, rough and smooth endoplasmic reticulum. In addition, the non-ciliated cells are characterized by a layer of membrane-bound granules, of unknown function, in the apical cytoplasm.

Phagocytes are frequently found associated with the basement membrane. They contain large membrane-bound granules and appear to move outwards between the epithelial cells to expel the granules at the outer surface of the gill. It is possible that the gill has an excretory as well as respiratory role in the physiology of the animal.

This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60–800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts.

Large-scale green tides of Ulva prolifera occur repeatedly in the Yellow Sea, and the microscopic propagules of U. prolifera play a critical role during the development of green tides. Ulva prolifera propagules and microalgae are both present in seawater and share similar niches, but their potential interactions are poorly understood. Nine species of microalgae were selected to study their interactions with the propagules of U. prolifera (gametes) in laboratory. The results showed that settlement of gametes could be inhibited by some microalgae, such as Alexandrium tamarense, Prorocentrum lima and Karenia mikimotoi, at the cell density of blooming (102–103 cells ml–1). Inversely, the germlings germinated from U. prolifera gametes had negative effects on the microalgae, the inhibition rate ranged from 28 to 66%. Our results demonstrated the complex interactions between microalgae and propagules of green algae, which may influence the formation of green tides and their ecological consequences in the Yellow Sea.

The Black Sea subspecies of the bottlenose dolphin (Tursiops truncatus ponticus) is threatened and has a small range. Its population structure is little known: it possibly includes a few local coastal populations. We assessed connectivity between coastal groupings in six localities along 800 km of the coastline based on records of photo-identified animals between 2004 and 2014. Abundance of these groupings, as estimated, ranged between 76 and 174 individually distinctive dolphins. In total, there were 350 identified individuals, of which 91 (26%) were resighted within the same areas. However, only three cases of individual movements between local coastal populations were recorded at the distances between 135 and 325 km. Therefore, despite the absence of physical barriers, the coastal Black Sea population is fragmented into numerous resident or locally migrating groupings with site fidelity. These local populations are loosely connected to each other with rare movements between them. This fragmentation can be a factor contributing to short-term fluctuations in abundance of Black Sea bottlenose dolphins and their decline in some localities, despite the potentially high population growth rate.

Early life growth of the short-finned squid, Illex illecebrosus (Mollusca: Cephalopoda), was reconstructed from periodic increments deposited on the gladius structure of squid collected in the Gulf Stream/Slope Water front and the Scotian Shelf. The general effects of environmental changes and lifestyle transitions in the variation of size-specific gladius growth was investigated. The offshore growth was exponential and at least six size-specific growth phases were distinguished. Paralarval growth ended at approximately 10 mm gladius length (GL). An important change in growth at 30–40 mm GL was associated with the shift from the macroplanktonic to micronektonic habitats and the transition from the Gulf Stream to Slope Water. The approximation to the Scotian Shelf/Slope Water Front was suggested as related to a growth transition at 68 mm GL. A change to linear growth occurred after the nektonic lifestyle was attained on shelf waters (90 mm GL).

The rising impact of invasive species and climate change on Mediterranean fish biodiversity highlight the urgency to evaluate the current status of natural assemblages. Here we investigated the rocky-reef fish of Malta and Lampedusa (Strait of Sicily, Mediterranean Sea), two islands of high biogeographical importance subjected to a different level of protection and anthropic pressure. By using underwater visual census, a total of 192 counts were performed in May–June and September–October 2007 using a hierarchical spatial design and four depth layers. Overall, 23 families and 61 different taxa were recorded. Out of them, two highly invasive species were censused (i.e. Siganus luridus and Fistularia commersonii) with relatively low abundances. Native Labridae and Sparidae shape the assemblage structure of both islands, and thermophilic species such as Sparisoma cretense and Thalassoma pavo occur with high densities. The fish assemblages of Malta and Lampedusa were relatively similar in species composition, richness and total abundance. Nevertheless, multivariate analysis depicted significant differences between these two islands, mainly attributable to the unevenness of Labridae. Significant differences in the size distribution of the most abundant species were detected between islands, with parallel variation across time. The pattern of spatio-temporal variability of the whole assemblage structure strongly resembled that of nekto-benthic fish, hence pointing out the relevance of this guild as an indicator species group in future monitoring activity. This study will serve as a current baseline against which future changes in the central Mediterranean fish assemblages can be assessed.

