Aricidea laubieri sp.nov. and six other species of the Paraonidae new to the British Isles were found during benthic surveys in the Celtic and North Seas. These increase the number of British representatives of the family to 15. New records of a further seven species are given, which in several cases extend the known geographical or bathymetric range. The identity of some previous records attributed to Aricidea Jeffreysii (McIntosh, 1879) and to Aricidea suecica Eliason, 1920, is discussed. A dichotomous key to British species is presented.

Waves and currents render the shallow sea a chaotic environment. Seaweeds broadcast into the water tiny dissemination phases whose powers of locomotion are at best puny in relation to the water forces that act upon them.

The life-cycle of the harpacticoid copepod Tisbe furcata (Baird, 1837) at 18 C was studied quantitatively. Stage durations were determined by two different methods, using synchronous cohorts. Combined nauplius stages last for 80·4 h; the successive copepodite stages take 23·0, 23·2, 28·0 (♀) to 23·2 (♂), 33·4 (♀) to 24·2 (♂) and 48·8 (♀) to 34·7 (♂) h, respectively. Females develop more slowly but more synchronously than males. Age-specific survival and fertility rates were used to calculate the stable stage distribution in an exponentially growing population. From life-table data the following demographic parameters were computed: intrinsic rate of natural increase rm = 0·233 day−1; net reproductive rate Ro = 94; minimum generation time Tmin = 14·9 days; parameters related to ‘generation time’: T = 19·5 days, = 16·4 days, Tc = 25·4 days.

The structure of the anal sacs of the echiuran Bonellia viridis Rolando was studied using SEM, TEM and light microscopy. The characteristic ciliated funnels which open into the coelom and connect it to the lumen of the sac were observed live by interference contrast light microscopy. Clearance of the extracellular marker inulin from the coelomic fluid (Vc = 9·6 ± 1·9 ml 100 g−1 wet weight of animal day−1) indicated that a filtrate of coelomic fluid is produced by the ciliary activity of the funnels. The flow of this filtrate into the sacs is unidirectional. Comparison of the ionic composition and osmolality of the anal sac fluid with the coelomic fluid, and surrounding sea water, indicates that the filtrate passes unmodified by absorptive or secretory processes to the outside. Thus the sacs do not appear to have a clear iono- or osmoregulatory function. During osmotic uptake of water in low salinities the rate of clearance of inulin by the anal sacs did not increase, indicating that their role in volume regulation is insignificant. The reddish-brown granules in the epithelium and lumen of the organ (which give the sacs their characteristic colour) may be important excretory products, and the primary function of the sacs their elimination.

Turbulence measurements taken at the water's edge at Derbyhaven beach, Isle of Man, indicated that maximum turbulence on any particular tide predictably occurred at the time of high water. However, long term monitoring failed to record any predictable semi-lunar modulation of the intensity of turbulence. Laboratory experiments showed that cycles of mechanical agitation applied for 2 h every 12 h for 4 days could entrain the endogenous circa-tidal activity rhythm of adult Eurydice pulchra. The effect was the same with shaking in constant light or constant darkness. However, when applied at different phases of an imposed L/D cycle, the synchronizer had a varying effect. The strongest entrainment occurred when shaking was phased to ‘midday’ and ‘midnight’ - a phase relationship paralleled by the high water of spring tides. Minimal synchronizer effect occurred when shaking was applied at ‘dawn’ and ‘evening’, the phase relationship of neap tide high water to the solar day. The varying response is suggested to be the origin of the semi-lunar modulation of activity seen in Eurydice pulchra.

Eulalia viridis (L.) is one of a group of polychaete species which are being used in an experimental analysis of the regulation of gametogenesis and reproduction. The back-ground to these studies and some of the preliminary results have been discussed recently by Olive (1980). Despite the abundant data demonstrating the frequent occurrence of well-defined reproductive cycles in marine invertebrates and observations on the correlations between reproductive events and environmental conditions, the mechanisms by which the reproductive cycles of individual species are controlled are very poorly understood. It has generally been accepted since the publication of the important paper of Orton (1920) that the temperature cycle in temperate and boreal regions plays an important role in determining the reproductive cycle, but the nature of the control mechanism is not, in general, understood and is likely to vary markedly between species. Environ-mental conditions such as relative daylength or biological factors such as the quantity and identity of the phytoplankton organisms (Himmelman, 1978, 1979) could also play important roles in regulating the sequence of cellular events which culminates in successful reproduction. These general problems have been discussed by Giese (1959) and more recently by Barnes (1975), Giese & Pearse (1975) and specifically in relation to Polychaeta by Clark (1979) and Olive (1980).

