Alpheus edwardsii Audouin and Alpheus lobidens de Man (Crustacea: Decapoda: Alpheidae) are two intertidal snapping shrimp that burrow in association with rocks. They are morphologically similar and are often found in the same intertidal zone. The competitive exclusion theory states that two co-existing species must partition resources. The partitioning of food items as a resource appears unlikely, as gut content analyses revealed that the two species have similar diets and the relationship of shrimp condition and shrimp density indicates that food supply was not in limited supply. Instead the two species partition the resources of space within the intertidal zone, and shelter. The two species were found to exist largely in isolation from each other. Alpheus edwardsii occurred across much of the intertidal zone. Within this range A. edwardsii were most abundant in substrata with a low proportion (<50%) of mud. These substrata are better suited to their elaborate method of burrow construction. The simpler burrow construction method of A. lobidens allows this species the potential to occupy a wide range of substratum types; however, they were found only in muddy substrata with substantial surface rock cover at tidal elevations of 1.18m above datum or below. The restriction of A. lobidens to this region of the intertidal zone is probably related, in part, to their physiological requirements. In regions of co-occurrence, A. lobidens were significantly smaller than A. edwardsii, and utilized smaller rocks as shelters, thus avoiding direct interspecific competition for this resource. The absence of large A. lobidens from these areas may reflect their ability to procure shelter in competition with A. edwardsii, as behavioural experiments conducted in this study found that A. edwardsii were the dominant competitors for this resource.

Ecological, behavioural and anatomical observations of a commensal bivalve, Peregrinamor ohshimai (Mollusca: Galeommatoidea), were carried out in a tidal mudflat in the Seto Inland Sea, Japan. The bivalve attached specifically to the longitudinal groove of the ventral side of the cephalothorax of thalassinidean burrowing shrimps, Upogebia major and Lf. narutensis (Crustacea: Decapoda), singly, dorso-ventrally and longitudinally, using its byssus, with its anterior part towards the head of the host. The mantle of the commensal bivalve has wide anterior (branchio-pedal) and narrow posterior (exhalant) apertures. In the living organism, the extended anterior edges of the mantle protrude from the shell and are inserted into the host's filtering basket, which is formed by the setal rows of the first two pairs of pereiopods and utilized for intercepting suspended matter. By beating its pleopods in a U-shaped burrow, the filter-feeding Upogebia shrimp creates water currents, which are also utilized by the commensal bivalve for filter-feeding. The shell length of the commensal bivalve was in proportion to the host's carapace length. This suggests that the veliger larva attaches to a young host and grows, thus maintaining the host-commensal morphological matching. The bivalve is a hermaphrodite and individuals of >8–5 mm in shell length were already producing eggs. Anatomical observations suggest that P. ohshimai is most closely related to the Montacutidae in Galeommatoidea.

Effects of oxygen supply on development rates of embryos in gelatinous masses were tested with natural masses of three species of opisthobranch gastropods and artificial masses made with embryos of a sea urchin and agarose gel. When diffusive exchange was restricted for embryos in such masses, increased oxygen alone was sufficient to maintain development rates of embryos. Diffusive supply of oxygen is therefore a limiting factor for embryos clustered in gelatinous masses. Development rates were constant over a wide range of experimentally altered oxygen concentrations but retarded with oxygen below about 10% of air saturation. Some opisthobranch embryos exposed to low oxygen concentrations hatched with shorter shells. Delayed hatching and shorter shells at hatching were both associated with a central position in the globose gelatinous mass of one of the opisthobranch species, even in air-saturated and vigorously stirred water. The pH near the centres of the masses was lower when embryos were at more advanced stages; thus the intracapsular stirring caused by cilia of embryos at later stages does not compensate for their greater metabolic rates. The pH in some egg masses was about seven or lower, and this pH affected development in separate experiments. The masses approach limits for removal of wastes, although oxygen becomes limiting for rates of development before accumulation of wastes becomes limiting. Embryos of opisthobranchs that are normally aggregated and embryos of sea urchins that are normally dispersed were similarly tolerant of low oxygen concentrations and low pH. In respect to tolerance of hypoxia and accumulating wastes, embryos in many clades are preadapted for aggregation into masses, but there are limits on the size of the aggregation. Egg masses are commonly at those limits.

