The oxygen uptake of eggs and larvae of Norwegian herring from Bergen (mean unfertilized egg dry weight about 035 mg) and of Baltic herring from Kiel (mean unfertilized egg dry weight about 0·10 mg) was measured by a reference diver and a Warburg respirometer. Anaesthetized Kiel larvae had values of about 0·10μl./larva/h and Bergen larvae 0·25μl./larva/h. When expressed as Qo (μl./mg dry weight/h) the values became Kiel 2·3, Bergen 2·5.

Oxygen uptake of embryos before hatching and of larvae, expressed as Qo, was most affected by activity, increasing in very active organisms by five to ten times the resting value of 1-2 μl./mg dry weight/h. Experiments to test the effects of temperature and salinity were done using anaesthetized larvae in some cases.

Temperature experiments with larvae gave a Q10 of about 2, the Qo, of anaesthetized Kiel larvae ranging from about 2·0 at 50° C to 35 at 14°C, and that of unanaesthetized Bergen larvae from 2·5 at 6° C to 50 at 140°C.

Eggs and larvae of both races reared in salinities from 5 to 50 %0 showed no detectable difference in oxygen uptake. However, abrupt transfer of anaesthetized larvae from one salinity to another caused violent fluctuations (by up to ten times) before adaptation took place. Buoyancy differences appeared to mask differences in oxygen uptake of unanaesthetized larvae in similar transfer experiments.

There was little tendency for oxygen uptake to become reduced during darkness in either Bergen or Kiel larvae.

The effect of age on oxygen uptake (expressed as Qo) was not marked, though there tended to be a peak at, and just after, hatching, with a tendency for a fall off during starvation.

During the course of earlier work with larvae of Ophelia bicornis Savigny it became increasingly clear that a major factor in stimulating these larvae to settle and metamorphose is the presence, on sand grains of suitable size, of living micro-organisms such as bacteria, in numbers neither too many nor too few (Wilson, 1954). It had been shown that an acid-cleaned sand (which is neutral or almost so) kept in sea water becomes increasingly attractive to these larvae with time. It had been admitted, however (loc. cit., p. 366), that these results were derived from a comparison of experiments not designed to this end, and that further tests, planned for the purpose, were desirable.

Metazoan meiofauna were studied in replicated multiple-corer samples obtained at a bathyal site (1320–1360 m depth) in the Porcupine Seabight (51°36′N 13°00′W) before (April) and after (July) the delivery to the seafloor of a phytodetrital pulse originating from the 1982 spring bloom. In all samples the metazoan meiofauna was dominated by nematodes; harpacticoid copepods and their nauplii were the second most abundant taxon. Population densities and biomass were very similar in both sample sets, the only significant differences being in the numbers of ostracods (higher in April) and nauplii (higher in July). Furthermore, vertical distribution patterns in the top 5 cm of sediment indicate that the meiofauna did not migrate towards the sediment surface following the phytodetrital pulse. The lack of a metazoan meiofaunal response contrasts with published evidence, based on the same samples, for a substantial increase in the foraminiferal abundance following the sedimentation event. Thus our results suggest that metazoans (as a whole) fail to exploit and utilize phytodetritus as rapidly as foraminifera. This probably reflects the energetic expense of egg production coupled with frequently slower rates of somatic growth among metazoans. In addition, foraminifera may outcompete metazoans for detrital food because they possess extremely efficient food-gathering organelles (granuloreticulate pseudopodia) and are able to raise their levels of metabolic activity very rapidly. However, metazoan responses at the species level, or over longer time periods (>3 months), would not have been detected and so remain a possibility.

An examination of infra-red satellite images of the North-West European continental shelf suggests that cross-frontal mixing takes the form of cyclonic eddies. These are about 20–40 kmin scale and persist for a few days. It is suggested that the dynamics of cyclonic eddies willbe important in the development of frontal phytoplankton blooms.

There are three species of chthamalids in Europe. Two of them, Chthamalus stellatus and Chthamalus montagui, overlap extensively in geographic range: they occur together along the whole Atlantic coasts of Britain, Ireland, France, Spain and N. Africa, and both also occur in the Mediterranean Sea. They have almost identical north-eastern limits to their distribution in the English Channel and N. Scotland, but C. stellatus may extend farther south along the W. African coast. These two species also show overlap in their vertical distribution, though C. montagui is usually commoner in the upper barnacle zone while C. stellatus may be dominant lower down. The species are separated by habitat, C. stellatus favouring wave-beaten open coast sites, C. montagui more embayed situations, but there is still extensive overlap. The third European species of chthamalid, Euraphia depressa, has a more restricted vertical distribution and is almost entirely confined to the Mediterranean Sea, where it favours high-intertidal levels in wave-beaten places, and also cryptic habitats.

