The capture of specimens of Crenilabrus bailloni Valenciennes, 1839 from Galway Bay, Republic of Ireland, and off the coast of Jersey, Channel Islands is reported. Occurrences of this species in northern European waters are discussed. It is concluded that this wrasse is a Lusitanian element in the northern fauna, and suggested that it may be more common in the fauna than records indicate due to its inhabiting a little collected habitat and on account of its similarity to the common corkwing wrasse C. melops (Linnaeus, 1758). Methods of distinguishing the two species are given.

Atelecyclus buries itself by digging backwards into the sand, sometimes until only the antennae protrude above the sand. In this position it is difficult for the animal to maintain an adequate respiratory current through the branchial chambers by pumping water in the normal direction.

Studies of the ventilatory behaviour of Atelecyclus have shown that, when on the surface of the sand, water flows through the branchial chambers as in most other crabs i.e. water enters the chambers at the base of the limbs and the exhalant water leaves anteriorly. This direction of flow is also maintained when the crabs are only partially buried but when more deeply buried, the direction of water flow is reversed by the reversal of the direction of beat of the scaphognathites and water is drawn down the antennal tube and leaves the branchial chambers at the base of the limbs.

Inactive Atelecyclus show a well-defined rhythm of pumping in which regular periods of active pumping alternate with periods during which the scaphognathites stop beating and ventilation of the branchial chambers ceases. The rhythm of ventilation is regular but the duration of the ventilatory pauses (apnoea) may vary considerably between animals.

During pausing, the activity of the scaphognathites and of the heart are closely synchronized. The cessation of scaphognathite activity is accompanied by a period of cardiac arrest, although single heart beats may sometimes occur during a pause.

As in many decapods, the Po of the post-branchial blood was high (Pa, o = 92 torr, Pv, O = 21 torr) but during a pause P, o gradually declined.

Populations of Idotea pelagica and Idotea granulosa were studied monthly at Carnsore Point, County Wexford, from July 1978 to October 1979. The density of I. pelagica in mussel beds varied between 26 and 180/100 cm, reaching a peak in June. Numbers of I. granulosa in samples of Gigartina stellata fluctuated from month to month and averaged 200/100 g dry weight of algae. Peak densities were recorded in September of both years. Both species exhibited continuous growth, and breeding occurred throughout the year but with a main breeding period starting in winter. I. pelagica grew more rapidly and had an extensive breeding period lasting from December to August with two generations, some members of both generations producing second broods. For I. granulosa, the main breeding period was January to April, after which most adults died. Some of their offspring reached maturity in late summer giving rise to a lesser breeding peak in late summer and autumn but most did not mature until winter. Summer breeders of both species were smaller than those breeding in winter. The breeding cycles are compared with those of other populations in Britain and the Baltic and the possible reasons for the differences discussed.

The distributions of Asterina gibbosa and A. phylactica in the Lough Ine area are described and compared. The species are shown to have different horizontal distributions with respect to wave exposure. Clear ecological separation is demonstrated where their distributions overlap as a result of micro-habitat preferences.

The shapes and dimensions of the statocysts of cephalopods have been measured and compared with the semi-circular canals of vertebrates. The cavities grow much more slowly than the body as a whole, but there are knobs, anticristae, which restrict the cavity, and these grow relatively faster. This ensures that the flow of endolymph across the cupulae remains small. Where the liquid is constrained within canals the radius of curvature of the whole canal, R, is similar to that of fishes, whereas its internal radius, r, is twice as large in non-buoyant and four times as large in deep-sea buoyant cephalopods as in fishes of similar size. As in fishes the restriction is greatest in the horizontal plane, providing for operation at higher frequencies in turning about the yaw axis.

