Samples of the mud shrimp Callianassa subterranea (Montagu) were taken at irregular intervals (September and October 1989, April and July 1990, August 1991) from a depth of 47 m at a fixed station in the North Sea (54°35′N 04°50′E). At this site, mud shrimps appear to have a contagious distribution, the mean density varied between 38 and 59 individuals m-2 and the sex ratio was biased significantly to males (mean male: female ratio, 1·9), except for shrimps of ≥8 mm carapace length (CL) which had an equal sex ratio. The combined samples for the full sampling period showed a bimodal distribution for males and females, with a possible third mode for males, suggesting a life cycle of between 2 and 3 years. Only females ≥7 mm CL carried eggs. Lack of samples over winter prevent any conclusive description of seasonal population patterns; however, reproduction (based on the presence of ovigerous females) extended from April to September with a peak in July and post-larval shrimps (<3 mm CL) were present each month. The allometric growth of the primary chela identified male (6·5 mm CL) and female (7·5 mm CL) size at maturity. Differences in allometric growth after maturity result in males having larger and more massive primary chelae than females of equal carapace length. The parasitic isopod Ione thoracica (Montagu) infected between 20% (October) and 10–8% (August) of mud shrimps, with males having a significantly higher level of infestation than females.

The distribution of Ampelisca aequicornis Bruzelius is said to extend from Norway southwards to the Gulf of Guinea (Dauvin & Bellan-Santini, 1988) and it has been recorded from British and Irish waters (Norman, 1900; Metzger, 1875). There do not appear to be any recent records. A number of specimens in The Natural History Museum, London (NHM) collections, labelled Ampelisca aequicornis, were examined by Lincoln (1979) who reported that only Galway Bay material was referable to A. aequicornis or “at least to the aequicornis complex”. This we can confirm from our own study of the NHM material. We have re-examined the Galway Bay specimen referred to by Lincoln (1979) and find it to differ from A. aequicornis in several ways and to be closest to A. dalmatina Karaman, previously known only from the Mediterranean and the Portuguese coast (Marques & Bellan-Santini, 1991, 1993). It also closely resembles A. pusilla Sars and A. ambylops Sars, but those two species lack cuticular eyes. Ampelisca aequicornis is therefore not confirmed to occur in the waters of the British Isles.

The winter of 1989/1990 was a year of marked warm water inflow along the Iberian, Spanish and French continental slopes and three anticyclonic eddies developed in the southern Bay of Biscay. Winter temperatures along the northern Spanish slope were examined in the belief that warm water inflow is related to the production of anticyclonic eddies in the southern Bay of Biscay. The annual cycle of temperature (at ~200 m depth) is most unusual in that the warmest temperatures occur in January, the coldest in the summer. Year-to-year variations are evident with the suggestion of a periodicity, though variable, of about five years.

In April 1992, an opportunity presented itself for a late winter eddy survey in the south-eastern corner of the Bay of Biscay from RRS ‘Charles Darwin’. Two Argos buoys were deployed in what was thought to be, or would develop into, an anticyclonic eddy, and one of the buoys was caught in the eddy. This buoy was drogued at a depth of 320 m in a relatively well-mixed part of the water column thought to contain the eddy core. This buoy made ~60 clockwise orbits in the eddy and remained within 15 km of the eddy centre over the 200-d observation period. The normalized relative central vorticity of the eddy had a minimum value of -0·6 and the eddy rotation period experienced by the buoy ranged from 2·5 to 6·5 d. The decay scale for the eddy was estimated at 250 ±100 d. The mean variance of the east-west velocity component was significantly larger than the north-south value, and the buoy's orbit was significantly elliptical towards the end of the period of the observations.

Samples of the large sublittoral sea anemone Urticina eques (Gosse) were collected from three localities in the northern North Sea and from one locality in the northern Irish Sea. Around the coast the total distance between sampling sites is approximately 1,200 km. The species has a large lecithotrophic larva which may not be planktonic. All samples were screened genetically for 13 loci coding for 11 different enzymes. Results overall indicated a high degree of genetic uniformity over the four populations sampled (FST = 0·025). The data are discussed in relation to current ideas of larval dispersal and results from other similar studies. It is concluded that the lack of genetic differentiation shown by Urticina eques is surprising given the apparently poor dispersive powers of the larva.

Tharyx retierei, a new species of bipalpate Cirratulidae (Polychaeta), has been collected from subtidal depths south of Safi, off the Atlantic coast of Morocco. The species differs from all other known bipalpate cirratulids in possessing aristate and pseudocompound neurosetae in posterior segments. The species is described and figured and its affinities are briefly discussed.

