In the Plymouth area Sabellaria spinulosa Leuckart is common on stones and shells below low tide mark in the Sound and on outside dredging and trawling grounds. It is often found on living Pecten maximus, much more rarely on Chlamys opercularis, and it is frequent on shells of Buccinum undatum, especially those inhabited by hermit crabs. Several tubes may be found close together, sometimes in contact, but it does not form massive colonies as it does on some shores bordering the North Sea and in deeper water of that region (McIntosh, 1922, pp. 14, 20). It is a smaller species than S. alveolata (L.) and its tubes, built mostly of mineral grains, are harder and stronger than those of the latter. At Plymouth the tubes attached to Pecten shells are usually larger, stronger, and include bigger grains, and are cleaner than are those on stones dredged in the Sound. Empty tubes are common, especially on stones and loose shells, and such tubes are sometimes tennanted by other worms.

The blue mussel, Mytilus edulis, and the Mediterranean mussel, Mytilus galloprovincialis, occur widely over much of northern Europe, and wherever they are sympatric they hybridize. The hybrid zone is large, ranging from western France to the north of Scotland, and is spatially complex, containing a mixture of pure, hybrid and introgressed individuals. Results from an Irish study in 1981, using partially diagnostic allozyme markers, indicated that mussels on the Irish Sea coast were solely M. edulis, but on Atlantic wave-exposed shores, and to a much lesser extent on wave-protected shores, mussels comprised an interbreeding mixture of M. edulis and M. galloprovincialis. In this study mussels were analysed from 20 locations on Irish coasts, using the Me15/16 nuclear DNA marker. The results showed a high frequency of M. galloprovincialis (0.378 ± 0.198) and hybrid (0.429 ± 0.175) genotypes, and correspondingly low frequencies of the M. edulis genotype (0.194 ± 0.107) at both exposed and sheltered locations on Atlantic coasts, indicating no apparent advantage for the M. edulis genotype at wave-protected sites. Mytilus galloprovincialis was virtually absent from the Irish Sea. Mussels in this area may be a self-recruiting population of M. edulis due to thermal front development at the northern and southern entrances to the Irish Sea in late spring, thereby preventing an influx of spring-spawned Mytilus larvae. The apparent change in the genetic composition of mussels on Atlantic coasts since the early 1980s could be related to climate change, or to aquaculture practice in Ireland whereby mussels from exposed shores are used to seed ropes in wave-protected bays and estuaries.

Various workers during the past century have figured sensory cells bearing cilia amongst the ordinary non-ciliated epidermal cells of the body surface. Similar sensory cells were also found on the buccal cirrhi, and on the velar tentacles at the entry to the atrium. This earlier work at the light microscope level was summarized by Franz (1923) in his excellent review. More recently Schulte & Riehl (1977) have re-examined the innervation of the oral region and buccal cirrhi at the ultrastructural level, and observed two types of sensory cell in these regions, distinguished by their apical structure. They suggest that these are both secondary sensory neurons (as Franz had previously surmised), but their figures hardly make this suggestion convincing. In this note we show that there is probably only a single type of sensory cell amongst the epidermal cells of the body surface and buccal cirrhi; that it synapses at its base with incoming axons of central cells, and that a different type is indeed found in amphioxus, but only in the velar tentacles.

The accumulation of radioactive Cs has been studied in species from the principal marine invertebrate phyla. In some species the accumulation of radioactive Cs has been compared with that of 42K and equilibrium levels of both isotopes have been related to the distribution of inactive K.

Radioactive Cs is always absorbed more slowly than 42K. Most of the inactive K is readily exchangeable with 42K so that at equilibrium inactive and active concentration factors are nearly equal. Whole animal concentration factors for radioactive Cs at equilibrium varied between 1·2 and 14 in unfed animals. These factors usually exceed those for inactive K because, although body fluid concentration factors are similar for both ions, the tissue/body fluid ratios for radioactive Cs exceed those for inactive K. Radioactive Cs penetrates rapidly into body fluids, so that uptake by the tissues is the limiting factor in accumulation. Although Cs is absorbed much more slowly than K, the eventual distribution of Cs between the tissues and body fluid of a particular species appears to bear a relationship to the distribution of K.

No evidence has been found to suggest that Cs is a necessary element which is absorbed specifically.

