Ensis directus (Bivalvia: Solenidae) was noted for the first time along the French coast of the North Sea in June 1991. High numbers of post larvae after a period of northerly winds indicate that settled larvae originated from adult populations in Belgian or Dutch coastal waters. Future dispersal of Ensis directus could be used as a biological tracer of coastal water movements between the Southern Bight of the North Sea and the English Channel.

The American jack knife clam, Ensis directus (Conrad, 1843), synonym Ensis americanus (Binney, 1870)sensu van Urk (1964,1972), was discovered in Europe in the German Bight for the first time in June 1979 (Von Cosel et al., 1982). This species is assumed to have been transported in its larval stage by a ship containing ballast water. Considering the dimensions of the specimens, this probably happened in the first half of 1978 (Von Cosel et al., 1982; Mühlenhardt-Siegel et al., 1983). Since then this species has spread rapidly in the North Sea in subtidal and intertidal areas. Dense populations were found along the German coast within a few years (Von Cosel et al., 1982; Mühlenhardt-Siegel et al., 1983; Swennen et al., 1985). In 1986 Ensis directus was reported from the north and east Danish coasts as far as the Belgian coast (Kerkhof & Dumoulin, 1987) (Figure 1). Since then no new records have been reported.

In the investigation described in this paper, respiration, resistance to desiccation and feeding behaviour of .the mid- to upper-tidal isopod Campecopea hirsuta was studied and compared with the analogous parameters of behaviour in the lower intertidal species Naesa bidentata

C. hirsuta occurs in the middle part of the shore where it can be found within empty shells of Chthamalus. Its preferred habitat, however, is the lichen Lichina pygmaea the vertical distribution of which extends from OD to MHWS.

Campecopea hirsuta feeds on the blue-green algae that make up the outer layer of the lichen L. pygmaea. When continuously submerged the isopod feeds in bursts, the timing of which is different in different specimens. This mode of feeding under experimental conditions is taken as reflecting the rhythmic way of life of this species in its natural environment but it seems to be controlled by endogenous factors. Naesa bidentata, on the other hand, does not display such endogenous rhythms in its feeding behaviour.

Eicosanoids are oxygenated derivatives of C20 polyunsaturated fatty acids known to play key roles in many physiological events in both invertebrates and vertebrates. The eicosanoid generating capacity of cypris larvae of the barnacle, Balanus amphitrite, was examined using enzyme immunoassay and high-performance liquid chromatography. These larvae generated the lipoxygenase products, 12-hydroxyeicosapentaenoic acid (HEPE), 8-HEPE and 8,15-diHEPE, together with the cyclooxygenase products, prostaglandin (PG) E, PGF and thromboxane (TX) B. Indomethacin, a selective cyclooxygenase inhibitor, caused a dose-dependent inhibition of PGE generation by B. amphitrite larvae, while esculetin and nordihydroguaiaretic acid (lipoxygenase inhibitors) also strongly inhibited the generation of 8-HEPE, 12-HEPE and 8,15-diHEPE. PGE2, PGE3 and 16,16-dimethyl PGE2 caused a dose-dependent inhibition of settlement of B. amphitrite larvae while indomethacin (25–100 μM) stimulated this process. Lipoxygenase products (8-HEPE, 12-HEPE and 8,15-diHEPE) as well as esculetin and nordihydroguaiaretic acid (10–100 μM) had no effect on the attachment of larvae.

INTRODUCTION

Until recently only two marine members of the phylum Tardigrada were known to occur in Britain. Echiniscoides sigismundi (Schultze), was found associated with mussels (Green, 1950) and intertidal barnacles (Crisp & Hobart, 1954). The interstitial species, Batillipes mirus Richters, was located at beaches in North Wales (Boaden, 1963) and Strangford Lough in Northern Ireland (Boaden, 1966).

Interstitial tardigrades have been reported from several localities around the North Sea. The fauna of the German coast is particularly well studied; Schultze, 1867; Richters, 1908, 1909; Schulz, 1935, 1951, 1953; Grell, 1937; Remane, 1940; Freidrich, 1963; Riemann, 1966a, b; Schmidt, 1969. This German fauna includes three species of Batillipes and single representatives of five other genera. In addition, E. sigismundi and B. mirus have been found in Norway (Tambs-Lyche, 1939–40). Along the French coast of the English Channel, eight species from six genera are reported. While most studies originated at RoscofT, including Cuénot, 1892; Cantacuzène, 1951; Guèrin, 1960; Swedmark, 1951, 1955, 1956a; Swedmark & Teissier, 1967; Thulin, 1942, two species of Batillipes have been located elsewhere on the northern coast of France (Renaud-Debyser & Salvat, 1963).

