The retinae of all the species of deep-sea fish which have been studied have been shown to contain golden coloured pigments, chrysopsins, which are especially suited to the light found in their natural environment (Denton & Warren, 1957; Munz, 1958). Amongst fish caught in shallow coastal waters this characteristic colour of retinal pigment is found only in the conger eel Conger conger (by Denton & Walker, 1958), and amongst freshwater fish only in the silver eel Anguilla anguilla (by Carlisle & Denton, 1957, referred to by Denton & Warren, 1957). Both these fish are species of Apodes, a group of which the vast majority of species are deep-water forms. Both species, more- over, begin their life in the deep sea and return to it again when mature to spawn and may therefore, in one sense, be regarded as deep-sea fish. Since immature conger eels in shallow coastal waters already have a retinal pigment characteristic of a deep-sea fish, it seems very unlikely that on returning to deep water they would change away from the deep-sea form which they already possess. It is probable therefore that the conger retains a deep-sea form of retinal pigment throughout the whole of its life.

Methods of extraction of the toxin from cultures of Gymnodinium veneficum are described. This is now done by dialysis and evaporation under reduced pressure. The toxin molecule must be large, as it cannot penetrate a dialysis membrane; it is soluble in water and the lower alcohols, but insoluble in ether and chloroform. It is unstable in acids, turning into another toxic product, and is decomposed by hot alkali, though in neutral solution is more or less thermostable. The toxin as it occurs in sea water is not the same as paralytic shellfish poison, but there are some resemblances between this and the 'acid extract', though much more work is needed to check this point.

The action of the toxin on a variety of animals is described, and an attempt is made to devise an approximate assay technique using gobies as the test animals.

The action has also been observed on a range of isolated preparations, and although the final conclusion as to the mode of action is not quite clear, we feel confident that the site of action in whole animals is in the nervous system, probably acting on ganglion transmission. With regard to the mode of action it depolarizes nerve and muscle membranes. It also abolishes the potential across frog skin without measurably altering the skin resistance.

This depolarization probably occurs by interference with the sodium exchange mechanism, allowing rapid entry of sodium into the cells.

From June 1995 to August 2002 we assessed green turtle (Chelonia mydas) population structure and survival, and identified human impacts at Bahía de los Angeles, a large bay that was once the site of the greatest sea turtle harvest rates in the Gulf of California, Mexico. Turtles were captured live with entanglement nets and mortality was quantified through stranding surveys and flipper tag recoveries. A total of 14,820 netting hours (617·5 d) resulted in 255 captures of 200 green turtles. Straight-carapace length and mass ranged from 46·0–100·0 cm (mean=74·3±0·7 cm) and 14·5–145·0 kg (mean=61·5±1·7 kg), respectively. The size–frequency distribution remained stable during all years and among all capture locations. Anthropogenic-derived injuries ranging from missing flippers to boat propeller scars were present in 4% of captured turtles. Remains of 18 turtles were found at dumpsites, nine stranded turtles were encountered in the study area, and flipper tags from seven turtles were recovered. Survival was estimated at 0·58 for juveniles and 0·97 for adults using a joint live-recapture and dead-recovery model (Burnham model). Low survival among juveniles, declining annual catch per unit effort, and the presence of butchered carcasses indicated human activities continue to impact green turtles at this foraging area.

The study reported here stems from experiments performed upon cirripedes and bivalve molluscs exposed to fluctuating sea water concentrations. It is obvious that these two groups of benthic organisms are capable of shutting themselves off to a greater or lesser degree from the external environment by opercular or shell valve closure, thus avoiding the osmotic stresses associated with exposure to lowered salinity levels. With the development by Davenport, Gruffydd & Beaumont (1975) of an apparatus to deliver fluctuating salinity regimes to experimental animals in a repeatable, routine manner, it has become possible to establish the sea-water concentrations at which such mechanisms operate.