The statocysts of seven species of Loligo all have similar proportions. The largest individuals of 16 genera of non-buoyant squids also have these same relative dimensions. The statocyst of Sepia is more like that of non-buoyant than of other buoyant cephalopods but yet differs significantly from that of Loligo at all sizes. On the other hand 21 genera of squids known to be neutrally buoyant are very different. Their statocysts are often larger than in the non-buoyant forms and there is less restriction of the cavity by anticristae. The greater flow of endolymph acting across the cupulae presumably provides greater sensitivity at the lower frequencies of turning of these deep-sea animals.

The data suggest that the cristae of the cephalopod statocyst may operate in the frequency band where they act as angular accelerometers whereas the vertebrate semi-circular canals operate at higher frequencies as angular velocity meters.

Phase-responsiveness to single pulses of simulated high tide has been tested for in the locomotor activity rhythm of Hemigrapsus edwardsi, a grapsid crab from a locality of equal semi-diurnal tides. The crab exhibits endogenous circatidal locomotor rhythmicity with only a weak circadian component. Exposure to a single 3 h ‘pulse’ of simulated high tide (immersion and low temperature, with or without light) in crabs kept otherwise in constant conditions (moist air; dim red light; 15°C), resulted in slight phase delays in the free-running rhythm when the tidal ‘pulse’ was applied in the first 2–3 h of the ‘expected’ high tide period. Tidal pulses initiated at and just after the expected time of high tide induce a phase advance. The results support the hypothesis of a phase-responsive curve on a tidal (12·4 h) rather than 24 h time-base. However, the phase advances and delays are small when compared with circadian phase response curves. It is suggested that the circatidal rhythms depend mainly upon repeated exposure to tidal variables for entrainment and that each individual tide is able to adjust the behavioural rhythm only slightly from its endogenous pattern. In this way, behaviour of populations of coastal animals is less susceptible to environmental perturbations associated, for example, with severe storms.

A complemental male was found on a solitary specimen of the primitive sessile barnacle Chionelasmus darwini. It was located on the scutal apex of the hermaphrodite and accommodated by a notch in the tergum. Its resemblance to complemental males of Bathylasma adds weight to the classification of the genus in the family Pachylasmidae rather than the Catophragmidae. Phylogenetic implications are discussed.

Measurements at sea in the Biscay and Celtic Sea have shown that the peak to trough displacement of the internal tide maximises at the shelf break of the Celtic Sea with peak to trough values in excess of 50 m at spring tides during the summer. In this region the internal tide generated at the top of the slopes is highly distorted by the shelf barotropic tidal currents. The internal tide propagates on-shelf towards the coast and off-slope towards the ocean as a decaying progressive wave. A simple model is developed that illustrates many of the observed features of the measured structure of the internal tide.

The ultrastructure, histochemistry and X-ray microanalysis of the metal-containing blood cells in three species of oyster, Ostrea edulis, Ostrea angasi and Crassostrea gigas are described. Granular cells containing both copper (up to 400 mM) and zinc (up to 1 M) are present in all three species. In addition,Ostrea edulis has two other granular amoebocyte types which specifically accumulate either copper (400 mM) or zinc (12 M). In all types of amoebocyte, the metals are stored in membrane-limited vesicles. The ultrastructure and histochemical staining characteristics of the vesicular contents vary according to metal composition. Zinc-containing granules appear basophilic after sulphide treatment and display homogeneous electron density; copper/zinc-containing granules are less dense and show varying degrees of crystallinity; copper-containing granules appear crystalline (however, any acidophilic or basophilic reaction is masked by the dark brown precipitate of copper sulphide).

Measurements during autumn and winter of the lower median lethal temperature of the barnacle Balanus balanoides (L.) under natural and modified environmental conditions in field and laboratory, show that the cold resistant state is advanced by three factors: short day photoperiod, reduced food assimilation and reduced temperature. Their relative efficacy is in that order.

These factors combine in promoting breeding and the acquisition of the cold tolerant state during autumn and winter. Although normally associated, breeding and cold tolerance are not mutually dependent; the one can be induced without the other under abnormal conditions.