In recent surveys of beaches in Britain, additional tardigrades have been located. Gray & Rieger (1971) reported their occurrence at several beaches on the north-east coast of Yorkshire, especially at Stoupe Beck, Robin Hood's Bay and Filey Beach near Scar-borough. Also, A. D. Mclntyre has found them in his collections at Firemore Bay in Loch Ewe on the west coast of Scotland. This paper describes specimens generously provided from these two studies.

Skin structures of nine different species of dorid nudibranchs were examined at the scanning electron microscope and the light microscope levels. From these observations the animals are grouped into three categories.

1. Dorids with spicule-supported tubercles carrying a sensory knob (Rostanga rubra, Jorunna tomentosa, Onchidoris sparsa, Onchidoris pusilla).

2. Dorids with small sensory papillae set in pits and distributed randomly between projecting spicules (Aegires punctilucens).

3. Dorids with tubercles differing in shape from one species to another, invested with numerous spicules but without conspicuous sensory structures. The tips of the tubercles do, however, contain single sensory epithelium cells (Archidoris pseudoargus, Acanthodoris pilosa, Onchidoris muricata, Onchidoris bilamellata).

A description is given of Squalotrema llewellyni gen.nov., sp.nov., a monocotylid monogenean from the nasal fossae of the spur-dog Squalus acanthias. The parasite differs from representatives of other monocotylid genera in the number and arrangement of loculi on the haptor. In order to accommodate the genus Squalotrema, the diagnosis of the subfamily Merizocotylinae (Yamaguti, 1963) has been amended.

The eggs differ in shape from those of other monogeneans. Each egg appears to be derived from a tetrahedron by flattening of one of the four apices. A long, coiled appendage projects from the flattened apex and the face of the egg from which the appendage projects also bears two spurs. The curved body of the fully developed, ciliated oncomiracidium occupies only two of the three rounded corners of the egg.

The swimming behaviour and photoresponses of the iridescent epipelagic copepods, Sapphirina gastrica and S. opalina were investigated in the laboratory. In continuous dark conditions, both species showed no significant diel variation in their swimming activities. When stimulated with light, they exhibited spiral-swimming in which the males showed a significantly higher speed and frequency of turning than the females. Both sexes of S. gastrica and S. opalina showed positive phototaxis at intensities higher than 0·05×1014 quanta  cm−2 s−1 for light sources of 430 nm and 580 nm. Sapphirina gastrica showed increased locomotion over a broad range of wavelengths from 430 nm to 580 nm, while S. opalina showed a gradual increase of activity with decreasing wavelength, with the highest value at 430 nm. The photoresponses of these two species suggest that light conditions play an important role in their daytime ascent and in determining the depth distributions that were observed in our previous study. It is suggested that the iridescence and fast spiral-swimming of males, and the species-specific photoresponses of both sexes constitute a putative mate recognition system in the open ocean.

During a study devoted to the characterization of the polychaete fauna associated with dead coral (Pocillopora spp.) in the Coiba National Park (Pacific coast of Panamá), nine species belonging to seven genera of sabellids (Annelida: Polychaeta: Sabellidae) were found. Three species new to science are described. Amphicorina bichaeta sp. nov. is characterized by having three pairs of radioles, smooth collar, broad thoracic notochaetae of two kinds (plus bayonet chaetae), and abdominal uncini with a large anterior tooth. Amphicorina perkinsi sp. nov. is characterized by having four pairs of radioles, six to eight abdominal chaetigers, smooth and oblique collar, broad thoracic notochaetae and thoracic uncini with main fang surmounted by a distinct subdistal tooth and a curved row of little teeth. Amphiglena jimenezi sp. nov. is characterized by having long radiolar appendages, medium-sized handles in thoracic uncini, and gametes in middle abdominal segments. Another six species are recorded: Branchiomma cf. bairdi and Notaulax occidentalis, which are new for the Pacific Ocean, while Notaulax nudicollis and Megalomma circumspectum, are new for the Pacific coast of Panamá. The presence of Bispira melanostigma and Pseudopotamilla intermedia is verified.

In July–August of three different years common surface-floating bottles were set adrift at International Station E2 (49° 27' N.—4° 42' W.). With them, various types of drag-fitted bottles were also put out. The journeys accomplished are discussed, and the striking differences as between year and year in the case of the common surface floaters, and as between the different types in the same year, are commented upon in the light of the prevailing winds. An inter-relationship of great simplicity is deduced between wind speed and the rate of travel of simple surface floating bottles up-Channel and across the North Sea from the results of experiments carried out in four different summers.

