Gametogenesis has been studied in four cirratulid polychaetes: Caulleriella caput-esocis, Tharyx marioni, Cirriformia tentaculata and Cirratulus cirratus.

In all four species, sperm development follows a similar course of events, with the sperm cells being grouped in spheres and then platelets before developing tails to give rosettes which finally disintegrate to release the active spermatozoa. Except in Cirratulus, there is a well-defined annual cycle in the development of sperm.

Oogenesis in Caulleriella and Cirriformia is similar in that the growth curve of the oocytes is roughly sigmoid. In Tharyx the release of the oocytes to the coelom is delayed and discrete ovaries are formed, only the later stages of oocyte growth taking place within the coelom. In contrast to the above three species, oogenesis in Cirratulus does not show an annual cycle.

Maturation of the oocytes within the coelom prior to shedding has been established in Tharyx, Cirratulus and Cirriformia. In the former two species meiosis proceeds as far as the metaphase I stage and in the latter to the anaphase I stage, before the oocytes are released. Fertilizations were achieved only with oocytes which had matured in all three species. In the fourth species, Caulleriella, no fertile oocytes were discovered.

The diameters of the mature oocytes and the main spawning seasons of the four species at Plymouth are as follows: Caulleriella, about 110 μ (August to October); Tharyx, 200– 220 μ (late October to early November); Cirriformia, about 117 μ (late June to early July); Cirratulus, 135–150 μ (throughout the year).

Little is known about cetacean communities in the tropical and sub-tropical Atlantic. This paper describes the cetacean community found east of Great Abaco in the northern Bahamas (26·5°N) during summer months between 1998 and 2001. Nine species of cetaceans were recorded, which could be divided into two distinct groupings: firstly, ‘permanent’ species, which had relative sightings rates between 0·026–0·084 sightings per hour and which were recorded on many occasions in all years and most months; secondly, ‘sporadic’ species, which had relative sightings rates an order of magnitude lower (0·004–0·008 sightings per hour) and which were recorded on very few occasions. The ‘permanent’ species were the Stenella frontalis (Atlantic spotted dolphin), Kogia simus (the dwarf sperm whale), Mesoplodon densirostris (Blainville's beaked whale) and Ziphius cavirostris (Cuvier's beaked whale). These four species differed significantly in the depth of grid squares utilized (χ=20·25, df=9, P<0·01) suggesting that these species occupied four separate niches. Stenella frontalis dominated the surface feeding niche, while the remaining three deep-diving species segregated into different depth ranges. Kogia simus was the dominant species in water depths of less than 200 m, M. densirostris in water depths of 200 to 1000 m and Z. cavirostris in water depths of greater than 1000 m. The overall relative density (2·533 individuals per hour of effort) and diversity of species in the study area was relatively low and may relate to low levels of local productivity. It is hypothesized that the four ‘permanent’ species may competitively exclude ecologically similar species, resulting in a reduced number of species and that ‘sporadic’ species may only enter the study area during times of higher than usual productivity when the ‘permanent’ species are no longer able to dominate their individual niches.

Rocky shore intertidal communities along the cold- and warm-temperate coasts of the south-western Atlantic are dominated by small mussels of the genus Brachidontes s.l. (Mytilidae), yet the status of species occurring in the region remains unresolved. Taxonomic studies have been based on shell morphology, but high phenotypic variability has led to much confusion. Based on mitochondrial and nuclear genes (COI, 28S rDNA and ITS1) from nine localities in Uruguay and Argentina we confirmed the occurrence of three species in the south-western Atlantic: Brachidontes darwinianus and B. rodriguezii in the warm-temperate and B. purpuratus in the cold-temperate sector. The latter two species coexist in the same beds along the transition zone (41–43°S). The phylogeny based on mitochondrial and nuclear genes, indicate an early divergence of B. purpuratus. At the intra-specific level, low genetic differentiation and absence of fossil record for B. purpuratus from the earlier Quaternary marine terraces of Patagonia likely result from a relatively recent (post-LGM) colonization originated from populations in the south-eastern Pacific. In the case of B. rodriguezii, by contrast, genetic intraspecific differentiation, a fossil record of phenotypically-related forms going back to the Late Miocene, and phylogenetic position in the COI-based phylogeny, prompts the hypothesis that this species is derived from a local stock with a long history of occurrence in the warm-temperate region of the south-western Atlantic. While intertidal mussel beds from the south-western Atlantic are ecologically similar in appearance, their assembly involves components clearly differentiated in terms of historical biogeography and phylogeny.

