The diet and predatory behaviour of the nudibranch Roboastra europaea (Mollusca) is described and compared with other nudibranch-hunting opisthobranchs. The natural diet in the Strait of Gibraltar was studied by the analysis of gut contents. Roboastra europaea is a specialist predator of nudibranchs, and the diet is comprised essentially of the polycerids Polycera sp., Polycerella emertoni, Limacia clavigera and conspecific R. europaea. One or several Polycera species appeared as the most dominant prey.  The complete assemblage of potential prey of this predator—the fundamental diet—was assessed in laboratory trials that included all likely prey groups. This predator consistently rejected both non-nudibranch species and non-polycerid nudibranchs. Roboastra europaea is exclusively a predator of polycerids and previously unencountered polycerids are also potential prey items.  As most of the hunter opisthobranchs, R. europaea exhibited cannibalistic behaviour, to the extent that aggressiveness prevailed over mating in intraspecific encounters. Roboastra europaea as prey showed a complex result in laboratory trials: (a) if one individual was small enough complete ingestion proceeded; (b) if there was not enough difference in size, a cannibal attack proceeded, but if ingestion was not possible, it could result in mating behaviour.

Caprellid amphipods, Caprella danilevskii were exposed to tributyltin (TBT) (100 ng 1−1) for ten periods after eggs were deposited in the brood pouch. Brood loss during incubation was found in six exposure periods between 12 and 72 h after spawning, although no brood loss was observed in the control. It was suggested that exposure to TBT half a day after spawning might be sufficient to damage reproduction during the caprellid's embryonic life. The female percentage was 38.7% in the control, whereas it was gradually increased to 60.0–71.4% in the four exposure periods between 12 and 48 h after spawning.

Although decorating behaviour is widely reported as a predator avoidance strategy among marine crabs, few studies have provided experimental evidence for this. Significance of decorating behaviour of the majid crab Tiarinia cornigera as antipredator response was examined by the field tethering and laboratory experiments. Survival of decorated crabs was significantly higher than that of non-decorated crabs after two days in an intertidal rock pool. In a laboratory experiment, crabs used more algae for decoration in the presence of predators (puffer fish) than when predators were absent. These data demonstrate that T. cornigera decorates with algae in response to predators to reduce predation pressure.

The holotype of the Antarctic octopodid Graneledone setebos was re-examined and found to lack the epidermal warts characteristic of the genus Graneledone. It is similar in its large size to another Southern Ocean species, Megaleledonesenoi. A comparative study of G. setebos and specimens attributed to M. senoi led us to conclude that M. senoi is a junior synonym of G. setebos. Although M. senoi is not valid, the genus Megaleledone can be separated from other genera by the structure of the radula (which lacks marginal plates) and we therefore consider the genus to be valid. We propose the new combination of Megaleledone setebos and have refigured the beaks and radula of the holotype herein and expanded the description. A search of museum specimens and the literature shows that Megaleledone setebos is more common in Antarctic waters than previously supposed.

The distribution of the warm-water barnacle, Balanus perforatus, was surveyed along the south coast of England and the north-east coast of France between 1993 and 2001, repeating work carried out between the 1940s and 1960s. The species has recovered from catastrophic mortality during the severe winter of 1962–1963 and was found over 120 km (UK) and 190 km (France) east of previous records on both sides of the Channel. The presence of the species in the eastern Channel refutes suggestions in the 1950s that larvae, and hence adults, would not be found east of the Isle of Wight because of reproductive sterility close to the limits of distribution. Brooding of specimens translocated to Bembridge, Isle of Wight, commenced in May, earlier than previously observed in British waters, and continued until September. The stage of embryo development at Bembridge in mid-August was comparable to that of the large population at Lyme Regis, Dorset 100 km further west. However the size of brood per standard body weight was greater at Lyme Regis. Factors influencing the rate of colonization and further geographic range extension of the species as a possible result of climate change, are discussed.