Yellow-phase American eels, Anguilla rostrata, were displaced 10–17 km between tidal fresh water and salinity-stratified water and followed to determine the degree of home site fidelity, swiftness of homing and whether environmental factors affect orientation or homing behaviour. Twenty-one eels were tracked continuously (eight eels displaced up the estuary, eight down the estuary and five controls) in the Penobscot Estuary, Maine, USA for 4–80 h each, while recording position every 20 min. Nine of the 16 displaced eels (56%) returned to their capture site either during the track or shortly afterwards. Three of the remaining seven eels made substantial progress towards their capture site within the time observed. Eels homed with equal frequency whether displaced up or down the estuary in an average of 220 h ±87 (SE). After release, no eel moved farther away from its capture site. The eels were active mostly at night but used only the appropriate tidal currents rather than directed swimming to move about their home range and to home. Control tracks provided a home-range estimate in this habitat of 6.7 ±1.6 km of estuary or 325 ±64 ha. Lunar phase or position of the moon did not appear to influence either homing behaviour or activity patterns. This study shows that orientation and homing to a specific site in eels occurs relatively quickly and with no initial errors in orientation.

The epibiotic communities on locally abundant macroinvertebrates, in particular the brachiopod Liothyrella uva and the limpet Nacella concinna, were examined from depths between 0 and 50 m at Signy Island, Antarctica. The percentage cover by epibionts on Liothyrella increased from <20% on the smallest individuals to >50% on the largest, and decreased slightly with depth. The percentage cover of Nacella by epibionts increased with size of individual over an approximately similar range of values, but in contrast with Liothyrella increased greatly with depth. Cheilostome bryozoans and annelids of the genus Spirorbis formed >90% (by area) of the colonists on Liothyrella and 30–60% on Nacella, the coralline alga Lithothamnion and sponges making up the remainder. The bryozoans, which generally dominated the epibiotic communities, comprised complex associations of species which could be described as either generalists, host-specific epibiotic, low specificity epibiotic or locally abundant background species. Positive associations of both occurrence and abundance were found between some of the bryozoans living epibiotically on the brachiopod Liothyrella. The overgrowth interactions recorded, between the three main epibiotic faunal taxa; sponges, bryozoans and annelids, were essentially hierarchical. Sponges usually overgrew Bryozoa, and Bryozoa overgrew Spirorbis as well as occasion-ally smothering small brachiopods. In four adult Liothyrella death may have been caused by the epibiotic bryozoan Arachnopusia inchoata growing over the gape, so preventing feeding and/or respiration.

A mid-shore colonial algal turf community is described. Samples were analysed to determine if species composition, invertebrate epiphyte density, algal mat biomass, and the amount of sediment trapped among algal thalli differed with respect to substratum slope and wave height.

Colonial algal turf was approximately 1–3 cm in height and predominantly composed of a mixture of four species of eurythermal red algae, including Gelidium crinale (Turner) Lamouroux (Rhodophyceae: Gelidiales), Centroceras clavulatum (C. Agardh) Montagne, Polysiphonia denudata (Dillwyn) Kuetzing, and Bryocladia cuspidata (J. Agardh) De Toni (Rhodophyceae: Ceramiales). More delicate algae and algal epiphytes were found at stations with lower mean wave height, while non-epiphytic coralline algae were found only at stations with higher mean wave height. Algal mat mass was significantly greater on horizontal slopes than on vertical slopes, but did not differ with respect to wave-height levels. Algal mats trapped significantly more sediment on horizontal slopes with lower mean wave height.

Densities of the three most abundant invertebrate epiphytes appeared to be related to sediment deposition. Like sedimentation patterns, disparities in population densities on different substratum slopes increased with lower mean wave height. The highest densities of the amphipods Elasmopus rapax Costa and Hyale frequens Haswell (Crustacea: Peracarida) occurred on horizontal slopes at stations with significantly lower mean wave height. The highest densities of the tree oyster Isognomon bicolor C.B. Adams (Mollusca: Pterioida) were on vertical slopes at stations with significantly lower mean wave height. Barnacle epiphytes occurred in higher densities at stations receiving greater mean wave height, while dominant species of other crustaceans and molluscs had higher densities at stations with significantly lower mean wave height.