The short-term response of Mediterranean upper infralittoral macroalgal species to experimental human trampling was investigated. Disturbances of six different intensities were applied within the integral reserve of the Ustica Island marine protected area (Italy, Mediterranean Sea). The dominant macroalgal species Cystoseira brachicarpa v. balearica and Dictyota mediterranea were strongly affected by human trampling. Higher levels of disturbance significantly affected both algal percentage cover and canopy at an increasing rate. Three months after trampling, for both variables it was highlighted that the algal recovery from disturbance was incomplete, being significantly different among trampling intensities. The current study revealed that in the short-term it was not possible to identify critical levels of trampling that are sustainable for this shallow community.

The relative distribution of sperm whales (Physeter macrocephalus) and sea surface temperature (SST) fronts have been studied in summer in the north-western Mediterranean Sea. We used passive acoustic data (778 samples) obtained offshore during dedicated surveys between 1999 and 2004 and Pathfinder/Modis remote sensing data to compute front maps and to calculate mean distances from sperm whale detections (N=132) to SST-fronts. Mean distances from sperm whale acoustic detections to SST-fronts were significantly lower (10.4 km) than from other acoustic samples to those fronts (17.0 km). The same result was obtained when calculating distances from sperm whales to the North Balearic Front surface signature. If sperm whales are commonly observed along the continental slope, we showed that offshore individuals were located close to SST-fronts. This bimodal distribution in the north-western Mediterranean is linked to sperm whale feeding strategy, demonstrating ecological opportunistic behaviour in this high level predator.

The predatory caenogastropod Hexaplex trunculus employed different methods to access different species of bivalve prey characterized by different shell thicknesses. Hexaplex trunculus drilled Callista chione and Venus verrucosa at their shell margins but the latter species also laterally. It also attempted to drill two species of Tapes but successfully penetrated these only after chipping the shell margin. Chipping, whereby a labral spine is forcibly pushed between the prey's valves, especially posteriorly, to break them followed by proboscis insertion, was typically applied to access the thinner shelled prey Cerastoderma glaucum whereas Modiolus barbatus and Mytilus galloprovincialis were either chipped or drilled. The pattern of M. galloprovincialis shell penetration appears related to predator and prey size. Small (40 mm shell height) H. trunculus tended to drill rather than marginally chip M. galloprovincialis. Medium sized (55 mm shell height) H. trunculus either chipped or drilled M. galloprovincialis in approximately equal proportions but also at the valve margin. Larger (70 mm shell height) H. trunculus tended to laterally drill average sized (35 mm shell length) and the biggest (65 mm shell length) M. galloprovincialis. When larger M. galloprovincialis are attacked it thus becomes increasingly more difficult for H. trunculus to chip and drill the shell margin, possibly because the periostracum is thicker here in such individuals, and the predator resorts to lateral drilling. This is possible because as the mytilid ages its surface periostracum becomes progressively eroded and thus thinner and easier to access. Scanning electron microscopy (SEM) identified shell microstructure damage which shows that the chipping and drilling behaviours of H. trunculus result from labral spine damage and dissolutional etching, respectively, rather than mechanical radula rasping. These observations have implications for the use of such predation marks to identify the predator taxon implicated from holes in either empty Recent shells or fossil material.

The nitrogen cycle in the sea is reviewed as a whole in accordance with the scheme set out in Fig. 1. This summary includes only original matter, since the survey of other work does not admit of further condensation. The metabolism has been discussed of the following sources of nitrogen available to plants in sea water: mono, di and trimethylamine, trimethylamine oxide, urea, amino-acids, ammonia, hyponitrite, nitrite and nitrate. The methylamines will interfere in analyses of ammonia by distillation. Thermodynamic methods have been extensively used. The equilibrium between urea and ammonium cyanate at sea-water concentrations favours the cyanate. In sea water containing 28 mg. ammonia N per cu. m., the equilibrium mixture will contain fifteen times as much cyanate as urea. Hydrolysis of urea is probably purely chemical.

