The position and structure of the North Atlantic Subtropical Front is studied using Lagrangian flow tracks and remote sensing (AVHRR imagery: TOPEX/POSEIDON altimetry: SeaWiFS) in a broad region (∼31° to ∼36°N) of marked gradient of dynamic height (Azores Current) that extends from the Mid-Atlantic Ridge (MAR), near ∼40°W, to the Eastern Boundary (∼10°W). Drogued Argos buoy and ALACE tracks are superposed on infrared satellite images in the Subtropical Front region. Cold (cyclonic) structures, called ‘Storms’, and warm (anticyclonic) structures of 100–300 km in size can be found on the south side of the Subtropical Front outcrop, which has a temperature contrast of about 1°C that can be followed for ∼2500 km near 35°N. Warmer water adjacent to the outcrop is flowing eastward (Azores Current) but some warm water is returned westward about 300 km to the south (southern Counterflow). Estimates of horizontal diffusion in a Storm (D=2.2×102 m2 s−1) and in the Subtropical Front region near 200 m depth (Dx=1.3×104 m2 s−1, Dy=2.6×103 m2 s−1) are made from the Lagrangian tracks. Altimeter and in situ measurements show that Storms track westwards. Storms are separated by about 510 km and move westward at 2.7 km d−1. Remote sensing reveals that some initial structures start evolving as far east as 23°W but are more organized near 29°W and therefore Storms are about 1 year old when they reach the MAR (having travelled a distance of 1000 km). Structure and seasonality in SeaWiFS data in the region is examined.

Species body size spectra have been constructed for macrofauna assemblages from four sites with contrasting sediment granulometry and heterogeneity in and around Plymouth Sound. The number of species and species turnover (β diversity) were higher on coarse sediment. While the fauna were distinct between sites, the median geometric size-class was conservative (class 14; 0.153–0.305 mg dry blotted weight). Only one site had significantly lower heterogeneity within the species size spectrum, yet this was the most heterogeneous sediment. As such, we were unable to reject the null hypothesis that species body size distribution patterns are conservative despite differences in sediment granulometry and heterogeneity.

Located at 22°N on the northern shore of the South China Sea, Hong Kong experiences a seasonal, monsoonal climate and its resident scleractinian corals, comprising some 50 species, live here at the limit of their ranges. Summers are hot and wet, winters cold and dry and this study was initiated to determine the effects of bioerosion and periodic episodes of strong wave action on coral death and beaching. Coral rubble washed up on Telecom Bay Beach in the Cape d'Aguilar Marine Reserve was collected every month from January 1996 until December 1997, inclusive. Quantities were greatest after typhoons and storms, with the average monthly weight of recently-living corals accounting for approximately 0.007%, by weight, of the total live coral in the bay. Seventeen species of Mollusca were recorded from within the skeletons of this rubble and included a new record for Hong Kong, Anchomasa yoshimurai (Pholadidae). Species of Lithophaga dominated, with highest mean abundances recorded from within Goniastrea aspera, the most abundant living coral in the bay and from within the heaviest fragments. The overall incidence of borers was, however, low although it appears that dead coral borers, notably the basally boring Lithophaga lima, act to weaken coral attachment resulting in dislodgement and beaching during and after storms. At this relatively unperturbated site, therefore, the significance of borers in weakening coral attachment with subsequent detachment and beaching during and after storms, respectively, is low, a situation also seen elsewhere.

The bibliography concerning the Mediterranean Sipuncula is reviewed, particularly that from the eastern Mediterranean. Additional data are provided from macrobenthic samples collected between 1974 and 1997 in the Hellenic waters. A total of 17 species are recorded, five of which (Sipunculus norvegicus, Golfingia elongata, Nephasoma lilljeborgi, Thysanocardiacatharinae and Aspidosiphon (Akrikos) mexicanus) are reported for the first time in Hellenic waters. Three more species (Onchnesoma squamatum squamatum, Aspidosiphon (Aspidosiphon) elegans, Apionsoma (Apionsoma) trichocephalus) which are found exclusively in the extreme eastern basin (Israel, Egypt) raises the number of eastern Mediterranean Sipuncula species to twenty.

A total of 13 boring species of spionid polychaetes were extracted from 28 different calcareous substrata (i.e. mollusc shells, coralline algae and barnacle tests) from Japan. The spionids were: seven Polydora spp.: Polydora brevipalpa, P. websteri, P. curiosa, P. uncinata, P. aura, P. glycymerica, Polydora sp; five Dipolydora spp.: Dipolydora concharum, D. bidentata, D. alborectalis, D. giardi, D. armata; and one Carazziella sp.: Carazziella reishi. All of them inhabited self-excavated burrows in living and/or migratory calcareous substrata and they were never found from soft sediments. Burrow structures were species-specific. The Polydora species basically excavated simple U-shaped burrows, while the Dipolydora species excavated more varied, distinct burrows. The boring activity seemed species-specific among polydorids. This study attempts to summarize and discuss the biological characteristics of these boring species inhabiting Japan. In addition, P. curiosa, P. glycymerica, Polydora sp., D. giardi and C. reishi are new to Japan.