Similar measurements made in the spring show that only a single factor is required to terminate the cold tolerant state — resumption of food assimilation. If feeding is discontinued in the spring, however, the cold tolerant state tends to return, but animals that have bred do not breed again until the following autumn.

Of the three well established mechanisms for seasonal cold tolerance — production of substances to cause freezing hysteresis, production of cryoprotective agents, and nucleating agents to promote freezing in the intercellular compartment — only the last can be entertained since the cold tolerant animal survives some 80% of the body fluids being converted to ice. The cold tolerant condition may also relate to higher levels of polyunsaturated fatty acids being present in the membrane lipid fraction in winter, so rendering cell membranes less prone to damage by ice crystals.

The suggestion is made that normal metabolic activity and tolerance of low chemical potential of water - the common factor in freezing and desiccation - are not compatible.

Techniques were developed to measure the adhesion of the barnacle Balanus balanoides (L.), over the post metamorphosis period. It was found that Balanus balanoides is capable of producing a proteinaceous adhesive material within one day of metamorphosis. This adhesive material was found to withstand applied forces of 1·7×105 Nm−2 before cohesive failure took place. The strength of the cement produced by older barnacles, measured at a time when the adult cement apparatus is known to be operating, was considerably greater and applied forces of 9·3 × 10 Nm were necessary to induce cohesive failure in the cement. The strength of B. balanoides cement was thus shown to be at least one tenth of that of commercial adhesives which have tensile strengths in the region of 107 Nm−2.

Variation in morphological characters seen in a large collection of specimens of the genus Echinosigra from the Rockall Trough can be arranged in a continuous ontological series. This growth series embodied forms agreeing with Mortensen's (1907) descriptions of both E. phiale and E. paradoxa. Bivariate biometrical study showed a well-defined allometric relationship of test length to other body dimensions, particularly the width of the ‘head’ and the width and height of the ‘body’. Immature specimens corresponded to E. phiale whilst the typically elongated ‘neck’ of adults corresponding to E. paradoxa was developed, along with the opening of the genital pores, at around a test length of 20–24 mm.

The shell growth of small coastal Mytilus edulis L. was measured at three different constant low salinities over short periods of time. Growth was significantly depressed in 6·4 and 16‰ S but not in 22·4‰ S. Fluctuating salinities between 0 and 32‰ S depressed growth whether the fluctuations were of sinusoidal or abrupt form. After 1 week of preconditioning to constant 32‰ S the growth of coastal (Bangor) mussels was better than estuarine (Conwy) mussels. However, after two weeks’ preconditioning to 32‰ S the estuarine mussels displayed the best growth. In the fluctuating regime, both coastal and estuarine mussels exhibited poor growth rates. The long-term response of the shell growth of coastal M. edulis was followed over a period of 44 days. Salinities in the range 1·8–9·6‰ S were lethal to the mussels within 10 days. In 12·8 and 16‰ S growth was initially delayed but recovered eventually. There was a gradual decline in the growth rate of the mussels exposed to the higher salinities (19·2–32‰) and an improvement in the growth of the mussels living in lower salinities (12·8 and 16‰) to levels nearly matching that of the high salinity animals by day 37. This suggests that acclimation of the shell growth of M. edulis to salinities in the 12·8–28·8‰ S range was achieved by the mussels during the experimental period.

Tidal micro-growth bands were used to study the annual cycle of shell growth of individuals dated predominantly by the immersion mark technique, in three common intertidal gastropods Nucella lapillus (L.), Littorina littorea (L.) and Patella vulgata L. growing naturally in the Menai Straits. Growth in all three species approximated to the von Bertalanaffy type. All three species grew throughout the year, N. lapillus and L. littorea with early autumn and summer maxima, respectively, and P. vulgata with two maxima, one in late spring and the other in early autumn. P. vulgata alone were observed during exposure to a 6-day period of sub-zero air temperature in January 1982 when shell growth was totally interrupted. In Nucella and Littorina shell growth was found to be closely related to ambient temperature but in Patella there was a summer depression in growth. The file technique when combined with the immersion mark technique in date marking, was found to be inferior to the immersion mark technique on its own, since filing occasionally affected growth adversely.

