Enzyme and colour phenotypes were determined within a single mid-shore aggregation (n = 106) of the anemone, Actinia equina L. on the east coast of Britain. On the basis of allelic variation at four enzyme loci, a large number (n ≃ 30) of genotypes were distinguished of which only three consisted often or more anemones. Little evidence was found of obvious genotypic clustering, a result which was unexpected since this species broods young which are genetically identical with their parents, and which are potentially available for local (within site) colonization. We propose that the unexpectedly high level of genetic variability encountered at this site, can be explained by the following factors: (1) site and anemone longevities are probably measurable in tens of years, (2) distances travelled by anemones during their lifetime may be considerable, thus resulting in extensive inter-digitation of clones over time, and (3) the reproductive strategy of A. equina incorporates sexual reproduction with a planktonic dispersal phase.

Nearest-neighbour analyses applied to the distribution of phenotypes within this aggregation revealed several examples of auto-phenotypic under-dispersion. These results, together with (1) departure from Hardy–Weinberg equilibrium at a hexokinase locus, (2) evidence of linkage disequilibrium between hexokinase and malate dehydrogenase alleles, and (3) linkage between alleles at both these loci with a colour phenotype (grey pedal disc), all indicate that the genetic composition of this group of anemones had been strongly influenced by founder effects followed by clonal reproduction.

A comparative analysis of the size distributions of the various phenotypes and genotypes yielded few conclusions relating either to colonization history or to differential selection; reasons are given to account for this failure.

Rainbow trout were exposed to five different concentrations of a unialgal culture of Gyrodinium aureolum in laboratory tanks. All the concentrations used proved lethal within 24 h. The gills of the dead fish showed no mechanical occlusion by the algae but all displayed marked histological changes characterized by necrotic degeneration and disintegration of the lamellar epithelium.

Oil/water extraction systems have been devised to study the lipid solubility of metal ions in sea water. Group B metals such as Cu, Zn, Cd, Hg appear to form inorganic complexes in saline solutions that are very lipid soluble. The implications of this are discussed in terms of the penetration of metals across cell membranes.

Vital staining with Janus Green, phase contrast and scanning electron microscopy were used to map the distribution of free neuromast organs from first hatching, 10 mm long larvae to 100 mm long juveniles of herring (Clupea harengus L.), with some further observations on juvenile sprat (Sprattus sprattus (L.)). Neuromasts are sparsely distributed on the head and trunk at hatching but soon proliferate on the trunk where, by a length of 13–15 mm, they occur one to every segment. Near metamorphosis there are at least three rows of neuromasts on the anterior trunk region, 6–9 single neuromasts on the caudal fin and as many as 50 on the head. The scales develop at about 40–50 mm and the neuromasts are then found singly or in groups of 2 or 3 on the surface of the scales of the anterior trunk.

The lateral line develops at 22–24 mm and appears to incorporate existing free neuromasts on the side of the head. Unlike the cupulae of the free neuromasts, which are cylindrical, the lateral-line cupulae are thin erect plates lying along the axis of the canals. They are probably continually growing and being shed, followed by renewed growth.

All neuromasts contain hair cells of opposing polarities; most free neuromasts are arranged with these polarities arranged fore-and-aft, but a few are dorsoventral.

A frontal region is predicted in Lyme Bay from a numerical model. A crescent-shaped feature is occasionally identified in the coastal-zone colour scanner imagery for this region. Measurements at sea confirm the development of a frontal zone which can show associated increases in levels of chlorophyll a. The surface distributions of inorganic nutrients indicate that nutrients and light levels are factors controlling the observed variations of surface phytoplankton.

Reproductive cycles are described for subtidal and intertidal populations of the, starfish Asterias rubens L. and for a subtidal population of the starfish Marthasterias glacialis L. on the south-west coast of Britain. Intertidal A. rubens had a clearly defined reproductive cycle with spring-early summer spawning. Pyloric caecum indices were inversely related to gonad indices. Subtidal A. rubens had lower gonad indices and less seasonal variation in the pyloric caecum indices. Gonad indices of M. glacialis suggest few animals in the population studied were breeding, but it is likely that this species also spawns in summer.

Plankton samples and larval rearing studies suggest a planktotrophic pelagic life of approximately 90 days for A. rubens. Field observations and laboratory experiments show larvae settle on a wide range of substrata. Recruitment to an intertidal population of A. rubens at Hollicombe Reef occurred in July 1980 and September 1981. Growth of juvenile starfish was followed for 17 months. Juvenile starfish feed carnivorously at the completion of metamorphosis. Early growth is rapid; however, there is a reduction in the growth rate during winter months. Feeding and growth of juvenile A. rubens is compared with published data on juvenile starfish of other species.

