Rotifers are microscopic aquatic animals that comprise more than 1800 species. Most rotifer species live in freshwater and limno-terrestrial habitats, while thalassic environments (brackish+seawater) are thought to host few species. No recent review of saline rotifers is available. Here we report the results of a review of the literature concerning rotifers from saline environments, distinguished into three categories: stenohaline, euryhaline, and haloxenous, and found both in truly marine habitats and/or in inland saline waters. A total of about 200 studies, mentioning fully identified rotifers from saline waters, allowed us to list as many as 443 rotifer taxa at either specific, subspecific and infrasubspecific rank, corresponding to 391 nominal species. Truly thalassic taxa, not found in inland saline waters only, accounted for 289, including the ‘stenohaline’ (143) and the euryhaline (146) ones. As for freshwaters, the majority of the thalassic rotifers inhabit the psammon, or display a benthic–periphytic way of life, while the plankton likewise is less species rich and less abundant. The geographical distribution of the brackish and marine rotifers largely reflects the distribution of rotifer investigators, therefore, no biogeographical analysis can be performed yet. In conclusion, the analysis of literature citing rotifers in salt waters, uncovers an unexpected rotifer fauna: the apparent richness of the group in thalassic environments is worthy of being addressed by further investigations, as many species have been reported only by their description, suggesting either considerable endemism or taxonomic errors.

Two new species of rotifer belonging to the Dicranophoridae, and provisionally placed in the genus Encentrum, are described from littoral psammon from the Ussuriyskiy Bay, Peter the Great Bay, Sea of Japan, Russia. Encentrumkutikovae sp. nov. is characterized by a long foot consisting of three pseudosegments, cylindrical toes, a hexagonal rami outline, and the right ramus showing an accessory chamber with alula. Encentrum ussuriensis sp. nov. is characterized by unusual stout toes with claw, an oblong-ovate and latero-caudal weakly angular rami outline, the right ramus bearing an alula, and the left one showing an accessory chamber.

‘Reefs’ are listed under Annex I of the Habitats Directive as a marine habitat to be protected by the designation of Special Areas of Conservation. Crucially for the implementation of the Directive, the distinction between what is considered as ‘reef’ and what is not is imprecise, particularly in relation to colonies of the tube-building polychaete Sabellaria spinulosa. Guidelines are proposed for the implementation of the Habitats Directive definition to provide a robust and transparent approach for the benefit of both regulators and offshore industry. Specifically, it is suggested that the conservation priority of a S. spinulosa aggregation could be determined using a scoring system based on a series of physical, biological and temporal characteristic reef features, weighted according to the perceived importance of each feature and augmented with a further score indicating the confidence in the feature score. Suggestions are given as to how these characteristics might be measured and scored, along with an example to illustrate the application of the approach.

We report the occurrence of a high diversity of minute (∼1 μm diameter) organic and siliceous protistan scales in small samples (total volume ∼35 μl) of superficial sediment from the Porcupine Abyssal Plain (PAP), north-east Atlantic (4850 m water depth). Many exhibit characters by which they can be identified to species. The organic scales belong to the haptophyte genera Chrysochromulina (8–9 species), Chrysocampanula and Dolichomastix (1 species each). The siliceous scales belong to the chrysophytes Paraphysomonas vestita and Meringosphaera sp. and to the heterotrophic flagellate genus Thaumatomastix (T. dybsoeana, T. formosa, Thaumatomastix sp.). As far as we are aware, this is the first time that non-calcareous protistan scales have been observed in deep-sea sediments (although siliceous skeletal plates and cysts are reported). All scales probably originated from the upper water column and were delivered to the deep-sea floor on rapidly sinking detrital aggregates. However, naked heterotrophic flagellates are known to thrive in abyssal sediment habitats and so the possibility that some scale-bearing protists also live in benthic deep-sea environments cannot be eliminated. Many species identified at the PAP site are common in coastal marine waters around Europe; some occur as far afield as Tasmania and New Zealand. Five Chrysochromulina species are known from central oceanic areas, including parts of the North Atlantic, while another species, C. pringsheimii, is reported from a British freshwater lake. We retrieved ∼15% of the 55 named Chrysochromulina species (∼8% of the estimated total number of species in this diverse group) in the ∼35 μl of abyssal sediment. Because the scales can persist and be identified after cell death, they may provide useful time- and space-averaged information about the distribution of protist species in marine habitats. The long-term fate of the scales on the sea-floor is unknown. It is possible that at least some of the organic scales are preserved as microfossils in deep-sea sediments.

