The regulation of total algal numbers in the symbiosis involving Anemonia sulcata and a marine dinoflagellate has been investigated in a series of experiments designed to test the effects of starvation and/or darkness on the host and its alga. The gross effect of these conditions (either separately or in combination) is detectable as a generalized weight loss in the symbiotic system. An electronmicroscopical study has shown that this weight loss can be directly related to changes in the ultrastructural morphology of both Anemonia and its symbionts. The significance of these findings is discussed in relation to current knowledge of the nutritional aspects of algal—invertebrate symbiosis.

This paper estimates the turbulent transport of heat, fresh water and nutrients through the seasonal thermocline. In order to obtain a representative estimate of the annual variation it is necessary to average data obtained at a single position over a number of years. The number of years of sampling required depends on the particular parameter being studied. This can be seen by comparing the annual variation with the standard deviation, σ, for a specific month. This is analogous to the signal to noise ratio. For example, the annual range of temperature (or signal) is about 8°C for the water of the western English Channel. The variability of temperature in the same area (or noise) is about o.6°C. This figure is the standard deviation for the temperature obtained in a specific month at a fixed depth when data from a large number of different years are available. This variability can be attributed to a number of causes, to list a few; horizontal patchiness, local weather, advection, long term climatic changes. Hence for temperature the signal to noise ratio is about 13 and the annual pattern of events will clearly be established on the basis of monthly values obtained at a position during a single year.

L-glutamate is shown to have excitatory effects on muscles of the lamellibranch, Pecten and of several cephalopods. These effects are reversibly blocked by known glutamate antagonists. In Pecten intracellular electrical recording revealed a similarity between the effects of topically applied glutamate and nerve stimulation.

Three macroalgae were studied: Enteromorpha sp. (Chlorophyceae), Hormosira banksii (Turner) Descaisne (Phaeophyceae), Corallina sp. (Rhodophyceae). Fractal dimensions (D) for the outlines of the three species were 1.24, 1.07 and 1.35 respectively in the step range 0.5–5.0 mm. All three species showed loss of epifauna on the falling tide; loss was greatest in Enteromorpha, least in Corallina. In Enteromorpha and Hormosira, most loss of epifauna was in the form of harpacticoid copepods; in Corallina loss was spread more evenly across the taxa. Epifaunal biomass and retention was much greater in Corallina than in the other two species, partially because of better water-retention properties. Enteromorpha and Hormosira both showed marked decreases in epifaunal diversity during emersion; Corallina did not.

In this paper the macroscopic and microscopic morphology of the gonads of Helicolenus dactylopterus dactylopterus (Pisces: Teleostei) were analysed as well as its seasonal histological changes. The testicles are of the lobular type. The cystovarian ovaries have a central rachis from which the ovigerous lamellae are radially suspended. The gonoducts remain independent until they join together at the urogenital papilla which, in males, can be projected towards the exterior serving as a copulating organ. Sperm production is important from July to February. In contrast, the females only have mature and vitellogenic oocytes in winter, from December to February. In the west Mediterranean spawning takes place during the months of January and February. The ovaries contain clusters of spermatozoa for some ten months, from May onwards. By means of an optical microscope a specialized structure is detected, situated at the base of the interlamellar space, where male sexual cells are stored for a long period of time. Nevertheless, for several months many individual spermatozoa are also detected in the interlamellar areas, floating in the ovarian fluid secreted by the epithelium of the ovarian wall. It is still unknown whether the species under study is oviparous or viviparous, as until now, no intraovarian embryos have been detected in any of the specimens analysed.

Monthly mean sea-water temperatures in Plymouth Sound, prepared by the Plymouth City Meteorologist, are presented as data for ecological studies in this laboratory. In the last 40 years there has been a rise in mean temperature of about 0·3°C.

Previous conclusions that it should be possible to forecast the intensity of settlements which will be obtained in fifty-fifty mixture of two sands, provided the relative attractiveness or repellence of each component is known, were fully confirmed. The results of these mixture experiments agree with the classification of sands as attractive, neutral or repellent.

It is shown that an attractive factor is capable of transference, in sea water, from fresh Bullhill Bank sand to acid-cleaned quartz sands, to calcareous oolitic sand and to an artificial sand of fused alumina. The attractive factor is present in water in which fresh Bullhill Bank sand had been shaken.

A similar transference of a repellent factor from fresh Salthouse Lake sand is not so clearly demonstrable. Water in which fresh Salthouse Lake sand has been shaken appears to contain the attractive factor. Thus both attractive and repellent factors may be present in Salthouse Lake sand.