A new species, Diopatra marocensis, is described from the fine sand Abra alba community, Sidi Boulbra, south Moroccan Atlantic coast. The new species is a member of the D. cuprea complex and is characterized by having crescentic nuchal grooves, short ceratophores, a short branchiate region, four pairs of modified parapodia with bidentate pseudocompound hooks, pectinate setae with 11–20 teeth, limbate setae with conspicuously serrated shelf, and subacicular hooks from setiger 13–15. Eggs of Diopatra marocensis sp. nov. are deposited in the parental tube, where they undergo direct development and remain until the young consist of 32–34 setigers.

Ciona intestinalis has a well developed nerve plexus associated with the dorsal strand, as first described by Marco Fedele. The dorsal strand plexus is immunoreactive with antisera against gonadotropin-releasing hormone. Immunoreactivity is seen in the cell bodies, which lie peripherally, and in processes which run throughout the dorsal blood sinus, enter the branchial sac and penetrate the brain via the visceral nerve. The plexus provides a rich innervation of the gonoducts, and processes have been seen in the gonads. The pericardium is not innervated by processes from the plexus and the rectum is poorly innervated, but the full extent of the plexus in the viscera remains uncertain. While this study confirms many of Fedele's observations, it does not support the view that the dorsal strand plexus is equivalent to the vertebrate visceral nervous system.

The recently described gutless Astomonema southwardorum Austen, Warwick & Ryan 1993, from North Sea methane seeps lives in symbiosis with oval, extracellular bacteria completely filling the lumen of a modified gut. The bacterial strand is tightly lined by a thin layer representing very long intestinal cells of the host. The bacteria are 5.5–6.0 µm in maximum length and 3.5–4.0 µm in width. In the anterior body the alimentary tract is completely reduced. The structure and size of the symbiotic prokaryotes, as well as their extracellular location in the lumen of a non-functional gut, differ substantially from those in A. jenneri, the single species of this genus thoroughly studied electron-microscopically (Ott et al., 1982). These structural discrepancies suggest a careful reassessment of the genus Astomonema.

The colonization of microscopic organisms, commonly called a biofilm, was examined on fibreglass panels situated intertidally at Quibray Bay of Botany Bay in New South Wales, Australia. Panels were examined by incident light microscopy, measuring percentage cover, and by a computer image analysis technique, measuring optical density. Optical density was positively correlated with and was therefore a reliable estimate of total percentage cover of the biofilm. Optical density has not been used before in this application and, although some drawbacks are discussed, it is a much more efficient sampling method than microscopic examination of panels.

Lipids of sulphur-oxidizing bacteria isolated from Thyasim flexuosa had large amounts of 18:l(n-7) together with lesser amounts of both 16:l(n-7) and 16:0 as their major fatty acids. Smaller amounts of the cyclopropyl fatty acids, cyclic δ9,10 C16 and especially cyclic δll,12 C18 were also present. A similar pattern was found for methylotrophic bacteria isolated from Thyasira, Myrtea and Lucinoma, except that 16:l(n-7) and 16:0 were both present in larger amounts than 18:l(n-7) and small amounts of cyclic δ9,10 C16 and lesser amounts of cyclic All,12 C18 were present in all cases. The fatty acids 18:l(n-7), 16:l(n-7), 16:0, cyclic δ9,10 C16, and cyclic δll,12 C18 were all present in varying amounts in several free-living, non-marine, sulphur-oxidizing bacteria analysed, and in one bacterium both cyclic δ9,10 C18 and cyclic δll,12 C20 were abundant. Branched-chain fatty acids and polyunsaturated fatty acids were not detected in any of the sulphur-oxidizing or methylotrophic bacteria analysed. The lipids of the sulphur-oxidizing and methylotrophic bacteria consisted largely of phosphatidylethanolamine, phosphatidylglycerol and cardiolipin. The results are discussed in terms of fatty acids as indicators of nutritional relationships in bacterial-invertebrate symbioses.

Development in the genus Diopatra has been reviewed and divided into four patterns, ranging from brooding in the parental tube to presumed broadcast spawning (Paxton, 1993). While some information is available for numerous species, the identity of some is uncertain, or the information is only anecdotal. Only three species have been studied in detail. Eggs of D. cuprea are released in a jelly mass that readily dissolves in sea-water (Allen, 1959). Although natural spawning has not been observed for D. neapolitana, Cazaux (1972) was able to fertilize the eggs artificially and culture the larvae. The larvae of both species are lecithotrophic and free-swimming, indicating that they are broad-cast spawners.

