The detail of the characteristic double whorled branchial crown of the tubiculous polychaete Bispira volutacornis, with its internal skeleton of large vacuolated cells and ciliated radioles, is consistent with the feeding apparatus of sabellids at large. Studies show that ingested particulate matter has at least one dimension less than 15 μm. Feeding seems to be most readily accommodated at current speeds from 1 cm s−1 to 3 cm s−1 with the crown apex angled downstream. Particulate matter passes through the alimentary canal in 7·7 h at 14°C, for an average sized specimen of 97 segments. Whilst the tube provides protection against predatory fish and crustaceans (with ample evidence of sub-lethal cropping of the branchial crown), it also has a role in irrigation and respiration. The worm will retreat within the tube when current flow exceeds 8·7 cm s−1.

Variability in recovery of the introduced green alga Caulerpa racemosa has been investigated on a subtidal rocky shore in the north-western Mediterranean Sea. Two removal experiments were performed. The first was designed to test the effects of season on the early patterns of recovery of C. racemosa on a rocky bottom and on algal turf. In the second experiment recovery of C. racemosa on the rocky bottom and on algal turf was estimated from July–October 2000, the end of the vegetative period of the alga. Recovery of experimental plots occurred from adjacent populations of C. racemosa by stolon growth. In the first experiment, recovery occurred from August to November in all the experimental units, while no growth was observed during winter and spring. Recovery was significantly higher on algal turf than on rock during all vegetative periods. In both the habitats, recovery was quicker in summer than in autumn, even if differences between dates within each season were also significant. In the second experiment, three months after removal, the mean per cent cover of C. racemosa in algal turf was twice that on rock.

This review discusses the structure and operation of the fine mesh ‘mucous’ feeding filters of tunicates. The function of the endostyle in producing the feeding filter and the different ways in which the filter is deployed are also described.

The fine structure of the filter includes new data, and the ultrastructural dimensions of the filter mesh and filament thickness are tabulated for the different tunicate groups. Histochemical data suggest that a peptide core is surrounded by a mucopolysaccharide sheath, and endostyle gland cell histochemistry and ultrastructure indicates protein synthesis. The construction of the filter by the endostyle was first considered in ascidians, and has been updated by observations on the simpler endostyle in salps, where there is evidence that secretions of gland cells pass to the bases of a fence of cilia, there to fuse and pass off the ciliary tips as fine filaments composing the filter net. Although all filters that have been examined when deployed have a rectangular mesh, reasons are given for supposing that when formed in the endostyle they have a square mesh in which both longitudinal and transverse filaments are of similar thickness and that the transverse filaments are stretched as the filter is deployed, so becoming thinner.

Finally, some ecological consequences of the filter parameters in the different tunicate groups are considered.

To investigate the palatability of abundant sub-Arctic sessile or sluggish invertebrates and their value as a food source, in situ experiments with natural consumer assemblages were performed in the Kongsfjord (Spitsbergen). These experiments were complemented with quantitative laboratory assays, using a generalist predatory starfish. Feeding preference and avoidance reactions were similar in both assays. Natural assemblages of predators in situ rejected nine out of ten species tested, and 12 out of 16 species were rejected in laboratory assays, indicating a high percentage of unpalatable invertebrates. Results were compared to the biochemical composition of the investigated species to see whether palatability and feeding preferences coincide with nutritional quality of the prey. Although nutritional quality, expressed as protein, lipid, nitrogen, carbon and water content, may account for some of the feeding preferences found, no overall relationship between nutritional value and palatability or feeding preferences was detected.

Changes in the intracellular free amino acid (FAA) concentrations of Tigriopus brevicornis when subjected to hypoosmotic (5 psu), normal seawater (35 psu) and hyperosmotic (70 psu) conditions for a three day acclimation period were investigated. Proline, alanine and lysine were the major contributors to the intracellular FAA pool. Under hypoosmotic conditions, alanine was the dominant osmolyte with proline concentration at its lowest. This trend was reversed under hyperosmotic conditions. However, the total FAA pool was at its highest concentration under normal seawater conditions, with the total FAA concentrations being reduced during hypo- and hyper-osmotic conditions.

Periodic surveys of the subtidal epifaunal community on the gorgonian Melithaea flabellifera were conducted over a five year period at the Izu Peninsula, southern Japan. The occurrence patterns of epifaunal species on M. flabellifera were examined. The epifauna consisted of 16 species representing five phyla. The amphipod Incisocalliope symbioticus dominated (usually >80%) and occurred throughout the study.