Larval development of Capitulum mitella (Cirripedia: Pedunculata) comprises six nauplius stages and a cyprid. Unilobed labrum, a larval trait of pedunculate and chthamalid barnacles, bears two groups of slender hairs and two pairs of strong teeth on the distal labral margin, and a pair of teeth on the lateral labral margin. Frontolateral horns extended under the anterior cephalic shield margin are diagnostic features through all nauplius stages. The posterior border of the cephalic shield bears a pair of distal cephalic shield spines in nauplius stages II and III, and a pair of long posterior shield spines in nauplius stages IV, V and VI. A hispid seta is consistently found at the fourth group of the antennal endopodite through stages II–VI. The dorsal thoracic spine, abdominal process and the paired posterior shield spines have numerous small spines. Morphological features such as the cephalic shield, labrum, abdominal process, antennules, antennae and mandibles in all nauplius and cyprid stages are illustrated and described. In this species, the numerical setations of the antennule are found to be beneficial for intra-specific identification of barnacle nauplius stages without the need for dissection.

Meio- and macrofauna density and biomass were estimated at the OMEX-transect across the continental slope of the Goban Spur at water depths ranging from 208 to 4460 m in the north-east Atlantic. A linear increase in the ratio between meio- and macrofauna densities with increasing water depth was found. At the continental shelf meiofauna densities were ∼50 times higher than macrofauna densities, whereas in the abyss meiofauna densities were more than 1000 times higher. This change in ratio was due to a significant decrease in macrofauna densities with increasing water depth, whereas the meiofauna densities stayed more or less at the same level. The ratio in biomass between meio- and macrofauna showed a dip at ∼1000 m. At this depth macrofauna biomass was ∼55 times higher than meiofauna biomass, whereas at ∼4500 m macrofauna biomass was only about three times higher. Macrofauna biomass was high at ∼1000 m, due to the high mean individual weight of the macrofauna, whereas meiofauna biomass and mean individual weight were low at this depth.

Meiofauna consisted of ∼90% nematodes. Within the macrofaunal fraction (>0.5 mm) a linear increase in the ratio between nematodes and macrofauna sensu stricto with depth was found. At the deepest station ∼20% of the macrofaunal fraction were nematodes, at the shallowest station only ∼2%. Thus, large nematodes became relatively more important with increasing water depth. Within the macrofauna a decrease in the abundance of filter- and surface deposit-feeders relative to the subsurface deposit-feeders with increasing water depth was observed, which may be related to a change in food input. As no decrease in mean individual weight with increasing water depth within either group could be observed, the change in meio:macrofauna ratios along the OMEX-transect merely reflects a change in taxonomic (functional) composition, rather than a change in size.

Dinoflagellate blooms occurred repeatedly along the coasts of France in 1978, and the question was raised, both in newspapers and in the report of the Inquiry Committee of the French Senate on the ‘Amoco-Cadiz’ disaster, of a possible relationship between these occurrences and the oil spilled from the tanker. This hypothesis does not, however, appear to be supported by the data regarding bloom occurrences. These are listed in Table 2, compiled from various sources. Those which concern Brittany and nearby areas, as well as the extent of coast fouled by the ‘Amoco-Cadiz’ oil, are shown in Fig. 2. It is clear from this map that some of the ‘red tide’ occurrences were quite remote from the site of the wreck at Portsall; those outside the area shown in Fig. 2 (e.g. Seine Estuary) were, of course, even more so.

During a survey of teleost skeletal muscle (Greer Walker & Pull, 1975) it was found that the morphology of the red or slow muscle fibres of the anchovy (Engraulis encrasicolus L.) was markedly different from that of other species. In transverse section the fibres appear flattened as lamellae and are considerably larger in area than those of comparable species. This paper describes some aspects of their morphology, function and growth in comparison with other species.