Ostrea puelchana is a larviparous oyster from the S.W. Atlantic coasts. This species is not being commercially exploited at present. Because of its high food qualities, however, it may constitute a resource of economic interest in the future.

Until now larval development and characteristics of the incubation period have been poorly known. This study describes the characteristics of the mode of brooding under laboratory rearing conditions and, using scanning electron microscopy, the morphogenesis of the hinge until larval release from the parents.

The larva develops two anterior and two posterior denticles during brooding. A comparison with larvae of other species of the genus Ostrea reveals that the main differences among them do not lie so much in the pattern of hinge dentition as in the rate of evolution of the hinge components, which is faster in Ostrea puelchana. This species has fully developed denticles at the time of release, which places the larva of this oyster as particularly evolved within the genus Ostrea.

The identification of foraging hotspots able to support the co-existence of multiple top predators provides a potential approach to addressing protection measures for marine ecosystems. In this study, we conducted visual surveys in the central Tyrrhenian Sea to determine areas with simultaneous presence of bottlenose dolphins, four species of seabirds (Audouin's gull, Yellow-legged gull, Yelkouan shearwater and Cory's shearwater), and baitballs occurring at the surface, indicating the presence of potential prey items. We also analysed their occurrence in relation to topography (depth, slope and distance from the shore) and seabed types. Kriging analysis identified areas with simultaneous presence of several marine top predators. Dolphin distribution appeared to be linked to gentle slope (6–10 m) and muddy seabed, possibly associated with prey distribution, whereas the four seabird species were more frequent in areas with a water depth of 100–150 m, gentle slope and muddy seabed, apart from Audouin's gull, which preferred a depth of 10–20 m. Baitball distribution was linked to depth (20–40 m), gentle slope (6–10 m) and muddy seabed. The overlapping presence of bottlenose dolphins, seabirds and baitballs allowed the identification of foraging areas, presumably representing biodiversity and productivity hotspots, located in waters of 50–100 m depth at the mouths of two rivers. This approach provides a promising tool for identifying highly productive coastal areas, and should also be recommended for wider-scale surveys.

Little is known of the larvac of the Pandalidac as is shown by Gurney (1939) in his Bibliography of the Larvae of Decapod Crustacea. Berkeley (1930,1938) describes the life histories of several species of Pandalus and of Pandalopsis dtspar from British Columbia, and Gurney (1937) the larvae and post-larvae of Chlorotocella, but beyond these the information is fragmentary. Sars’ (1900) work on Pandalus borealis and P. bonnieri was formerly regarded as typical of pandalid larvae but these were proved to be Caridion (Lebour, 1930). Sars (1900), however, described in part in an excellent manner the larvae of Pandalus montagui and Pandalina brevirostris and Stephensen (1935) the early larvae of Pandalus propinquus.

Aspects of the feeding behaviour of Ergalatax contractus (Muricidae) were studied. Field experiments demonstrated that large numbers of individuals of this species, comprising ∼90% of a suite of gastropod scavengers, were attracted to baited traps in the subtidal sands of Lobster Bay, Cape d'Aguilar Marine Reserve, Hong Kong. Laboratory experiments identified the effective chemo-detection distances of E. contractus as 60 cm in still and >80 cm in flowing water, respectively. The average times to arrival at bait in still and flowing water were 92.3 and 69.0 min, respectively, but were significantly less for individuals experiencing a longer period of starvation. The mean time taken for E. contractus to consume a meal was 70.6 min.