This paper presents results of an ecological study towards high-tide level near the mouth of the Dovey estuary, carried out in 1925–6. The area was treated as an extension of the sea floor, the only comparable work at that time being submarine. Petersen (1918) showed that on the bed of shallow seas the fauna could be grouped into “animal communities”, whose constitution was determined by depth, distance from shore, shelter and salinity. Analysed with regard to distance from high-water mark, and degree of shelter, the fauna of this part of the estuary shows Petersen's Macoma community over most of the area, with a Corophium community at high tide in the more sheltered part. Davis (1925), in the North Sea, substituted “soil associations” as an alternative ecological unit, a certain grade of soil carrying its typical fauna wherever it might be found. The two groupings already found in the Dovey estuary clearly emerged as soil associations, after adoption of a reliable method for analysis of fine-grade soils. Up to the present, oceanographers have used sieves or elutriation for soil analysis. Up to the present, oceanographers have used sieves or elutriation for soil analysis. These methods are unsatisfactory for examinations of estuarine soils, with their large proportion of fine material.

Eight species of the Gobiidae were recorded in weekly samples taken between July 1972 and June 1977 from the intake screens of Oldbury Power Station in the inner Severn Estuary. Buenia jeffreysii, Aphia minuta, Gobius paganellus and Gobius niger occurred infrequently and Crystallogobius linearis was only common in the late spring and summer of 1975 and 1976. Pomatoschistus microps, which peaked in numbers in the winter, increased in abundance each year between 1972 and 1977. The most numerous gobies were those belonging to the Pomatoschistus minutus complex which were separated into P. minutus and P. lozanoi only between June 1974 and July 1975. Seasonal trends in the abundance of these two species were similar, with elevated numbers occurring between July and September 1974 and in January 1975. Gonadosomatic indices and other data indicate that the decline in numbers after the latter month represented an emigration to spawning areas further down the estuary or in the Bristol Channel. Although P. minutus attained a larger body size than P. lozanoi, both these species and P. microps typically had a one year life cycle with only a small number of individuals surviving for a further few months. The fecundity of P. lozanoi, which ranged from 410–2453 (mean 1270), was lower than that reported for P. minutus in this and other studies. Analysis of stomach contents showed that the diet of both species was similar, consisting predominantly of gammarids and mysids. While both species were infected with Ligula intestinalis, the incidence of infection and the parasite index was greater in P. lozanoi than in P. minutus.

Culture of mussels, Mytilus edulis L. is a developing industry in Irish coastal waters. Settling larvae are collected on 10 m long ropes which are suspended from g.r.p. rafts at a density of five ropes per square metre or from paired long lines, buoyed by plastic floats, at a density of some four hundred ropes per hundred metres. Mussels are harvested after eighteen months when the ropes yield up to 5 kg live weight per metre or approximately 250 kg m−2. Commercial culture at this density clearly exerts a considerable effect on energy and nutrient flow in the coastal ecosystem. In order to quantify the role of cultured mussels we investigated the carbon and nitrogen budget for production rafts and long lines in Killary Harbour, a fjordic inlet on the Irish west coast (Rodhouse et al. 1984) and compared these with estimates for the wild population on the shore.

The Aegean Sea, due to the complexity and variety of morphological features, bathymetry, hydrological, hydrodynamic features and climatic characteristics, offers a unique opportunity for monitoring the spreading and/or invasion of alien biota. It is known that the establishment of warm/tropical marine alien species is related mainly to the increase in sea temperature. A significant increase in aliens' number along the southern Aegean (Dodecanese) coasts has been documented in the last twenty years, while their arrival has produced evident changes in coastal ecosystem composition and function. Although the study area acts as a crossroad for tropical alien species introduction in the eastern Mediterranean Sea, a direct attempt to link temperature alterations with new alien species arrivals has not been performed. Satellite and in situ derived marine temperature data showed that the study area has gone through a remarkable warming, while the link between global temperatures and regional ones revealed that this warming is not a local phenomenon but part of global climate trends. Examining relationships between new alien species arrivals data since 1929 against global temperatures, it is shown that their introduction rate parallels the significant increase of marine temperatures. The association of alien introductions with marine water warming, as well as potential effects on ecosystem functioning of selected species is discussed.