From among the factors determining the seasonal changes in growth rate, temperature was of major importance. Seasonal reproduction may also have an influence, especially in P. vulgata where gametogenesis coincides with the depression in growth rate during summer months.

Alternative methods used in gastropod growth studies were compared. In the light of inadequacies associated with other methods of measuring growth, micro-growth band measurements in gastropods offers a new method with high resolution suitable both for short and long-term growth studies. It has potential also for ecological and physiological aspects of growth measurements.

The benthic fauna of a fly-ash dumping ground off the Northumberland coast has been studied in comparison with that of the surrounding natural sediments and a designated offshore spoil ground. Continued ash dumping has resulted in an increase in the silt fraction of the sediments, together with the appearance of pozzolanic aggregates at the sites of greatest dumping, some 3·5 km offshore. The sediments here show a more rapid decline in Eh values with depth. The natural benthic macrofauna represented a typical Echinocardium-filiformis community, giving way throughout the offshore spoil ground to a ‘ Paraonis-Magelona’ community dominated by smaller polychaete species more tolerant of poor sediments, while the stations at the centre of the ash dumping showed an anomalous community structure. The density of the fauna was reduced at the centre of the ash dumping, the worst station yielding only eight individuals in 0·2m. Contours of numbers of macrofaunal individuals and species, of faunistic diversity and biomass, and of meiofaunal numbers all show a similar pattern of some depression along the spoil ground, and greater depression at the ash-dumping centre. Statistical analyses confirm a significant negative correlation between faunistic parameters and ash content. Deposit-feeding species represented a lower proportion of the community at sites of high ash content. The negative correlation between faunistic diversity and ash content was statistically significant over an area of 43 km around the centre of the dumping. The faunistic impoverishment is considered mainly to be a response to the dumping per se, and options for reducing this effect are discussed.

A karyometric analysis of the diploid complement of Procerodes dohrni (Turbellaria: Tricladida) was carried out on mitoses from regenerative blastema. P. dohrni has seven pairs of homologous chromosomes. Chromosome lengths decrease gradually and homologous pairs cannot be grouped. With reference to centromere position, chromosomes 1, 2, 3, 4 and 6 are metacentric, their centrometric indices vary from 46·74 to 39·82, while chromosomes 5 and 7 are submetacentric, their centromeric index being 34·63 and 29·86 respectively.

Much evidence has suggested that calcification in Carcinus and certain other marine organisms may arise at least partly by the local formation of base. The extent of changes of pH needed to precipitate calcium carbonate from sea water or from the blood of the crab are not known with certainty. These have been investigated, using sea water and crabs from the coast of Maine.

Mean sea water pH, mostly as measured in aerated samples used for experiments in the laboratory, was 8·00, a little below the values commonly found close to the shore in summer. The corresponding mean blood pH was 7·12. Crushing calcified crab cuticle in sea-water raised the pH, showing the sea water to be below saturation with the salts concerned. The rise in pH was slightly greater in the more dilute suspensions, an effect attributed to the mixed composition of the calcifying salts. Thus in one group of experiments cuticle crushed in sea water in proportions 1:20 and 112·7 raised its pH by 0·66 and 0·62 units respectively, and extrapolation suggested that interstitial fluid of almost zero volume would equilibrate at 0·38 pH units above sea water. Crushing cuticle in crab blood in proportion 1:2·7 raised its pH by 1·03 units, showing the plasma also to be unsaturated with carbonate.

Carbonates were precipitated from sea water by rendering it alkaline with sodium hydroxide; in four experiments the first crystallites were found in samples in which in 3 days after addition of base pH had fallen to between 8·46 and 9·30. In a longer series of experiments with crab plasma, crystals were first seen in samples in which after three days the mean pH had fallen to 8–09. Crystallites at the surface formed mosaics of spherulites closely resembling those of normal crab cuticle.