Herring (Clupea harengus L.) show a marked ‘startle’ response when subjected to sound stimuli from a vibrating source (Blaxter, Gray & Denton, 1981c). The response, which occurs at a consistent threshold, is elicited by the first cycle of a tone burst or noise, the threshold to one cycle being the same as for a burst of many cycles. Furthermore, if the onset of the tone burst is ‘ramped’ so that it takes several cycles for the full amplitude to be reached, the threshold is markedly raised. Under some conditions the fish move away from the source, showing that they can determine its direction even though the stimulus is confined to a single cycle. The relative roles of sound pressure and particle velocity in providing information about the amplitude and direction of the noise have not been firmly established. Present evidence suggests that pressure is important in triggering the response and probably in measuring the strength of the stimulus. A vector such as particle velocity provides the directional information used in the response. The response can be very fast with a latency of about 25 msec and a contraction time of about 20 msec (Blaxter, Denton & Gray, 1981 b). In these very fast reactions the Mauthner cells probably constitute the motor pathway (Diamond, 1971).

The diet of Dipturus chilensis was composed mainly of the nototheniid fish Patagonotothen ramsayi, squid Illex argentinus, hake Merluccius hubbsi, serolid isopods, and crustaceans. Our results suggest that D. chilensis feeds selectively on some teleosts and rejects eel-like fishes. Total length of consumed P. ramsayi was significantly correlated with the skate's mouth width.

Spirorbis rupestris sp.nov. has a sinistrally coiled, unridged tube and is distinguished from S. borealis Daudin only by colour, small morphological details and striking differences in larval behaviour. Though the larvae are capable of swimming, they do not usually do so, but crawl about and soon attach themselves to rock surfaces near the tubes of their parents, particularly when stimulated by the presence of the coralline alga Lithophyllum incrustans. They will not settle on Fucus serratus.

S. rupestris is found typically on rock surfaces in well-illuminated places throughout the lower half of the shore, generally associated with Lithophyllum. It is abundant on the shores of south-west Britain, except where there is scouring by wave-borne particles.

Rainbow trout were exposed to five different concentrations of a unialgal culture of Gyrodinium aureolum in laboratory tanks. All the concentrations used proved lethal within 24 h. The gills of the dead fish showed no mechanical occlusion by the algae but all displayed marked histological changes characterized by necrotic degeneration and disintegration of the lamellar epithelium.

The biology of young scallops Pecten maximus (Mollusca: Bivalvia) was examined using SCUBA diving. Within shallow and sheltered bays settlement took place near adult populations. Surfaces to which scallops attached were generally free of silt; these included algae, invertebrate tests and inorganic materials. Detachment could take place amongst individuals of 1 mm; however, in sheltered bays most remained attached until 4–13 mm. Following detachment scallops recessed in sediment. They were subject to dispersal by water turbulence and swimming induced by sea-stars. There was evidence to suggest high mortality from crab and sea-star predation during the summer and autumn.

The caridean shrimp Rimicaris exoculata, Chorocaris chacei and Mirocaris fortunata, together with bathymodiolid mussels, dominate the vent fauna along the Mid-Atlantic Ridge. Vent shrimp show the characteristic reproductive patterns of caridean decapods. The gonads are paired organs overlying the digestive gland under the carapace. In the ovaries, the oogonia (∼20-30 μm diameter) proliferate in the germinal epithelium at the periphery of the gonad, developing into previtellogenic oocytes. The previtellogenic oocytes grow to 70-100 μm before undergoing vitellogenesis. The maximum size for mature oocytes ranged between 200 and 500 μm depending on the species and the sample. The oocyte size–frequency data show no evidence of synchrony in oogenesis at population level for any of the species studied. Mirocaris fortunata is the only species where gravid females are commonly collected. The brood is carried on the pleopods, and the number of eggs per female ranges from 25 to 503, with a mean egg length of 0.79±0.14 mm. There is a positive correlation between fecundity and body size, characteristic of crustaceans. One ovigerous C. chacei and two R.exoculata have been studied. The former was carrying 2510 eggs and the later 988 small eggs in an early stage of development. The fecundity of M. fortunata, C. chacei and R. exoculata is significantly higher than that of species from the Acanthephyra group collected in the north-east Atlantic.

The defensive behaviour of 11 species of sea anemone when attacked by the nudibranch Aeolidia papillosa is described. An attempt is made to correlate their defensive responses with the habitat, and with the food preferences of Aeolidia. Actinia equina responds first by tentacle and column retraction, and then by inflation of the column, pedal locomotion, and detachment from the substrate. Anthopleura elegantissima responds in similar ways, but Anemonia sulcata, which has much longer tentacles, uses these in active defence against the eolid. Anemonia also crawls away but it does not detach.