Effects of oxygen supply on development rates of embryos in gelatinous masses were tested with natural masses of three species of opisthobranch gastropods and artificial masses made with embryos of a sea urchin and agarose gel. When diffusive exchange was restricted for embryos in such masses, increased oxygen alone was sufficient to maintain development rates of embryos. Diffusive supply of oxygen is therefore a limiting factor for embryos clustered in gelatinous masses. Development rates were constant over a wide range of experimentally altered oxygen concentrations but retarded with oxygen below about 10% of air saturation. Some opisthobranch embryos exposed to low oxygen concentrations hatched with shorter shells. Delayed hatching and shorter shells at hatching were both associated with a central position in the globose gelatinous mass of one of the opisthobranch species, even in air-saturated and vigorously stirred water. The pH near the centres of the masses was lower when embryos were at more advanced stages; thus the intracapsular stirring caused by cilia of embryos at later stages does not compensate for their greater metabolic rates. The pH in some egg masses was about seven or lower, and this pH affected development in separate experiments. The masses approach limits for removal of wastes, although oxygen becomes limiting for rates of development before accumulation of wastes becomes limiting. Embryos of opisthobranchs that are normally aggregated and embryos of sea urchins that are normally dispersed were similarly tolerant of low oxygen concentrations and low pH. In respect to tolerance of hypoxia and accumulating wastes, embryos in many clades are preadapted for aggregation into masses, but there are limits on the size of the aggregation. Egg masses are commonly at those limits.

It is conclusively shown that cyprids of the barnacle Balanus balanoides (L.) use a secretion released onto the antennulary discs for temporary attachment. This secretion does not stain with conventional histochemical techniques but was shown to be proteinaceous by staining blue in Bio-Rad protein-dye reagent normally used in protein assay. The discovery of this proteinaceous secretion adds further evidence to suggest that cyprids use a form of Stèfan adhesion for temporary attachment during exploration prior to settlement.

Introduction

Although recent advances have been made in the measurement of cyprid temporary adhesion (Yule & Crisp, 1983), the question of the precise mechanism has remained speculative. Earlier suggestions that the attachment organs of the antennules operated by suction (see Saroyan, Lindner & Dooley, 1969) were challenged on morphological grounds by Nott & Foster (1969) and finally disproved by the force measurements of Yule & Crisp (1983).

Nott (1969) and Nott & Foster (1969) were able to show numerous unicellular glands opening out, individually, onto the surface of the antennulary disc arranged in two concentric rings, one near the margin, and the other around the central sense organ. It was considered that these glands could produce a tacky secretion used for temporary adhesion. Yule & Nott (unpublished, reported in Yule & Crisp, 1983) failed to find any traces of such a tacky secretion on glass surfaces after cyprids had walked across them. To establish the presence or absence of a fluid secretion on the antennulary disc is fundamental to the further understanding of the type of temporary adhesion employed by cyprids.

In this paper we present evidence for female mimicry in a population of Salaria pavo (Pisces: Blenniidae). Parental males differ markedly from females by the presence of a large crest on the head and anal glands on the two spiny rays of the anal fin. We found a proportion of smaller and younger males that are almost identical to females both in morphology and behaviour. These ‘female-like’ males lack secondary sexual characters and actively court parental males, displaying the female's colour pattern and courting behaviour. These males are sexually mature and their gonadosomatic indices are higher than those of parental males. Female mimicry is considered to be a functional way to achieve sneak fertilizations.

1. A study of the histology of the eyes of some cartilaginous fishes has been made with special reference to their reflecting tapeta.

2. The rate and way in which the pigment in the melanophores spreads over the reflecting cells of the tapetum of Squalus acanthias when it is lightadapted are described.

3. The reflecting plates in the tapeta are about parallel to the plane of the retina in the centre of the eye, but as we move towards the periphery they become more oblique, until near the ora they are almost perpendicular to the plane of the retina. It is shown that when we take account of the way in which the pupil limits the light which can reach the retina in all these situations the plates are arranged to be roughly perpendicular to the incident light. They reflect light either back through the pupil or on to the very black inside surface of the iris and do not scatter it to other parts of the eye.

4. The reflectivity of tapeta for various angles and various wave-lengths of light has been found by several different methods, and a new and simple way of measuring the reflectivity of natural tissues is described. For the blue and green lights which will be those reaching the eye in life the reflectivity is very high, over 80%, and so approaches that of a good metallic mirror.

5. The external segments of the retinal rods of cartilaginous fishes which have well-developed tapeta are only about half as long as those of other fish living in the same environment, and the retinal optical densities of photosensitive pigments in these fish are only about a half of those of fish without reflecting tapeta.

The breeding season of the lugworms of the Whitstable area is a sharply defined one, extending for 14 days between the new moon and full moon spring tides in the second half of October. Spawning begins slowly and reaches a maximum at the intervening neap tides and then declines in intensity.

Both eggs and sperms are discharged from the burrows at extreme low water to lie on the surface of the sand. Here fertilization occurs.

No germ cells were detected in the body cavity from November to June, but from August onwards to the end of October 98% of the adult worms are ripe.

At the end of the spawning period about 40% of the adults die.

A brief description of gametogenesis and of the mature gametes is given.

Germ cells are discharged through the nephridia.