A study was made of the life cycle and reproductive ecology of Gammarus duebeni in the Test Estuary on the south coast of England. The species is towards the southern limit of its distributional range in the north-east Atlantic, which results in breeding continuing throughout much of the year. The breeding strategy employed was found to vary with season. The size of eggs produced and the rate of egg production were both temperature dependent, whereas the proportion of production expended on eggs and the number of eggs per brood, although probably influenced by temperature appeared to be controlled by food availability and female size. Factors affecting the mortality of eggs within the marsupium and breeding synchrony were considered in relation to season. The life cycle consisted of two major overlapping generations.

Measurements were made of the strength of temporary attachment of the cypris larvae of Balanus balanoides using a sensitive micro-balance. The strength of adhesion on arthropodin treated slate panels exceeded that on clean panels and the measured forces increased as the season progressed. The observed maximum cyprid attachment strength reached 3·8 × 105 N m−2, considerably less than the bond strength of a commercial epoxy adhesive (107 N m−2) but of the same order as the force required to remove limpets (Patella) from a slate substrate. The results are discussed in the context of substrate recognition by barnacle cyprids and the possible mechanisms of adhesion involved.

During a routine North Sea demersal fish survey, very low fish catches were recorded at two primary stations off the Danish coast in September 1981. The catch of benthos at thesestations was much greater than the previous year, and underwater photographs from a headline camera revealed that this was a result of most infaunal species having emerged from beneath the sand. The phenomenon was assumed to be caused by low oxygen concentrations in bottom water following the collapse of a bloom of the dinoflagellate Ceratium furca.

Profound cyclical changes were observed in the epidermal thickness and in the concentrations of goblet cells and epidermal melanophores in an inshore population of winter flounder, Pseudopleuronectes americanus Walbaum. There is sexual dimorphism which is particularly prominent in the thickness of the epidermis during the pre-spawning period in the spring. At this time the male develops a significantly thicker lower epidermis. During and shortly after the spawning period (lower skin), or somewhat earlier (upper skin), there is a significant thinning of the epidermis in both sexes. Significant increases occur in goblet cell frequency, those of females being greater than males, during autumn and early winter and the April/May pre-spawning period. Goblet cell frequencies decrease in mid-winter (January–March) when general activity is low, and in the thin summer epidermis. These observations are compared with data from other teleosts and discussed in relation to hormones possibly affecting the epidermal structure of teleosts and in relation to known hormonal cycles in winter flounder.

The shell strengths of seven species of barnacle were investigated by carrying out a series of compression and tension experiments. All species were tested under compression as solitary individuals. In addition the shell strength of crowded Semibalanus balanoides was determined. Results of the compression experiments show Balanus balanus and B. perforatus to be the strongest species with Verruca stroemia the weakest. All species were much weaker in tension than compression, particularly those with a calcified base, B. balanus being the weakest of the five species tested in this way.

The possibility of adaptive design of the barnacle shell to withstand wave action and predation techniques is discussed in the light of the results from the compression and tension experiments. Finally the importance of carrying out a wide range of tests of the shells when trying to determine their strength is discussed.

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.

Nucella lapillus and Littorina littorea afford examples of turbinately coiled shells with no space between the columella and the inner face of the whorls. Three constants are sufficient to determine the form of such shells: λ, the ratio between diameters of successive whorls; β, the semi-apical angle and ρ, the ratio of aperture length and breadth in the apertural plane passing through the axis. The variation of these three constants with size was examined and shown to be relatively small and insignificant in Nucella, but in Littorina it was significant.

For Nucella and Littorina these shell characteristics were used to relate for the nth whorl, the length along the shell spiral (ln) to the shell height (Hn), the latter being the measure usually employed in growth studies. This relation was derived mathematically and confirmed empirically as

where α is the angle of the logarithmic spiral given by α = tan−1 2π sin β/loge λ. The increased resolution of the micro-growth band increments, which are measured along the shell spiral was directly related to the ln:Hn ratios.

Since the formula for the ln/Hn ratio (= shell conversion factor) includes λ, β and ρ, the three constants necessary to determine shell form in turbinately coiled shells of the type described, the shell conversion factor may be a better index of shell shape than indices based on a single constant. In species where the shell grows isometrically this ratio will remain constant, whereas changes in shell shape with size will influence this ratio. Such changes in shell shape during growth can be quantified in terms of the shell constants and when included in calculating the shell conversion factor, will show the relative magnitude of shell shape changes brought about by growth. The shell conversion factor may also be used to study the effects of ecological variations on the geometry of the shell.

The conical shell of the limpet, Patella vulgata, is geometrically a much simpler system in which direct shell measurements were used to relate length along the direction of maximum growth to the antero-posterior diameter of aperture.

The analysis under a scanning electron microscope of young larval and postlarval shells of Mytilus edulis and Margaritifera margaritifera reveals some primitive characters. Among these features, the most important are the ligamental formations which are described in detail during ontogenesis. In M. edulis a primitive ligament appears in a pit under the cardinal plateau immediately following metamorphosis. A second ligament later develops on the posterior edge of the shell, and becomes the only ligament present in the adult. In M. margaritifera a provisional internal structure acts as a ligament in the young glochidia fish parasites. A definitive external ligament only develops following metamorphosis of the glochidia.