Microbial films represent the site at which grazers exert their influence upon the recruitment of settling macroalgae and animals. The overall purpose of this study of seasonal and spatial variation in abundance and composition of epilithic microbial films was to relate such patterns to macrobenthic community dynamics within the Fucus-bar- nacle mosaic characteristic of moderately exposed rocky shores on the Isle of Man. Additionally selective grazing in Patella vulgata was examined by comparing dietary and epilithic microalgal assemblages and how this varied seasonally and spatially within the mosaic. Chlorophyll analysis was used as an index of microalgal standing crop while SEM allowed in situ estimation of microalgal abundance.

In a recent paper we reported on the discovery of an adhesive antennular secretion used by exploring cyprids of Balanus balanoides (L.) and hinted at its possible implication in settlement behaviour (Walker & Yule, 1984). This secretion is thought to be modified integumentary protein. Since the integumentary protein of adult B. balanoides is widely accepted as a powerful stimulus to settlement (Knight-Jones, 1953; Crisp & Meadows, 1962, 1963; Larman, Gabbott & East, 1982), we devised settlement experiments in May 1984 to investigate whether cyprid antennular secretion acts in a similar manner. The outcome of these experiments with B. balanoides cyprids is presented here.

The organization, cellular composition and function of the digestive diverticula has been described for a large number of molluscs (Nakazima, 1956; Owen, 1966; Purchon, 1968). Changes in the digestive cells which are associated with intracellular digestion have also been widely recognized (Graham, 1938; Carriker, 1946; J. E. Morton, 1955, 1956, 1959; Owen, 1955, 1966, 1970, 1972; Sumner, 1965, 1966a, b, 1969; Morse, 1968; McQuiston, 1969; Walker, 1970; Merdsey & Farley, 1973). In general the digestive cells show three cyclic phases, (1) absorption, (2) digestion, (3) fragmentation and excretion, and these phases, with only minor modifications, are typical of most molluscs (Owen, 1966). In many groups, especially gastropods, the changes in the digestive cells within the tubules of the digestive diverticula often appear to be synchronized and consequently the tubules have a uniform appearance throughout the diverticula. In the Bivalvia, however, this type of synchrony has not generally been recognized. Since bivalves have been considered to feed more or less continuously (Purchon, 1971; Winter, 1973) it is not surprising that a homogenous appearance was only exceptionally observed, e.g. J. E. Morton (1956), J. E. Morton, Boney & Corner (1957).

The biology of the bass in British and Irish waters has not been studied in the same detail as the biology of commercially important species, such as gadoids, flatfishes, mackerel and herring.

Photographic recording at hourly intervals of a group of animals contained in a small tank kept in continuous darkness has revealed a 24 h cycle of locomotor activity in Daphnia magna and in Calanus helgolandic

A change in periodicity of the rhythm in Daphnia kept under continuous illumination suggests that the cycle is not determined by external stimuli

The phasing of the cycle differs in the two animals, but in both there is an increase in activity during the hours of darkness.

In Calanus and possibly also in Daphnia, the cycle of activity is absent in the winter months.

Globigerinoides sacculifer (Brady), a common planktonic foraminifer collected by SCUBA off Barbados, was maintained under six feeding regimes at constant light and temperature conditions. Five groups of 63 specimens each were fed 1-day-old Anemia at the rate of one nauplius per specimen every 1, 2, 3, 4 or 7 days. A starved control group received no Anemia. The rate of chamber formation and shell size increased proportional to the feeding frequency. However, an inverse correlation existed between survival time and feeding frequency. Normally, survival time ends with gametogenesis which terminates the life of the mother cell. Organisms fed more frequently reached maturity and underwent gametogenesis more rapidly than those fed less frequently. The average survival time of G. sacculifer in culture ranged from 7 days for the daily-fed group to 11 days for the group fed every 7 days. While the latter grew more slowly they eventually reached maturity. Starved individuals rarely formed chambers and often died without undergoing gametogenesis. Symbiotic zooxanthellae presumably prolonged survival of starved organisms. Extrapolation of survival data suggests G. sacculifer has a variable life span of 2 to 4 weeks depending on food availability.