Actinia, Anthopleura and Anemonia are the preferred foods of Aeolidia. They commonly live in dense colonies where locomotion and detachment are likely to result in escape. Tealia felina is less preferred and is much less responsive when attacked by Aeolidia.

Anemones which possess acontia normally eject these when they are attacked by Aeolidia. Although Aeolidia does occasionally eat acontian anemones, evidence is presented which suggests that acontia have some deterrent effect on this predator. Although most acontian anemones are probably able to move by pedal locomotion and to detach from the substrate, these responses are much less frequently given than by Actinia equina.

Evidence is presented from a study of Actinia equina var. mesembryanthemum at Bembridge, Isle of Wight, which suggests that brooded young do not represent a random sample from a free-living larval pool. Parents in the laboratory will not accept juveniles placed on their oral disc. A. equina are, therefore, unlikely to be adoptive parents. Esterase heterozygote parents contain only heterozygote young. Sexual reproduction cannot account for this observation unless a parent selects its brood. As A. equina can distinguish self from non-self and juveniles may reproduce asexually, a fertilization - selection - cloning theory of reproduction is considered which could account for what is otherwise a conflicting body of evidence.

INTRODUCTION

The common mussel Mytilus edulis L. is one of the most successful shore molluscs. It is widely distributed in the northern hemisphere and is abundant not only in the most sheltered bays and loughs but also in conditions of extreme exposure (Lewis, 1964; Seed, 1976). Attachment to the substratum is by means of the proteinaceous byssus complex, the strength of which has been shown to vary seasonally (Price, 1980b). This variation could be a response to seasonal fluctuations in wave action, as suggested by Pieters et al. (1978), or may result from the seasonality of other environmental variables. Some of these, e.g. salinity and sea temperature, have been shown to influence byssus production (Glaus, 1968; Van Winkle, 1970; Allen et al. 1976), Phytoplankton density, spawning and the reduced ‘scope for growth’ during winter months (Bayne & Widdows, 1978) may also play a role in determining byssus strength.

In the present study, the relationships between byssal attachment strength and environmental and other variables are examined in a population of mussels on the South Wales coast.

Tigriopus fulvus can live normally within a salinity range of from 4·2 to 90%.

In waters of salinities above 90% it falls into a state of apparent death from which it can recover if transferred back to lower salinities.

The relation between immersion period and the recovery period is only slightly different at different salinities.

The lethal temperatures vary between 32·0 and 41·8°C depending on the salinity of the sea water, the lethal temperature being higher in higher salinities.

The fluctuations in salinity and temperature in the pools where the animals were collected are well within their tolerance limits.

T. fulvus is well adapted to its habitat.

On the north-eastern coast of Sardinia, from November 2004 to January 2006, the first attempt in the Mediterranean basin to obtain information on encounter rate, group size and incidental capture of bottlenose dolphins in a marine fish farm was assessed, combining direct observations from fish farm boats with photo-identification studies. During 15 months of research, 79 d (65.3% of the total monitored days) were spent in direct observation of 146 groups of bottlenose dolphins around the fish farm cages. There was a peak in bottlenose dolphin presence during winter. Photographs were taken in the fish farm area during 79 encounters on 61 different days (totalling 34 marked individuals). The regular occurrence of some dolphins suggests individual preferences for the fish farm area. The incidental bottlenose dolphin capture observed in large, loose predator nets (1 dolphin per month) is cause for concern, as it is questionable whether or not the bottlenose dolphins in the area can sustain incidental capture of this magnitude. The information gained from this study shows the necessity for further regulations to be established, both in the use of predator nets and management of marine fish farms.

Studies of the dispersal behaviour of marine and estuarine benthic invertebrates have concentrated on the majority of species where the individuals disperse as a planktonic larva. The view that seems to be prevalent, summarised by Crisp (1974, 1976), is that larvae are an adaptation to allow species to colonise transient habitats and for species with adults of limited mobility to colonise distant habitats. The spreading of the species over wide areas has the advantages of reducing competition and facilitating greater genetic diversity, leaving the species more adaptable to subsequent environmental changes. These advantages are greater with longer distances travelled, and are an explanation for larvae spending up to several weeks drifting in the plankton, despite the acknowledged high mortality rates associated with the pelagic existence.