Multi-locus DNA fingerprinting was used to determine the degree of genetic relatedness within localized assemblages of the intertidal isopod, Jaera albifrons (Crustacea: Isopoda). This isopod has marsupial development, restricted adult vagility and specific habitat preferences, which will tend to isolate groups of animals on a shore and can potentially maintain the integrity of broods after release from the mother. Total genomic DNA was extracted from six individuals from each of ten ‘rock-populations’ in the South Wales area, restricted with Rsal, Alulll and Haelll endonucleases, and probed using a (TCC)5 oligonucleotide probe. Band-sharing analysis of the fingerprint patterns indicated significantly higher genetic relatedness within rock-populations (mean within rock-population band-sharing value = 0–374 ±0–023 SE) than between (maximum between rock-population band-sharing value = 0–301 ±0033), and at a level that equates to a relatedness between individuals within rock-populations of slightly below half-sibling status. The significance of such findings, in terms of the potential for localized inbreeding and population genetic structure, is discussed.

Coelenterazine chemiluminescence is now established as the most common chemistry responsible for bioluminescence in the sea, being found in seven phyla. However, the organisms which synthesize coelenterazine have yet to be identified. In order to deter-mine whether the luminous midwater shrimp Systellaspis debilis (A. Milne Edwards) (Arthropoda: Decapoda) is capable of luciferin biosynthesis, a developmental series of eggs was assayed for its luciferin, coelenterazine. The advantages of this system are that S. debilis eggs are autonomous and therefore have no external nutrient supply, the embryos can be ranked for developmental stage and the large egg size allows clutch numbers to be determined accurately. Recombinant apo-aequorin, which requires coelenterazine for luminescence, was used to quantify coelenterazine during the developmental sequence. An increase of almost two orders of magnitude was detected in coelenterazine content per egg between the first and final stage of development (mean values of 1 pmol and 71 pmol). This demonstrates de novo biosynthesis of coelenterazine for the first time.

Thalassomonhystera bathislandica sp. nov. (Nematoda: Monhysteridae) was found in abundance in a few gelatinous phytodetritus aggregates collected from the surface of bottom sediments in the north-eastern Atlantic at depths of about 4000 m. The new species resembles T. islandica (De Coninck, 1943), an inhabitant of saltmarshes. Viscous detrital aggregates, including sediment agglutinations made by the nematodes themselves, are perceived as the preferred habitats of nematode species in fluffy surficial muds. It is suggested that physical constraints prevent nematodes from a fast invasion into freshly sedimented, loose detritus deposits.

Ridgeia piscesae from a hydrothermal vent and lucinid and thyasirid bivalves from inshore Canadian and UK waters, known to contain sulphur-oxidizing symbiotic bacteria, had lipids rich in 16:0,16:l(n-7) and 18:l(n-7) fatty acids in both bacteria-rich trophosome or gill tissue and in tissues without symbiotic bacteria. The results are consistent with the animals deriving these fatty acids from their sulphur-oxidizing symbionts. Ridgeia piscesae, Lucinoma annulata, Parvilucina tenuisculpta, Lucinoma borealis and Myrtea spinifera also contained substantial amounts of the non-methylene-interrupted dienoic fatty acids 20:2δ5,13 and 22:2δ7,15. It is proposed that these fatty acids are produced by chain elongation and δ5 desaturation in animal tissues of 18:l(n-7) produced by the bacterial symbionts. Thyasira flexuosa did not contain 20:2δ5,13 or 22:2δ7,15 but instead contained 18:l(n-ll) and 20:l(n-13) which were not present in the other species analysed. It is proposed that 18:l(n-ll) and 20:l(n-13) arise from the δ9 desaturation of 20:0 and 22:0, respectively, followed by chain shortening of the mono-unsaturated fatty acid products of δ9 desaturation. It is considered that 20:2δ5,13 and 22:2δ7,15 are formed in the animals in response to a relative excess of 16:0, 16:l(n-7) and 18:l(n-7), accompanied by a relative deficiency of (n-3) and (n-6) polyunsaturated fatty acids. The results are discussed in relation to the lipid nutrition of marine invertebrates containing bacterial symbionts.