The impact of date-mussel fishery on substratum rugosity was evaluated at Capo Noli and Isola di Bergeggi (Savona, north-western Italian coast) in the summer of 2004. A new measure of substratum rugosity was used as a surface-dependent index of complexity. The results were compared between impact and control sites using two-way analysis of variance and suggested that the mussel fishery reduces substratum complexity.

A first record of the genus Aciculites in the Mediterranean Sea and the description of Aciculites mediterranea sp. nov. are here presented from a faunistic survey in a dark shallow marine cave of the north-western Sardinian karstic area. The new species is characterized by a massive cerebellum-like growth form, and a peculiar distribution of inhalant and exhalant areas, respectively, in depressed and elevated portions of the sponge surface. Oscules show a long narrow atrial cavity. Ectosomal skeleton is made of tangential anisostrongyles on elevated areas, and more or less vertical tufts of anisostrongyles in depressed inhalant areas. Anisostrongyles are smooth or with tips ornated by irregular tubercles. Sigmaspire microscleres are lacking. Choanosomal skeleton with tubercled irregular rizhoclone desmas and few scattered and variably oriented anisostrongyles. A comparative analysis of Aciculites mediterranea sp. nov. versus morphological diagnostic traits, geographical range and habitat of the species hitherto ascribed to Aciculites confirms that the peculiar distribution of the genus supports its relic condition of an ancient Tethyan fauna in the Mediterranean Sea.

Eleutheria dichotoma, a hydrozoan not previously recorded from the southern hemisphere, was found at high densities at several locations along the coast of New South Wales (NSW), Australia, between August and November 2005. The identity of the species was confirmed by morphological and molecular (16S rDNA) comparisons with European specimens. Local densities, distribution and habitat (algal substrate) were examined. The medusae were found along a 400 km stretch of coastline between Bateau Bay (33°23′S 151°29′E) and Pebbly Beach (35°35′S 150°43′E), primarily on the green alga Ulva, at mean densities of more than 50 individuals per 10 cm2 plot. The species is probably a recent introduction to Australia.

Kinds and distribution of nematocysts of the cubomedusa Carybdea marsupialis were described by light and scanning electron microscopy. Three kinds of nematocysts were found in tentacles: heterotrichous microbasic euryteles, flattened holotrichous isorhizas and subspherical holotrichous isorhizas. The microbasic euryteles of the tentacles show a characteristic detachable multilayered lancet, already described in the euryteles of Carybdea alata. A possible explanation of the function of the lancet is proposed. The pedalia and the umbrella are armoured by holotrichous isorhizas together with an unidentified kind of small, drop-shaped nematocysts. Gastric cirri, characterized by a rough and ciliated surface, contain heterotrichous microbasic euryteles.

During the expedition EASIZ II with RV ‘POLARSTERN’ in 1998 a multibox corer yielded 151 quantitative samples from 26 stations between 120 and 2415 m water depth for benthic community analysis. From this material a total of 235 polychaete species out of 37 families was determined. Forty-seven species are new to science. The polychaete fraction contributed 41.9% to total benthic abundance and 6.5% to total benthic biomass at these stations. Overall mean polychaete abundance (ind m−2) and biomass (g wet weight m−2) at the stations were 1617 and 49, respectively.

Multidimensional scaling procedure clearly grouped the stations into south-eastern Weddell Sea shelf stations, deep-water stations, and stations mostly around the Antarctic Peninsula. Differences between these groups existed in terms of polychaete abundance and biomass as well as species composition, diversity, and evenness.

A SCUBA-based fast repetition rate fluorometer (FRRF) was used to study differences in the functional absorption cross-section of Photosystem II (σPSII) between areas of a coral colony of Astreoporamyriophthalma that were infested with spionid polychaetes vs areas lacking worms. The mean value of σPSII in infested areas (mean±SD=347.62±30.67 Å2) was significantly higher than in the areas that were not infested (316.32±17.49 Å2; P<0.0001). Several physiological mechanisms are discussed that may contribute to the observed differences.

A new species of the corophiidean amphipod genus Corophium (sensu stricto) from the estuary of the Oka River (Basque Country, northern Iberian Peninsula) is presented. Data on the ecology and distribution of the species are included, which is comparable to other species of the genus, but has several differences. Two amendments to the diagnosis of the genus are proposed. A key of the European species of the genus is also included.

