The closure response to low external salinity of three species of intertidal and estuarine barnacle (Balanus balanoides, B. crenatus and Elminius modestus) when exposed to various rates of salinity change were investigated. Comparisons were made between the responses of specimens collected from estuarine and coastal sites. In addition the responses of the brackish water barnacle Balanus improvisus were measured.

Squids (teuthoids) fall into two distinct groups according to their density in sea water. Squids of one group are considerably denser than sea water and must swim to stop sinking; squids in the other group are nearly neutrally buoyant. Analyses show that in almost all the neutrally buoyant squids large amounts of ammonium are present. This ammonium is not uniformly distributed throughout the body but is mostly confined to special tissues where its concentration can approach half molar. The locations of such tissues differ according to the species and developmental stage of the squid. It is clear that the ammonium-rich solution are almost isosmotic with sea water but of lower density and they are present in sufficient volume to provide the main buoyancy mechanism of these squids. A variety of evidence is given which suggests that squids in no less than 12 of the 26 families achieve near-neutral buoyancy in this way and that 14 families contain squids appreciably denser than sea water [at least one family contains both types of squid]. Some of the ammonium-rich squids are extremely abundant in the oceans.

The herring, Clupea harengus, in common with other clupeoids, has ducts between the swimbladder and the exterior and has no apparent gas secretion organs. Experiments under pressure show that the central regions of the swimbladder wall are very compliant and collapse as the fish moves deeper in the sea, leaving the end sections patent. Gas is thus always held where it is available to maintain the gas-filled bulla system.

The status of our knowledge of the organic nutrition of algae has been summarized in tabular form from time to time. Albritton (1954) listed a mere 14 taxa of pigmented algae as having been examined from this point of view. Eight of the 14 were species of Euglena and only ‘Nitzschia dosterium' (= Phaeodactylum tricornutum Bohlin) was marine. This paucity of information reflected in part the lack of suitable denned culture media as prerequisites of nutritional experiments. By the early 1960s this lack had been overcome to a large extent (see, for example, Provasoli, McLaughlin & Droop, 1957) and Thomas (1968) could list some 280 species, both freshwater and marine, on which nutritional work in terms of organic requirements had been undertaken. The vitamin requirements (or lack of them) of most of these species were known, but knowledge of their ability to grow in the dark on organic carbon sources and of their ability to utilize different nitrogen sources in the light was fragmentary. It still is, despite the fact that some of the gaps in Thomas's tables have been subsequently filled and the list of species has been extended.

The allometric relationships between shell length and shell breadth, shell height, shell weight, wet tissue weight and dry tissue weight are described for a population of Cerastoderma edule living at a high tidal level in the Dovey Estuary, West Wales. Seasonal fluctuations in standard animal values for shell weight and dry weight are interpreted in terms of the cycles of reproduction and food availability; the dangers associated with the use of wet weight in growth studies are demonstrated. The population structure is described using a combination of length-frequency and growth ring analyses and comprised nine year-classes with overlapping size ranges. The growth of the population was very slow and the relative growth rate was almost constant; associated with this slow, atypical growth pattern was considerable longevity and a small maximum size. The reasons for these characteristics are discussed.

The information received by a fish about a vibrating source will depend on the patterns of excitation of various groups of receptors. Sprats, herrings and other clupeoids have bullae containing gas which are closely related to the sense organs of the utriculi, sacculi and the lateral lines. Structures of particular relevance to the functioning of this system are described and an account of their mechanical responses to low frequency pressure stimuli is given.

The morphology and ultrastructure of the heart and excretory system of the marine lamellibranch bivalve mollusc, Mytilus edulis (L.) are described. This paper supports the view that ultrafiltration of the blood occurs in the pericardial cavity. The auricles, pericardial glands and afferent oblique veins contain podocytes which are usually ascribed to the specific function of ultrafiltration. These cells are absent in the ventricle. The pericardial cavity communicates with the exterior via a very short (ca. 1–2 mm) renal tubule. The kidney comprises of a series of highly branched diverticula of this tubule and displays little or no structural differences throughout the organ. The kidney cells form a single layered columnar epithelium with a brush border, basal nuclei, infolded basal membranes and are characterized by the presence of many membrane-limited granules occupying as much as 20% of the cell volume. These granules and those of the podocytes are subsequently shed into the lumen of the kidney tubule and are excreted in the urine which is therefore largely paniculate.

There is now considerable evidence that benzo[a]pyrene hydroxylase (aryl hydrocarbon hydroxylase: AHH) is involved in the metabolism of petroleum hydrocarbons by several species of marine fish (see review by Varanasi & Malins, 1977), as well as by certain species of marine invertebrates, including crabs and lobsters (Payne, 1977). Several workers (Payne & Penrose, 1975; Payne, 1976, 1977; Bend, James & Dansette, 1977) have found increased activities of this enzyme in fish previously exposed to petroleum hydrocarbons and related compounds: similar findings have been made in a study using two species of polychaete (Lee, Furlong & Singer, 1977 a). No evidence of such enhanced activity, however, has been found in experiments with crabs and lobsters (Payne, 1977).

The mechanical responses of several structures in the auditory and lateral-line systems of the sprat Sprattus sprattus(L.) and the herringClupea harengus L. to oscillatory pressure changes have been observed over a range of frequencies from 0·014 t0 2600 Hz. The pressures required to give constant responses of the bulla membrane, and the lateral recess membrane varied relatively little between 0·014 and 1000 Hz; above 1000 Hz the sensitivity fell quickly as frequency increased.

The dry weight condition index and water content of two groups of mussels, one with heavy infestations and the other with mild infestations of Polydora ciliata, were determined over a period of 15 consecutive months. The results were seasonally variable, but for most months the heavily infested mussels had a condition index significantly lower, and a water content significantly higher, than the mildly infested mussels. This suggests that heavy infestations of P. ciliata are associated with reduced flesh content in mussels.