A field experiment investigating the effects of algal removal on benthic invertebrates and estuarine birds was carried out during September and October 2001. A randomized block experimental design was employed and three treatments were used: sites with algal cover maintained, when necessary by the addition of algae, sites with algal cover removed and control sites that were not manipulated in any way. Total invertebrate numbers increased during the experiment, but species varied in their response to the different treatments. Although Hydrobia ulvae showed the greatest increase in cleared sites after two months, there was no significant difference between treatments. Corophium volutator showed significant colonization of cleared sites during the experimental period, and numbers of Phyllodocemaculata also increased in the cleared sites. Results showed that while more sedentary benthic infauna are less capable of adjusting to the affects of algal clearance, more mobile epifauna and polychaetes show an ability to disperse to cleared sites in a relatively short period of time. Wading birds, however, did not enter the study site in any abundance during the experiment. Black-headed gulls (Larus ridibundus) were significantly more abundant in cleared sites than in algal cover-maintained or control sites when foraging.

Field studies were carried out along a Mediterranean rocky shore to describe the foraging behaviour of the hermit crab Clibanarius erythropus, a common intertidal Diogenidae. The spatial strategy adopted during foraging activity was investigated through monitoring the movement of ten individuals, each followed for two hours. This revealed that hermit crabs maximized the space explored while in search of food and that shell type was one factor influencing the extent of movement. The evaluation of hermit abundance on different algal substrates provided clues to understanding the pattern of food utilization. This study shows that ‘generalist’ hermit crabs display a certain degree of selectivity, mostly foraging on assemblages of filamentous algae and corticated macrophytes. The conclusion is that C. erythropus selects substrates where good foraging can occur; whether hermit crabs eat within the selected substrates every food item they encounter or select food at the level of individual items is still an unanswered question.

The foraminifera of Gelidium pristoides were examined on exposed and sheltered shores around False Bay, South Africa, during the summer and winter of 1998/1999. Twenty-five species were recognized, seven are potentially new. Multivariate statistics indicated that the assemblages on plants from exposed shores were distinct from those on sheltered shores, and two species of foraminifera were confined to exposed shores. Plant size and the quantity of trapped sediment were positively correlated, and plants on exposed shores were significantly bigger than those on sheltered shores. Plant size and sediment weight were linked to assemblage diversity and abundance; assemblages on exposed shores were generally more diverse and abundant than those of sheltered shores. Different species dominated on the two shore types, and larger foraminifera tended to be more common on exposed shores.

Total arsenic concentrations were determined in three teleost species (herring Clupea harengus; cod Gadus morhua, and flounder Platichthys flesus) taken from four locations in the Baltic and North Sea with salinities ranging from 8 to 32 psu. Individual arsenic concentrations ranged from 0·04 to 10·9 mg/kg wet mass, and there was a positive linear relationship between arsenic concentration and salinity for all three species (r2 0·44 to 0·72, all P<0·001). Although it is well known that marine fish contain much higher concentrations of arsenic than do freshwater fish, the data reported here are the first showing a relationship between the total arsenic concentration in fish and salinity.

The micro-erosion patterns of some sponge species belonging to the boring genera Cliona and Aka have been compared. The scanning electron microscope analysis of the excavations of species of the two genera sharing the same substratum clearly indicates that the scars produced on the walls of the boring chambers are different. The pits of Cliona are regular, almost circular and smooth; those of Aka are more irregular and show a multi-layered concentric pattern. These differences constitute a successful means of distinguishing the bio-erosion agents both in recent and in fossil substrata.

The re-establishment of adult Lanice conchilega washed out from the sediment was studied in the laboratory in calm and wave conditions. Worms left in their tubes on the sand surface buried and built new tubes within 48 hours. In still water the fringe of the new tube was thinner and extended to all directions, while under a wave regime the individual branches were thicker and positioned perpendicularly to the direction of the waves.

In April 2000 a massive recruitment of the barnacle Semibalanus balanoides was observed in the Clyde Sea. At one location 700 cyprids 1−1 of this species were recorded. This is ∼3500 times more abundant than previously recorded, and resulted in metamorphosis of some cyprids whilst still in the plankton, as well as massive settlement, with recruits found on adults and in the splash zone. The maximum density recorded was 109 settlers cm−2. Over the next 60 d mortality averaged 85%, resulting in a mean density of 8.4 recruits cm−2 in June 2000. Recruitment varied spatially at the km and m scale (site, shore height) but there was no evidence that it was affected by the presence of adult conspecifics.