Analyses of the ampharetid polychaete Melinna palmata have shown that this species consistently contains a high concentration of copper. The related species Melinna cristata also has a high copper content but Ampharete acutifrons and Amphicteis gunneri have low copper contents. M. palmata usually contains copper in concentrations in excess of 600 μg/g (dry weight) and often above 1100 μg/g; much of this copper is embodied in the branchiae which have concentrations of 0·4–1·2% copper and, although these organs account for only 3–4% of the dry body weight, their copper content represents 30–40% of the total body burden. X-ray microanalysis shows the copper in the branchiae to be concentrated in special epidermal cells. The function of the copper in these cells does not appear to be associated with detoxication, luminescence or an antifouling mechanism but feeding trials have shown the branchiae of Melinna palmata, but not of Ampharete acutifrons, to be distasteful to certain small fish. Thus it is thought the copper may reduce the palatability of the tissues and is accumulated by Melinna palmata as a chemical defence against predation.

Crassostrea gigas spat were fed diets of Pavlova lutheri, Dunaliella tertiolecta or Tetraselmis suecica. The D. tertiolecta diet contained no fatty acid longer or more unsaturated than linolenic acid (18:3ω3) and the T. suecica diet was deficient in decosahexaenoic acid (22:6ω3). The algal diets were supplemented with micro-encapsulated triolein, oyster lipid extract or 22:6ω3. Spat were also starved or fed carbohydrate diets.

The tendency under field conditions for settling Balanus balanoides larvae to space out from conspecific adults but not from adults of other species is reaffirmed. Explanations are advanced for the opposite conclusions reached recently by other workers. The general avoidance by B. balanoides larvae of settling on top of older barnacles is examined. It is suggested that there must be a strong inhibiting influence, so far unexplained.

The luminescence of a number of amphipods of the genera Scina, Parapronoe, Cyphocaris, Megalanceola, Thoriella and Chevreuxiella/Danaella is described. The flashes of Scina spp. are rapid, 80–300 ms in duration, and may be elicited repetitively by electrical stimuli. Cholinesterase inhibitors are potent inducers of luminescence both in whole animals and in isolated appendages. A characteristic postural response is usually associated with mechanically induced luminescence of the larger species of Scina. Cyphocaris and Chevreuxiella/Danaella species also respond to electrical stimuli but the luminous responses are of longer duration than those of Scina and are not stimulated by eserine sulphate. In Parapronoe luminescence can be most easily induced with dilute hydrogen peroxide and the photogenic cells are associated with a brown pigmented area restricting the light output to a ventral direction. Secretory luminescence has been observed only in Megalanceola.

The hepatic photophores of species of Sergestes (organs of Pesta) contain fluorescent paracrystalline platelets which are the sources of the luminescence. The cells containing these crystals are contiguous with cells filled with lipid droplets which act as a diffuse reflector. The optical properties of the organ as a whole derive from the different arrangement of the various regions in the mosaic of individual tubules. The hepatic photophores of Parapandalus, Thalassocaris and Chlorotocoides have a similar anatomical position but differ considerably in structure. They do not contain paracrystalline material and they have a diffuse reflector, probably not composed of lipid, which is separated from the tubules that make up the photocytes. The organs in Thalassocaris and Chlorotocoides are very similar in structure. Luminescence in the photophores of all four genera is probably intracellular.

The respiratory function of the naked body of sea slugs (Opisthobranchia) has long been recognized. The gross anatomy of the gills of dorid nudibranchs was first published by Hancock & Embleton (1852) and was later revised and corrected by Eliot in 1910 in his supplement to the Ray Society monograph by Alder & Hancock (1845–55). Herdman (1890) and Rao (1936) give histological details, but do not seriously add to the understanding of the function of dorid gills or their circulation system. While the gill ciliation of bivalves (Atkins, 1938) and prosobranchs (Yonge, 1947) has been thoroughly examined this is not so in dorid nudibranchs and only the ciliation of the notaspid Pleurobranchus membranaceus has been described in any detail (Thompson & Slinn, 1959; Thompson, 1976) and the dorsal mantle of some dorids (Kress, 1981). Much of the general anatomy of opisthobranchs is reviewed by Hoffman (1939).

The nutrient requirements of many algae are well documented, with most algae being found to need only one or two vitamins. In the case of their predators, only a handful of microinvertebrates have had their diets and even fewer their vitamin requirements denned. Thus, any progress in this field together with the mode of nutrient uptake, must lead to a better understanding of the component-transfer in the food chain.

