Spawning and post-gastrula development of planula larvae of the ahermatype Caryophyllia smithi are described. Gametes develop within the mesenteries of the adults usually between January and March, are discharged through the mouth of the polyp and fertilized externally in the sea water. Ova are either brown or cream in colour, spherical or slightly oval in shape and are 130–150 µm in diameter. Planulae are fully formed after 48 h, when feeding commences. A large apical tuft (30–60 µm in length) is present but only during the first six weeks of pelagic life. After 8–10 weeks of feeding in culture larvae reach a length of 800–1000 µm: they are then fully developed and ready to settle. Attention is paid to the effects of sea water temperatures on reproduction; locomotion and feeding behaviour of planulae are also discussed.

The distribution of dinoflagellate cysts in sediments is a subject of increasing interest. There have been several approaches, of which two are relevant to this investigation. The studies of palynologists who endeavour to relate the distribution of cyst assemblages to environmental factors (for example Reid, 1972; Wall et al. 1977; Harland, 1983) and the studies of phycologists, concerned with toxic dinoflagellate blooms, who concentrate on the distributions of cysts of bloom species (for example Anderson, Kulis et al. 1982; Thayer et al. 1983). Consequently an increasing amount of information on quantitative distribution of cysts has become available. In 1976 Dale reported the investigation of sediments from Trondheimsfjord, relating the abundance of cysts to the percentage abundance of finer sediment. Wall et al. (1977) provided a more comprehensive picture of this relationship showing that cyst density (numbers of cysts per gram dry weight of sediment) increased logarithmically with increased percentage of the silt plus clay mineral fraction to a level where this comprised 50–60% of the sediment, after this no further increase occurred.

An account is given of a flagellated protist isolated from Atlantic sediments at a depth of 1500 m. The organism forms part of the microbial food web by consuming suspended bacteria. The organism was originally described by Ruinen as Cryptobia libera. On the basis of its ultrastructure, assignment to the genus Cryptobia is regarded as inappropriate, and Jakoba is proposed as a new generic vehicle.

Some features of the organization of the endostyle of Ciona intestinalis are described. Autoradiographs show that bound iodine is present in a limited area of the epithelium (zone 7), where it is associated with characteristic secretory inclusions which are found only in this zone. These are regarded as providing the molecular basis for the iodination process, and are termed 'thyroidal granules', since they resemble in certain properties the similarly named granules of the endostyle of the ammocoete; it is concluded that they are homologous with these and, through them, with thyroid colloid. Their existence provides evidence that the iodination process is a product of biochemical specialization, and implies that it results in the formation of an hormonal secretion. It is concluded from the distribution of bound iodine over the pharyngeal epithelium and in the food cords that this iodinated secretion is carried in the latter into the intestine. Bound iodine is also present in the cuticle of the test; it is suggested that this may differ from the situation in the endostyle in being a consequence of the iodination of a skeletal protein secretion such as is known to occur in many invertebrates. Prior immersion of the animals in thiouracil solution largely eliminates bound radio-iodine from all of the sites mentioned, although a little may sometimes be detectable in the food cords and cuticle. The results are discussed in the light of recent work on Amphioxus and the ammocoete larva, and attention is drawn to their bearing on current views on the relationship between vertebrates and protochordates.

Observations on the density of pelagic marine fish eggs have indicated that they are near neutral buoyancy for most of development and have a tendency to become denser towards hatching (see Russell, 1976). However, most of this information has been based on limited laboratory observations on the relative buoyancy of eggs; only a few experiments have given more precise estimates of the absolute density of eggs based on the salinity of water in which they are neutrally buoyant (e.g. Franz, 1910; Sundnes, Leivestad & Iversen, 1965). Recently, a new technique (Coombs, 1981), based on the use of a stable column of continuously graded sea-water concentration has allowed more precise and routine measurements of the density of fish eggs throughout development.