Activated charcoal stimulates larvae to settle and metamorphose, but needs to be in granular form, or associated with neutral grains, to exert its full influence. The charcoal contains copper in minute proportion, but whether this has any significance for metamorphosis is undetermined.

The grade of a sand was again shown to be a settlement factor of some importance. The most attractive grain sizes appear to be those of which the bulk of the Bullhill Bank surface sand is composed.

Analysis shows that the surface sand of Salthouse Lake (St. II) contains some three times the organic nitrogen content of the surface sand of the Bullhill Bank.

Long-term growth experiments and experiments using 15 as tracer show that extracellular nitrogen liberated by the blue-green alga Calothrix scopulorum is removed from solution by a variety of algae, fungi and bacteria. Active and passive processes are involved in the uptake, the relative importance of each process varying with the test organism and the extracellular products.

Measurements of glycogen in the body wall of Arenicola indicate that glycogen is consumed during anaerobic conditions. Estimations of lactate and pyruvate show that neither is accumulated, accounting for the absence of an oxygen debt previously found by other workers, and suggesting that glycogen breakdown leads to other acids. In Owenia most of the glycogen is stored in coelomic cells and these deposits are not drawn upon during anaerobic periods, yet this species can survive long periods without oxygen, apparently by becoming quiescent. Oil content in both species has also been measured, and was found not to fall under anaerobic conditions. It is suggested that survival of anaerobic periods may be mainly due to an ability to suspend normal activity.

Burrows inhabited by Upogebia deltaura (Crustacea: Thalassinidea) were studied over a two-year period on two maerl beds at 10 m below Chart Datum (CD) in the Clyde Sea area, Scotland. Labelled burrows proved to be stable features on each ground, with animals able to withstand the impacts of scallop dredging and storm disturbance by re-building the damaged upper sections of their burrows. Resin casts excavated using an air-lift showed that these burrows were inhabited by single individuals. Burrows were deeper, larger and more complicated than was previously thought typical for U. deltaura and other members of the genus. Mapping of burrow systems revealed average densities of 2.9 ind m−2 with up to ten openings m−2. These elusive animals were the deepest burrowing megafauna (to 68 cm) and the most abundant large crustaceans within the maerl bed habitat.

Zinc is one of the most important of the essential trace metals and more than 90 zinc-containing enymes and proteins have been discovered: furthermore, zinc increases the activity of many other enzymes (Vallee, 1978). It is not surprising, therefore, that in some groups of animals the body concentration is regulated against fluctuations in intake. Decapod crustaceans comprise one such group, although the ways in which regulation is achieved vary from species to species. In the freshwater crayfish, Austropotamobius pallipes, excretion in the faeces is a major pathway for removing zinc (Bryan, 1967a) whereas in the shore crab Carcinus maenas losses over the body surface also assume considerable importance (Bryan, 1966). On the other hand, preliminary work on the lobster Homarus gammarus (formerly H. vulgaris) suggests that in this species urinary excretion plays a major role in regulation (Bryan, 1964). The present work continues the study of zinc regulation in lobsters and its main aims are: (1) to measure rates of absorption from sea water over a wide range of concentrations and study the uptake mechanism; (2) to examine absorption from the stomach under different conditions; (3) to determine the relative importance of different pathways for the removal of zinc in response to various levels of intake.

INTRODUCTION

A considerable amount of data now exists on the relationship between metabolism and body size in a wide range of organisms from bacteria and protozoans through to large mammals. Much of this information has been reviewed by Kleiber (1932, 1947), Brody and Procter (1932), Brody (1945), Zeuthen (1947, 1953), Hemmingsen (1950, i960) and Bertalanffy (1957). In general the metabolism has been shown to be proportional to a fractional power of the body weight thus eggs, the larger metazoan poikilotherms and even homoiotherms is proportional to a constant power of the body weight. This factor has been shown to be 0.751 ± 0.015 by Hemmingsen (i960). Superimposed upon this general relationship are variations according to the weight range of the organisms concerned. Thus both Zeuthen (1953) and Hemmingsen (i960) have shown that the value of the constant b for unicellular organisms is approximately 0.7 (Zeuthen, 1953) or 0.751 (Hemmingsen, 1960), whilst that for small metazoans is 0.95 (Zeuthen, 1953) or 1.0 (Hemmingsen, 1960). Finally, the slope of the line relating the metabolism to body size in larger metazoans is 075 (Zeuthen, 1953) or 0.751 (Hemmingsen, 1960). That is, the value for b — 1 in equation (2) is likely to be between -0.3 and -0.249 in unicellular organisms; 0 and -0.05 in small metazoans and approximately -0.249 in larger metazoans.