Further analyses of the body components of the two groups of mussels, showed that the mantle tissue of heavily infested mussels was reduced much more than the nonmantle tissue. Since the mantle is the main repository of gametes, this suggests that heavy infestations of P. ciliata might lower the fecundity of mussels.

Many marine animals that live at depths greater than about 500 m are deeply coloured (generally red, brown, black or purple) even though there is little or no down-welling light in these regions (Clarke & Denton, 1962). The nature and function of many of these pigments are obscure. Partly, no doubt, because of the difficulty of provenance, there have been very few chemical and biochemical investigations on such pigments (see Crozier (1974) for a review of pigments in fishes). We report here an investigation of the pigments of meso- and bathypelagic medusae. The work was initiated following preliminary identification of protoporphyrin in Atolla wyvillei and Periphylla periphylla (Herring 1972): the present work confirms and considerably extends these observations (Head, 1976, M.Phil. Thesis, University of London).

The composition of subtidal meiobenthic associations off the Isle of Man is analysed, with particular reference to the harpacticoid copepods. By comparisons with surveys in other seas it is suggested that coherent associations of benthic copepods can be recognized in the sublittoral fringe area of tidal fine sand beaches and in offshore fine sand in Europe. The heterogeneity of offshore coarse deposits and muddy sands results in the inability to distinguish communities or isocommunities in these deposits. As muddy sand grades into mud some evidence is presented to suggest that, given similar temperature and salinity regimes, a consistent association of copepods may develop.

Zinc (Zn II) and iron (Fe III) were demonstrated histochemically in cytoplasmic inclusions shown to be lysosomes in a number of cell types in Mytilus edulis. The cellular distribution of the metals differed between the sexes; males were shown to have more zinc (Zn II) in the kidney than females, the latter appearing to use oocytes as an additional means of excretion. Differences in cellular distribution of the metals was also demonstrated between the two populations studied probably reflecting availability of the metals in their respective environment.

Predation of the barnacles Balanus balanoides and Elminius modestus by the common dog-whelk, Nucella lapillus was studied in the laboratory. Greater numbers of B. balanoides were taken as prey unless the whelks had been previously subjected to an extensive period of starvation.

Selective predation is discussed in the light of similar studies on Nucella and related predatory species. The effects of prey selection on the competitive interactions of the prey species are also considered.

The method of predatory attack involves either a drilling or a prizing technique. The latter is used predominantly when Nucella attacks E. modestus, whereas drilling is employed to a far greater extent when attacking B. balanoides. Attacks using the drilling technique are usually made at the occludent margins of the opercular valves.

Traditional scale reading methods have been compared with [C]glycine uptake data to study scale growth in bass.

Both methods are capable of being used to age young fish and determine their rate of growth. The glycine incorporation rate is, however, of more value in studying shortterm changes in fish growth. When applied in this way, it indicates that the apparent isometric relationship between scale and body length is actually the sum of a number of allometric interactions. Some of the errors that can occur in scale reading are demonstrated by the application of these methods.

There can be little doubt that competition for space, both inter- and intraspecific is a major factor in barnacle ecology. Southward & Crisp (1956) first pointed out the role of competition between Balanus balanoides (L.) and Chthamalus stellatus (Poli) in south-west Britain which Connell (1959, 1961) later demonstrated experimentally. Crisp (1958) discussed competition between the indigenous B. balanoides and the immigrant Elminius modestus Darwin in the intertidal zone, and measurements of growth rates, using manipulated populations of these two species, indicated that inter- and intraspecific competition for space after settlement is intense (Crisp, 1964).

The ultrastructure and dimensions of the solenocytes of Branchiostoma lanceolatum are reviewed briefly. The functional ability of these units is calculated upon theoretical grounds in a manner similar to that applied to flame cells. Their more delicate construction would suggest that Branchiostoma would have great difficulty in maintaining any significant osmotic pressure difference between the medium and its body fluids.

Gills of fresh-water and sea-water eels were perfused at a constant pressure with physiological Ringer containing 10−6 M sodium orthovanadate and examined by light microscopy. The secondary gill filaments were markedly vasoconstricted in both freshwater and sea-water fish although the peripheral blood route around the secondary filaments was unaffected. The central venous space in the primary filament was largely unaffected. Significant constriction of both afferent and efferent arteries on the primary filament occurred. We conclude that orthovanadate vasoconstricts eel gills mainly at the level of the secondary filaments. The study also emphasizes that chloride cells are located on both the primary and secondary filaments of fresh-water gills but solely on the primary filaments of sea-water gills.

Settlement behaviour of barnacle cyprids has been investigated extensively. There are two opposing tendencies. The cyprids settle gregariously over distances of several centimetres (Knight-Jones, 1953a, b; Knight-Jones & Stevenson, 1950; Knight-Jones & Crisp, 1953; Crisp & Meadows, 1962,1963). However, at closer range of a few millimetres they tend to space themselves out (Crisp, 1961; Knight-Jones & Moyse, 1961).

The electrophoretic mobilities of 13 enzymes in two species of Chthamalus, C. stellatus Poli and C. montagui Southward, were compared. These species differed absolutely for eight of the enzymes and exhibited some species-specific allozymes for a further four enzymes. No evidence of hybridization was found. The observed mean heterozygosity was 0087 for C. stellatus and 0179 for C. montagui.

A sample of ‘C. montagui’ from Venice differed from two samples from south-west England in external shell characters and in allozyme frequency for two enzymes. These differences are thought to be the result of a geographical cline rather than a distinct separation of subspecies.