Many sacoglossan sea slugs utilize chloroplasts ingested from food algae for photosynthesis (functional kleptoplasty), and the extent and duration of kleptoplast retention differs greatly among sacoglossan species. Although most recent studies focus on the genetic, microscopic, or physiological mechanisms responsible for this unique phenomenon, its effects on the life history traits of sacoglossans have not been fully explored. To study the effects of light conditions on survival and weight retention, adult individuals of two sacoglossan species, Elysia trisinuata and Plakobranchus ocellatus (‘black type'), were reared under light conditions (a 14-hour light: 10-hour dark photoperiod with an irradiance level of 28 µmol m−2s−1) or complete darkness for 21 days. There was no significant difference in the survival rate between the light and dark treatments for E. trisinuata, and its wet weight relative to the initial weight was smaller in the light than in the dark. However, both the survival and relative weights were greater in the light than dark for P. ocellatus. Based on the fluorescent yield measurement using pulse-amplitude-modulated fluorometry, the retention duration of functional chloroplasts was longer (>17 days) for P. ocellatus than E. trisinuata (<4 days). These results indicate that P. ocellatus benefits from photosynthesis for survival and growth, whereas E. trisinuata does not under starved conditions. This interspecific difference is likely related to the period of functional chloroplast retention.

Xenophyophores are a group of giant deep sea protists characterized by intracellular barium sulphate (BaSO4) crystals. X-ray diffraction, electron diffraction and electron microscopy studies have been performed on barium sulphate crystals from three xenophyophore species (Aschemonella ramuliformis, Reticulammina labyrinthica, Galatheammina lamina) obtained at bathyal and abyssal depths in the north-eastern Atlantic. Two populations of crystals were observed. The first were tablets, ~2μm in length and rhombic or hexagonal in outline. In both cases, the tabular face was of index (100). The second population consisted of much smaller particles (<0·5 μm) of poor crystallinity. A comparison of the larger xenophyophore crystals with synthetically grown crystals indicated that the former probably grew at low supersaturation (S<25) in solutions of low to moderate ionic strength (I<l·0 M). Some preliminary observations of the cellular organisation of A. ramuliformis are reported. The protoplasm is multinucleate and characterized by what seems to be a system of extracellular lacunae formed by imaginations of the cell wall. Similar features have been observed in the deep sea foraminiferan Rhizammina algaeformis. Possible origins of the BaSO4 crystals and the taxonomic relationship between xenophyophores and certain foraminiferans are discussed.

Manatee mortality in Ceará State (north-eastern Brazil) is analysed from twenty-five strandings between 1987 and 2002. The majority of the causes were related to the ‘dependent calf’ category (83.3%). Direct human-related causes were attributed to incidental catches in fishing gear (shrimp trawling and gill-nets) (12.5%) and direct capture (4.2%). Spatial distribution was not uniform, with the highest number of strandings on the east coast. The number of strandings has increased since 1999, and the seasonal distribution showed peaks in February, March and January, in that order. The stranding of manatee calves in Ceará State seems to be indirectly related to human activities that impact coastal nursing habitats.

A global study of latitudinal gradients in biodiversity of marine shallow-water, motile epifauna of hard substrata has been initiated by Plymouth Marine Laboratory and the International Association of Meiobenthologists. It is based on the use of artificial substratum units (ASUs) consisting of four pan-scourers and emphasizes the standardization of habitat type and complexity, sample area, sampling strategies, sample processing and analysis. Non-comparability of these factors has invalidated some of the few previous studies on global patterns in biodiversity of marine benthic communities which are reported in the literature. A list of sampling locations and participating research organizations is given along with some preliminary results from one location (south-west England).

