The present study investigates correlations between abundances of nematodes (at the genus level) and benthic microalgae on an intertidal mudflat in the Westerschelde Estuary (south-west Netherlands), using both multi- and univariate methods. Two sample series, covering surface areas of 10 cm2 (meioscale) and 1.25 cm2 (microscale) per sample were analysed. Trophic type analysis indicated that an average of 31% of the nematode community were candidate grazers of microalgae. Multivariate data analysis indicated that only a limited part of the variation in the nematode data could be explained in relation to pigments. Total nematodes did not show any correlation with the pigment data. On the meioscale, the genera Tripyloides and Calyptronema correlated negatively with chlorophyll concentration (chl-a and chl-c, respectively), while Prochromadorella correlated positively with the ratio of fucoxanthin to chl-a, a ratio which at the present sampling site can be considered to be a measure of the proportion of diatoms in the total microalgal standing stock. On the microscale, up to ten genera, comprising 76% of total nematode numbers, were correlated with pigments. A majority (74%) correlated specifically with the ratio of fucoxanthin to chl-a, while much fewer nematodes showed a direct correlation to pigment concentrations. Whereas many of these correlations could be explained in terms of direct trophic links, several others probably represented indirect relationships, trophic or other. Food densities may be less important structuring factors of nematode communities on tidal flats than relative abundances of particular food sources. It is suggested that nematodes actively migrate towards ‘optimal’ food patches, and that this dynamic aspect of nematode–microalgae correlations is best revealed at a spatial-scale small enough to allow a rapid response of nematodes to changes in adjacent patches. Apparently, the microscale used in the present study is more adequate for the study of such intricate interactions than the meioscale.

The common cockle Cerastoderma edule is intermediate host to several species of digenean trematodes. However, little is known about the factors influencing the settlement of trematode larvae in cockles as well as their effects on the host. Aspects of the transmission ecology, behaviour and effects on juvenile host specimens of trematode larvae belonging to the genus Himasthla and utilizing mudsnails Hydrobia ulvae as their first intermediate host and various waterbirds as their definitive host have been studied. Cercariae of Himasthla spp. (more than 90% of the metacercariae were identified as H. continua post-experimentally) exhibited a host size-dependent selection within the host size range from 2 to 6 mm. Infection efficiency was reduced by the presence of substratum allowing cockles to burrow, suggesting that the foot and visceral region may be attacked by cercariae. No increased mortality due to parasite infections could be demonstrated within 5 d after infestation. The metacercariae within experimentally infected cockles were primarily located in the connective tissue within the foot and visceral region. Although some cockles were completely filled with metacercariae only small functional effects were detected, such as a slightly prolonged burrowing time of infected specimens.

The secondary production of Nereis diversicolor and Scoloplos armiger (Annelida, Polychaeta) was studied at Stiffkey saltmarshes (north Norfolk coast). Production estimation on the basis of monthly sampling (August 1992–July 1993) gives 17.91 g C m−2 y−1 for N. diversicolor, 3.37 g C m−2 y−1 for S. armiger. Oxygen consumption of individuals was studied using a respirometer at four temperatures (5, 10, 15 and 20°C). At 15 °C, the relationships between O2 consumption (mg h−1) and body dry weight (mg) is Y=0.003X0.695 for S. armiger and Y=0.003X0.498 for N. diversicolor. Ammonia excretion of S. armiger tends to increase with decreasing temperature whereas it increases from 5 to 15 °C for N. diversicolor. Carbon loss through respiration for the sampling period is estimated at 32 g C m−2 y−1 for S. armiger, and 31.7 g C m−2 y−1 for N. diversicolor. About 20% of the potential supply of phytobenthic carbon in the marsh would be converted by the populations of both species. Estimations of carbon and nitrogen budgets of S. armiger are discussed.

In situ grazing activity of mesoplanktonic copepods was investigated by the fluorometric method during an algal spring bloom in a zone of oyster farming in Marennes-Oléron Bay. The grazing activity of copepods was overall higher during the night than during the day for three species (Temora longicornis, Paracalanus parvus and Acartia clausi), but peaks also appeared during the day for all of them. Individual ingestion rates and daily rations were higher during neap tide (low suspended particulate matter (SPM) concentrations) than during spring tide (high SPM concentrations). During ebb tide (when SPM concentrations were the lowest) the feeding activity of T. longicornis, P. parvus and A. clausi was significantly negatively correlated with algal concentration. Our work suggests that during the algal spring bloom in the farming area of Marennes-Oléron Bay the pressure exerted by mesoplanktonic copepods on the algal stock was very low, as a consequence of: (i) high algal concentrations in the field (resuspension and high phytoplanktonic production); (ii) low ingestion rates when high algal concentrations were observed. The likely ingestion of non-fluorescent particles by copepods is discussed.

