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.

Previous studies on cirral activity in thoracican cirripedes have established two basic patterns of feeding action. In the Lepadomorpha, the Verrucomorpha, and the chthamaloid and coronuloid Balanomorpha, prolonged cirral extension provides the basis for captorial feeding. The cirri are held extended and are used, individually or collectively, to capture small live prey. Investigations on these species have yielded no evidence of sustained rhythmic cirral activity as a component of food collection among a variety of species (Crisp, 1950, 1967; Southward, 1957, 1962, 1967; Mori, 1958, 1961; Southward & Southward, 1958, 1967; Barnes & Reese, 1959; Howard & Scott, 1959; Patel, 1959; Crisp & Southward, 1961; Southward & Crisp, 1965; Bieri, 1966; Jones, 1968; Stone & Barnes, 1973; Klepal & Barnes, 1975).

Actinocoryne contractilis is a new marine, benthic and stalked member of the Centrohelidia (Heliozoa) whose biology, motile behaviour and cytology are described. Preliminary results concerning the life cycle are given. The stalked form emits small subspherical planktonic heliozoans which settle and give rise to the stalked stage again.

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.

A key to all nine described marine species of naked lobose amoebae classified in the genus Vannella Bovee, 1965, is presented. All six species studied with the electron microscope have the characteristic surface structure found also in freshwater members of the genus. The key includes five species isolated from British waters, including three new species; a fourth new species is from the Persian Gulf area. Generic identification of Vannella, even in mixed material, can be made readily with the electron microscope, which is sometimes necessary for positive distinction from Platyamoeba. Further identification to species is a light-microscopical procedure. Members of this genus are cultured on bacteria, which are probably their main food in nature.

Intertidal estuarine barnacles suffer cyclic changes in salinity and temperature, the latter being most marked and often quite abrupt at the time of tidal immersion and emersion.

The Marine Biological Association (1957) lists the poor cod Trisopterus minutus minutus (L.) (=Gadus minutus) as being parasitized by two monogenean gill parasites Diclidophora luscae and D. denticulata but at various times over the past 25 years we have, between us, examined the gills of upwards of 1000 specimens of T. m. minutus without ever having found a monogenean parasite. We concluded that the 1957 records were probably due to a misidentification of the hosts. However, in January 1979 one of us (J. E. G.) found several specimens of a monogenean very closely resembling D. luscae (Beneden & Hesse) on the gills of poor cod. D. luscae is normally found at Plymouth (Llewellyn, 1956) on only the pouting Trisopterus luscus (L.), a fish which from time to time is caught in the same trawl as T. m. minutus, e.g. in a total of 46 standard hauls between July 1976 and June 1978 (information supplied by Mr A. D. Mattacola), on 11 occasions (23%)T. luscus and T. m. minutus were caught together. On eight of these 11 occasions the lesser abundant of the two fish species constituted 10% or more of the combined total, and on three occasions the lesser abundant fish made up at least 40% of the combined total. Thus there is evidence that T. m. minutus and T. luscus from time to time occupy the same or neighbouring habitats (a standard haul may be over a distance of up to 8 km) and so presumably there has been opportunity for parasitic invasion from one species to the other to take place. That this has not in fact happened we have regarded as an example of the very strict species-specificity to their hosts manifested by most monogeneans and especially by diclidophorans on gadoids (Llewellyn & Tully, 1969). It was decided therefore to investigate how the sudden appearance in 1979 of a monogenean parasite on a previously uninfected population of poor cod may have come about.

The hydrostatic permeability of the aboral integument of the starfish Asterias rubens L. was found to be 5·1 ± 2·1 × 10−6 cm3/cm2/s/cm H2O. A sudden increase in permeability around 5 cm water pressure was found to coincide with the bursting of the dermal branchiae.

The area of protracted dermal branchiae per cm2 of aboral integument has been estimated and, if only this region represents the permeable areas of the skin, the above figure may well rise to 1 × 10−5 cm3/cm2/s/cm H2O.

While collecting acanthocotylid monogeneans for various investigations (Kearn, 1967; Lyons, 1972; Macdonald, 1974) Mr J. E. Green of the Laboratory of the M.B.A. at Plymouth has very occasionally found specimens of what each of these authors has suspected may be a new species. In July 1978 nine more living worms were collected, the material was indeed found to require the erection of a new species and we propose to call the parasite Acanthocotyle greeni.

The connective tissue layer of the large intestines of Brissopsis and Echinocardium spp. is shown to contain a massive quantity of ferric iron in the form of ferric phosphate. The ferric phosphate is present as a granular extracellular deposit. In large mature specimens of Brissopsis, the weight of iron present may account for almost 30% of the dry weight of large intestinal tissue. The iron deposit appears to be cumulative with age. It is speculated that the deposit is derived from oxidative deposition of a soluble ferrous salt ingested in reducing conditions.