The digenetic trematode Proctoeces subtenuis (Linton, 1907) is recorded from the kidney of the lamellibranch Scrobicularia plana (da Costa). At Chalkwell in Essex all of nearly a thousand S. plana examined were found to be infected, as were three of approximately 150 S. plana at Whitstable in Kent. The average number of parasites per host was between four and five. No Proctoeces subtenuis were found in Scrobicularia plana examined from other localities in Essex, Devon, Wales and Suffolk. The environmental conditions of a parasite in the lamellibranch kidney are discussed. It was found that the kidney fluid surrounding the parasites varies in osmotic pressure.

The anatomy of the parasite is described. The excretory bladder has a cellular wall, thus disagreeing with the inclusion of Proctoeces subtenuis in La Rue's superorder Anepitheliocystidia. The red colour of the parasite is due to a native haem pigment. The egg capsules are hardened by a quinone-tanning mechanism, but incubation with catechol, protocatechuic acid, and dopa failed to reveal the presence of a phenol-oxidase.

The species of Proctoeces are reviewed, and some revisions suggested. P. magnorus Manter, 1940 is considered a synonym of P. subtenuis, and the synonymy of P. erythraeus Odhner, 1911 with P. subtenuis is confirmed. The differences between P. insolitus (Nicoll, 1915) and P. subtenuis, and between P. maculatus (Looss, 1901) and P. subtenuis, require re-examination. It is considered that P. macrovitellus Winter, 1954 should be excluded from the genus Proctoeces. A definitive host list of Proctoeces spp. is given.

The adult nature of P. subtenuis from Scrobicularia plana is discussed, and it is suggested that Proctoeces subtenuis in the Thames estuary shows an abbreviated life cycle restricted to invertebrate hosts.

Data on the distribution of dinoflagellates in the surface waters around the British Isles in July 1977 were analysed by correspondence analysis. Four communities of dinoflagellates were recognized, and the occurrence of each was related to various environmental parameters. The vertical stability of the water column is considered to be the most important factor in determining the relative abundance of individual species.

A comparison of the years 1923, 1924 and 1925 as regards the phosphate content of the water at Station El in the English Channel has shown that the vernal diminution was earliest in the year 1924, and latest in 1923, the extreme difference being approximately two months. These differences stand in direct relation to the spring sunshine, that of 1924 for the daily average of the 9th to 12th weeks inclusive being 2-3 hours in excess of the normal, 1923 being 0-1 hr. in deficit and 1925 being 0-6 hr. in excess. Since the phosphate diminution is proportional to the increase in phytoplankton the year 1924 must have been exceptionally early in this respect.

The year 1925 was in general similar to the other two in having a summer phosphate minimum and a winter maximum; but it was noticeable for marked periods of regeneration of phosphate, followed by utilization, within the main cycle.

The maximum value at El was 40 mg. per m3 of phosphate as P2O5, the minimum 5-1 mg. for thewhole water column, 0-70 metres.

Much additional evidence has been found to show that the deep water of the ocean is a reservoir of phosphate, containing 50-80 mg. per m3, or more.

The water of the North Sea was markedly richer in phosphate in the spring of 1925 than in that of 1924, as was also the water around the Faroe-Shetland Channel in July, 1925, as compared with the previous July. A causal connection may be sought.

In tropical waters the intense light normally results in the utilization of all phosphate down to at least 50 metres, and the winter cooling never suffices to effect mixing with the deeper water. At about 38N. latitude the water may be expected to be isothermal in winter to a depth of 350-400 metres, and further north the isothermal column has its base deeper down; accordingly the seasonal phosphate cycle must become more pronounced.

Kidney and spleen tissues from flounder Platichthys flesus (L.) collected from Neal Point in the estuary of the river Tamar were examined by x-ray microanalysis for the presence of heavy metals within the melanomacrophage centres. Ultrastructurally these centres consisted of groups of pigment-containing macrophages in which melanin was the most prominent pigment, but lipofuscin and haemosiderin were also present. Some of the macrophages also contained irregular metal particles and minerals with associated metals. The metals identified within these inclusions were Ti, Cr, Fe, Co, Ni, Cu, Zn, Sr, Ag, Sn, Ba, La, Ce, Nd, W, Au, Pb, Th and U. The results are discussed in relation to the sediment chemistry of the River Tamar, and the possible routes of uptake by the fish.