An analytical method for the simultaneous determination of five booster biocides (Sea-Nine 211, Dichlofluanid, Duiron, Irgarol 1051 and Pyrithiones) and degradation product of Irgarol 1051 (M1) in sediment from Vietnam was developed by LC/MS-MS. The recovery rates and relative standard deviation of the booster biocides in the sediment were in the range of 71–108% and 1.5–12%, respectively, and the detection limits were in the range of 0.04–2 μg kg−1 dry. An analytical method for the simultaneous determination of three booster biocides (Sea-Nine 211, Duiron and Irgarol 1051) and M1 in clams was also developed by LC/MS-MS. The recovery rates and relative standard deviations of the booster biocides in the biological samples were in the range of 60–99% and 3.4–6.8%, respectively, and the detection limits were in the range of 0.24–1.1 μg kg−1.

The booster biocides in sediment from the coastal area of northern and central Vietnam were measured using this analytical method. Sea-Nine 211, Dichlofluanid, Duiron, Irgarol 1051, M1 and Pyrithiones were detected in the range of 0.09–1.3 μg kg−1 dry, <0.10–13 μg kg−1 dry, 0.11–3.0 μg kg−1 dry, 0.05–4.0 μg kg−1 dry, <0.1–0.43 μg kg−1 dry and <2–420 μg kg−1 dry, respectively. The detection frequencies of Dichlofluanid, M1 and Pyrithiones were low. The species and levels of detected booster biocides varied between sampling stations.

Irgarol 1051 and its degradation product M1 were not detected in clams.

Chthamalus proteus sp. nov. is described as a distinct species based on its clear separation by starch-gel electrophoresis of enzymes. A redescription is given of C. fragilis, a related species, which differs absolutely from C. proteus in 3 out of 16 enzymes. Given the distinction of C. proteus from C. fragilis by enzyme methods, it has been possible to devise morphological criteria, involving simple measurement of the opercular valves and first maxilla, which can separate the two species in 99% of individuals. Although the morphological characters overlap slightly, the enzyme results show no evidence of hybridization. A species previously confused with C. proteus, C. bisinuatus from Brazil, differs considerably in morphology and is briefly redescribed.

Bivalve larvae constitute an important part of the plankton and there is a pressing need to be able to identify the various species.

The study of the development of the larval and post-larval hinge by scanning electron microscopy of 18 bivalve species shows the importance of this structure, which represents the principal character in identification of the young larval stages. This paper presents the principal distinguishing characters of the hinge (denticles, teeth and ligament) in eight families of bivalves.

Annual reproductive cycles of two commercially important bivalves, the razor clam Ensis siliqua and the clam Venus striatula were investigated. Specimens of both species were sampled monthly from a site off Vilamoura, south of Portugal, between June 1992 and May 1993. Gonadal development was monitored using standard histological methods. Observed gametogenic progression was categorized by six stages: (0) inactive; (I) early active gametogenesis; (II) late active gametogenesis; (HI) ripe; (IV) partially spawned; and (V) spent. Both males and females showed a synchronism in gonadal development. The gametogenesis in the razor clam began in December and by late April the gonads were characterized morphologically by an abundance of ripe eggs and sperm. Partially spawned individuals were first encountered in May. All were spent by July. The gametogenic activity in V. striatula began in the months of October/November and continued until March. Spawning occurred between April and early August. Both species reached maturity during the first year of life.

It has long been known that the corneas and lenses of some vertebrates are yellow in colour, and therefore affect the spectral quality of the light that reaches the retina. Various functions have been attributed to such intraocular yellow filters, such as the reduction of scattered light, chromatic aberration, and ‘glare’; and also possibly an increase in the contrast of some objects viewed against certain backgrounds (see Walls & Judd, 1933; Muntz, 1972, for reviews). It is of course likely that the yellow filters of different animals serve different functions, but it is also clear that in all cases, by absorbing a proportion of the incident illumination, they must reduce the animal's absolute sensitivity. In agreement with this, there is a general tendency for animals with yellow filters to be diurnal, and occupy brightly lit environments. Among the fishes in particular, there is a tendency for yellow lenses and corneas to be especially common among diurnal groups, which avoid the consequences of the inevitable loss of sensitivity by remaining inactive at night (Muntz, 1973).