A compilation has been made of new data on the distribution of the deep-water coralLophelia pertusa(L.) derived from trawling records, grab and dredge stations and submersible dives, together with the few published records. The coral is widely distributed and occurs on all the offshore banks of the north-east Atlantic, with some records from the deepest water of the Minches and Sea of the Hebrides.

The tenacity of the barnacle cyprids of Balanus balanoides (L.) during temporary adhesion to a variety of modified Perspex surfaces was tested using a sensitive microbalance. The Perspex panels were painted on the undersides with five colours of cellulose paint. Control measurements of the magnitude of temporary adhesion to clean slate panels were of the order of 2 × 10 N m. Untreated smooth Perspex panels and panels coated with an adsorbed layer of bovine serum albumen gave low figures of tenacity of the order of 0·8 × 10 N m. Roughening the panels with carborundum or treating with an adsorbed layer of barnacle extract protein resulted in higher tenacity measurements (1·0–1·8 × 10 N M), whereas the highest measurements were obtained when roughened Perspex panels were coated by an adsorbed layer of barnacle extract protein (1·6–2·2 × 10 N M). When the surfaces were made more attractive to barnacle cyprids by roughening or coating in barnacle protein the forces measured on dark coloured panels were higher than on lighter coloured panels. The results of the temporary adhesion measurements were closely paralleled by the numbers of cyprids found exploring the various surfaces during preference settlement experiments.

The algal symbiont of Convoluta roscoffensis (Graff) has been studied with the light and electron microscopes both in situ in worms collected from four localities on the coast of Brittany and in various forms of isolates in culture. The same organism has also been obtained from populations of free-living monads collected from sand and water samples adjacent to the Convoluta colonies. Its structure and behaviour in culture are described and illustrated. Platymonas convolutae sp.nov. is a very distinct species with a rough-surfaced theca and a pyrenoid with some new characters not previously recorded in other members of the group. Some new information on scale and theca production from the Golgi system has also been obtained.

The magnitude of geographical variations of stable isotope ratios of carbon and nitrogen was examined in ten squid species captured in seven areas of the world's oceans. The average of all 139 squid was −17.4±1.4‰ for δ13C and 11.6±1.6‰ for δ15N. The δ13C of squid showed a clear-cut negative correlation with the latitude of the sampling locations, reflecting the well-known latitudinal characteristics of phytoplankton δ13C, while squid δ,15N did not correlate with the latitude significantly. The δ15N reflected the regional characteristics of nitrogen metabolism such as denitrification and N2 fixation, and it was conspicuous in the intraspecific variation in Sthenoteuthis oualaniensis ranging from 10.0±1.5‰ off Japan to 16.3±0.6‰ off Peru in the Pacific Ocean. Significant isotopic variations were also found in the local area among the five species off Japan in the Pacific Ocean and among the three species in the Japan Sea. Attention must be paid to the isotopic variations of primary producers as well as those of squid in examining the trophic positions of squid.

The recognition that non-essential metals, such as mercury, cadmium and lead, could, upon entering aquatic environments, produce harmful effects to man, directly or through food chains, has resulted in studies directed towards the identification of potentially hazardous levels.

This review examines the biology of the two main cockle species Cerastoderma edule and C. glaucum found in coastal areas around the north-east Atlantic from Norway to Morocco and through the Baltic, Mediterranean and Black Sea. It considers those factors in particular that impact on the overall health and survival of individuals as well as populations. Methods for the discrimination of the species are reviewed as well as the approaches being taken to delineate different populations, which is crucial to appropriately manage individual fisheries. Cockle populations generally undergo sexual maturation during their second summer and sexes are separate. Eggs are pelagic, with larvae being both benthic and pelagic before settling on the sediment and becoming benthic adults. However, data are lacking on basic larval biology and dispersal mechanisms. Data are provided on predator–prey relationships including information on types of food of importance to cockles. Main predators of cockles include brown shrimp, shore crabs, gastropods, polychaetes, fish and a variety of birds and these can be important in structuring cockle populations. Predation of larval cockles by adult cockles through larviphagy can lead to reductions of up to 40% of the population. Cockles are sensitive to a wide range of chemical contaminants but few data are published on impacts on cockles, in particular larval stages. The review concludes with an assessment of future climate change scenarios on cockles and considers some areas of future research required to preserve this ecologically and economically important species.