During a cruise in the southern North Sea and English Channel in 1948 a series of measurements on light penetration was secured.

The apparatus used has been described, and methods of handling it discussed. A description of the experiments for determining the transmission curve of the niters used in the photometers, has been included.

Of the systematic and random errors to which the photometer measurements were liable the most serious lay in not knowing the precise depth of the sea cell.

Extinction coefficients have been determined from the gradients of logarithmic transmission-ratio/depth graphs, and the results tabulated for each station.

Temperature gradients were never large, usually of the order of 0·02 degrees per metre, the temperature usually dropping with increased depth, frequently there was no gradient at all.

Phytoplankton from Loch Creran, Argyll was maintained in continuous culture for 41 days. During most of this time the mixture of species retained the diversity and dominance pattern typical of summer phytoplankton in the loch, notwithstanding the manipulation of algal nutrient status to bring about phosphorus control of growth. Results suggest that most detritus was washed out early in the experiment.

The aim of the experiment was to test the applicability to natural multispecies phytoplankton of part of Droop's (1974, 1975) model of nutrient-limited algal growth. ‘Quasi-steady states’ with respect to concentration of chlorophyll, particulate carbon (PC), particulate phosphorus (PP) and particulate nitrogen (PN), wereobserved at two levels of input of dissolved inorganic phosphorus. At other times the algal phosphorus quota (estimated from the ratio of PP to PC) varied from about 0·002 to 0·015 atoms P per atom C. Specific growth rate was estimated from the rate of increase of PC. During part of the experiment, growth rate was linearly related to reciprocal phosphorus quota, thus confirming the applicability of the model.

The present work reports the existence of parasitic castration induced by the bopyrid isopod Argeiopsis inhacae parasitizing the branchial chamber of female Stenopus hispidus. Parasitized and unparasitized females of S. hispidus displayed similar intermoult periods (14 ± 2 d) and exhibited similar mating behaviours. However, despite exhibiting typical mating behaviour, parasitized females were never able to produce any egg clutch when paired with unparasitized males; neither displayed the typical ‘dorsal bright green spot’ evidencing the presence of large vitellogenic oocytes. The idea that bopyrid infections generally lead to the ‘reproductive death’ of the decapod host is reinforced and the apparent existence of a heavily sex-biased infection towards females in S. hispidus may just be a consequence of the still limited number of surveyed specimens.

There can be little doubt that competition for space, both inter- and intraspecific is a major factor in barnacle ecology. Southward & Crisp (1956) first pointed out the role of competition between Balanus balanoides (L.) and Chthamalus stellatus (Poli) in south-west Britain which Connell (1959, 1961) later demonstrated experimentally. Crisp (1958) discussed competition between the indigenous B. balanoides and the immigrant Elminius modestus Darwin in the intertidal zone, and measurements of growth rates, using manipulated populations of these two species, indicated that inter- and intraspecific competition for space after settlement is intense (Crisp, 1964).

The general morphology of the antennary and maxillary glands, which form the major renal system of adult Crustacea, has been described and reviewed by Goodrich (1945). However, studies on the fine structure are restricted mainly to the antennary glands of decapods, including Orcotiectes sp. (formerly Cambarus sp.) (Anderson & Beams, 1956; Beams, Anderson & Press, 1956), Orconectes affinis (Kümmel, 1964), Procambarus clarkii (Miyawaki & Ukeshima, 1967; Schaffner & Rodewald, 1978), Procambarus blandingi (Peterson & Loizzi, 1974), Austropotomobius pallipes pallipes (Riegel & Cook, 1975) and Uca mordax (Schmidt-Nielsen, Gertz & Davis, 1968). The maxillary gland of Artemia salina is the only excretory system of a non-decapod which has been studied in detail (Tyson, 1968, 1969a, b). Morelli & Tobolla worked independently on the antennary glands of amphipods, Gammarus sp. (cited Kümmel, 1973), but their studies were restricted to the site of filtration.

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

five raja species are displayed in the ‘ray reef’ at dolfinarium harderwijk and, from 1993–2001, 41,772 eggs were laid, of which 39% contained a yolk sac and 3% hatched successfully. different egg-laying periods were distinguished between species. no annual differences in the egg-laying period were observed for raja microocellata, while hatching periods, and thus incubation periods (4.8–7.0 months), differed significantly. no correlation between seawater temperature and incubation time was found.