Concentrations of Zn have been determined in the tissues of normal lobsters from sea water containing about 5μg/1. of Zn. The blood usually contains about 6 μg/g of Zn, mostly in the serum, while the soft tissues contain between 10 and 50 μg/g. Long exposure to sea water containing 100/μg.g/l. of Zn fails to alter the Zn concentrations of the blood, muscle and gonads, but increases the levels in the urine, excretory organs, hepatopancreas and gills. This result suggests that extra Zn is absorbed from high Zn sea water, possibly via the gills, and that two methods by which this is removed from circulation are by urinary excretion and absorption by the hepatopancreas.

Changes in the blood Zn concentration produced by injection are rectified quite rapidly in the same way. Injections failed to change the Zn concentrations of muscle and gonads.

Further experiments showed that Zn can be absorbed rapidly from the stomach and reaches the blood partly at least via the hepatopancreas. Again, this extra Zn is removed from the blood by urinary excretion and by absorption in the hepatopancreas. Eventual removal of Zn in the hepatopancreas probably takes place via the blood and excretory organs rather than via the gut. The role of the gills and gut in the regulation of the body Zn content has not yet been studied.

An apparatus in which it is possible to observe the horizontal migrations of zooplankton in gradients of phytoplankton is described, and an account given of its use in experiments involving various organisms. A preliminary search for toxic organisms is also described.

The experiments comprise a demonstration of a migration by various animals into concentrations ofthe diatoms Skeletonema, Thalassiosira, Biddulphia, Nitzschia and various mixed cultures and the flagellates Chlamydomonas, Peridinium, Dicrateria, K, and Oxyrrhis. Cultures of Rhodomonas and Gymnodinium II are found to produce the opposite effect, and no reaction towards Lauderia, Coscinodiscus, Eucampia, Syracosphaera and Exuviaella could be shown. Results with bacteria cultures andvarious inorganic gradients are also discussed.

A second apparatus in which it is possible to observe the vertical migrations of zooplankton in the presence and absence of phytoplankton is also described, and an account given of experiments in it involving various organisms.

The experiments comprise a demonstration that greater numbers of animals swim up in the presence of mixed phytoplankton cultures, Coscinodiscus, Skeletonema, Ditylum, Chlamydomonas, Gymnodinium I and II and Oxyrrhis than in unenriched water. Flagellate One has no effect and Chlorella possibly depresses the number swimming up.

Under-water observations on the swimming movements of some of the animals used are described. The possible application of the observations towards resolving the problem of the inverse distribution of phytoplankton and zooplankton in the sea is discussed, and the hypothesis is proposed that this may be accounted for by a combination of migration and grazing. It is considered that plankton animals must migrate both horizontally and vertically into patches of phytoplankton and, when present in sufficient numbers, graze these down very quickly.

Between 1984 and 1993, levels of imposex (the induction of male characters including a penis on females) were measured in gastropods Nassarius (Hinia) reticulatus (L.) at localities in south-west England. Since tributyltin (TBT) was thought to cause imposex, concentrations in tissues and sea-water were also determined. Measurements made prior to the restriction of TBT usage in 1987 showed that intensities of imposex were related to TBT levels in females. Tissue concentrations were also related to those of sea-water and concentration factors (dry tissue/water) were approximately 30,000 at 10 ng Sn I-1 and 75,000 at 1 ng Sn I-1. Penis development in females was initiated at about 1 ng Sn I-1 and in this respect JV. reticulatus appears less sensitive to TBT than the dog-whelk Nucella lapillus.

As result of the TBT restrictions, concentrations in sea-water and tissues at some of the more polluted sites decreased by factors of 5–10 times between 1987 and 1993. However, population imposex declined very slowly. This was attributed to the longevity of the snails, the slow decline of penis-length in older females and the limited recruitment of less-affected females.

It was concluded that N. reticulatus is a useful alternative to N. lapillus as an imposex-based TBT indicator at contaminated sites. However, when environmental TBT concentrations are declining fairly rapidly, analysis of N. reticulatus tissues provides a far better indication of change than measurements of population imposex.

INTRODUCTION

In an earlier study (Corner et al. 1974) the copepod Calanus helgolandicus (Claus) was found to feed actively on nauplii of the barnacle Elminius modestus Darwin, one adult female ingesting a maximum daily ration equivalent to 25% of the body nitrogen. The present work, in which Elminius nauplii have again been used as a diet, extends the earlier study by determining how efficiently Calanus digests an animal food. In addition, the methods used have provided information on other aspects of carnivorous feeding by Calanus, including the relationship between food concentration and size of ration ingested as well as gross growth efficiency, i.e. the proportion of ingested food invested in growth.

