The Arctic abyssal anemone Bathyphellia margaritacea, type species of the genus and of the family Bathyphelliidae is redescribed. Acontia in this species are highly variable both in quantity and in cnidome characteristics, implying that this genus is one of the links between acontiate and nonacontiate mesomyarian actiniarians, and has to be considered a ‘late’ mesomyarian according to the scheme proposed by Schmidt (1972b, 1974). By contrast, the new abyssal species Daontesia porcupina has normally developed acontia, a cuticle consisting of multistratified sheets and a more archaic and diverse cnidome, suggesting its systematic allocation within the ‘early’ mesomyarians. The allocation of the genus Daontesia to the family Bathyphelliidae is questionable.

Quantitative sampling for the genus Eurydice (Isopoda: Cirolanidae) was conducted on 25 sand beach sites along the Atlantic coast of the Iberian Peninsula. Five species were recorded intertidally: Eurydice affinis, E. pulchra, E. naylori sp. nov., E. lusitaniensis sp. nov. and E. spinigera. Physical data collected were used to construct an index of exposure to rank each site. The distribution of intertidal Eurydice sp. is described in relation to exposure to wave action and to tidal level. Peak abundance of E. affinis, E. pulchra and naylori occurred most frequently between mean high water neap (MHWN) and mean tide level (MTL). Whilst E. affinis occurred over a wide range of exposure, E. naylori exhibited a marked preference for exposed sites and E. pulchra was only recorded from sheltered and semi-exposed sites. Surf plankton collections revealed the presence of E. lusitaniensis, but as only two specimens were collected, its ecology remains unknown. The zoogeographical distribution of the genus on North Atlantic and Mediterranean coasts is briefly reviewed.

One Scottish and two Aegean samples of Nephrops norvegicus (Crustacea: Decapoda) were allozymically tested using a total of 110 individuals and compared with two already characterized Adriatic populations. Three main characteristics of their genetic structure emerge: a highly homogeneous allele pattern, a strong heterozygote deficiency at some loci and a significant genotypic variance among populations, mainly caused by the Pgm locus. Population subdivision, intraunit inbreeding, bottlenecks and selective constraints are taken into account to allow for these genetic features, although none of them proved decisive. The search for straightforward characters differentiating Norway lobsters of geographically different areas proved unsuccessful, although a significant genotypic differentiation was noticed among our samples. Observed D values among the geographically distant samples indicate a very low genetic divergence, so that no clear phyletic conclusions can be traced on the sole allozyme-gene analysis.

The vertical distribution, morphology and diet of Proboscidactyla stellata (Cnidaria: Limnomedusae) were studied in Lough Hyne over a two year period. Vertical hauls of four depth strata, 40–30 m, 30–20 m, 20–10 m and 10–0 m, were taken monthly and at 4 h intervals for a period of 48 h in July and 24 h in September 1994. Proboscidactyla stellata was largely concentrated in the lower 20 m of the water column reaching a maximum of 21 m−3 at 30–20 m depth in June 1993. An oxythermocline occurred at 25–30 m depth in the summer and autumn months of 1993 and affected the vertical distribution of the medusae. Six morphs of the species, varying in the number of gonads, were found in the lough. Bivalve veligers, which P. stellata actively selected, formed 83% of the diet.

The Porcupine Abyssal Plain in the north-eastern Atlantic Ocean is subject to periodical deposition of phytodetritus and has a highly diverse benthic fauna dependent on this source of organic matter. Among the most abundant species from the northern study site of the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL) at ~48°50′N 16°30′W, 4850 m, is Iosactis vagabunda gen. nov., sp. nov. (Cnidaria: Actiniaria, Iosactiidae fam. nov.), a small endomyarian sea anemone. The fact that this species is a burrower, with a smooth, unspecialized column, and a rounded aboral end provided with a central pit, makes it stand out from the other families of endomyarian anemones and prompted the establishment of the new family Iosactiidae. There is evidence that the closest relatives of the new family are the ‘deep water actiniids’ (e.g. Bolocera, Liponema, Leipsiceras), and the Andresiidae. Long-term in situ time-lapse photographs indicate a unique behaviour of this anemone in that it moves out of its hole at times, presumably exhibiting a hemisessile lifestyle in this peculiar abyssal habitat.

