Distinctive flask-shaped cysts have been observed within the loricae of the tintinnids Favella serrata (Mobius),Helicostomella subulata (Ehrenberg), Parundella caudata (Ostenfeld) and Leprotintinnus pellucidus (Cleve) from samples taken by the Continuous Plankton Recorder. Similar cysts occur as a common element in palynological preparations of intertidal sediments from the British Isles. Encystment in tintinnids is now known for over 20 species and appears to be a more important process in the tintinnid life-cycle than previously believed. A possible relationship between tintinnid cysts and the extinct microfossil order Chitinozoa is proposed.

The Mediterranean proliferation of Caulerpa taxifolia provides an opportunity to examine the extent to which an introduced species can modify biodiversity. During 1992, benthic invertebrates were sampled in Roquebrune-Cap Martin area, at depths of 6 and 10 m, from a Caulerpa station and a reference station. Species richness is slightly lower at 6 m within Caulerpa while the number of specimens is much reduced at both depths. Similarity indices compare well between reference and Caulerpa stations.

Caulerpa taxifolia, distributed in tropical seas, was recorded for the first time in the Mediterranean in 1984, as a single 1 m2 patch. This surface increased to 3 ha by 1990, 30 ha in 1991, 100 to 430 ha in 1992, and 1000 to 2000 ha at the end of 1993 (Meinesz & Hesse, 1991; Boudouresque & Meinesz, 1994).

Maximum colonization is between 2 and 6 m depth, but the alga has been observed down to 99 m. Density can reach 350 m of fronds and 14,000 leaves per m2. Caulerpa taxifolia colonizes any type of substrate and invasion results in a drastic impoverishment of the algal components of the communities (Boudouresque et al., 1992; Verlaque & Fritayre, 1994). According to these authors, maximal poverty of communities coincides with the maximal development of C. taxifolia (summer-autumn) and epiflora is negligible, except during spring.

These changes may induce functional and structural modifications of the fauna that lived in the communities before infestation. Invasion, particularly of photophilic algae and Posidonia beds (Ros et al., 1985), can modify quality and intensity of physical, chemical and hydrodynamical factors, number and quality of shelters, quantity and quality of food, and exchange of individuals between communities and populations.

Planktonic, benthic and littoral Crustacea were collected from localities around the British coast, from Norwegian and Faeroese waters and from the Antarctic, and their content of preformed vitamin A and carotenoid pigments was measured.

Methods are described for the preservation of specimens, the extraction and separation of vitamin A and carotenoids and the measurement of vitamin A by chemical, physical and biological tests, and of carotenoids by physical tests.

Free-swimming euphausiids were found to contain, in addition to large quantities of astaxanthin, high concentrations of preformed vitamin A, but no β-carotene.

The presence of fin whales in the Mediterranean Sea has been documented since ancient times. In spite of this, reliable information on their ecology and distribution is limited to the north-western part of the basin. Recent genetic studies have demonstrated that Mediterranean fin whales comprise a separate population with very limited gene flow with their North Atlantic co-specifics. Although both published and anecdotal information reports their presence in the south central Mediterranean during winter, there is no information on habitat use. In February 2004, a 14-day boat survey was carried out in the waters surrounding the island of Lampedusa, where fin whales occur at this time of the year. A total of 20 fin whale groups (average group size two animals) were encountered. In each encounter the animals were engaged in surface feeding activity. From plankton samples and underwater video, the prey species was identified as the Euphausiid, Nyctiphanes couchi. The information obtained suggests that this area may be an important winter feeding ground for fin whales. The results represent significant new information on fin whale ecology in the Mediterranean, with associated conservation and management implications.

The newest chamber of a cuttlebone is always incomplete and full of a watery solution. This contains sodium and potassium in concentrations close to those of sea water.

The second newest chamber contains a gas space and sometimes contains liquid. This liquid is rarely localized at the siphuncular end of the chamber. It is not certain that liquid is initially extracted through the siphuncular wall of the chamber, although this is possible.

When liquid is pumped out of a newly formed chamber the salt which it initially contains is not left behind, either free or bound into the structure of the bone.

The 3rd to about the 10th newest chambers usually contain no visible liquid. But their siphuncular walls are permeable to liquid and liquid does enter these chambers when the cuttlebone becomes very dense.

At cuttlebone densities around 0·6, i.e. close to values which will make the cuttlefish neutrally buoyant, the older and more posterior chambers are almost full of liquid. This liquid can, however, be pumped out. When a cuttlebone has a density around 0·5 very little liquid can be seen in any of its chambers.