Ecological features of Syllidae inhabiting shallow-water benthic habitats of the Aegean Sea were analysed by utilizing some univariate and multivariate statistical methods. A total of 121 benthic materials collected in a variety of substrata and depths (0–76 m) contained 90 syllid species belonging to the four subfamilies Autolytinae, Exogoninae, Eusyllinae and Syllinae. Among the subfamilies, Syllinae were characterized by a high number of species and Exogoninae by a high number of individuals. Although dominant species varied according to substrata, the two species, Grubeosyllis clavata and Syllis prolifera, accounted for up to 51% of the total syllid populations in the area. Among the biotopes sampled, Posidonia oceanica seems to be particularly suitable for the settlement of syllid species, whereas bare sand and mud harbour only a few species, mainly Exogoninae. The cluster- and ordination analyses detected species associations on soft and hard substrata, and suggested that syllid assemblages are strongly affected by the habitat structure. Species compositions associated with algae appear to be related to complexity of the algae, so that the ones with relatively small thalli, such as Padina pavonica and Halopteris spp., constituted a group with a high similarity-index value. Samples of Posidonia oceanica collected at different stations showed a high consistency in terms of syllid assemblages.

The nauplii of Balanus amphitrite (Cirripedia: Thoracica) were cultured on a daily diet of Chaetoceros gracilis at different concentrations. Both young (zero-day old) and aged (six-day old) cyprids were subject to attachment assays, followed by studies of juvenile growth and survival for two weeks under laboratory conditions. The TAG/DNA ratio of cyprid increased in the following order of food concentrations: 106>105>104 cells ml−1. More than 70% of cyprids metamorphosed in the presence of conspecific settlement factor, irrespective of their TAG/DNA ratio. The juvenile growth and survival in young cyprids surpassed that of the aged cyprids. The TAG/DNA ratio had no significant effect on juvenile growth and survival in both young and aged cyprids. The negative effect of delayed metamorphosis on juvenile growth and survival appeared to be independent of the TAG/DNA ratio.

The common phenomenon of sublethal predation in soft-bottom bivalves usually involves nipping of siphons. Here we show that foot cropping, hitherto documented only in Donax spp., is widespread in the New Zealand cockle Austrovenus stutchburyi (Veneridae). Depending on the locality, cropping frequency ranged between 14 and 34% of cockles, and the average proportion of the foot area cropped ranged between nine and 21%. Estimates of biomass lost to croppers at the time of sampling varied between 235 and 2040 mg ww m−2. It is emphasized that foot cropping in Austrovenus is likely to affect the population dynamics of the cockles.

The subunit composition of haemocyanin (Hc) from the semiterrestrial beachflea Orchestia gammarellus exhibited less heterogeneity and less (qualitative) between-individual variation than most decapod Hcs. While between-population variation was detected, no clear trends in Hc subunit composition from four populations along a salinity gradient were observed. Salinity had no detectable effect on Hc subunit composition or HcO2 binding in the laboratory. The degree of phenotypic variation in laboratory-held beachfleas was less than that displayed by any of the natural populations examined. Furthermore, examination of the O2 binding characteristics of five of the most common Hc phenotypes showed that each phenotype had the same O2 binding properties. Differences in Hc subunit composition between individuals and between populations may exist, but it should not be automatically assumed that such variation will have consequences for intrinsic Hc O2 binding properties.

The patterns and variability of pinnation angle along the length of apodemes, and the scaling of apodeme surface area, were investigated in the American lobster (Homarus americanus) and the snow crab (Chionoecetes opilio) to assess the morphological variation between legs and species, and how these may affect force generation. Muscle fibre pinnation angle shows general patterns of decline along the disto-proximal axis of the apodeme, but the specific patterns of each apodeme or leg are highly variable. There is only small change in pinnation angle along the length of the apodeme or between flexed and extended positions. It appears that changes in pinnation angle are not of sufficient magnitude to contribute significantly to force generation in these pinnated muscle systems. The apodeme surface area as a function of carapace size shows positive allometry for all legs of the snow crab, and for some of the apodemes of legs 2, 3, and 5 of the lobster. The flexor apodeme within the snow crab is larger than the extensor in legs 2 to 4 implying a greater force generating ability in flexion than extension, and legs 2 to 4 all possess much larger apodemes than leg 5. The lobster indicates some specialization of apodeme surface area between the legs along the length of the body, with the anterior legs having larger flexor apodemes than extensor. This pattern is reversed for the last pair of legs. This suggests that each of the four walking legs of the lobster may generate approximately equal forces in extension, while leg 4 has the ability to generate greater forces in flexion than legs 2 or 3, which in turn likely produce larger forces than leg 5. The apodeme surface area is suggested to play a much greater role in determining force generation in crustacean walking legs.