Comparisons were made between Ergalatax contractus and Nassarius nodifer, representative of a suite of sympatric scavenging nassariids in Lobster Bay. The nassariid arrived significantly faster at bait in both still (30.2 min) and flowing water (20.8 min) than E. contractus and fed faster (25.7 min), as is typical of representatives of the Nassariidae. Although the two species partition carrion resources temporally, manipulation experiments provided evidence for inter-specific competition between them. That is, although E. contractus possesses the morphological and behavioural characteristics of a predator, its opportunistic scavenging abilities have led to its success and numerical superiority on the shallow subtidal sands of Lobster Bay. The dominance of E. contractus in Lobster Bay, and elsewhere in Hong Kong, is unusual. Here, the normally predatory E. contractus, far outnumbers all other scavengers, possibly because of an enhanced, largely allochthonous, supply of food which it is able to exploit by virtue of its previously identified opportunistic habit of scavenging the leftovers of other predators. The presence of inter-specific competition between E. contractus and a sympatric suite of nassariids enhances, not impedes, carrion exploitation.

Recent studies indicate that monothalamous (single-chambered) foraminifera are an important component of meiobenthic communities in the brackish, coastal waters of the Black Sea. The dominant taxa include Psammophaga and Vellaria, both of which are common in estuarine settings in other parts of the world. Here, we describe Tinogullmia lukyanovae sp. nov. from the Crimean and Caucasus regions of the Black Sea. The new species is several hundreds of microns in size. It is characterized by a more or less symmetrical, spindle-shaped to cylindrical, organic-walled test with two terminal apertural structures, usually in the form of rounded or more elongate, nipple-like projections. The protoplasm is finely granular and a nucleus is not visible. The new species typically occurs in well-oxygenated water at depths of a few tens of metres or less. A specimen from a 250-m deep site off the Caucasus coast, tentatively assigned to T. lukyanovae sp. nov., is of particular interest because it occurs at a depth where the bottom water is anoxic and sulphidic.

Beach ecosystems extend from dune to offshore areas along most coasts, and provide essential services that are not provided by any other ecosystem. Indeed, sandy systems contain unique biodiversity and supply nursery and foraging areas for numerous commercially important marine species, such as flatfish. However, these systems are threatened by increasing anthropogenic pressure. Green tides (GT, i.e. accumulations of green opportunistic macroalgae) are a major human-induced threat to marine ecosystems, from inshore to nearshore. This eutrophication process greatly affects both benthic invertebrate communities and flatfish communities, within sheltered and non- or microtidal systems. However, the responses of dynamic open macrotidal sandy systems to eutrophication in the form of macroalgal mats are not yet fully understood. In particular, understanding the effects of GT on two connected biological compartments (infauna and flatfish) within two connected habitats (intertidal and subtidal) is crucial. Here, we set out to assess the influence of several environmental variables, including Ulva biomass, on the variability in infauna and flatfish communities in both the intertidal and the subtidal at four sites impacted or not by GT. In total, 110 biodiversity samples were analysed with classic and novel analytical approaches. Our results demonstrate that the presence of GT specifically impacts intertidal macroinvertebrate communities. However, small effects of GT on subtidal infauna communities, as well as on species-specific flatfish at both intertidal and subtidal, were still detectable. Our findings underline the vulnerability of highly dynamic ecosystems exposed to anthropogenic stress, in particular intertidal sandy shores.

Pinna nobilis is an endemic Mediterranean species of high economic and cultural importance. Nowadays, it is under strict protection as a dramatic decline in its populations has been recognized, assigned to the combined effect of fisheries and habitat degradation. This study attempts to evaluate, by non-destructive sampling, the current status of P. nobilis populations in the south Aegean Sea (Dodecanese island complex), where they have been affected for centuries by practically uncontrolled harvesting. Population density and total length of individuals was estimated by diving along strip transects at six islands. Two stations were randomly selected per island, and two depth zones were surveyed per station. Additionally, temporal sampling was carried out at Astypalaia Island from March 2004 to June 2006, to assess relevant trends in density of individuals and size structure of the population. In total 1372 P. nobilis individuals were measured in situ to estimate maximum shell length. The studied populations showed increased density in the shallower depth zone and sheltered sites; small-scale environmental regimes are proposed as shaping factors of P. nobilis distribution. Increased density was also detected during the cold period of the year, probably related to recruitment success. In the lower depth zone the P. nobilis population consisted of larger individuals. A significant decrease in size was detected temporally as mean length was smaller in December 2004; in the same month the presence of small-sized juveniles was depicted in a left-shift in size–frequency distribution. These observations are probably related to the reproductive biology of the species.