To determine whether modern theories predict snail growth responses to trematode infestation a field growth study of Onoba aculeus, Littorina saxatilis and L. obtusata infected with two closely related Microphallidae trematodes was conducted in the White Sea. In each of the three host–parasite combinations studied trematode infection causes inhibition of snail reproduction. However, contrary to the classical interpretation of the gigantic growth of infected snails as a side effect of parasitic castration, the presented study failed to demonstrate that Microphallus piriformes causes gigantism in Littorina. The infection tended to stunt growth in L. obtusata and had no significant effect on growth rate of L. saxatilis. In contrast, gigantic growth was observed in O. aculeus infected with M. pseudopygmaeus. Considering that both trematode species are very similar biologically, the discrepancy is attributed to differences in the life history of the snail's hosts. Onoba aculeus is a relatively short-lived snail (2.5–3 y). The lifespan of L. saxatilis and L. obtusata is much longer (up to 9–11 y). These findings agree with a previously reported ‘energetic’ hypothesis that predicts growth alterations in accordance with life history variations of the snail species.

Eight samples of Littorina tenebrosa and L. saxatilis (Mollusca: Gastropoda) from Ireland and Britain, including pairs of each form from two locations in Ireland, were screened for genetic variation at 12 polymorphic enzyme loci using starch gel electrophoresis. Levels of polymorphism and heterozygosity were similar in L. tenebrosa and L. saxatilis, apart from a sample of L. tenebrosa from Britain which was less polymorphic than the Irish samples. No alleles were found to be unique to either form. Phylogenetic analysis using UPGMA showed that L. saxatilis and L. tenebrosa populations clustered as a monophyletic group. Nevertheless, the mean genetic distance between parapatric populations of L. saxatilis and L. tenebrosa (D=0.076) was similar to the mean for allopatric populations of either species (D=0.080). This indicates that there is a barrier to gene flow between the two forms Despite this, L. tenebrosa does not merit specific status since populations of this snail do not cluster as a distinct group, separate from L. saxatilis populations.

Burrows inhabited by Upogebia deltaura (Crustacea: Thalassinidea) were studied over a two-year period on two maerl beds at 10 m below Chart Datum (CD) in the Clyde Sea area, Scotland. Labelled burrows proved to be stable features on each ground, with animals able to withstand the impacts of scallop dredging and storm disturbance by re-building the damaged upper sections of their burrows. Resin casts excavated using an air-lift showed that these burrows were inhabited by single individuals. Burrows were deeper, larger and more complicated than was previously thought typical for U. deltaura and other members of the genus. Mapping of burrow systems revealed average densities of 2.9 ind m−2 with up to ten openings m−2. These elusive animals were the deepest burrowing megafauna (to 68 cm) and the most abundant large crustaceans within the maerl bed habitat.

Two species of the genus Eudorella (Crustacea: Cumacea) were collected and examined from the Yellow Sea. A new species and one new record of Eudorella are described and illustrated. This new species Eudorella hwanghaensis sp. nov. closely resembles E. intermedia, but it differs from the latter species in bearing a distinct apical spine of endopod with uropod peduncle. The distribution of the new species is confined to the central portion of the Yellow Sea, and its distributional range coincides well with that of the Yellow Sea Bottom Cold Water Mass. Eudorella pacifica is recorded for the first time in Korean waters. It occurred in shallow waters and was distributed widely on both coastal sides of the Yellow Sea.