Antarctic krill, Euphausia superba, normally live in social aggregations (schools) but rarely aggregate in laboratory tanks. In order to study the effect of stress on solitary living we tethered krill to wooden skewers and measured heart rate both when they were held isolated from conspecifics and when they were held at normal schooling distances (∼1 body length). Heart rate did not differ significantly with sex or body size. However, intermoult krill had a significantly lower heart rate than postmoult animals. When two individuals were held at schooling distance, with one slightly higher in the water column than the other, the heart rate of the higher individual slowed significantly (106–98 beats min−1), while that of the lower individual remained the same. We interpret these results to mean that krill living solitarily are stressed but will respond to neighbouring individuals by decreasing their metabolic rate and saving energy.

Spinosphaera is a Terebellinae genus with three species described from the Pacific Ocean, S. pacifica from Japan, S. oculata from California, and the doubtful S. cowarrie from Western Australia. The genus is presently unknown in the Grand Caribbean region. Spinosphaera is characterized by the absence of branchiae, by the great number of notopodia, and the presence of a special type of notochaetae, called ‘Spinosphaera-chaeta’. These chaetae have three different regions: distal denticulate blade, neck separating the former from a middle swollen spinous region, and a proximal smooth or bilimbate region; two sizes are present. The genus is redefined, with redescription of all species currently known. Three new species are described here, two from the Mexican Caribbean coast, S. hutchingsae and S. carrerai, and one from California, S. harrisae. A taxonomic key to identify all species is given. Hutchingsiella gen. nov. is proposed for S. cowarrie; it differs from Spinosphaera in having notochaeta from segment 5 and neurochaetae from segment 6, and for lacking Spinosphaera chaeta.

A new genus of terebellid polychaetes is described, from material collected from living colonies of a stony coral (Mussismilia hispida) in the State of São Paulo, south-eastern Brazil. Articulatia is characterized by possessing notopodia from segment 5, neuropodia from segment 5 or 6 with double rows of uncini from segment 7 until near pygidium. Up to segment ten, notopodia with bilimbate capillaries; from segment 11 onwards two types of notochaetae are present, articulated chaetae, due to a deep cut at the sulcus of the third tooth, as well as capillary chaetae, both types with serrated blades. The presence of deep-cut chaetae is unique among all previously described terebellomorph polychaetes. This new genus is compared with other terebelline genera, and the phylogenetic analysis previously performed for the group is rerun, in order to determine the position of Articulatia within the subfamily. The type species of the new genus, A. aberrans, is also new to science and herein described.

Demographic and life history characteristics of the intertidal isopod Excirolana braziliensis (Isopoda: Cirolanidae) were compared between populations of two exposed sandy beaches with contrasting morphodynamics (reflective vs dissipative) during 22 consecutive months. Most population processes and life history traits did not give support for the ‘habitat harshness hypothesis’ (HHH): abundance of males, females, ovigerous females and juveniles was significantly higher at the reflective beach population, which also presented higher growth rates in size and weight with respect to the dissipative beach population. No significant differences in weight-at-length were found between beaches. Among the compared parameters, only the lower natural mortality rates at the dissipative beach gave support for the HHH. The results were not consistent with a previous analysis of Excirolana braziliensis along Pan-American beaches, which showed that this isopod occurs almost invariably in fine sands of tropical and temperate beaches. The results give strong support to recent findings that show that in macrofauna species capable of sustaining large populations across a wide spectrum of physical conditions, such as Excirolana braziliensis, beach morphodynamics should not be considered the primary factor affecting abundance and life history traits. Instead, our results reinforce the view that sandy beach populations are controlled by the intertwined forces of biotic and abiotic factors operating together.