This study tested the hypothesis that predator odours alter behavioural responses of hermit crabs to other chemical stimuli. Stimuli that cause alarm and shell-related behaviour (hermit crab haemolymph and two gastropod flesh extracts), and stimuli that did not cause shell-related behaviour (sea-water and predator haemolymph) were used. Individual hermit crab responses to stimuli were observed in ambient sea-water and predator odour. In the absence of predator odour, hermit crab haemolymph and gastropod flesh extracts stimulated shell grasping behaviour. Locomotion was the major response to sea-water and stone crab haemolymph. Crabs behaved consistently when repeatedly exposed to a particular stimulus. In general, addition of predator odour to mixtures, resulted in decreased shell grasping and increased locomotion. Shell fit was a poor predictor of behaviour for the size range of crabs tested. Hermit crabs respond to, and discriminate, a variety of complex odour mixtures.

Marked genetic differentiation in the intertidal isopod, Jaera albifrons (Crustacea: Isopoda) has been shown to occur on a scale of just a few metres on British shores. Allozyme electrophoresis at 21 enzyme-coding loci has been employed to examine genetic structure in other UK members of the complex (Jaera forsmani, J. ischiosetosa, J. praehirsuta), and explore the relationship between genetic diversity and perceived niche-width. Comparisons were made with the nonsibling species J. nordmanni. Three subpopulations of each species taken from each of two shores on Anglesey, UK (subpopulations N=30) were assayed for electrophoretic variability. Data from 11 polymorphic loci (P0·95) demonstrated marked genetic differentiation in all populations of J. albifrons and J. praehirsuta, and on one shore for each of J. ischiosetosa and J. nordmanni, with J. praehirsuta (GST=0·207) and J. albifrons (GST=0·121) showing the highest genetic differentiation. In contrast, J. forsmani exhibited population homogeneity on both shores studied. Genetic diversity ranged markedly across species (H0=0·165—0·040), with the two most widely distributed species, J. albifrons (H0=0·135) and J. ischiosetosa (Ho=0·165) exhibiting the highest genetic variability, providing support for the niche-width variation hypothesis. Data indicate that although habitat fragmentation and direct development is associated with microgeographic differentiation in Jaera spp., localized factors such as habitat continuity and exposure to water movements determines the magnitude of such effects.

Scanning electron microscopy was used to study the microstructure and internal growth lines of the temperate ahermatypic coral Caryophyllia smithi (Cnidaria: Anthozoa). The arrangement of internal growth lines in combination with the orientation of aragonite crystals were used to describe the pattern of skeletal development in C. smithi. The observed pattern was verified using observations from another study on skeletal development in C. smithi, but which was based only on external observations of skeletons of living and dead specimens in different stages of development. The pattern of skeletal development in C. smithi is suggested to be subdivided into three stages, based on the deposition of specific skeletal elements during the development of the skeleton. In the first ‘juvenile’ stage, various primary skeletal elements are formed: the basal plate, the septa and a primary and secondary septotheca. The second ‘half full grown’ stage is characterized by development of apparently only an extended basal attachment, which enlarges the attachment area to the substratum. In the third ‘full grown’ stage, the edge zone of the polyp tissue is retracted from the extended basal attachment to the calice, and upward growth of the coral predominates followed by lateral thickening of the septotheca, costae, septa and columella. Internal growth lines were found throughout the skeleton and may be composed of, or resulting from the presence of organic matter. The septotheca and the extended basal attachment, which are important for a strong skeletal structure and a strong attachment to the substratum, respectively, are probably thickened faster than the other skeletal elements. Attachment scars were found in areas where attachment of the coral tissue to the skeleton is critical.