The deep sea protobranch bivalve species Ledella pustulosa recently has been described as comprised of four subspecies, differentiated on subtle and qualitative differences in shell morphology. Two of these, L. p. pustulosa and L. p. marshalli, possess overlapping geographic distributions, L. p. pustulosa occurring on the continental slope, and L. p. marshalli occurring on the continental rise and at upper abyssal depths. Principal components analysis was applied to six samples of Ledella pustulosa from the Rockall Trough in order to explore patterns of variation in shell shape and to test whether the variability follows a depth-related cline which might be under environmental control. Two of these samples had previously been identified as L. p. pustulosa and L. p. marshalli, respectively. The distributions of shapes at every depth overlapped broadly with the distributions from other depths and none of the depths had uniformly distinct shells. However, the mean shapes of the six samples divided into two clusters: a shallow cluster characterized by a lower dorsal profile (smaller ‘shoulders’) and a deep cluster with larger ‘shoulders’. No bathymetric cline in shape was found within these clusters. A discriminant function based on training samples of L. p. pustulosa and L. p. marshalli correctly identified 84% of the shells in the training samples and was applicable over a wide range in shell size. It showed that the subspecies differed primarily in the dorsal profile. The discriminant function was applied to 598 shells from depths of 1632–2900 m in the Rockall Trough in order to test the hypothesis of depth-related segregation of the subspecies. Although individual variability was high, the results indicated a gradual transition from L. p. pustulosa dominance at ∼2000 m to L. p. marshalli dominance at 3000 m depth, but not marked segregation. A sample from 1632 m depth with large proportions of both subspecies disrupted the bathymetric trend and suggested a latitudinal gradient in distribution. Possible environmental factors, including bottom currents, acting on a common genotype to cause the observed pattern of differentiation, are also discussed.

In 1994 a warm-water barnacle Solidobalanus fallax was recorded for the first time in the UK (Southward, 1995). The naupliar development of this immigrant species is now described, from larvae reared in the laboratory. The planktotrophic nauplii of S. fallax reached the cyprid stage 8 d after hatching, at 25°C. Larval development includes six naupliar and one cyprid stage, following the typical pattern of the thoracican Cirripedia. Naupliar stages have a broad rounded convex cephalic shield without dorsal and marginal spines. Nauplii have a trilobed labrum with the small teeth found in other warm-water species. The abdominal process becomes nearly equal to the dorsal thoracic spine in stage VI. The arrangement of abdominal spines and larval setation are in the usual balanoid pattern. The significant difference of the S. fallax larvae from those of the related temperate-water archaeobalanid species Hesperibalanus hesperius supports the classification of these species into separate genera.

Preliminary observations of limpet activity at Lough Hyne, in south-west Ireland, showed that individuals on steep slopes were primarily active at night, when emersed; while those on near-horizontal rocks were often active during daytime submersion. Observations of limpet populations over an 11 d period of limpet populations on a near-vertical and a near-horizontal site, only 45 m apart, confirmed that animals on the near-vertical site were active on nocturnal low tides, whilst those on the near-horizontal site were active on daytime high waters. A short-term survey at ten sites, which had limpets on both extremes of slope (i.e. either near-vertical or near-horizontal), showed that limpets on near-horizontal surfaces were, on average, more active at daytime high waters than those on near-vertical faces. In 1996 and 1997 surveys of activity at daytime high, and nocturnal low waters were conducted at sites (14–15) with varying rock slopes (∼3–87°). In all cases, limpets on more steep slopes were active at nocturnal emersion whilst animals on more gentle slopes were active on daytime submersion periods. In most cases these trends were significant and explained between 22–40% and 37–44% of the variation in activity with site in 1996 and 1997 respectively. Analysis of the head orientation of limpets on their home scars showed that animals orientated in a down shore direction at all sites (1997 data) suggesting that limpets do perceive and respond to slope. Whilst slope does appear to influence the timing of limpets' activity (and especially on very steep or gently sloping sites) it does not account for a large degree of the variation in activity and, on sites with slopes between 30 and 60°, is likely to work in combination with other factors.

Siphonaria pectinata (Mollusca: Gastropoda) at Gibraltar foraged when exposed continuously or intermittently to air, when the relative humidity at the rock surface exceeded 75%. The paths followed by individual limpets were either single or compound loops beginning and ending at a home scar. In the main, outward and inward tracks were independent and there was little evidence of trail following. Siphonaria pectinata exhibited a range of crawling speeds but spent much of the excursion stationary or moving very slowly. Both duration of excursion and maximum foraging distance were very variable. No correlation between the size of S. pectinata and the duration of the excursion was apparent. The timing of activity may reflect an adaptive response designed to provide enough time to forage while avoiding predation, desiccation and dislodgement by waves.