The variability of shell morphology and relative growth of the invasive pearl oyster Pinctada radiata was studied within and among ten populations from coastal Tunisia using discriminant tests. Therefore, 12 morphological characters were examined and 34 metric and weight ratios were defined. In addition to the classic morphological characters, populations were compared by the thickness of the nacreous layer. Results of Duncan's multiple comparison test showed that the most discriminative ratios were the width of nacreous layer of right valve to the inflation of shell, the hinge line length to the maximum width of shell and the nacre thickness to the maximum width of shell. The analysis of variance revealed an important inter-population morphological variability. Both multidimensional scaling analysis and the squared Mahalanobis distances (D2) of metric ratios divided Tunisian P. radiata populations into four biogeographical groupings: the north coast (La Marsa); harbours (Hammamet, Monastir and Zarzis); the Gulf of Gabès (Sfax, Kerkennah Island, Maharès, Skhira and Djerba) and the intertidal area (Ajim). However, the Kerkennah Island population was discriminated by the squared Mahalanobis distances (D2) of weight ratios in an isolated group suggesting particular trophic conditions in this area. The allometric study revealed high linear correlation between shell morphological characters and differences in allometric growth among P. radiata populations. Unlike the morphological discrimination, allometric differentiation shows no clear geographical distinction. This study revealed that the pearl oyster P. radiata exhibited considerable phenotypic plasticity related to differences of environmental and/or ecological conditions along Tunisian coasts and highlighted the discriminative character of the nacreous layer thickness parameter.

The ciliate Euplotes encysticus Yonezawa, 1985 was insufficiently described so far regarding its living morphology, infraciliature and silverline system. Recently, a China population was isolated from brackish water (salinity 6‰) near a coastal sandy beach (114°32′E 22°43′N) of the Daya Bay, South China Sea and subsequent investigations were performed on it in detail. Based on data available, the morphology of this species was summarized and a new diagnosis is given which is characterized by: medium-sized body with consistently 9 frontoventral, 2 caudal and 2 left marginal cirri; 30–40 adoral membranelles; 7 dorsal kineties; dorsal silverline system consisting of complex type with irregular network; capable of encystment. Both the morphology and SSr RNA gene sequence show, with high support, a close relationship of E. encysticus and Euplotes muscorum.

Bacteria have been isolated into pure culture from the gills of Lucinoma borealis, Myrtea spinifera, Thyasira flexuosa and T. sarsi collected from several British and Scandinavian coastal sediments. It is proposed that these bacteria are symbiotic with the animals. The bacteria were either autotrophs, obtaining energy from oxidation of inorganic sulphur compounds, or methylotrophs using methanol or methylamine as the source of carbon and energy. The latter could also oxidize thiosulphate to tetrathionate and precipitate elemental sulphur. The pure cultures have been characterised in some detail, showing that (1) their DNA base composition falls in the range 47–58% guanine + cytosine; (2) although all grow well at the natural environment temperatures of 8–15°C, their optima lie between 30 and 35°C; (3) all produce copious amounts of extracellular slime when grown at low temperatures; (4) the autotrophic isolate is facultatively heterotrophic, containing a repressible ribulose bisphosphate carboxylase, and excreting up to 30% of its carbon dioxide fixation into the culture medium; (5) the methylotrophs include some containing high activities of hexulose phosphate synthase for assimilation of formaldehyde by the ribulose monophosphate cycle; others may have novel assimilatory metabolism. The possibility is discussed that environmental factors may determine whether a methylotroph-animal or autotroph-animal symbiosis is established rather than the symbiont type being an invariable species-specific character.