Distributions of suspended matter, light attenuation and chlorophyll a were measured in the Shannon Estuary over the period 1988–1990. Light attenuation was found to be highly correlated with levels of suspended matter, and the availability of underwater irradiance was found to be the dominant influence on phytoplankton biomass and chlorophyll levels over most of the estuary. Though levels of suspended matter, and hence light attenuation, were highest in the upper estuary, depths of mixing were relatively shallow resulting in less light limitation of phytoplankton growth than elsewhere. Turbidity maxima in the upper estuary were associated with chlorophyll maxima, the magnitude of which appeared to be related to river discharge.

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.

The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.

The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.

The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.

The application of these measurements to estimates of the food requirements of the copepods is discussed.

Sixteen coral sites in the coastal waters of Hong Kong were examined for the corallivorous muricid gastropods Drupella rugosa and Cronia margariticola. These were recorded from all sites where there was significant hard coral cover and observed feeding upon species of Platygyra, Leptastrea, Stylocoeniella, Porites, Favites, Cyphastrea, Goniastrea, Favia, Acropora, Montipora, Pavona, Lithophyllon, Hydnophora, Echinophyllia and Plesiastrea. One large aggregation (~2000 individuals) of, mainly, D. rugosa was observed but much smaller groups (<20 individuals) were more typical. Five sites were chosen for more detailed study and surveyed during winter and summer. Despite being characterized by different coral communities, inter-site densities of D. rugosa were not significantly different and, usually, ~2 individuals · m2 were recorded. Seasonal differences were, however, significant with numbers greater during the summer, possibly related to reproduction. Feeding activity followed a similar pattern and was also largely confined to summer.

Prey selection by Drupella rugosa was complex in the field and changed according to the relative abundance of each coral taxon. Acropora was strongly selected for at all sites where it was present and Montipora, Platygyra and Pavona were usually fed upon in greater proportions than their abundances. Leptastrea, Cyphastrea, Favites, Favia and Goniastrea were fed upon but in proportions lower than suggested by their abundances. Goniopora was never fed upon despite being relatively common. The seasonality of feeding, low density, rarity of large feeding aggregations, prey selection and aspects of the feeding behaviour, that is, generally only consuming the coral's coenenchyme (the polyps surviving), suggest that while D. rugosa is widespread in Hong Kong, and contrary to other views, it poses little, if any, threat to local coral communities. Thus, reported feeding clusters of D. rugosa are probably not ‘plague’ outbreaks but examples of seasonally fostered ‘aggregations’ of feeding (and probably reproducing) individuals. Indeed, no ‘plague-like’ outbreak of any species of Drupella has been reported upon in the literature since 1999.

The behaviour of herring subjected to stationary and vibrating obstacles in their swimming path was recorded in daylight and darkness using an infra-red sensitive TV system. The herring avoided stationary obstacles using visual stimuli and usually collided with such obstacles in darkness. They showed strong avoidance to a continuously vibrating sound source in darkness but the speed of turning was relatively slow and there was no evidence for habituation. As they approached the source they usually responded when the sound pressure reached 10–20 Pa, about 70 dB above the threshold. Particle velocity within the lateral line canals was calculated and was 40–60 dB above threshold. Herring seem to be able to adapt their avoidance behaviour to suit the urgency of the situation.

INTRODUCTION

In earlier papers we have given an account of work on the three kinds of chambered shells which are found in living cephalopods, i.e. those of Sepia, Nautilus and Spirula, and shown that, although these animals differ markedly from one another in the structure of the shell and its position in the animal, there are nevertheless great similarities in the pattern of events leading to the formation of a new chamber and the way in which liquid is pumped out of it and gas diffuses into it (Denton & Gilpin-Brown, 1961 a, b, c; 1966; Denton, Gilpin-Brown & Howarth, 1961, 1967). We advanced the hypothesis that this pattern must have been the same for all the chambered shelled cephalopods, including the fossil nautiloids, ammonites and belemnites.