The dynamics of egg production by a Mediterranean population of the terebellid polychaete Eupolymnia nebulosa was assessed both in the field and in the laboratory between 1992 and 1994. Our results confirm the occurrence of several peaks of jelly mass production at the population level. They show that such peaks result from the production of several broods per individual female (the number of produced broods increasing with female size). Jelly masses produced at the end of the breeding season tend to be smaller and to contain fewer eggs than those produced at the beginning of the breeding season. Worms produced significantly larger jelly masses in 1994 than in 1993 and 1992, without noticeable change in corresponding fecundities. The computation of temporal changes in eggs produced per unit of surface area in the cove of Paulilles shows that most of the eggs are produced during the first two peaks of jelly mass production. These results are discussed relative to the different hypotheses invoked to account for the occurrence of several spawnings in Mediterranean populations of E. nebulosa. It is concluded that no single explanation, such as the allometry constraint hypothesis or heterogeneity in oogenesis rates, can be retained.

This study demonstrates that the two species of lugworm, previously classified as Arenicola marina occupy distinct zones within sandy beaches around South Wales. Arenicola marina (sensu stricto) or blow lug, is found higher up the shore, tending to be concentrated at mid-tide level, whilst A. defodiens Cadman & Nelson-smith, 1993 or black lug is most numerous at or below mean low water of spring tides and, unlike A. marina in this area, also apparently extends subtidally. Arenicola marina is found in estuaries, unlike A. defodiens, and seems to inhabit slightly less exposed beaches. Degree of sorting, mean and median particle size do not appear to be a significant factor in determining lugworm distributions. Some possible explanations for these observed differences, including differences in burrow depth and salinity tolerance, are discussed.

Field observations and laboratory experiments were made on Cyclope neritea, a small (~10 mm diameter) burrowing stenoglossan gastropod with a flattened shell found in very high densities (>200 m2) in Paleohori Bay on the south coast of Milos (Aegean Sea). Cyclope neritea forms a high proportion of the biomass at seeps in this bay, where the medium to fine sand overlies hot, sulphidic brines. About half the animals were found on the surface in the daytime, an exception to the normal habit of this species which usually emerges from the sediment only at night. The C. neritea were aggregated on the thinner bacterial mats over the seeps. In the laboratory, C. neritea remained active for 3 h at sulphide concentrations up to 1 mM, the highest concentration in the interstitial water in the upper 25 mm of sediment at the seeps. Although the species can tolerate elevated salinity and temperature, it shows little adaptation for sulphide detoxification by oxidative pathways. It may survive at the seeps by its behaviour pattern, especially the use of the extensible siphon to access oxic water above the sediment boundary layer, and perhaps by exclusion of sulphide from the tissues. Cyclope neritea ingests large quantities of sand together with adhering bacteria and diatoms, but also scavenges on other animals killed by the extreme conditions of the seeps.

Tissue growth in Crustacea occurs at specific stages of the moult cycle and is influenced by a number of physical, hormonal and environmental factors. In order to understand the mechanisms responsible for controlling intermittent muscle growth in Crustacea, the effects of various factors on rates of protein synthesis and gene expression for the myofibrillar proteins, have been examined. These studies include the effects of mechanical stretch on muscle fibres; the influence of the moulting hormones, ecdysteroids; and the effect of temperature which is an important environmental variable. Sarcomeric proteins have been cloned and used to measure mRNA levels of actin, myosin HC and tropomyosin in various muscles over the moult cycle. Results from these studies demonstrate that both transcriptional and translational regulation occurs in response to hormonal and mechanical stimulation. Temperature has a direct effect on rates of protein synthesis and transcription in intermoult muscles but overall protein turnover may remain unchanged due to a concomitant increase in protein degradation rates.

Genome size (or C-value) in benthic polychaetes was studied from both experimental data and literature. Nuclear DNA content variation was analysed as related to both phylogenetic relationships of various families, general life habit of the species (interstitial vs macrobenthic), diploid chromosome number (2n), and mean body size (length). Experimental data on genome size were obtained for 43 lower taxa (genera and species) by means of microdensitometric analysis of the amount of Fuelgen-stained haploid DNA in interphase nuclei. These data, added to those available in the literature (36 taxa studied by Conner et al., 1972) gave a total of 79 taxa (genera and species), representing 30 families and 14 orders. Twenty-one of the species studied belonged exclusively to interstitial (=meiofaunal) families or genera.