In an attempt to identify the causes of the natural population fluctuations on British rocky coasts, an exploratory programme on the recruitment fluctuations of certain ‘key species’ has been operating for several years. The choice of species and the emphasis upon their recruitment have been discussed elsewhere (Lewis, 1976) and were justified as the most economical means of gaining the ability to (a) ‘explain’ major changes in the general character of rocky shore communities, and (b) make predictions about natural events against which to detect regional or temporal consequences of man-made changes in water quality. Mussels, barnacles and limpets are being studied but it is the last with which most interpretative progress appears to have been made, and this paper is concerned solely with Patella vulgata L. It is, however, essentially a preliminary report in a continuing study and it illustrates the practical and interpretative problems inherent in formulating and substantiating hypotheses in this type of work.

The role and quantitative importance of free-living nematodes in marine and estuarine soft sediments remain enigmatic for lack of empirical evidence on the feeding habits and trophic position of most nematode species. Here we use natural abundances of carbon and nitrogen stable isotopes of some abundant nematode species/genera from estuarine intertidal sediments to assess their trophic level and major food sources. In all stations, δ15N of different dominant nematode species/genera spanned a range of 3.6 to 6.3 ppt, indicating that at least two trophic levels were represented. The large nematodes Enoplus brevis, Enoploides longispiculosus and Adoncholaimus fuscus consistently had high δ15N, in line with mouth-morphology based predictions and empirical evidence on their predacious feeding modes. Daptonema sp., Metachromadora remanei, Praeacanthonchus punctatus and ‘Chromadoridae’ (dominated by Ptycholaimellus ponticus) had comparatively lower δ15N, and δ13C suggesting that microphytobenthos (MPB) is their major carbon source, although freshly sedimented particulate organic matter may also contribute to their nutrition in silty sediments. The trophic position of Sphaerolaimus sp., a genus with documented predacious feeding mode, was ambiguous. Ascolaimus elongatus had δ15N signatures indicating a predacious ecology, which is at variance with expectations from existing feeding type classifications. Our study shows that—despite limitations imposed by the biomass requirements for EA-IRMS (elemental analyser—isotope ratio mass spectrometry)—natural isotope abundances of carbon and nitrogen are powerful tools to unravel trophic structure within nematode communities. At the same time, the prominence of different trophic levels results in a large span of δ15N, largely invalidating the use of nitrogen isotope abundances to assess food sources and trophic level of whole nematode communities.

It is known from earlier work (Blaxter & Jones, 1967; Blaxter, 1968a; Blaxter & Staines, 1970) that the larvae of many species of teleost have a pure-cone retina. The rods only appear well after hatching and often as late as metamorphosis. This means that much of the larval life may be spent without fully developed eyes. The rods are difficult to resolve under the light microscope using paraffin sections (about 5 µm) and it is therefore easier to compare the number of cones with the prominent visual cell nuclei in the outer layer (ONL) in such preparations. The ratio has been found to be 1:1 in the early stages and changes as the rods develop, reaching ratios of 1:15 or more in adult fish. Thus, for every cone there may be 14 or more rods.

The type species of Prasinocladus has been re-investigated in cultured material from the Devon coast and studied electron-microscopically by whole mounts and by sections. Salient findings include: the presence of two layers of scales together with characteristic hairs on all four flagella; the arrangement of the flagellar bases in a row, and of characteristic flagellar ‘roots’; the presence of an unusual condition of the pyrenoid with respect to the nucleus; and the structure and behaviour of the theca as different from that of an ordinary cell wall. It is concluded that the genus could appropriately serve as the type of a group to include all known genera and species of monads containing chlorophyll b that possess scaly flagella, but no recommendations are made as to whether the name Prasinophyceae (Christensen, 1962) should be restricted to these or be permitted to cover other known green flagellates lacking scales on their flagella. This investigation is continuing.

The macrofauna, defined as infauna retained on a ½ mm sieve, was investigated on a flatfish nursery ground at less than 10 m depth in a Scottish westcoast sea loch during spring and late summer of 1965. The substratum consisted of well-sorted sand of 180–260 μ median diameter, and the infauna had a mean density of 755 individuals and biomass of 1·3 g dry weight/m2 on the beach and 3055 individuals and 3·7 g dry weight in the sublittoral. There was little overall change in the biomass during the period studied, increases in amphipods and some polychaetes being balanced by decreases in other polychaetes, and in Tellina for which no recruitment took place. The distribution of the fauna was studied in detail between high-water mark on the beach and a depth of 10 m below low-water springs. There were 62 species on the beach and 116 on the sublittoral sand. The number increased as the water deepened, the poorest zone being just below low-water mark. Most species showed a distinct zonation. The epifauna of the sand, which was dominated by juvenile stages of plaice and dabs, is briefly described