The annual cycles of the Abra tennis populations in the Plym Estuary and the Fleet (Dorset) were studied from March 1980 to June 1982. In the Plym Estuary the highest numbers occurred in autumn following juvenile recruitment and the lowest numbers were recorded in mid-summer. In the Fleet such an annual cycle in numbers was not apparent since juvenile recruitment in 1980 was very high but in 1981 it was very low. The recruitment failure in 1981 may have resulted, at least in part, from the heavy summer infection of A. tenuis by digenean parasites that destroy the gonads of the host, thereby reducing the population fecundity.

A. tenuis spawns in July and August: the mature egg has a diameter of 140 μm and is enclosed in a sticky gelatinous envelope. Females produce 450–1800 eggs which, when fertilized, are laid in a mass within the sediment and, following a direct development, the juveniles hatch as miniature adults after 2–3 weeks. This non-pelagic, lecithotrophic development is interpreted as being a means of ensuring the maintenance of populations within restricted estuarine habitats. Data suggest A. tenuis lives for 1 or 2 years and that the species is monotelic.

A new method is proposed for the determination of total dissolved free fatty acids (FFA) in sea water. After preliminary extraction by chloroform, a copper complex is formed which is then extracted by a chloroform-heptane solution. Copper concentration is measured by atomic absorption spectrophotometry. The method is particularly adapted to the determination of long chain FFA (longer than C10) and dissolved organic matter usually present in sea water gives no interference. At the 30 μ/l. level the standard deviation is 1 μ/l. for seven determinations.

Bulla hydatis is a mollusc of relatively rare occurrence in the Plymouth district, although fairly common across the Channel at Roscoff. Intermittent dredging and collecting in the Salcombe estuary over a period of about five years, and some rearing experiments carried out in the department of zoology, University College, London, have afforded some insight into its apparently peculiar distribution and also a few facts of certain general interest.

One of the more recent aims of deep-sea biological investigations has been to assess the rates and processes involved in the recolonisation of deep-sea sediments by the in situ fauna (Grassle, 1977; Desbruyères etal., 1980, 1985; Levin & Smith, 1984). The spur to such initiatives has been the prospect of deep-sea mineral exploitation and the dumping of radioactive and other chemical wastes (Desbruyères etal., 1 985), in addition to the testing of hypotheses about deep-sea community regulation (Levin & Smith, 1984; Smith, 1986). These experiments have shown that perturbated or defaunated sediments incubated for periods of several months are readily recolonised by deep-sea animals, although the process is much slower than in comparable shallow-water situations (e.g. Levin, 1984; Zajac & Whitlach, 1982a, b). Furthermore, the resulting community of colonists may be quantitatively and qualitatively different from the ‘background’ fauna (Grassle, 1977; Levin & Smith, 1984). Similar experiments have examined the effect of large ‘food-parcels’ on the in situ sediments and fauna (Smith, 1986), and a review of the responses of benthic faunas to disturbed sediments has been published by Thistle (1981).

Seasonal variations in the range of air vesicle and leaf shape upon the brown alga Sargassum muticum (Yendo) Fensholt provide some discrepancies with descriptions of material from the alga's indigenous Japanese and introduced British Columbian habitats.

Experimental observations indicate that mucronate air vesicles are most common at low (i.e. 10 °C) and high (i.e. 25 °C) temperatures, with those of 30 °C being injurious to plant growth. Air vesicles with spiked proliferations are also seen to increase in occurrence with an increasing light intensity at 20 °C. Excised ‘winter’ form leaves collected in February were able to regenerate ‘summer’ form leaves from their damaged bases, under culture conditions.

Field and laboratory investigations show that leaf and air vesicle shape tend to vary seasonally and may be experimentally changed by both temperature and light intensity. Such plasticity observed in the morphology of these characters in S. muticum raises doubts as to the taxonomic status of many species ascribed to the large genus Sargassum.