Despite this apparently fundamental relationship between metabolism and body size, there are many instances where for a particular species the relationship may not apply. Indeed in some species the metabolism may vary in its relationship to body weight according to conditions such as salinity, shore level, experimental temperature and acclimation temperature.

Eggs of Dicentrarchus labrax (L.) have been collected from the mouth of rivers or inshore waters of salinity greater than 30 p.p.t. (Barnabé, 1978; Kennedy & Fitzmaurice, 1972). The main spawning period is between April and June (Kelley, 1979; Kennedy & Fitzmaurice, 1968), though ripe males have been reported as early as February and as late as mid-July (Kennedy & Fitzmaurice, 1972). The fertilised eggs 1·15—1·51 mm in diameter, are pelagic, take between two and five days to hatch and the prolarvae are 3·25—4·05 mm in length when they emerge (Barnabé, 1976; Bertolini, 1933, pp. 310–331; Lumare & Villani, 1973; Jackman, 1954). Postlarval stages have been recorded from the Bristol Channel in mid-June and mid-July (Russell, 1980) as well as off Plymouth between mid-March and mid-July (Russell, 1935, 1976; Russell & Demir, 1971). Although a few juveniles have been encountered, from the middle and lower reaches of estuaries, during their first summer (Kennedy & Fitzmaurice, 1972), it is not until the autumn/winter that relatively large numbers of o + bass have been reported from British estuaries (Claridge & Potter, 1983; Hardisty & Huggins, 1975; Hartley, 1940; Murie, 1903; Van den Broek, 1977; Wheeler, 1979). Juvenile bass have also been recorded from lagoons and coastal waters, during their first summer, indicating that these are important nursery areas (Arias, 1980; Barnabé, 1978; Chervinski & Lourie, 1972; Ferrari & Chieregato, 1981; Gandolfi, Rossi & Tongiorgi, 1981).

Examination of the reproductive biology of three closely related sympatric astropectinid asteroidshas revealed two distinct reproductive strategies. In Plutonaster bifrons and Dytaster insignis the gonads are serially arranged and open at gonopores located at the tip of genital papillae found on the dorsal arm surface between the bases of the paxillae. The ovaries of these species produce numerous small (ca. 120/«n diameter) eggs which in Plutonaster bifrons appear to show a distinct synchrony of production. Initiation of gametogenesis occurs in June to August of each year with oocyte growthcontinuing until March with a spawn-out in the period March to early June. In specimens where spawningdoesnot occur, there would appear to be internal oocyte degeneration, or after spawning relict oocytesundergo phagocytosis. In males initiation of spermatogenesis may occur in August/September of eachyear but after this synchrony of sperm development is not evident. In Psilaster andromeda gonads are located at the base of the arms and each gonad opens at a single gonopore. A number of small (<300 /«n) oocytes are produced by each gonad. Some of these are phagocytosed and some undergo vitellogenesis and grow to a maximum size of 950 fim before being spawned. Unspent oocytes undergo internal degeneration. In neither females nor males is there any evidence of reproductive synchrony. From these egg sizes, fecundities and gametogenic strategies, we infer indirect planktotrophic development for Plutonaster bifrons, the transfer of a seasonal surface production to deep water providing a food source for developing larvae. The egg size and or close to the sea-bed, as there is no evidence of brooding in this species.

The role of habitat structure in controlling the composition of assemblages has often been studied, but is rarely manipulated so that it is distinguishable from other factors. Differences in habitat structure as determined by differences in mussel size structure may affect the diversity of assemblages associated with mussel beds. Previous studies examining the effect of the size of individual mussels in a patch on the diversity of associated macro-faunal assemblages confounded the age of the patch with the size of the mussels. We manipulated the age of mussel patches and the size of the mussels within them to test experimentally whether the size of mussels influenced the structure of associated assemblages. At one of the two locations considered, the structure of macro-faunal assemblages in patches of larger mussels differed significantly from those in patches of the same age composed of smaller mussels. At this location, the size of mussels did not affect species richness but the abundance and proportion of organisms present differed depending on the size of the mussels. Here patches of larger mussels contained greater numbers of Nematodes and Oligochaetes and a lower abundance of taxa such as Jaera forsmani and Lepidonotus clava. We also found that invertebrate assemblages in general differed between the two locations. The effect of the size structure of mussels, however, varied spatially demonstrating that the effect of habitat structure on the diversity of associated assemblages is context dependent.