The behavioural repertoire of the Scopimerinae crab, Dotilla fenestrata, is the result of a juxtaposition of rigid and plastic patterns, as an adaptation to the intertidal habitat. On the one hand, the activity of D. fenestrata can be classified in a number of stereotyped behavioural patterns, the occurrence of which may change throughout the low water or on the basis of the crabs' relative size, according to an expected schedule. For example, digging is more pronounced in larger individuals and mostly occurs when the crab emerges or just before it seals itself inside the burrow at the flooding tide. In contrast, maintenance of the burrow is a constant behaviour. Feeding rate, estimated from the number of pseudofaecal pellets emitted, is constant both throughout low water, with the exception of noon when it decreases, and with the feeding crab's size. The behavioural patterns that assure water uptake and temperature regulation (sponging and visits inside the burrow) are more frequently performed around noon. Agonistic patterns are mostly performed by larger individuals; the rate of aggression by resident crabs, against neighbours but mostly against smaller passers-by, increases with the flooding tide. On the other hand, for a surface deposit-feeder like D. fenestrata, plastic behaviour is mainly caused by the unpredictable distribution of food over the emerged platform. The result is a number of adaptive flexible behaviours, like: (1) the presence within the same population of both burrow-centred crabs and wanderers; (2) the construction by the former subpopulation of two types of burrows (feeding-trench burrows and igloos); and (3) significant differences in the behavioural budgets of the inhabitants of the two burrows. The ability to ‘switch’ modes of activity allows responses to both the predictable and unpredictable elements of intertidal environments, the mangrove swamp included.

Supralittoral splashpools representing 312,000 m2 of shoreline in Barkley Sound, British Columbia, were surveyed seasonally for tidal elevation, size, water properties, macroflora and faunal constituents coincident with colonization by Tigriopus californicus (Arthropoda: Copepoda). Overall, 90.1% of pools containing T. californicus were found between 3.0 and 5.0 m above lowest normal tide, with an average surface area-to-volume ratio of 7.06. Copepod populations were found at water temperatures of 6–33°C; salinity of <1–139 psu; pH of 6.1–9.5; and of 1.1–13.7 mg l−1 oxygen. Sediment and vegetation was sparse in T. californicus pools (mean cover 15.79±10.6% in 9.4±11.1% of pools, all species), and consisted most commonly of Enteromorpha compressa and Scytosiphon lomentaria and its Ralfsia-like alternate phase. Common fauna included mites, amphipods, littorines, and nematodes, with the highest diversity of co-inhabitants occurring in spring. Factors such as wind, wave action, and incidental fauna are discussed as potential agents of dispersal for splashpool copepods.

Sexual maturity in brachyurans is often associated with an allometric change in the relative growth of the animal. Maturity of Liocarcinus depurator was examined by analysing the monthly percentages of mature females (determined by the stage of gonad maturation and the presence of brood and sperm plugs) by size-class and the relative growth of different body parts: length and width of the carapace, length, height and width of the cheliped propodus; width of the abdominal segments in females and length of the first pleopod in males. Using the reproductive criteria the size at the onset of sexual maturity (carapace width at which 50% females are mature) in females of L. depurator is around 30–34 mm cephalothorax width. Principal component analysis (PCA) showed that the main source of morphometric variation for both sexes was due to heterochelia and allometric changes in growth. Morphometric variables were fitted using different regression techniques to one and two-phase growth models. The length of the first pleopod and the propodus of the right cheliped in males, and width of abdominal segments in females showed two clearly differentiated phases. Estimated maturity size (carapace width) corresponding to 50% mature animals was greater in males than in females. In males, size at the onset of maturity ranged between 31.4 and 35.7 mm, depending on the methods and variables used. The size at the onset of maturity in females ranged between 25.5 and 31.5 mm. In the Ría de Arousa, the size at maturity in females of L. depurator estimated using reproductive criteria is considerably greater than the size found based on morphometric criteria. The size at maturity based on morphometric criteria is greater in males than in females.

The Pacific oyster Crassostrea gigas (Mollusca: Bivalvia) was introduced to Ireland in 1965 and is farmed at many sites around the coast. The reproductive biology of 1377 oysters from two sites on the south coast of Ireland was examined from April 1996 until December 1997 for variations in maturation rate and condition indices. Qualitative data were compiled by staging gonadal development using histological sections. Environmental parameters of temperature, dissolved oxygen and chlorophyll-a levels, as well as parasites and pathology were monitored. Unusually high sea temperatures led to oysters in Dungarvan (site 1) spawning in both years of the study. Although sea temperatures were significantly higher, oysters in Cork Harbour (site 2) did not spawn but instead reached ripeness and then started a process of gametic degeneration called resorption. Lack of spawning was not attributed to environmental conditions monitored but was tentatively attributed to levels of pollutants in the water. Oyster condition in Cork Harbour was significantly affected by the presence of blistering due to tributyltin levels in the water and also by Polydora sp. (Polychaete) in the shell. Oyster condition in Dungarvan was not affected by the presence of the exotic species Mytilicola orientalis (Copepoda: Cyclopoida).