The similar pattern of development of these ligaments in both species may represent the development of the ligament in the first bivalves.

A chromatographic/fluorcmetric method was used to measure changes in the proportions of four planktonic dihydroporphyrin pigments during the spring bloom of 1979 in two f jordic sea-lochs, Creran and Etive, on the west coast of Scotland. Very little pheophytin a was detected during the bloom. Chlorophyll a, and to a lesser extent chlorophyllide a, were the two main pigments found during the bloom. During senescence the main pigment breakdown route appeared to be via chlorophyllide a to pheophorbide a. These results suggest that standard methods for measurement of ‘chlorophyll’ which do not distinguish between chlorophyll a and chlorophyllide a might significantly over-estimate the photosynthetic potential of phytoplankton.

The extrinsic nerves of the stomach of dogfish and skates regulate the frequency and amplitude of contraction by inhibition followed by rebounds. By contrast the nerves of the spiral intestine are excitatory.

Stimulation of the vagus nerve of the ray produced slight reduction in the amplitude of spontaneous contractions of the cardiac stomach. Much greater inhibition was produced by stimulation of the sympathetic nerves and was followed by large rebound contractions. These effects were imitated by adrenalin and serotonin which altered the frequency and amplitude of contraction in various ways. These actions were not blocked by either propranalol (1–5 × 10−5 M) or phentolamine (2 × 10−5 M) and indeed were often increased. The excitatory response to adrenalin was not blocked by TTX even after this had blocked the response to the nerve. Responses both to the nerve and adrenaline were blocked by trazodone. Acetyl choline caused some contraction of the stomach but only at high concentration.

Muscles of the spiral intestine of Raja or Scyliorhinus were activated by stimulation of their sympathetic nerves and by adrenalin. These responses were not blocked by phentolamine and only reduced by propranalol They were blocked by trazodone. The response to adrenalin continued after the nerve was blocked by TTX. Acetyl choline had very little effect on the spiral intestine.

The striking differences between the responses of the stomach and intestine are probably related to the fact that the plexus in the latter contains no nerve cells. The neurons in the stomach are therefore presumbly connected with the inhibition and large rebound contractions.

The athecate hydroids Coryne pintneri Schneider and Thecocodium brieni Bouillon, previously unreported from British waters, have been found near Oban, western Scot-land. Descriptions and figures are given, with observations on behaviour in culture. It is considered that Coryne pintr.eri is specifically distinct from Coryne filiformis (Rees). The feeding response of Thecocodium brieni is described, and it is concluded that it ismediated chemically by diffusion of exudate from captured prey. Response to mechanical stimulation is also described: it evidently is transmitted through the stolonal network, but it is not known whether this is via nervous or non-nervous tissue. The occurrence in Scotland of thesetwo species, previously known only from north-west France and the Mediterranean, is attributedto their probable introduction on oysters from Brittany, France.

Fertilized herring eggs were hatched in large sea water enclosures containing natural populations of phytoplankton and Zooplankton and the developing fish sampled at intervals for a period of 90 days to determine the levels and composition of their depot triacylglycerols. The percentage of triacylglycerols in total lipid declined from hatching to about 40 days post-hatch and then increased markedly during the remaining 50 days. During the first 30 days from hatching the acyl groups of the triacylglycerols were dominated by polyunsaturated fatty acids, especially 18:4 (n−3), 20:5 (n−3) and 22:6 (n−3), characteristic of a predominantly phytoplanktonic diet. For the remainder of the 90-day experiment the percentages of polyunsaturated fatty acids decreased, to be replaced by increasing percentages of 20:1 (n−9) and 22:1 (n−11 ) fatty acids characteristic of a predominantly zooplanktonic diet.

The results of detailed sterol analyses on the livers of seven species of sharks are presented. The sharks appear to have a very specific requirement for cholesterol as their sole component sterol (> 99 % total sterols), which several species of bony fish do not. In fact, from their sterol composition, sharks appear more similar to terrestrial vertebrate classes than bony fish. If, as has been suggested, sterol composition is a measure of evolutionary advancement, then this work presents biochemical evidence that sharks are not as primitive as has sometimes been assumed.

The spread of the immigrant brown alga Sargassum muticum ( Yendo) Fensholt, within European waters is chronicled from 1973–1981. New populations of the attached alga are listed together with maps indicating the annual addition of sites. No populations of the alga were known beyond the bounds of the Solent region, southern Britain, until after 1975.

The age of the original Sargassum population found at Bembridge in 1973, and the discovery of drifting S. muticum in 1971, seems to date the initial introduction of the alga in the Channel as possibly the late 1960s.

This paper presents the establishment of Sargassum muticum as a permanent addition to the European marine flora. It is hoped that its future spread will continue to be documented, providing useful information upon the invasion strategy of an ‘aggressive’ introduced marine species.