The pressure of gas within a newly ‘pumped out’ chamber is very low, but by the time a chamber has become the ninth newest the pressure of gas is close to the average value for the whole cuttlebone, i.e. about 0·8 atm.

The low pressure of gas found in the newest chambers is explained by the slowness with which gas diffuses into a space created by the active removal of liquid.

We examined recent arguments that leptocephali of the European eel, Anguilla anguilla, swim in an oriented manner, rather than drift, to reach the continental shelf of Europe and the Mediterranean Sea. There is a cline of increasing body length of leptocephali from south to north and from west to east from the Mid-Atlantic Ridge (30°W) to the continental shelf, which could represent migration from south-west to north-east, transport eastward at all latitudes, or increased growth rate with latitude. Evidence that this cline is a trend in age of arriving glass eels along the European coast, and that the duration of migration is less than one year, is weak. Ages reported in the literature for specimens from Morocco to The Netherlands were based on the unvalidated assumption that rings in otoliths were deposited daily. The assumption is unwarranted because of low metabolic rate and uncertainty of nutritional mode of leptocephali. If the assumption were accepted, calculated hatching dates of eels arriving at the European coast imply year-round spawning. Lengths of leptocephali in the Sargasso Sea at various times imply that eels spawn only in late winter and spring. Leptocephali contain tiny amounts of muscle, especially aerobic muscle for sustained swimming. They probably have insufficient capability to swim across the Atlantic in the less than 1–2 y reported by others.

All species of the Mysidacea (Crustacea) lay their eggs into a marsupium, thus allowing direct counts of brood sizes to be made. The different forms of the young stages in the marsupium are closely similar in all species. The most detailed embryological studies are those of Manton (1928) on Hemimysis lamornae (Couch), Wagner (1896) and Needham (1937) on Neomysis integer (Leach), and Nair (1939) on the tropical species Mesopodopsis orientalis (W. M. Tattersall). Kinne (1955) describes and figures the general body forms of the different stages of development of the larvae in the marsupium of Neomysis integer; Vannini (1930) examines the larvae of Leptomysis lingvura (G. O. Sars), while Kane (1904) illustrates the most advanced larval stage of Mysis relicta Lovén. The larvae of several non-British species have been described -Boreomysis arctica (Kröyer) by Jepsen (1965), Mysidium columbiae (Zimmer) by Davis (1966) and Neomysis intermedia Czerniavsky by Murano (1964b).

The brown shrimp Crangon crangon (L.) is a burrowing caridean decapod, inhabiting sandy, sandy-mud and muddy substrata down to 90 m, but occurring mainly in shallow water and between tidemarks (Lloyd & Yonge, 1947; Allen, 1966b). The species also exhibits seasonal inshore and offshore migrations, reportedly in relation to salinity, temperature and availability of food (Ehrenbaum, 1890; Havinga, 1929, 1930; Meyer, 1935; Broekema, 1941, Academy Thesis, Groningen; Lloyd & Yonge, 1947; Allen, 1966a, b; Tiews, 1970). In addition Hartsuyker (1966) reported up and downshore migrations on each tidal rise and fall in the Wadden Sea. In contrast, Havinga (1929) stated that the species rests quietly buried in the substratum by day and feeds at night, and nocturnal emergence was confirmed by Lloyd & Yonge (1947) in aquarium observations. However the latter authors found no difference between field catches during day and night tides in the Bristol Channel and Severn Estuary. Tiews (1970) reported greatest activity at dusk and that C. crangon continued to swim during the night even after feeding. So far there is therefore evidence of nocturnal and tidal rhythms of emergence in C. crangon which deserves further experimental investigation.

In a previous paper (Hancock, 1955) an account was given of the feeding behaviour of the starfish Asterias rubens L. and the common sunstar Solaster papposus (L.) on Essex oyster beds. In discussion, it was stated that there was no evidence that, in the conditions described, a cultivated oyster ground provided a greater attraction than an uncultivated one. The present work was undertaken to provide information on this subject, and also on the movements, growth and ecological relationships of starfish. Further experiments were made on feeding behaviour, particularly of the young starfish.

Previous (workers who have examined the gut contents of members of the genus Parathemisto, and who have kept and fed specimens in laboratory conditions, have concluded that they are chiefly carnivorous in habit, feeding largely on zooplankton, and to a lesser extent on phytoplankton (Conover, 1960; Baker, 1963; Kane, 1967).

The gut of P. gaudichaudi has been found to contain almost intact copepods, especially Calanus and occasionally Temora (Bigelow, 1926 – Gulf of Maine); young specimens of Euphausia superba (Hardy & Gunther, 1935 – Antarctic); and copepods (Nemoto & Yoo, 1970). Siegfried (1965 – west coast of S. Africa) found P. gaudichaudi to be a rather indiscriminate feeder, its gut contents reflecting the composition of the plankton.