Ovaries of 39 large jumbo squid Dosidicus gigas (415–875 mm mantle length (ML)) of different stages of maturity from the Gulf of California and Nicaragua were analysed. Oocyte development is asynchronous during female ontogenesis, with predominance (>85–90%) of small protoplasmic oocytes 0.1–0.2 mm in diameter for all stages of female maturity. Potential fecundity (PF) is determined at late immature stage II with average values around 18–21 million oocytes. The maximum PF estimated, 32 million oocytes, is so far the largest recorded for any cephalopod. PF is closely related to female size. Nicaraguan females, of smaller size (415–720 mm ML), show lower fecundity (5–15 million oocytes). Eggs were analysed in oviducts of mature females (540–875 mm ML), 7 from the Gulf of California and three females from Nicaragua. Eggs measured 0.9 × 1.1 mm in diameter and weighed 0.45 mg on average. The oviducts of the largest female (875 mm ML) held 1.2 million eggs, representing 4.6% of PF and no more than 14% of all vitelline oocyte stock of that squid. Variability in oviduct filling is very high and unrelated to ovary weight. However, a strong correlation was found between oviduct fullness and nidamental glands development. These observations suggest that spawning is extended and intermittent. A female spawns no less than half of the initial PF, and the minimal number of spawning activity events (egg batches) is roughly estimated at 8–12. During this terminal spawning stage females continue actively feeding and grow between egg-mass laying periods.

Details are given of the nets used and the sampling procedures adopted to investigate patterns of vertical distribution in an oceanic pelagic fauna. Ancillary gear and laboratory methods are described. The paper concludes with a discussion of the limitations of the sampling.

The spring diatom increase in the open sea and probably also in inshore waters is one of the most important annual biological events and information regarding it or its causes is likely to be of value. In an inshore area changes are not only more pronounced, but also take place more rapidly than in the open sea and, for this reason among others, the increase was studied in Loch Striven, a well-sheltered loch in the Clyde Sea Area. A general description of the weekly changes occurring in this loch has already been made (Marshall and. Orr, 1927). The changes during the spring, however, are so rapid that an examination at even closer intervals during this period was thought advisable. Such an examination was made in 1927 and 1928, the interval between successive visits being generally two days. The methods used were the same as those described in the above-mentioned paper.

1. The observations were made on the Hunterston Sands, Ayrshire, opposite the Cumbrae.

2. Small cockles appear on the ground about the beginning of August. This points to the breeding season being in summer and not spring, as is usually stated.

3. By the end of the first autumn some few of the spat are as much as 10 mm. in length, but most are under 6 mm. The winter ring is faint and easily overlooked.

4. The first of the several well-defined rings is therefore not the first but the second winter ring.

Loch Craiglin cannot be considered as merely an isolated basin of Loch Sween. Its shallowness, the great growth of vegetation round the shore and the fluctuations in salinity make it atypical. On the more complete isolation of the loch with the making of the dam, these conditions led to a lack of circulation, a consequent development of hydrogen sulphide in the deep water and very high pH values near the surface. One could not therefore expect the plankton to be very similar to that in the outside loch (see, however, Marshall, 1947). Unfortunately there are no records of seasonal variation before fertilization was begun. In spite of these drawbacks Loch Craiglin was a convenient and manageable area for small-scale experiments on fertilization.

The experiments may be divided into two groups, those which were not followed up in detail and those in which the plankton and hydrographic results were followed from day to day. The former, made during the earlier stages of the work, are mainly described in the previous papers and led to the conclusion that the richness in phytoplankton of Loch Craiglin in 1943 was probably caused to a large extent by fertilization. Those of the second group, described above, were made to test special points and different fertilizers. Two experiments made during the summer of 1944 had apparently no effect on the phytoplankton but a third in which a very large excess of fertilizer (ten times the normal quantity) was added, gave a good increase after an initial lag. At that time the attached algae were abundant and their needs apparently had to be satisfied before any nutrients could be used by the phytoplankton.

The remaining experiments, which were therefore made during the winter, showed that commercial ammonium sulphate, ammonium nitrate and monoammonium phosphate could replace the sodium nitrate and superphosphate used hitherto. Two further experiments in the following spring using ammonium chloride and urea did not, however, prove effective. All the salts used had been found in laboratory tests by Miss F. A. Stanbury to be suitable for diatom growth, and the reason for the failure of these two in the loch is unknown.

The utilization of the nutrients was extremely rapid even in winter but it is probable that their disappearance is not entirely caused by the phytoplankton or bottom-living algae but partly by adsorption on the bottom mud or by suspended matter. On one occasion it may have been caused by a serious fall in loch level.

The zooplankton which during the first year of fertilizations was richer in Loch Craiglin than in the outside loch diminished in the second year and remained poor thereafter in spite of, or perhaps because of, the intensive fertilizations. The dense phytoplankton and other vegetation raised the pH at times to levels dangerous to animal life.