Brachionus plicatilis Müller has been reported to require vitamin B12 (Droop & Scott, 1978). The work described in this paper sought first, to confirm this and then to establish the mode of uptake. The alga Brachiomonas submarina var. pulsifera Droop was used to investigate the first of these questions as the writer had previous experience with it in steady-state energetics work. The alga Dunaliella SMBA Strain 246 was used to examine the mode of uptake by the rotifer since this had also been found to be a good food organism. The possibilities considered were uptake: (a) via the algal cell; (b) directly from solution; (c) a combination of both. Mode of vitamin B12 uptake is of particular interest as it may be representative of the pathway of many of the rotifer's water soluble micronutrients.

Before considering the influence of the vitamin on Brachionus investigations were made into the relationship between the vitamin and the two food-algae. It has already been established that Brachiomonas has a definite requirement (Droop, 1961) and Dunaliella no requirement for vitamin B12 (Turner, 1979). It was of interest to see if they took-up the vitamin in the manner shown by Monochrysts, a B12 requirer, and Phaeodactylum a non-requirer (Droop, 1968).

The hepatosomatic indices (HSI) of eight groups of Myxine glutinosa with different gonadal conditions are calculated and compared with each other. Female animals with eggs longer than 10 mm differ statistically significant in their HSI from all other groups. The production of a vitellogenetic protein in the liver of Myxine is concluded.

An apparatus has been developed which allows the complete replacement of interstitial water in sediments without disturbance. In principle, it can be adapted to handle sand or mud, different solutions, and different volumes of sediment. The apparatus was tested with 0·05% (wt/vol.) eosin in sea water. After replacement of the interstitial water, the eosin was evenly distributed throughout the sediment. Interstitial water in samples of sediment was replaced by sulphide solutions in sea water, at a range of concentrations. The responses of Corophium volutator to these sediments was tested in choice and non-choice experiments. In the choice experiments, animals avoided burrowing in sediments containing sulphide at concentrations greater than about 5·8 × 10−5M. In the non-choice experiments, animals were progressively inhibited from burrowing when the sediment sulphide concentration was greater than about 5·8 × 10−4M. No mortality occurred during the experiments.

Skin structures of nine different species of dorid nudibranchs were examined at the scanning electron microscope and the light microscope levels. From these observations the animals are grouped into three categories.

1. Dorids with spicule-supported tubercles carrying a sensory knob (Rostanga rubra, Jorunna tomentosa, Onchidoris sparsa, Onchidoris pusilla).

2. Dorids with small sensory papillae set in pits and distributed randomly between projecting spicules (Aegires punctilucens).

3. Dorids with tubercles differing in shape from one species to another, invested with numerous spicules but without conspicuous sensory structures. The tips of the tubercles do, however, contain single sensory epithelium cells (Archidoris pseudoargus, Acanthodoris pilosa, Onchidoris muricata, Onchidoris bilamellata).

The development of the oocytes of Nereis (Hediste) diversicolor and Nereis (Nereis) pelagica takes up to 18 months from their first appearance in the coelom to maturity, and in the natural conditions experienced by the population studied in north-east England the females are in their second year before the oocytes begin to appear. The duration of spermatogenesis is less than that of oogenesis, taking up to 6 months for completion. This information permits a more rigorous interpretation of the size frequency data which have been obtained from a biometrical study of the jaws. In the populations of both species the majority of individuals seem to reach maturity when 3 years old.

Coxal plates 1–5 of Epimeria cornigera form a closely interlocking series keyed by the head such that ventral flexion of the peraeon is severely curtailed. The clamp formed by coxae 4 and 5 is interpreted as an adaptation facilitating copulation in a species with feeble gnathopods and non-prehensile antennae. The morphology of the posterior three pairs of peraeopods can also be regarded as an adaptation for gripping the female. Other possible functions (e.g. predator deterrence and feeding grip) of coxal structures are also examined.

The ellobiopsid genus Thalassomyces is of uncertain systematic position, having been allied at various times with the fungi, algae and protozoa, and little is known of its biology. Discovery of a flagellate stage suggested to Gait & Whisler (1970) that the genus is a member of the achlorophyllous Dinophyceae (Dinoflagellata). T. fagei (Boschma, 1949) appears to be restricted to euphausiids (of which there are 85 valid species in 11 genera-see Mauchline & Fisher, 1969). According to Vader (1973), T. fagei has been recorded in different areas from various euphausiid species, i.e. in 11 (perhaps 12) species of Euphausia, two of Nycliphanes, three of Thysanoessa, and in Nematoscelis difficilis and M. novegica. Other Thalassomyces species are found in mysid, decapod and amphidpod crustaceans (Vader, 1973).

The thin band between growth increments in the shell of Cerastoderma edule is laid down at the end of the period of emersion, when the pH of the mantle and extrapallial fluids are at a minimum of pH 7·0 and 7·2 respectively. The growth increment is formed during immersion when the pH of the extrapallial fluid is 7·5–7·7 and the mantle 7·6–7·8, which is close to that of sea water (pH 7·8).