Lysmata wurdemanni is a protandric-simultaneous hermaphroditic shrimp. Individuals reproduce as males first and late in life as simultaneous hermaphrodites. I examined whether sex allocation (resources devoted to ova vs sperm) varies with group size in shrimps that have just matured as hermaphrodites. Focal males were reared with different numbers of hermaphrodites (1, 2, 5 or 10). Sperm stored in the ejaculatory ducts and eggs brooded underneath the abdomen were retrieved and weighted immediately after focal shrimps matured as hermaphrodites. Hermaphrodites should invest more into sperm with increasing group size to cope with more intense sperm competition. The proportion of focal shrimps that lost their first clutch of eggs after maturing as hermaphrodites increased with group size. This suggests male gender preferences by hermaphrodites experiencing large group sizes. No differences in sex allocation among group sizes were recorded for shrimps that did not lose their first clutch of eggs. Thus, group size does not affect sex allocation in terms of ova and sperm mass. This lack of phenotypic plasticity might be explained if sperm competition is not important in L. wurdemanni. It should not pay in terms of fitness for shrimps to produce and inseminate female-role hermaphrodites with large amounts of sperm when full paternity is assured in the absence of multi-male mating. In agreement with this idea, a second experiment demonstrated that female-role hermaphrodites invariably mated only once with a single other shrimp.

The cuttlefish (Sepia officinalis) is the most important traditional fishing activity in the Sado estuary. In order to analyse the spatial and temporal distribution patterns and to study the reproductive cycle of this species, twenty sampling areas were towed along the estuary on a monthly basis from May 2001 to April 2002. The higher densities were obtained in summer and autumn in the lower and southern area of the estuary while spring showed the higher biomass. Mature individuals prevailed in the inner zone of the estuary during spring while juveniles were dominant in autumn and concentrated in the lower part of the estuary. Almost all individuals leave the estuary during winter. The weight–length relationship was significantly different according to sex, being females heavier than males for individuals larger than 106 mm. Sex-ratio was similar to 1:1 in every season. Females had high values of gonadosomatic index during the spawning season with a major peak in June, while males showed similar values throughout the spawning season. The length at first maturity was estimated at 80 mm mantle length (ML) for females and 59 mm ML for males. In the Sado estuary only one generation of cuttlefish breeders were found with an average of 110 mm ML for males and 122 mm ML for females, which is consistent with breeders in their first year.

Norway lobster (Nephrops norvegicus) larvae have been investigated in northern European waters, particularly in the Irish Sea where biomass estimation studies are used for the annual larval production method. However, nothing is known of their distribution in southern European waters, off the Portuguese coast or in the Mediterranean Sea. From zooplankton sampling off the Portuguese coast between October 1986 and March 2001, planktonic larvae of this species were known to occur from January to April off the north-west and south coasts. In the north, larvae were only observed over the shelf, shoreward of the upper limit of the adults' distribution. Larvae were never collected off the south-west coast of Portugal, even though this is one of the largest fishing grounds for this species off the Iberian Peninsula. The absence of larvae from all surveys in this region may relate to the local oceanographic conditions and shelf width.

In September 1993 the Irish Sea floor near the Sellafield nuclear reprocessing plant was surveyed by towed video to assess the distribution, abundance and behaviour of large burrowing invertebrates believed to be important in the transport and mixing of radionuclide-contaminated sediments. Sixteen stations were surveyed, covering a range of sediment types. Burrow openings and mounds were counted and assigned to species where possible. Particular attention was paid to the similarities and differences between the features observed and those produced by the same species in Scottish sea lochs, the source of most relevant ecological data. Several different burrowing communities were identified from bottom topography. Offshore muddy sands supported dense populations of the thalassinidean crustacean Callianassa subterranea, in burrows similar to those described from the North Sea. Coarse sediments closer inshore had C. subterranea at lower density, with the thalassinidean Upogebia deltaura and the crab Goneplax rhomboides also present. Softer muds were dominated topographically by ejecta mounds of the echiuran Maxmuelleria lankesteri and burrows of the Norway lobster Nephrops norvegicus. The thalassinideans C. subterranea, Jaxea nocturna and Calocaris macandreae were also present at low density. Surface bioturbation features in this habitat were very similar to those described from sea lochs. Population densities estimated from surface bioturbation features were always lower than counts of specimens from box-cores. The visual survey therefore gave minimum estimates of population density. Available data on rates of bioturbation by the species concerned are collated to give rough estimates of biogenic sediment transport in the habitats surveyed.