During remotely operated vehicle operations on the UK continental shelf to the west of Shetland (60°6′N 4°4′W) at a depth of 400 m, Munida sarsi, a common benthic crustacean was observed actively preying on the northern krill Meganyctiphanes norvegica. Video footage shows the individual using its chelipeds to catch prey items as they swarm around its burrow. These initial observations indicate that predation forms a new feeding strategy for a species previously believed to be an active scavenger.

The present short note reports the first occurrence of the Caulerpa racemosa ‘invasive variety’ in the Adriatic sea.

The locomotor performance of the Mediterranean sea urchin Paracentrotus lividus was investigated under laboratory conditions. Individuals were placed singly in the centre of a glass surface positioned either horizontally or vertically in tanks with seawater, and their locomotor activity was recorded. For locomotion on a horizontal surface, speed increased with both sea urchin diameter and their straightness of path. Speeds on a vertical surface were size-independent and not related to the straightness of path, although they were affected by vertical path orientation, with the highest speeds occurring for downward movements and the slowest speeds for the upward movements. Taken together, these results suggest that the scaling of sea urchin locomotion may follow similar laws to those of legged animals, for which locomotor performance increases with size on horizontal surface, while their relative cost of locomotion increases with body size on inclined surfaces. It is suggested that differences in horizontal vs vertical locomotion may also be related to differences in the underlying locomotor mechanisms, i.e. using adhesive appendices (tube feet) or levers (spines). In a second experiment, the sea urchin speed obtained during a negative phototactic response to a direct light stimulus was recorded. The results show that speed during light stimulation is higher than that during spontaneous locomotion in sea urchins of intermediate size (2·5–4 cm), suggesting that, in addition to the direction of locomotion as shown by previous studies, light can also have an effect on speed.

Size at sexual maturity was studied in Zidona dufresnei through analysis of gonadal tissue samples and secondary sexual characters. Individuals were sampled during two reproductive seasons (austral spring–summer) in the Mar del Plata area, Argentina. Gonadosomatic index was estimated for males and oocyte size frequency was used to estimate the stage of gonadal development in females. Gonadal maturity occurred prior to the development of secondary sexual characters. Size at first gonadal maturity in females was 12·8 cm shell length and in males 12·0 cm shell length, but size at which 50% of the population was mature was 15·7 cm in females and 15·0 cm in males. The results of this study could help to establish a minimal catching size.

An ecologically unique cirripede, Octolasmis unguisiformis sp. nov. (Cirripedeia: Thoracica: Poecilasmatidae), was found to be ectosymbiotic with an ocypodid crab, Macrophthalmus milloti, on tidal flats of the Amami Islands, the Ryukyu Archipelago, Japan. The cirripedes were attached to the ventral side of the crab carapace, around the bases of the first and second ambulatory legs. The cirripedes resemble the chelipeds of male host crabs. Adult cirripedes were found only on female crabs, whereas juvenile cirripedes were present on crabs of both sexes, suggesting that the survival rate of the cirripedes on female crabs was higher than that of those on male crabs. The cheliped-like appearance and female-biased distribution of the cirripedes are discussed from the standpoint of mutualism between the crab and the epizoic cirripede.

Interannual and seasonal variation in recruitment of serpulid tube worms was monitored at two depths at each of four sites between February 1999 and January 2001 in Bantry Bay, Ireland. In both years, a single peak in recruitment was observed. The timing of the peak was similar in both years, but the magnitude of the peak differed significantly. More individuals recruited onto the underside than on the upperside of the horizontally orientated panels. A higher density of recruits was observed at a depth of 7 m than at 4 m during recruitment maxima. There was little variability in recruitment rates either within or between sites. The proportions of Pomatoceros triqueter and P. lamarckii recruiting per deployment were examined. Juvenile mortality was high. Based on ongrowing laboratory experiments, the dominant species was P. lamarckii. Serpula vermicularis was also present in low abundance. Examination of the spatial patterns of distribution of the serpulids indicated that the recruits were aggregated within panels. The degree of aggregation was correlated with the overall density of recruitment per panel.

The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing SCUBA diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuroids reached densities eight times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately after escaping from the dredge.