The functional morphology of the coelomocytes of larval oysters, Crassostrea virginica and C. gigas, based on observations of live animals and histological and ultrastructural examination of tissues, is presented. Two predominant types of coelomocytes were found in the larval oysters. One, the SER cell, not found in the adult oyster, is large with a spheroidal nucleus, and exhibits basophilic cytoplasm which consists of abundant smooth endoplastic reticulum. This cell appears to participate in metabolic conversion processes. The other predominant cell type, the phagocyte, appears identical to the phagocyte observed in the adult oyster. Both differential cell types were observed from one day post fertilization to metamorphosis, the oldest stage studied.

Scallops of the bivalve family Pectinidae are very valuable shellfish and the subject of various important commercial fisheries around the world. Most of these fisheries are at present dependent upon natural populations, which can fluctuate widely in abundance from year to year due to irregular recruitment and overfishing. In recent years there has been considerable interest in the possibilities of cultivating various scallop species and some success has been obtained in rearing larvae of Pecten maximus (L.) in the laboratory (Comely, 1972; Gruffydd & Beaumont, 1972). However, by far the most successful cultivation system developed for pectinids has been carried out for several years in Japan for Patinopecten yessoensis (Jay). Naturally produced spat settling on Collectors made from artificial materials are grown on to market size in cages in the sea or used to restock natural beds (Ito, Kanno & Takashashi, 1975; Querellou, 1975; Motoda, 1977).

Analyses of the jaws of Nereis virens have shown that various metals are present in detectable quantities; in order of decreasing concentration these are (with ranges (μg/g dry weight) in brackets) – zinc (10130–18360), sodium (1150–2690), magnesium (616–1080), calcium (531–1130), iron (444–1180), manganese (510–952), potassium (270–960) and copper (4–80), with also lead (8·7), cadmium (0·1) and silver (< 0·1). The most concentrated metal, zinc, is not uniformly distributed throughout the jaw, the highest level occurring in the distal tip (45740 μg/g), falling to a much lower level in the basal part (1790 μg/g). The contribution of some jaw metals to the total body burden varies according to body size: in small worms the jaw zinc accounts for over 40% of the total but in large worms it accounts for 30% or less; jaw manganese contributes over 50% of the total in small worms, dropping to about 20% with increasing size. For silver, cadmium, copper, iron and lead the jaws generally contribute less than 1% to the total body burden.

The abundance of calanoid copepods in marine plankton and their importance as food for certain fishes has prompted numerous studies of their biology, including several concerned with fecundity (Marshall & Orr, 1952; Mullin & Brooks, 1967; Paffenhöfer, 1970). These studies, however, have all involved animals maintained on various diets in the laboratory: data for egg-production by Calanus under natural conditions in the sea are still needed.

To ensure the survival of the young of many animal species to the stage of independent feeding, biochemical energy in the form of lipid is stored within the egg. During a recent survey of Calanus helgolandicus (Claus) from the English Channel the level of lipid, mainly in the form of wax esters, in Stage V copepodids was found to be substantially greater than that in female adult stages (Gatten et al. 1979). The difference was particularly noticeable during spring periods when egg-laying was in progress. This observation indicates a major role for wax esters during the reproduction of Calanus.

The present study seeks to establish the fate of the lipid reserves in Stage V and female adult Calanus with particular emphasis on the extent to which the size of such reserves can be used as an index of the fecundity of this copepod.

It is well established that crustaceans can overcome infection and clear foreign material introduced into the circulation (Cornick & Stewart, 1968; Tyson & Jenkin, 1973; Stewart & Zwicker, 1974). In the absence of vertebrate-type specific acquired immunity, the non-specific activity mediated by the circulating blood cells appears to be of considerable importance in resistance to disease (Sindermann, 1971). Among the cellular defence mechanisms of the Crustacea, phagocytosis has received most attention and there is considerable evidence from in vitro studies that this process plays an important part in the removal of foreign particles from the blood (McKay & Jenkin, 1970a; Paterson & Stewart, 1974; Tyson & Jenkin, 1974; Paterson, Stewart & Zwicker, 1976; Smith & Ratcliffe, 1978). Such studies, however, may not always reflect the true in vivo condition, and there is a great need for correlated in vitro and in vivo investigations.

Overall incidence of metacercariae of Maritrema arenaria differed substantially at each of the three sites investigated. In each case, however, numbers were higher than those previously observed in the British Isles. Results indicate that gulls rather than waders are the more important final hosts of this parasite in the areas investigated. At one site where a more detailed survey was carried out metacercariae were more abundant on the upper half of the shore and they displayed a marked preference for barnacles on living Littorina littorea shells as compared to barnacles on rocks. Evidence would suggest that the two most likely molluscan hosts of this trematode are Littorina saxatilis and Nucella lapillus.