The crustacean moult cycle is a convenient model system in which to study calcium (Ca) homeostasis as vectorial movement across Ca transporting epithelia (gills, gastric epithelium, cuticular hypodermis, antennal gland) which occurs in either direction at different stages of the moulting cycle. Intermoult crustaceans are in relative Ca balance. During premoult, at the same time as the cuticle decalcifies, epithelia involved in Ca storage (e.g. gastric) calcify and/or increase their intracellular Ca stores. Premoult Ca balance is typically negative as Ca is excreted. During postmoult the soft new cuticle is remineralized largely with external Ca taken up across the gills and gastric epithelium (positive Ca balance); conversely during this time internally stored Ca is remobilized. This review (1) compares the relative roles of Ca transporting epithelia in Ca balance for crustaceans from different habitats; (2) proposes up-to-date cellular models for both apical to basolateral and basolateral to apical Ca transport in both noncalcifying and calcifying epithelia; (3) compares kinetics of the Ca pump and exchanger during intermoult; (4) presents new data on specific activity of calcium adenosinetriphosphatase (Ca2+ATPase) during the moult cycle of crayfish and (5) characterizes a partial cDNA sequence for the crayfish sarcoplasmic reticular Ca2+ATPase and documents its expression in gill, kidney and muscle of intermoult crayfish. The physiological and molecular characterization of Ca transporters in crustaceans will provide insight into the function, regulation and molecular evolution of mechanisms common to all eukaryotic cells.

The Nassarius reticulatus complex (Mollusca: Gastropoda) is a common and morphologically variable organism of the Lusitanian marine province. The taxonomic status of the different morphs has been the subject of considerable debate for over a century. About 50 individuals of each N. nitidus and N. reticulatus morphs were collected in November 1994 from the same area (Ria de Vigo, north-west Iberian Peninsula). Preliminary screening by allozyme electrophoresis for 27 enzymes resolved 24 presumptive enzyme loci. There were no deviations from the Hardy-Weinberg expected proportions at most polymporphic loci for any morph. Five and two enzyme loci were completely and partially diagnostic loci, respectively, between the morphs. The genetic identity of morphs (1=0.658 ±0.095) was characteristic of congeneric species. The absence of electrophoretically recognizable hybrids in sympatric populations provides clear evidence that the two morphs are reproductively isolated within the study area. These genetic results corroborate other reported biochemical, morphological and behavioural differences between the morphs. Consequently, these data strongly suggest that the taxa N. nitidus and N. reticulatus must be considered as separate species.

Thirty-five specimens of the articulate brachiopod Neorhynchia strebeli were collected from a site at 814 m in the Weddell Sea. This was only the second species of the order Rhynchonellida to be found in Antarctica. Formerly N. strebeli was known solely from abyssal Pacific Ocean localities. A circumantarctic distribution is suggested in addition to the known deep-sea Pacific range. The specimens of this collection showed considerable commissure variation, suggesting that the previously proposed erection of two subspecies on the basis of this character is erroneous, and emphasises the phenotypic plasticity of some articulate brachiopods. The valve lengths and the number of alpha growth rings in the sample showed a normal distribution and a von Bertalanffy growth function was fitted to the data: Lt = 23 (1-exp[-0·228t]). If the alpha growth rings were of annual periodicity, the ages attained by the Antarctic N. strebeli of 11 y would be substantially lower than those reported for other Weddell Sea brachiopods. The epibiotic communities occurring on the valves of N. strebeli were impoverished, which is characteristic of deep water Antarctic brachiopods. The few specimens collected with their substratum were attached to small pebbles, but the typical attachment substrata may be different.