Laboratory and field observations were made on the food and feeding of the starfish in relation to its role as a predator on oyster beds in the rivers of Essex, particularly in the river Crouch.

Asterias rubens was found most likely to be associated with large numbers of Crepidula, the most serious competitor of the oyster.

Laboratory experiments showed that although Asterias occasionally ate spat and adult oysters, the greater part of its food was made up of organisms which are competitors of the oyster. The smaller sizes of Asterias ate large numbers of barnacles, with occasional spat of oysters and Crepidula. The larger occasionally ate oysters and oyster spat, but almost always exhibited a preference for mussels and, in the absence of these, for Crepidula, and sometimes even for Urosalpinx.

Some observations were made on the method and rate of feeding and distribution of Asterias and Solaster papposus, and certain aspects of the feeding behaviour of the stone crab, Hyas araneus.

It was concluded that Asterias is not such a serious enemy of the oyster as was previously supposed, and that under certain conditions, its presence may be beneficial to oyster culture.

Coralline algae are important reef-builders which can form nodules, known as rhodoliths, occurring worldwide in beds sustaining a high biodiversity. Although considered a non-renewable resource, they are exploited as a source of calcium carbonate used mainly for agricultural purposes. In Brazil between 96,000 and 120,000 metric tonnes of rhodoliths are extracted per year. Besides the direct impact caused by removal on the coralline bed, the dredge process may also produce a plume of fine sediment, which can change the primary production of the remaining organisms. In this study, four treatments, with three replicates, were used to acquire Lithothamnion sp. net photosynthetic rates with and without a sediment layer using a Clark-type oxygen microelectrode and micromanipulator. The results demonstrated that, under controlled conditions, the addition of a thin sediment layer resulted in a 30% reduction of the irradiance, decreasing the Lithothamnion sp. net production in 70%. For this reason direct and indirect effects of mechanical exploitation of the rhodolith beds should be included in future studies that focus on environmental impacts of dredging activity, whether it is linked to the extraction of these algae.

Cultural experiments were made with marine organisms in enriched crude sea water and in bacteria-free cultures with the phosphorus supplied in different forms. It was found that pyrophosphate cannot be utilized as a source of phosphorus as effectively as orthophosphate by the organisms cultured, i.e. Phaeocystis Pouchetii, Skeletonema costatum and Nitzschia closterium. Growth of Phaeocystis Pouchetii was a little better and lasted longer when phytin was supplied to natural sea water as a source of phosphorus than when orthophosphate was supplied. Phytin can also support a growth of Skeletonema costatum and Nitzschia closterium as good as, or a little better than, orthophosphate.

The organic phosphorus compounds used in these experiments were found to be broken down into orthophosphate in natural sea water. In bacteria-free cultures phytin and glycerophosphoric acid can be effectively used as such by Nitzschia closterium forma minutissima as a source of phosphorus, while sodium nucleinate and lecithin can not be effectively used as such. The organic phosphorus dissolved out from the blades of Laminaria can also be utilized by this diatom as effectively as orthophosphorus.

It would seem, therefore, that not only the dissolved orthophosphate as generally assumed, but the dissolved organic phosphorus in the sea may also be absorbed and utilized by plants.

Since the publication of Heincke's classic treatise on the herring the counting of vertebrae has become a standard operation in the biometric analysis of samples of teleostean fishes taken at random from local populations. But while such routine counting has undoubtedly added greatly to our knowledge of the incidence and magnitude of vertebral variation in a number of economically important species, it has occasioned no little confliction of opinion as to the significance of this variation. Difficulties arising out of my own work on the herring at Plymouth have led me to make a general study of the teleostean backbone in as many species as possible, in an endeavour to learn more of the nature, extent and cause of vertebral variation. After examining over one hundred species, mostly from local waters, I have come to the conclusion that the subject presents a great and varied field of research which is at present but little explored. It would be idle to suggest, therefore, that the present paper should be considered as anything more than an introductory survey of the many problems awaiting detailed investigation. Even so, it may serve to indicate the scope and present position of the Plymouth studies, and prepare the way for fuller work in the future, both at Plymouth and elsewhere.

I have received the greatest assistance from Mr L. S. Wisdom, Laboratory Attendant at the Plymouth Laboratory, whose skill in preparing skeletons for study, and keen interest in all matters relating to the research, I most gratefully acknowledge.