Since the first visual observations of hydrothermal vents in the Eastern Pacific in 1976 (Lonsdale, 1977) these areas of the sea bed have been characterized by their spectacular, and in most cases, novel fauna. Of the 236 macrofaunal species described from hydro-thermal vents, 223 were new to science according to the most recent estimate (Tunniclif f e, 1991), although there are many species still awaiting description. The vent areas are characterized not only by the organisms present but by those which are apparently absent. Absentees include sponges, brachiopods, bryozoans, echiurans and echinoderms, although the last phylum is represented by occasional sightings of echinoids, ophiuroids and holothurians (Grassle, 1986; Tunnicliffe, 1991; Segonzac, 1992).

In the North Atlantic, the tubular agglutinated foraminifer Bathysiphon major occurs at bathyal depths off the coasts of North Carolina and north-west Africa. Apart from its large size (up to almost 10 cm long), the most distinctive feature of this species is the appearance of the test wall which has a sooty black outer layer, about 20μm thick, overlying a much thicker layer, pure white in colour and consisting of sponge spicules and small quartz grains. The black layer is composed of irregularly shaped, plate-like particles, 1–25 (xm in size. The nature and composition of these particles has been studied using light and electron microscopy, x-ray microanalysis, electron diffraction analysis and infrared spectroscopy. The particles contain calcium and phosphorous and have electron diffraction patterns and infrared spectra consistent with a hydroxyapatite composition. Minor amounts of iron are probably responsible for their black colour. We believe that this represents the first report of apatite-like (phosphorite) particles occurring in the test of an agglutinated foraminifer. The particles are most likely to originate as phosphorite grains which are agglutinated by the foraminifer, although the possibility of authigenic precipitation cannot be eliminated. The function of the outer black layer is unknown.

Induction of metallothionein synthesis in Littorina littorea exposed to cadmium (400 µg I-1) is tissue dependent. Concentrations of the metal-binding protein increased by a factor of four in the gills and by a factor of three in the kidney.

Gel filtration chromatography of heat-treated cytosolic extracts reveals that cadmium, accumulated in both the gills and the kidney, is bound principally to the newly formed metallothionein. Cadmium saturation of the protein (at an MT:Cd molar ratio of 1:5) and the approach of steady-state condition for Cd accumulation was indicated in the latter tissue, but there was little evidence for Cd equilibrium in gills.

Metallothionein levels in the kidney of L. littorea can be determined on a routine basis in laboratory experiments and in field samples by differential pulse polarography of wholecytosol preparations: heat-treatment/centrifugation is sufficient to remove most of the interference from high-molecular-weight thiolic proteins. In contrast, the use of gelfiltration chromatography is recommended alongside polarographic analysis of the gill cytosol to enable quantification of, and compensation for, such interferences, and hence to ensure that only metallothionein is determined.

Measurements of metallothionein induction in the kidney of Littorina may therefore prove useful in the determination of sublethal biological response to metal contamination. Background metallothionein concentrations of 3–4 mg g-1 (measured polarographically) serve as a baseline against which samples from contaminated sites can be assessed.

INTRODUCTION

Exposure of marine organisms to metals such as cadmium can induce the synthesis of low molecular weight, cysteine-rich proteins, metallothioneins (MTs), which are capable of sequestering and detoxifying excess intra-cellular metal.

Population dynamics and production of the spionid polychaete Marenzelleria viridis were studied at Great Sippewissett salt marsh (Massachusetts, USA) for two years. Marenzelleria viridis was the main contributor in biomass and production to the macroinfaunal assemblages of the sandy organic sediments of the marsh. Marenzelleria viridis spawned during the cold part of the year and the appearance of settled larvae on sediments was observed from January to May. The density of M. viridis rose sharply from winter to late spring followed by a striking drop through summer. The estimated mean annual production of M. viridis was 60.0 g dry weight m2 during the first year and 26.3 g dry weight m2 during the second year. The population of M. viridis is affected by different processes during the year. The number of initial recruits seems to be largely governed by meteorological conditions. The numbers of recruits are then affected by competition for resources, and later, as predators become active, predation pressure determines the abundance of the population of M. viridis.