This study aimed to assess the population biology and reproduction of the fiddler crab Uca chlorophthalmus at its limit of geographical distribution, Saco da Inhaca mangrove, southern Mozambique. Monthly samples were conducted at low tide periods between January and December 2003. The size distributions showed uni- and bimodal patterns, with males reaching larger sizes than ovigerous and non-ovigerous females. Females were slightly more abundant than males, but the overall sex ratio (1:1.01) did not differ significantly from 1:1. Uca chlorophthalmus displays continuous reproductive patterns with peaks of breeding in March and December. Moreover, linear correlations revealed that breeding in this crab is controlled by both temperature and rainfall. Similarly, juvenile recruitment was constant, but was more intense in winter (May–July). Brood size was positively associated with female size. Timing of the observed breeding pattern in the study area may enhance reproductive output and recruitment of the species.

Fecundity, hatching rhythm, and the planktotrophic larval development of the hermit crab Pagurus comptus from sub-Antarctic waters of the Beagle Channel (Tierra del Fuego) were studied under controlled laboratory conditions of temperature, light cycle, food supply, and salinity. Fecundity was low, ranging from 134 to 848 eggs per female (cephalotoraxic shield length, SL, 2.3–5.0 mm). Hatching observed in the laboratory ranged from 6 to 30 d. The larval development was studied in laboratory cultures fed with Artemia sp. nauplii and kept at constant 7.0±0.5°C. Larvae invariably passed through four zoeal instars and one megalopa stage. Mean durations of the zoeal stages I to IV were 14.3±1.8, 16.7±4.6, 23.2±6.5, 33.4±9.2 d, respectively. Combined with the 43.8±5.6 d recorded for the survived megalopae, we suggest that the complete larval development lasts about four months. Starved larvae, on average, survived for 22±8.1 d (maximum 38 d) by far exceeding the zoea I duration in fed larvae, but did not reach the moult to the zoea II stage. Unlike other sub-Antarctic decapods, which show a tendency towards abbreviated or endotrophic larval developments at high latitudes, hermit crabs, at their southernmost distributional limit on Earth, show an extended and fully planktotrophic larval development and thus need to synchronize larval release with short periods of high primary production.

The occurrence of imposex in Adelomelon brasiliana during two consecutive years near to Mar del Plata (the principal fishery port of Argentina) and its relation to tributyltin (TBT) and dibutyltin (DBT) content in muscle tissue and digestive gland was investigated using gas chromatography. Percentage of imposex affected females increased to over 80% in spring and summer of both years. However, its intensity, given by the relative penis size index (RPSI), fluctuated around low values. Adelomelon brasiliana digestive gland samples showed a very low concentration of TBT (36–46 ng/g dry weight). Egg capsules presented normal viable embryos, which had TBT concentrations similar to the capsule wall (15 ng/g) while the intracapsular liquid was only 2 ng/g, similar to the sediment concentration. The proportion and distribution of butyltin compounds (BTs) in sediments indicate a major contamination event.

Kingiella chilenica, a brooder mollusc, inhabiting soft bottoms of estuarine tidal flats of southern Chile, is well suited to study larval recruitment. It is a tiny semelparous clam with an annual cycle, and whose recruits must survive an inhospitable winter season prior to growing and reaching reproductive maturity in the following summer season. The population dynamics of this clam was studied through periodic sampling over two successive years to follow fluctuations in its' abundance. Obtained data on embryo production and recruit survival over both periods shows that population abundance varied widely between the two years of study. A high level on recruit survival through the winter of the first year resulted in high numbers of adults in the corresponding summer reproductive season. An inverse situation occurred in the second year, with lower recuit survival and, consequently, fewer reproducing adults. However, the lower abundance of adults in the second year was compensated by their having a higher survival rate over the reproductive season as compared with adults of the previous year. Independently of the abundance of the adults, the number of embryos incubated per female was very similar between both periods. Consequently, we suggest that the net contribution of juveniles produced by females per unit substrate was similar between the annual cycles studied. As predicted for a semelparous species (high reproductive effort), the maximization of the reproductive contribution was clearly reflected by a drop in adult somatic weight, particularly in incubating females. Previous data on abundance for this population suggested inter-annual differences of a high magnitude, with periods (e.g. 1986–1988) with abundances reaching 2–6× that presently reported. Probably, stable environmental conditions (e.g. 1986–1988) promote high abundance and survival of reproducers allowing a large contribution of recruits, which in turn show high degrees of survival through the adult phase. The years reported here (2003–2005), however, represent a period of population decline to lower, perhaps minimum, levels.

The statoliths of 14 species (193 right statoliths from subadult to adult individuals), belonging to five Cephalopoda families (Sepiidae, Loliginidae, Enoploteuthidae, Ommastrephidae and Octopodidae) were analysed using morphometric methods based on landmarks (geometric morphometry). The aim of the current study is to determine the discriminating power of statolith shape analysis in species identification of Mediterranean cephalopods. Discriminant analyses of the partial warps were able to fully identify (100% discrimination) the species of all families, except Octopodidae which showed some misclassification (correctly classified about 68–90%). These results were also shown by relative warp analysis. Octopodidae statoliths were studied for the first time using geometric landmark-based methods. Greatest differences in statolith shape between Octopodidae species, were in the area that unites the statolith dome with the flat wing. Landmark analysis applied to statoliths can be a useful taxonomic tool in the identification of closely related species.