The annelid community of a shallow Mediterranean lagoon (Gialova Lagoon, Ionian Sea) was studied on a seasonal basis. Out of the 39 species identified eight are reported for the first time from the central Mediterranean. The dominant species were the polychaetes Capitella capitata, Neodexiospira pseudocorrugata, Malacoceros fuliginosus, Perinereis cultrifera, Hediste diversicolor, Heteromastus filiformis and the oligochaete Limnodriloides maslinicensis. Uni- and multivariate methods were employed to study the community structure. The coenocline observed is strongly related to the degree of isolation; its main features (i.e. number of species, density, geometric abundance and size-classes) in space and time are presented and discussed in detail. The distribution pattern of the annelid community has been found to be governed by a different set of environmental factors in each season. Although this narrow lagoonal habitat suffers severe dystrophic episodes it manages to recover, demonstrating a seasonal community pattern.

Observations of female genital structures using light and scanning electron microscopy in 25 species of Acartiidae (Copepoda: Calanoida) show the presence of paired gonopores and egg-laying ducts with a typical semicircular configuration in all specimens. In the genus Acartiella, there is no seminal receptacle and the external genital area serves as storage site of the spermatophoral products forming an external mass. Unlike in the other acartiids, the genital structures present a complex organization with paired adjacent gonopores and copulatory pores. In almost all the species, the seminal receptacles exhibit characteristic loop-shaped seminal ducts which connect them to the egg-laying ducts. The functional morphology and taxonomic relevance of genital structures are discussed. The present results do not justify the Steuer's subgenus division of the genus Acartia, the very predominant one of the family.

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.

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.

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.

An allozyme analysis on three species of Mediterranean Veneridae (Mollusca: Bivalvia): Callista chione (subfamily Pitarinae), Venus verrucosa (Venerinae) and Chamelea gallina (Chioninae) is presented. The results were compared with the previously obtained allozyme data on Tapes philippinarum, T. decussatus, Venerupis aurea and Paphia undulata (all pertaining to the subfamily Tapetinae). The newly analysed species showed remarkable departures from the Hardy–Weinberg proportions, as commonly observed in several populations of Bivalvia. The present analysis revealed a high level of relationship between C. gallina and Venus verrucosa and suggested that the genus Tapes, as presently defined, should be regarded as an unnatural taxon. The allozyme results are consistent with mitochondrial 16s ribosomal DNA and satellite DNAs analyses on the same species, with the only exception of Callista chione which seems to be basal to (UPGMA method) or even included (Neighbor-Joining method) in the Tapetinae cluster.

Geographical differences in the shell growth rate of several populations of the bivalve Arctica islandica (Mollusca: Bivalvia) were estimated by using the growth lines laid down during their first ten years of life. Attention was focused on populations from the North Sea, but for comparison small samples from adjacent waters were also analysed. A four-fold difference in the average growth rate was found between the slowest and fastest growing shells.

Principal component analysis was used to summarize the inter-relationships between environmental variables and growth rates. Shell growth correlated positively with primary production and temperature and inversely with depth and the silt content of the sediment. The North Sea specimens were found to have a strong positive correlation with grain size. Since sediment characteristics also depend on bottom currents, it is suggested that these increased rates reflect lateral seston flux as additional food supply.

In a multiple regression model, applied to all available data, average annual temperature, primary production and the interaction between production and water depth explained 50% of the variance. The derived standard coefficients for temperature, primary production and the interaction between depth and primary production were 0.90, 0.47 and −0.92 respectively. The results of this study suggest that the temperature effects on in situ shell growth are easily overruled by other environmental factors.

If a similar model was calculated with North Sea data only, 75% of the variance was explained by temperature, primary production and depth×primary production. The standard coefficient for primary production was 1.26. The role of temperature in explaining the observed growth differences is negligible since the standard coefficient is −0.098. The interaction term, depth×primary production had a standard coefficient of −0.95.

Three species of cheilostomate Bryozoa are described, and illustrated by scanning electron micrographs. One was previously poorly characterized and is here stabilized by the selection of a neotype; a second is recognized as distinct from an Arctic congener while the third is entirely new to science and represents the first record of the genus Codonellina from the north-east Atlantic.

The reproductive biology of two aplacental viviparous deep sea sharks, Centroscymnus coelolepis and Centrophorus squamosus has been studied from 1735 and 675 specimens respectively, collected with bottom trawls between 600 and 1400 m depth off the west coast of the British Isles. A macroscopic maturity scale indicates that for both species, size at first maturity is greater in females than in males. In Centroscymnus coelolepis, genital maturity occurs at an average length of ∼86 cm for males and ∼102 cm for females. In Centrophorus squamosus, males are mature near 98 cm and females near 124 cm total length (TL). Smallest juveniles of both species are absent from catches: no specimens of Centroscymnus coelolepis shorter than 58 cm, nor specimens of Centrophorus squamosus shorter than 84 cm have been recorded. Ovarian fecundity is higher in Centroscymnus coelolepis than in Centrophorus squamosus. A maternal supply has been demonstrated for Centroscymnus coelolepis. Litter size has been estimated only in C. coelolepis because no pregnant females of Centrophorus squamosus were recovered. A dwarf embryo and a pair of twins have been observed. Segregation by sexual stage of development shows that immatures are generally found at greater depths than adults.