INTRODUCTION

In the Bivalvia the two valves and connecting ligament are parts of a single shell each composed of three layers secreted by continuous surfaces of pallial epithelium as shown in Fig. 1. The superficial periostracum is formed in a groove at the base of the inner side of the outer (secretory) fold of the mantle margin and is continuous around the pallial lobes and within the embayments at each end of the ligament. The outer calcareous (prismatic) layer of the valves and the anterior and posterior outer (lamellar) ligament layers are formed by the outer surface of this outer fold which hypertrophies in the depths of the embayments where ligamental material is secreted. The inner calcareous (usually nacreous or porcellanous) layer of the valves is produced by the general pallial surface except along a mid-dorsal strip, the mantle isthmus (Owen, Trueman & Yonge, 1953; Yonge, 1953) which secretes the inner (fibrillar) ligament layer.

Kellia suborbicularis (Montagu) has long been known to be viviparous. Lovén (1848) mentions this fact and Jeffreys (1863, p. 227) quotes Mr Clark who “found in the ovary of one individual ova in an advanced state with fully formed testaceous fry.” It is probable, however, that these shelled larvae were in reality contained in the gill pouch where later workers have found them. Pelseneer (1935, p. 517) says that the eggs are incubated in the internal gill lamella, and this was also observed by myself.

It is striking that although the shelled larva is extremely small when liberated (shell 0.064–0.08 mm. in length), the late planktonic larva is very large (shell 0.30–0.37 mm. in length) and one of the most conspicuous bivalve veligers in the plankton. This indicates a prolonged free-swimming life quite unlike that of the oyster, Ostraea edulis, whose shelled larvae are liberated only to lose the velum in a few days. These late larvae of Kellia have been kept in bowls and plunger jars in the Plymouth Laboratory until they metamorphosed and for months afterwards, growing into beautifully clear and transparent individuals which undoubtedly belonged to this species.

Kellia suborbicularis is placed by Winckworth (1932) in the Erycinidae, but this family is closely related to the Leptonidae, Montacutidae and Galeommatidae, most or all of whose members are viviparous. Lovén (1848) described the young shelled stage of Montacuta ferruginosa and M. bidentata, the latter species now being referred by Winckworth toMysella. Both keep their young in the gill pouch until the shelled stage and Lovén's beautiful figures show that the early shelled stage in each of them is very like that of Kellia.

The present report continues the observations on the seasonal abundance of the pelagic young of teleostean fish in the plankton off Plymouth(Russell, 1937) and gives the results for the year 1937. These results are published in the same form as in previous reports. The dates on which collections were made with the 2-metre stramin ringtrawl are given in Table I and the monthly average catches of the young fish per half-hour haul in Table II. In Fig. 1 is given the curve for the average catches for each fortnight of all young fish, excluding clupeids, and superimposed upon this the corresponding curve for the average catches over the period 1930–1934 inclusive.

First-stage zoeal larvae of the green (shore) crab, Carcinus maenas (Crustacea: Brachyura: Portunidae), ingested three types of particles offered in sea-water suspensions. In experiments using two types of fluorescent particles (1–2 µm and 1–7 µm ) and living Dunaliella tertiolecta cells (5–7 µm), particles were ingested in at least 40% of the zoeae examined with brightfield, darkfield, and epifluorescence microscopy. These results suggest that green crab larvae may be capable of utilizing planktonic particles in the size range of bacteria, small algal cells, and organically-enriched detrital particles in their natural diet.

Mr. Leigh-Sharpe, in his account of the external structure of this interesting Copepod (1926), concludes that it is most nearly related to the Ascomyzontidæ. Having recently obtained a number of larvæ, hatched from adults obtained at Plymouth, and finding that my own conclusion as to the relationship of the genus differs from that of Mr. Leigh-Sharpe, it seems worth while to describe the larvæ and the bearing they seem to have upon the systematic position of the adult.

The larvæ hatch and become active inside the egg-sac. Immediately after becoming free they swim vigorously for a short time, but very soon sink to the bottom and remain quiescent, with occasional spasms of activity.