The current study examines the reproductive patterns found within four ovoviviparous, brooding periwinkle populations on one shore in the north-east coast of England; the boulder dwelling populations Littorina saxatilis H (upper-shore form with thin shell and large aperture) and L. saxatilis M (mid-shore form with thick shell and small aperture), and the barnacle-dwelling L. saxatilis B (small form similar in morphology to L. saxatilis M) and L. neglecta. Littorina saxatilis H showed distinct seasonality in reproductive activity, unlike L. saxatilis M, and produced significantly larger eggs and embryos than the latter population. Littorina saxatilis M maintained a significantly higher weight-specific fecundity and reproductive activity throughout the year than L. saxatilis H and produced a larger number of small embryos.

The two barnacle-dwelling populations also showed distinct seasonality in reproductive activity and neither of the populations contained reproductively active females during the winter months. There was no significant difference in egg size between the two populations, but L. saxatilis B produced larger crawlaways than did L. neglecta. Even though L. saxatilis B was significantly larger in body and shell size, L. neglecta had a higher weight-specific fecundity than the former population. The possibility that the observed differences in egg and juvenile size, fecundity and seasonality between the four populations can be attributed to microscale adaptation to the local environment is discussed.

Triplicate samples of rockpool algae were collected at each of three tidal elevations (upper, mid and low) from four shores on the north-east coast of England. Two moderately exposed (Ravenscar, the exposed shore at Filey Brigg), and two moderately sheltered (Selwicks Bay, the sheltered shore at Filey Brigg) shores were sampled during one week of spring tides during June 1996. A total of 6866 individual ostracods comprising of 26 ostracod species were recovered from the algal samples. Some species showed significant differences in abundance with tidal elevation across the four shores, e.g. Hirschmannia viridis was significantly more abundant in the upper shore pools. Other species, e.g. Heterocythereisalbomaculata, showed no significant difference in abundance either with tidal elevation or between shores. Significant differences in abundance occurred between shores at a given tidal height in some species, e.g. Semicytherura nigrescens was absent from Selwicks Bay but abundant on the remaining shores. Other species had markedly disjunct distributions, e.g. Callistocythere badia only occurred in the exposed upper shore pools at Filey Brigg. Ostracods were significantly less abundant in the low shore pools. Cluster analysis showed that low shore samples had a high degree of similarity between the four shores whereas the upper and mid-shore samples clustered primarily to shore. A two-way ANOSIM indicated that there was a significant difference in assemblage similarity between the four shores and also between the different tidal elevations.

Two recently-distinguished species of Chthamalus (Cirripedia) are found on rocky shores in the north-eastern Atlantic: C. stellatus predominant on islands and headlands and C. montagui more abundant in bays. Larvae of the two species were produced in laboratory cultures to describe and compare the morphology and to allow identification in plankton samples. Nauplius larvae of C. stellatus are up to 30% larger than those of C. montagui. Differences in setation are minor. The two species are easily distinguishable from the size and shape of the cephalic shield. Chthamalus stellatus has a subcircular shield with longer body processes in later stages while C. montagui is more ovoid. The former develop more slowly in culture than the latter. Chthamalus stellatus larvae in a culture at 19 °C reached stage VI in 16 d compared to 11 d for larvae of C. montagui at the same temperature. The morphology and longer development time of C. stellatus larvae suggests adaptation to a more oceanic lifestyle and wider dispersal to reach more fragmented habitats than larvae of C. montagui.

The population structure of the European flying squid Todarodes sagittatus was studied using data of about 5000 squid caught in waters off the western Sahara between 1969 and 1997. The bulk of the population consisted of winter-spawned squid, which occurred as juveniles of 80–120 mm mantle length (ML) over the slope in spring, and as immature squid of 160–180 mm ML both on the shelf and slope in summer. In autumn, the squid attained 220–280 mm ML, matured, and shifted to the slope, where the spawning was supposed to occur in winter. Age and growth of T. sagittatus was studied using statolith ageing techniques. Assuming daily production of putative growth increments within statoliths, as well as sizes and proportions of immature and maturing females, the lifespan of the west Saharan populations of T. sagittatus lasts ∼1 y. Todarodes sagittatus is a fast growing squid at juvenile and immature ontogenetic phases. Early maturation (at ages 220–230 d in males and 250–260 d in females, respectively) and subsequent decrease of somatic growth rates caused rather small modal sizes of mature squid (250–300 mm ML) compared with those of their northern counterparts (350–420 mm ML). Both hatching dates and seasonality in occurrence of mature females shows that in waters off the western Sahara T. sagittatus spawns throughout the year with a well-pronounced winter peak.