Two types of artificial substrate (nylon pan-scourers) have been shown to be highly efficient collectors of cryptofauna on rocky shores. The communities which develop in them are closely similar to those which develop in naturally occurring red algal turfs in Bantry Bay. The physical structure of the red algae appears to be the prime factor in determining the development of populations of most of the cryptofaunal species studied. In monitoring protocols artificial substrates of the types described here can be substituted for naturally occurring red algae in studies on shore cryptofauna obviating the necessity for destructive sampling of algae and facilitating statistical analysis by providing a standard ‘unit’ of substrate for comparative purposes. Furthermore, recruitment intensity of two species of gastropod has been shown to be similar in the artificial substrates to that in natural turfs

Enclosures of various sizes and configurations have been employed to maintain natural planktonic communities and to examine their responses to pollutants (e.g. Menzel & Steele, 1978; Steele, 1979). Studies on feeding, growth, and mortality of larval fishes, at times conducted in conjunction with pollution experiments, have also been successfully conducted in large enclosures (Koeller & Parsons, 1977). Implicit in these and other comparable studies has been the expectation (or hope) that a balance could be achieved between the advantages and difficulties inherent in more traditional field and laboratory studies. Field studies offer the realism of working with the natural assemblage with its many interacting components and links, but also suffer the disadvantage associated with a turbulent and advective system, which generally makes the repetitive sampling of the same populations impossible. Laboratory studies reverse the balance; control and definition of the components are gained at the expense of realism. The use of large containers represents a hybrid approach characterized by a partial control over a moderately realistic ecosystem. In the ideal case, the use of large containers allows sufficient control to permit experimental manipulation of (and the testing of hypotheses concerning) planktonic assemblages which are sufficiently realistic to permit extension of the experimental results to the ‘real world’.

Diel variations in the emergence of the burrowing prawn Nephrops norvegicus (L.) have been investigated by direct field observations (Chapman & Rice, 1971; Chapman, Johnstone & Rice, 1975; Chapman & Howard, 1979; Atkinson & Naylor, 1976), and indirectly by sequential trawling during 24 h periods (Höglund & Dybern, 1965; Simpson, 1965; Hillis, 1971; Farmer, 1974; Atkinson & Naylor, 1976; Oakley, 1979). Peak emergence appears to be related to temporal and depth-dependent variations in daylight penetration, since Nephrops are apparently nocturnal in shallow waters, crepuscular as the depth increases, and diurnal at the greatest depths of their occurrence. This lends support to the suggestion that emergence occurs at an optimum light intensity (Hillis, 1971; Chapman, Priestley & Robertson, 1972; Chapman, et al., 1975; Chapman & Howard, 1979). However, additional factors influencing emergence of Nephrops from their burrows have also to be taken in account, since laboratory studies of locomotor activity in Nephrops have consistently revealed nocturnal activity patterns in light-dark (LD) regimes, with light inhibiting locomotor activity even at extremely low irradiance levels (Arechiga & Atkinson, 1975; Atkinson & Naylor, 1973, 1976; Naylor & Atkinson, 1976). Moreover, Hammond & Naylor (1977 a) have presented qualitative evidence that the nocturnal locomotor activity peak appears to be synchronized by falling light intensity at dusk. The differences between these experimental results and emergence patterns deduced from trawl catches and underwater observations of Nephrops have not been fully resolved by studies of the role of light intensity and of gradual light transitions (Arechiga & Atkinson, 1975; Hammond & Naylor, 1977 a, b). Thus the behavioural responses of Nephrops both in the field and in the laboratory need to be assessed in relation to more accurately quantified light changes. Also, despite earlier evaluation of the problem (Atkinson & Naylor, 1976; Hammond & Naylor, 1977a) it is necessary to reconsider the possibility that the patterns of locomotor activity recorded in the laboratory are influenced by experimental conditions, as has been demonstrated for minnows (Jones, 1956), and flatfish (Verheijen & de Groot, 1967).

The production of tubes by the serpulid polychaete Mercierella enigmatica is compared with somatic growth and reproduction, and is shown to account for the greatest portion of production energy expenditure.

INTRODUCTION

The tube of a serpulid polychaete consists of two major fractions, a conspicuous calcareous component comprising small crystals of aragonite or calcite, and a more diffuse organic matrix (Hedley, 1956; Neff; 1971). The continuity of the organic matrix was demonstrated by Hedley (1956), who showed that careful decalcifkation failed to disturb the form of the tube of Pomatoceros triqueter (L.).

The serpulid Mercierella enigmatica Fauvel (Ficopomatus enigmaticus cf. ten Hove & Weerdenburg, 1978) secretes a hard, calcareous tube shortly after it settles from the plankton (Rullier, 1955; Vuillemin, 1965). Initially, tube growth is relatively fast, but as the tube increases in length so the rate of growth declines. However, the tube of the adult worm can be as much as 80 mm in length, or more than four times the length of its body.