Food resource partitioning and trends in feeding strategies were examined in 3882 individual decapod crustaceans collected from 1989 to 1990, using bottom trawls at depths between 380 and 2261 m in the Catalan Sea (western Mediterranean). The vertical distribution of available food resources near the bottom was the most important factor responsible for food resource partitioning among bathyal decapod crustaceans by depth stratum and season. Decapods were assigned to five different trophic groups according to the food resource exploited and feeding strategy employed (macroplankton feeders, macroplankton-epibenthic feeders, epibenthic feeders, epibenthic-endobenthic feeders, and deposit feeders). There was little dietary overlap, indicating that species did partition the available resources. Overall, dietary overlap values among species increased with depth. Although a trend to increase H’ values for diets with depth was observed, this was not significant (P < 0.10), whereas differences in the percentage of empty stomachs and the frequency of foraminiferans and pteropods in the foreguts increased significantly (P < 0.05) with depth. This last result is indicative of a progressive increase in the importance of deposit feeding in decapod crustaceans as depth increases.

Experiments are described which test the hypothesis that the cuttlefish controls the relative volumes of gas space and liquid within its cuttlebone by an osmotic mechanism acting across the siphuncular surface of the bone. When the animal is at the bottom of the sea it would maintain the gas space within the cuttlebone by balancing the hydrostatic pressure of the sea by an osmotic force between the liquid within the cuttlebone and the blood.

In cuttlefish kept for some weeks in shallow water in an aquarium all the liquid taken from the cuttlebone is almost isotonic with the animals’ blood.

In animals recently hauled from the bottom of the sea the cuttlebone liquid is markedly hypotonic to sea water and hence to the blood.

These lower osmotic concentrations are given chiefly by reduction in the concentrations of the sodium and chloride ions.

After bringing animals up from about 70 m to the surface of the sea the osmotic concentration of the cuttlebone liquid rises from about 75% of sea water some 40 min after starting to haul the trawl, to about 97% of sea water 6 h later. Extrapolation back to the time at which hauling began gives a concentration of salts close to that predicted by the osmotic hypothesis.

Whilst the cuttlebone liquid is increasing in ionic concentration the liquid deeper in the cuttlebone is hypotonic to that just inside the siphuncular surface. This is explained in terms of the slowness of exchange of salts along the narrow channels between the lamellae of the cuttlebone.

Hydrobia ulvae has featured in many reports on the ecology of estuaries and mud-flats, yet surprisingly there are few detailed studies on population structure, growth and the breeding cycle. Population densities fluctuate widely from one locality to the next, and the variation in size recorded for the adults suggests significant differences in growth rate and the size at which the snails become sexually mature. The occurrence of Hydrobia in the stomachs offish and birds is well documented (Clay, 1960) and the suggestion that this species may influence the breeding success of some species of bird (Anderson, 1971) illustrates its importance in the ecology of estuaries and salt marshes.

Nassarius reticulatus, like most other members of the Nassariidae and Buccinidae, is a scavenger. It apparently relies on the rapid detection and location of a food supply which is intermittently and unpredictably available. The olfactory reactions of Nassarius species are well-adapted for finding dead or damaged animals (Copeland, 1918). Stimuli indicating the presence of food provoke an impressive increase in activity of most starved Nassarius (Dimon, 1905; Copeland, 1918). Recently-fed whelks, however, often fail to respond to the same stimuli (Crisp, in preparation).

The peculiar and exacting environment of Tigriopus fulvus is discussed and a census of Tigriopus from a series of pools in the Isle of Man is given.

Experiments have been made determining the resistance of Tigriopus to desiccation and its revival in favourable circumstances.

The life history has been worked out, times taken in development noted, and the various stages compared and contrasted with those described by Guiglia.