The study of growth rates in the prosobranch snails Hydrobia ulvae and H. ventrosa under field conditions showed that growth rate of snails infected by different trematode species is species-specific. Trematodes from the families Microphallidae and Heterophyidae cause gigantic growth whereas species from families Notocotylidae and Bunocotylidae have no effect on growth rate. This discrepancy is attributed to the different pathogenicity of the parasites. However, under experimental conditions with different host population densities the effect of infection by Bunocotyle progenetica effect varies from a tendency to stunt the growth (under high density) to a significant increase in growth rate (under low density). The effect of Himasthla sp. (Echinostomatidae) was shown to be population-specific. These findings agree with a previously reported hypothesis that the growth response of trematode-infected snails depends (among other things) on supplement of host-parasite system with food. Trematode infection caused parasitic castration in all studied host-parasite combinations. It is argued that the phenomenon of gigantism in infected snails is a consequence of the reduced sexual ability of the host. The correlation between snail growth rate and penis size of infected males was negative. The correlation between growth rate and penis size was not found in uninfected snails from the same age group

Dyopedos monacanthus inhabits self-constructed mud whips on marine soft-bottoms. Juveniles stay on the mud whip of their mother for extended time periods after they hatch from her brood pouch. During the main reproductive period in the spring, parental females have been observed in the aquarium and collected from the field. Specimens of D. monacanthus have been collected simultaneously from the intake filter from the sea-water laboratory. Several consecutive clutches have been found on the whip of one female. Most juveniles are small (1 mm in size), but they grow to sizes of >2 mm on the whip of their mother. In the aquarium, juveniles usually hatched immediately after the females had been attended by males. They then clung to their mother's whip for about two weeks. Most parental females in the aquarium produced three broods during a time period of about six weeks. In the field an average of 36 parental females m-2 were found in April, and an average number of 75 juveniles clung to each female's whip. The average number of juveniles found on the females’ whips declined in May and June. Many juveniles appeared in the sea-water intake filter starting in mid April. Most juveniles caught in the intake filter were between 2 and 3 mm in size which corresponds well with their size at leaving the female's whip. In mid May, all amphipods disappeared within a few days from the aquarium, when shrimp Crangon septemspinosa started to become more active again. Many big females disappeared in the field at that time too, and in mid June parental females were smaller than in the previous months. The amphipod D. monacanthus belongs in the category of epibenthic suspension-feeding amphipods. It is probably very susceptible to epibenthic predation and extended parental care is primarily a mechanism to lift very small juveniles above the viscous sublayer in the benthic boundary layer.

A series of field and laboratory experiments were conducted in order to assess whether the burrow-dwelling amphipod Corophium volutator, is a significant bioturbator of inter-tidal mud and sand flats where it often occurs at densities of tens of thousands per square metre. Comparisons of sediment characteristics, redox potential and meio- and macro-faunal populations in treatments with enhanced, natural and reduced densities of Corophium revealed effects on sediment physico-chemistry and on small meiofaunal-sized species, but these were weak and not always consistent. High densities of adult Corophium consistently depressed the abundance of smaller conspecifics although the mechanism of this interaction has not been identified. The results are discussed in the context of the ability of Corophium to promote the recovery of organically enriched sediments.

Sulphide occurs widely in marine sediments and is highly toxic to most organisms. Its principal poisoning effect occurs at extremely low concentrations and is the result of inhibition of mitochondrial cytochrome c oxidase. Mud-shrimps (Crustacea: Thalassinidea), construct burrows in sublittoral muddy sediments. The sediment in which they burrow is markedly reduced and conditions within the burrow are usually hypoxic and hypercapnic. Field measurements indicate that the shrimps may be exposed to potentially toxic levels of sulphide in the burrow water (range 0–206 μM, N=37). Laboratory experiments carried out on Calocaris macandreae, Callianassa subterranea and Jaxea nocturna have shown that these species have a high tolerance of sulphide. An oxygen dependent detoxification mechanism exists to defend cytochrome c oxidase from sulphide poisoning. The main detoxification product of this mechanism is thiosulphate which accumulates rapidly even during brief exposures to low concentrations of sulphide. Sulphite also appears as a secondary detoxification product. Aerobic metabolism can be maintained even under severe hypoxia and toxic sulphide conditions. The mud-shrimps switch to anaerobiosis when the detoxification mechanism is saturated. These data indicate that mud-shrimps are physiologically adapted to tolerate elevated levels of sulphide that they may encounter in their natural habitat.