The present study forms part of a more extensive one on the ecological factors which govern the distribution of the microfauna inhabiting seaweeds on rocky sea-coasts. This part of marine ecology is lagging far behind other branches. I wish to stress two points in particular: fasirst, that our understanding of the composition of the littoral (intertidal) fauna would increase very much if this fauna can be linked with the true infralittoral fauna, and, secondly, problems involving the synecological aspects of marine biology cannot be approached before more is known about the autecology of the animals composing the cryptofauna (i.e. those living in the shelter of algae) and the causal factors determining their occurrence and distribution within a given area under stated conditions. On this point the work of T. A. Stephenson is especially relevant: as a result of his extensive investigations on the composition of the intertidal flora and macrofauna he has come to stress the importance of autecological rather than of biocenological work on the shore (Stephenson et al. 1942; Stephenson, T. A. & A., 1949). Moreover, he has clarified the intertidal terminology and introduced the most useful terms “supra-” and ‘infralittoral fringe”. Since his terminology appears to be the best suited to meet the needs of ecologists, I hope it will be generally applied in future. Most work on littoral ecology has been limited to macro-organisms, valuable data on the ecology of microfaunas of seaweeds have been supplied by Colman (1940), Kitching, Macan & Gilson (1934), and Dahl (1948).

A variety of methods are available to extract chlorophyll from epilithic biofilms using solvents. The relative efficiency of these has not been determined simultaneously and there is no recognized standard procedure. In this paper techniques for sample collection, storage, preparation and extraction are reviewed and compared experimentally.

Extraction of chlorophyll was incomplete unless biofilms were fully hydrated. This factor was highly significant for all the solvents tested, with at least three times more pigment being extracted from hydrated samples than from dry ones. Methanol was the most efficient solvent, releasing over 96% of the total chlorophyll during a single extraction; hot ethanol extracted 86%, while acetone extracted less than 50%. Sonicating samples during extraction did not release any additional pigment. Centrifuging to remove suspended material did not alter estimates and was not advantageous. Rugose rock surfaces released more chlorophyll than smooth ones. However, a simple method to quantify surface rugosity at an appropriate scale was not available.

Based on these observations, a standard method for chlorophyll extractions from epilithic biofilms using 100% methanol at room temperature (20°C) is proposed. This technique requires considerably less supervision than previously preferred methods and gave a chlorophyll extract which was stable for 15 h.

Isolated individuals of certain species of cirripedes are known to remain unfertilized at the time when the majority of contiguous individuals are carrying egg masses. From a very large number of observations on both Balanus balanoides (L.) and Elminius modestus Darwin (Crisp, 1950, 1956) there remains little doubt that in these two species copulation is necessary before eggs are brought into the mantle cavity where they are fertilized. Though fewer field observations have been made, Balanus crenatus Bruguière appears to behave similarly, isolated specimens grown on raft-exposed panels never bearing fertilized egg masses (Crisp, 1950; Barnes, unpublished observation). B. balanus (L.) (= B. porcatus da Costa) is also in all probability an obligatory cross-fertilizing hermaphrodite, though the available evidence does not exclude the possibility of self-fertilization in rare instances (Crisp, 1954; Barnes & Barnes, 1954).

This paper represents the second and final part of a study of the depth distribution and diurnal migration of pelagic decapod crustaceans in an area of the eastern North Atlantic. Part I (Foxton, 1970) dealt with the Caridea; Part II now considers the Penaeidea. In the discussion the data as a whole are analysed and the resulting patterns of vertical distribution and migration discussed.

The exhalant siphon of Xylophaga is greatly reduced and its opening is situated within the burrow. Faeces accumulate in the posterior end of the burrow in a compact mass.

The ctenidia and labial palps of Teredo, Bankia and Xylophaga are modified and reduced, unlike those of the Pholadidae. The ctenidia are flat and homorhabdic and possess no ciliary sorting mechanisms; they consist of the outer demibranch only.

The ctenidia of Xylophaga are composed of a direct lamella; those of Teredo and Bankia are divided into anterior and posterior portions connected by a branchial groove which is an extension of the marginal food groove of the gill. The number of filaments in the anterior portion of the gill varies according to the species, and is of assistance in identification.

The labial palps of Teredo norvegica are least reduced; in Xylophaga dorsalts reduction is greater, though selection of food material is still exercised. The greatest reduction has occurred in Teredo megotara and in T. navalis where there is no selection.

The ciliated mantle tracts in Teredo and in Xylophaga play an important part in limiting the quantity of food particles passed from the ctenidia to the mouth.