One hundred and fifty intertidal fishes were captured at Jeffreys Bay in July 1996 and February 1997, and at De Hoop Nature Reserve in April 1997, South Africa. Caffrogobius caffer, Chorisochismus dentex, Clinus superciliosus, and Clinus cottoides were all parasitised by haematophagous larvae of the isopod, Gnathia africana, and between 22 and 81% of fishes were infested with 1 to 76 larvae each. Of those fishes examined for blood parasites, 35/46 (76.1%) had an intraerythrocytic haemogregarine identified as Haemogregarina (sensu lato) bigemina, but only Clinus superciliosus and Clinus cottoides were infected. Gamonts of the haemogregarine, some undergoing syzygy, were also present in 50% of stained batches of the anterior hindgut contents of G. africana larvae which had fed on Clinus superciliosus, but were absent from larvae taken from Clinus cottoides and Chorisochismus dentex. This study provides new host records for H. bigemina and further evidence that gnathiid isopods play a role in the transmission of the haemogregarine.

The current distribution and abundance of Elminius modestus (Crustacea: Cirripedia) were examined at 15 sites along the Portuguese coast in March/April 1998. Elminius modestus was found at two sites only but was absent from a site where it had previously been recorded. The site at Faro is the most southerly location on continental Europe where Elminius has yet been recorded and it is nearly 300 km south of where it was previously found.

Attached cypris larvae and less than one month old metamorphs of Chthamalus stellatus and C. montagui (Crustacea: Cirripedia) were sampled from random quadrats on two shores in County Cork, Ireland, from July 1996 to June 1997. Cyprids of C. stellatus were much more abundant than those of C. montagui, but the relative abundance of metamorphs of the two species did not differ significantly. Cyprid abundance predicted metamorph recruitment intensity during peak settlement in C. stellatus but not in C. montagui.

Interbreeding between two populations (Estero de Punta Banda, Baja California, Mexico (PB) and Mission Bay, California, USA (MB)) was tested using the live progeny (nauplii) of the marine calanoid copepod Acartia californiensis, in a male to female ratio of 3:1. The laboratory conditions were 18±2°C and a 12:12 h L:D cycle, during an experimental period of one week. The first filial progeny (F1) present in the replicates were used in four combinational experiments (non-hybrids: PB-PB and MB-MB, and hybrids: PB-MB and MB-PB). To investigate the production of the F2 generation, males and females were selected from F1 and 16 combinational experiments were conducted with five replicates each (non-hybrids: PBPB-PBPB and MBMB-MBMB, and hybrids: PBPB-MBMB, PBPB-PBMB, PBPB-MBPB, MBMB-PBPB, MBMB-PBMB, MBMB-MBPB, PBMB-PBPB, PBMB-MBMB, PBMB-PBMB, PBMB-MBPB, MBPB-PBPB, MBPB-MBMB, MBPB-PBMB and MBPB-MBPB). Statistical analysis for F1 showed no significant differences of the mean for live progeny between the non-hybrids and hybrids and between non-hybrids, but a significant difference between hybrids was found. For F2, the mean live progeny between non-hybrids and hybrids, between hybrids and between non-hybrids was found to be non-significant. These results show successful interbreeding between the populations studied.

Two members of the scallop genus Pecten (Bivalvia: Pectinidae) occur in European waters. Pecten maximus is largely an Atlantic species whilst Pecten jacobaeus is almost completely confined to Mediterranean waters despite slight overlap of distributions in the western Mediterranean. Genetic distances between these species were estimated using both allozyme electrophoresis and mitochondrial DNA PCR–RFLP and shown to be of a similar magnitude to intraspecific values, considerably lower than expected for congeneric species. These data are discussed in the light of recognised morphological differences, hybrid rearing trials and previous studies examining genetic distance by allozyme methodologies.

The effects of shell resource and interspecific competition on sexual size dimorphism of the hermit crab, Pagurus middendorffii (Decapoda: Paguridae), were examined from population comparisons. Degree of size dimorphism and mean shell size occupied by male and female P. middendorffii differed among adjacent sites, and there was a significant correlation between them. Although most large P. middendorffii occupied large Chlorostoma lischkei shells in both shell-limited and shell-unlimited populations, P. lanuginosus, a sympatric species, occupied large C. lischkei shells more frequently than P. middendorffii did in a shell-limited population. Environmental factors, shell availability and interspecific competition for shells, might play important roles in determining the degree of sexual size dimorphism of P. middendorffii.