This research reports on the kinematics of lobster and snow crab walking, documents changes in the moment arms of the mero-carpopodite joint during rotation, and examines scaling effects of morphological and mechanical variables in these crustacean species. Forward walking lobsters and lateral walking crabs were recorded and images analysed to describe the kinematics of these animals, and subsequently morphometric and moment arm measurements made. During forward walking the lobster maintains fixed mero-carpopodite joint angles during both the power and recovery strokes, though each of the walking legs maintains different joint angles. Legs 3 and 5 are maintained at angles which appear to equalize the flexor and extensor moment arms, and leg 4 joint angle appears to maximize the extensor moment arm. The snow crab has a joint excursion angle of between approximately 50° to 150° and, during flat bed walking, the leading and trailing legs move through similar excursion angles. The length of the meropodite for both species are longer for the anterior two leg pairs relative to the posterior two pairs and the rate of growth of the meropodite is largely isometric for the lobster while consistently increases with positive allometry in the crab. The flexor and extensor moment arms generated as the joint undergoes flexion/extension show two distinct patterns with the extensor moment arm being maximized at relatively low joint angles (55°–115°) and the flexor moment arm reaching a plateau at joint extension with angles between 95° and 155°. The flexor apodeme possesses the largest moment arms in all legs for both species, suggesting the flexors are able to generate greater torques. It appears that, mechanically, these laterally moving animals may be ‘pulling’ with the leading legs to a greater extent than ‘pushing’ with the trailing legs.

The variability of larval morphology in the caridean shrimp Nauticaris magellanica cultivated in the laboratory was analysed, and its applicability for the identification of larval stages collected from the plankton evaluated. Both morphometric and meristic variability of selected appendages was analysed comparing larvae from the rearing experiment with those obtained from the plankton. Larval development in the laboratory consisted of at least nine zoeal and five decapodid stages, followed by the first juvenile stage. Larvae collected from the plankton, comprising individuals from zoea II to, presumably, zoea VIII, were generally more developed and had a larger size than the corresponding stages reared in the laboratory. Cultured larvae showed a high exophenotypical variability starting with zoea IV, which impeded an immediate determination of larval stages obtained from the plankton.

The aim of this study is to improve rearing device of Crepidula fornicata (Mollusca: Gastropoda) reported in the literature, by determining the best arrangement between densities and feeding frequency in reared enclosures. Optimal growth (26·4 μm d−1) and survival rates (55·1%) were obtained when larvae were reared at 500 ind l−1 and fed every two days.

The geographic distribution of Verruca stroemia and V. spengleri are reviewed. Verruca stroemia ranges from the White, Barents, Norwegian, and North Seas south to Portugal to the Algarve and to Gorringe Bank. All of the records of this species from the Mediterranean Sea are considered to be V. spengleri. Verruca spengleri occurs in the Azores and Madeira archipelagos, in southern Spain (Cádiz), throughout the Mediterranean Sea from Gibraltar to Lebanon, and in the Black Sea. But a distinct deep-water Verruca species seems to occur in the deep Mediterranean.

Natural abundance, 13C/12C ratios (δ13C) of Californian sea hares, Aplysia californica, (Gastropoda: Opisthobranchia) were measured for comparison with the animals preferred red algal diets, Plocamium cartilagineum and Laurenciapacifica. Isotopic compositions of animals collected from around Santa Catalina Island, did not reflect those of the favoured red algal diets, nor the majority of algal species found in the field. However, animals held in seawater tanks and fed diets with a constant carbon isotopic composition exhibited δ13C values similar to their food. Fast turnover tissue, such as the muscle tissue of actively growing juveniles or egg masses laid by adults, showed δ13C values within ±2‰ of the algal diet. Slow turnover tissue, such as the muscle tissue of large adults, reflected the diet over several months. Stable carbon isotope ratios thus proved a useful tool to clarify the extent to which specialized feeding in A. californica can occur upon algae which are only moderately to rarely common.

Elaphognathia cornigera is a temporary fish-parasitic isopod crustacean that inhabits intertidal sponges. The life cycle and growth rate of this species were investigated using a laboratory rearing experiment. In addition, a wild population of this gnathiid isopod was sampled at fortnightly intervals over a 2-year period on an intertidal rocky shore at Oura Bay, Izu Peninsula, southern Japan. The population dynamics of this species were assessed using data from the laboratory experiment. Under laboratory conditions, individuals reached maturity after alternating between the parasitic feeding stage and the independent moulting stage three separate times. The mean larval period at 25°C was around 52 days. All life stages were observed in the natural population between spring and autumn. The density curves for all larval stages showed three to four distinct peaks, with the exception of the first larvae just after eclosion. According to the emergence patterns and growth rates derived from the laboratory experiment, E. cornigera appeared to alternate generations three to four times per year. During the winter months, only larvae in the second post-feeding phase and adult males were observed. This may have resulted from a halt in the development of larvae at the second post-feeding stage, triggered by cold winter conditions, and the post-reproductive death of semelparous females. Overwintered larvae and adult males became the source of the new population the following spring.