The influence of size and density of the blue mussel, Mytilus edulis and the common barnacle, Semibalanus balanoides on the foraging behaviour of the sea urchin Psammechinus miliaris was examined in laboratory studies. Urchins of two size-classes offered six size-categories of barnacles exhibited a constant preference for the smallest category ([les ]7.5 mm plate length). Ingestion rates were independent of the size–frequency distribution of mussels presented to large urchins of 38–46 mm test diameter, which showed a preference for small–medium sizes (>13.4–17.8 mm shell length). Large urchins ingested a maximum of six mussels a day and increased their consumption in a density dependent manner until reaching a plateau once more than ten mussels were offered. In most cases, the rate of successful attacks decreased with mussel size.

Pairwise comparison experiments to determine the ingestion rate of fronds of the algae Laminaria saccharina showed that P. miliaris had no preference for old fronds with or without epifauna, but young fronds of the algae were frequently rejected. These results highlight the omnivorous nature and semi-selective behaviour of this urchin and demonstrate the potential for it to have an important role in structuring algal and epifaunal communities.

Arbacia punctulata and Lytechinus variegatus are widely distributed echinoid species in shallow water in the western Atlantic Ocean, Caribbean Sea and Gulf of Mexico that seem to have different life history strategies. We evaluated the effect of two types of stress (high temperature and starvation) on gonad production and scope for growth. We hypothesized that A. punctulata has a stress tolerant life strategy and would be more tolerant to stress and L. variegatus has a competitive–ruderal strategy and would be less tolerant to stress. Gonad production by A. punctulata was not as greatly affected by temperature as L. variegatus, suggesting the hypothesis was correct. Arbacia punctulata had a significantly higher excretion rate indicating greater energy allocation to maintenance than production. Lytechinus variegatus had a significantly greater consumption rate but did not absorb significantly more energy. Arbacia punctulata compensated for its lower food consumption by a higher absorption efficiency. Measured energy expenditure and calculated scope for growth did not differ. However, the percentage change in energy absorbed and energy expenditure was greater for L. variegatus than for A. punctulata with a change in temperature. Feeding had a greater effect on production than temperature suggesting that the biotic stress of low food availability is more important than an abiotic stress such as temperature on energy budgets.

Spatio-temporal variability in the population structure of long-spined black sea urchin, Diadema antillarum, was investigated at two islands (Gran Canaria and Tenerife) in the Canarian Archipelago over a year. The mean abundance of D. antillarum across all counts was 2.70±0.07 ind m−2 (mean±SE, N=1440), while the mean biomass was 105.76±3.75 g m−2 (mean±SE, N=1440). Abundances and biomasses of D. antillarum differed consistently between vegetated and unvegetated bottoms; however, locations within each habitat at each island fluctuated following different trends. For the overall study, mean densities and biomasses in the barren locations varied between 3.36–6.97 ind m−2 and 93.76–405.13 g m−2, respectively; while mean densities and biomasses in the algal stand locations varied between 0–0.33 ind m−2 and 0 – 7.34 g m−2, respectively. Striking differences existed in the size-structure among locations; however, larger size-classes (test diameter >3.5 cm) were present at all locations, and usually dominated in terms of abundance. The majority of individuals in the algal stands were large-sized, probably as a result of the high abundance of the most palatable food. In contrast, small-sized individuals (test diameter <1.5 cm) only occurred in the barren habitat, suggesting that recruitment of D. antillarum could be favoured by the presence of high densities of congeners, as a way to decrease the risk of predation.

To clarify the morphological variety of larval skeletons, a detailed morphological comparison among the species of the family Echinometridae was performed. Through conspecific comparison of larval skeletons among different ages, we found five skeletal characters of the body skeleton that are stable in the four-armed pluteus and thus useful in homologous comparison among the species. The morphological variation was summarized as the difference in the number of spines and posteroventral transverse rods, and differences in the shape of the body skeleton. Significant correlations were found between some skeletal characters, such as between upper body length and bottom width of body skeleton and between lower body length and the number of spines. We found that the larval skeletons of tropical species tend to have fewer spines and rods than those of temperate species, which is consistent with the hypothesis that a reduction in skeletal elements decreases the specific gravity of larvae as an adaptation to tropical waters.