A further 69 recaptures are reported from a tagging study of pelagic sharks initiated in 1970 in the north-east Atlantic. Galeorhinus galeus tagged in England were recaptured in the eastern Atlantic from southern Spain to north-west of Iceland. Among the 42 G. galeus recaptured the longest time at liberty was about 12 years and the greatest distance travelled was 2461 km. Among the 21 Prionace glauca recaptured the l ongest time at liberty was 10.7 years, and seven sharks moved distances between 4362 and 7176 km. One shark tagged in south-west England was recaptured in the South Atlantic off South America. An Isurus oxyrinchus was at liberty for 4–6 years and a Lamna nasus for up to about 13 years. Lamna nasus were recaptured from northern Norway to northern Spain. The growth rates of the tagged sharks were close to the predicted values for G. galeus, were slower for P. glauca and faster for L. nasus.

Summer outbreaks of Gyrodinium aureolum in European coastal waters have been described since 1966 (Braarud & Heimdal, 1970). The coincidence of G. aureolum blooms and observations of noxious effects on fauna (Widdows et al., 1979; Tangen, 1977; Jones et al., 1982; Southgate et al., 1984; Potts & Edwards, 1987; Thain & Watts, 1987) is well documented. However, great differences in toxic effects have been found in in vitro studies (Partensky & Sournia, 1986), with critical cell densities varying from 6×105 cells 1−1 to 3×107 cells 1−1. Production of a lethal agent has been suggested by Turner et al. (1987). More recently, the toxic principle has been identified by Yasumoto et al. (1989).

Total arsenic concentrations were determined in three teleost species (herring Clupea harengus; cod Gadus morhua, and flounder Platichthys flesus) taken from four locations in the Baltic and North Sea with salinities ranging from 8 to 32 psu. Individual arsenic concentrations ranged from 0·04 to 10·9 mg/kg wet mass, and there was a positive linear relationship between arsenic concentration and salinity for all three species (r2 0·44 to 0·72, all P<0·001). Although it is well known that marine fish contain much higher concentrations of arsenic than do freshwater fish, the data reported here are the first showing a relationship between the total arsenic concentration in fish and salinity.

This study evaluates the role of protozoa in larval fish feeding by describing protozoa in larval fish diets and testing the hypothesis that, in the Irish Sea, larval fish feed on protozoan prey at rates that potentially sustain their food requirements. Gut contents of 11 taxonomic groups of larval fish were examined, and protist prey occurred in the diet of all of them. Protozoan prey were identified, which provided an insight into their trophic role. Most of the protozoan prey were autotrophic or mixotrophic. In general, larval fish diets were constant over the spring/summer period, regardless of prey availability in the field and the composition of larval fish assemblage (taxonomy and size). A laboratory experiment on ingestion rates of flounder larvae as a function of ciliates concentration was conducted. Combined laboratory and field data showed that, in the Irish Sea, it is unlikely that ciliates are often the primary food source of flounder larvae, and, by implication, other larval fish as well. However, ciliates and other protozoa could be a substantial component of the larval fish diet, and they may potentially prevent food limitation.

A population of the lamellibranch Tellina tenuis in the Exe estuary is shown to be uniformly distributed, indicating a significant degree of ‘over-dispersion’.

By plotting the position of each shell in squares of m.2 area it is shown that fewer individuals than would be expected occur less than 1 in. from their nearest neighbour, and none occurs closer than 0·6 in.

When the population density was artificially increased on the shore the same characteristic spacing was found at a moderate density, but not at a rather higher density.

It is suggested that spacing is correlated with the foraging activities of the inhalent siphon on the soil surface.

Very dense populations have been found by Stephen in other areas, indicating that the size of the ‘territory’ does not limit density. His results show no evidence of the same phenomena as observed in the Exe.

The results of the writer's investigations on the ciliary mechanisms on the gills of Mollusca and Amphioxus (1 and 2) gave rise to the suggestion that similar mechanisms might probably also occur in Brachiopods, for it is a well-known fact that Brachiopods—like some Molluscs and Amphioxus—feed on the smaller organisms which are to be found floating in the sea. Owing to the kindness of Dr. H. C. Williamson, of Aberdeen, I have been able to examine living Crania which were obtained by dredging in Loch Fyne, and living Terebratula have also been obtained from Naples. An investigation of the living gill-filaments—or lophophoral cirri, as they are frequently termed in this group—showed that the ciliary mechanisms on these filaments are essentially the same as those occurring on the gill-filaments of Amphioxus, Lamellibranchs, some Gastropods, and most Ascidians. As it was found that existing accounts of the mode of feeding in Brachiopods are vague and incomplete the following description of the process has been written.