Sex can be determined at the fourth copepodid stage. Females are normally fertilised as fifth copepodids, but the males are not functional until the adult stage. A single female may produce several egg sacs giving rise to living nauplii from a single fertilisation.

There is no evidence for parthenogenesis.

Data from nearly 900 individual herring sampled in the North Shields, Whitby and East Anglian fisheries during the period 1956–60 demonstrate a linear relationship between the percentage fat and the percentage water contents for whole herring minus gonads and gut content, and the fat/water line derived from the data is described.

The salt-marsh under investigation is situated at Aberlady Bay on the south shore of the Firth of Forth, fifteen miles east of Edinburgh.

The marsh is small and occurs at the mouth of a stream. The character of the soil on the two banks differs, being on the one side muddy with permanent pools, and on the other sandy, so that the pools tend to drain dry. The vegetation of the pools is variable, some containing species of Zostera, Ulva, Enteromorpha and Vaucheria, others having only diatoms.

The unicellular cyanobacterial species Synechococcus and Prochlorococcus are known to be vital components of marine ecosystems, especially in the vast oligotrophic areas. Lytic cyanophages infecting unicellular phytoplankton are prevalent and have been demonstrated to act as important constraints on community composition contributing to the seasonal succession in genotypes. Lysogeny in Synechococcus has been documented experimentally in natural environments by prophage induction. At this time it is completely unknown how prevalent lysogeny is among Synechococcus populations. This study was performed to document important features such as size, morphology and the incidence of the T4-like capsid portal protein gene (g20) in a group of lytic Synechococcus cyanophages (35 isolates) isolated from the Gulf of Mexico. A group of Synechococcus isolates (24 strains) were isolated concurrently to investigate the virulence and cross-infectivity of the lytic cyanophages and to determine the frequency of lysogeny by detection of inducible prophage. The host range of the cyanophages toward these Synechococcus strains ranged from 1 of 25 (host of isolation only) to 17 of 25 (68%). Of the 35 cyanophage isolates the large majority were myoviruses (94%) and only two (6%) were of the podovirus type. The expected polymerase chain reaction product for g20 was detected in 20 of the phages (63%). The presence of a detectable g20 was associated with low-infectivity cyanophages at the 90% confidence interval. The Synechococcus strains varied in their resistance to lytic infection from 11% to resistance to all of the phage isolates utilized in testing. The prevalence of inducible prophage-like particles was determined in the Synechococcus strains using mitomycin C and enumerating viruses by epifluorescence microscopy. A statistically significant increase in viruses was detected in 11 of the strains (46%) in response to mitomycin C. There was no observed relationship between the occurrence of prophage induction in the Synechococcus isolates and their resistance to lytic infection. One putative lysogen was induced by continuous high light and contained a prophage-like particle with a single-stranded DNA (ssDNA) genome. Such a prophage-like particle is unlike any prophage described to date, implying that the process of lysogeny is unique in certain marine Synechococcus strains.

After initial trials a technique was devised which made it possible to rear about 12 % of newly hatched larvae of the pilchard Sardina pilchardus (Walbaum) to a point well beyond the yolk-sac stage. A survival rate of this order was considered quite satisfactory for larvae which are so small at hatching.

Specimens of Littorina littorea from unpolluted (Menai Bridge) and metal polluted (Restronguet Creek) sites have been analysed for ten metals in eight different tissues. The concentrations of metals in whole animals and in individual tissues have been subjected to linear correlation analysis to establish metal/metal and tissue/tissue interactions. The results indicate that copper and magnesium are accumulated independently by specific connective tissue cells. Group A metals are largely accumulated by the digestive gland whereas group B metals are concentrated by the kidney. At low levels of metals there may be competition for particular ligands but at higher levels of pollution new ligands may be induced in particular cells. The implications of these interactions are discussed in terms of cell physiology and related to the significance of the use of biological organisms as indicators of metal pollution.