Perinereis nuntia brevicirrus (Grube 1857), collected from a rocky shore at Qingdao (China) were cultured under different temperature, daylength and moonlight regimes. Ripe individuals were found in the field after an increase of water temperature in early summer, with a semilunar spawning peak from the beginning of June to the end of September. In laboratory experiments, daylength has no influence on maturation and reproduction. Temperature-controlled culture produces gravid, reproducing specimens at any time of the year after an increase in water temperature. For reproduction both sexual partners leave their burrows and swarm at the water surface in the early morning, performing a nuptial dance. The spawning behaviour, the nuptial dance and the release of gametes, are controlled by sex pheromones which are present in the coelomic fluid of mature worms. A sex pheromone from Platynereis dumerilü, 5-methyl-3-heptanone, is found in Perinereis nuntia brevicirrus and causes an increase in swimming activity during reproduction and the release of a small amount of sperm from males. This signal induces the release of eggs by the females followed by the release of masses of sperm by the male due to a second female pheromone.

Between 8 May and 3 June 1987 horizontal distribution of Owenia fusiformis larvae (Annelida: Polychaeta) was studied in the eastern part of the Bay of Seine on two spatial scales to determine the role of larval dispersal by hydrodynamic factors on the population dynamics of a benthopelagic species. Larval dispersal occurred in two main directions, north-west and north-east, according to the residual tidal circulation. There was a substantial transport of larvae to a distance of 30–40 NM (48–65 km) from their emission point, resulting in a sizeable loss of larvae to the adult population. However, their densities were low in comparison with those observed in the eastern part of the bay, near the adult population. Larval densities remained highest near the adult population, principally under the influence of tidal processes. In contrast, there was a significant wind-induced larval movement at a time scale of a few days. The action of wind at a time scale of one month, the duration of larval life, appeared to be insignificant for dispersal in 1987 because of the frequent changes in wind direction. Climatological data collected between 1951 and 1980 showed that the wind effect observed in 1987 is probably typical of most years. The horizontal transport of Owenia fusiformis larvae, combined with the ontogenic vertical migration observed previously, causes a retention of these larvae in the eastern part of the Bay of Seine; this favours recruitment and may be one of the factors explaining the temporal stability of the adult population.

Expected lifetime investment in eggs and related parameters are described for a lagoonal population of Hydrobia ventrosa (Mollusca: Gastropoda) in East Anglia, UK, and these are compared with those of East Anglian lagoonal populations of H. neglecta and both lagoonal and intertidal-marine populations of H. ulvae. In contrast to an earlier study on Danish populations, which suggested that H. neglecta and H. ventrosa are at opposite ends of the hydrobiid spectrum of investment in reproduction, the order of increasing relative allocation of resources to egg production runs H. neglecta = H. ventrosa → lagoonal H. ulvae → intertidal-marine H. ulvae. That is, from the two small, short-lived, specialist lagoonal species producing few, large, directly-developing eggs, to the larger, potentially longer-lived H. ulvae that produces many small eggs which develop into veliger larvae. The lagoonal populations of all three Hydrobia species, however, are very similar to each other in terms of reproductive investment. When like cohorts are compared, in each, the annual egg weight is equal to the annual adult growth increment, and the weight of eggs produced per expected lifetime is half the adult growth increment at the time of death. These lagoonal populations are markedly dissimilar to intertidal-marine populations of H. ulvae, which produce an annual weight of eggs some 15 times the annual adult growth increment, and an expected lifetime egg weight some two-and-a-half times the adult growth increment at the time of death.

On an intertidal mud flat in the Ria Formosa (southern Portugal) Abra ovata (Mollusca: Bivalvia) showed effective meiobenthic and macrobenthic dispersal (i.e. of individuals smaller and larger than 1 mm). This was important to compensate for mortality caused by shore crabs during summer. It was observed in the laboratory that A. ovata deposited eggs in capsules on the sediment surface; after 11–15 d at 20°C benthic juveniles of 210–220 (im shell length hatched from these capsules. A pelagic larval stage was missing. Large numbers of specimens of about 1 mm shell length colonized protected buckets between February and June.

Rates of occurrence and degrees of imposex, and tissue concentrations of organotin compounds (tributyltin, TBT; dibutyltin, DBT; butyltin, MBT; triphenyltin, TPT; diphenyltin, DPT; and phenyltin, MPT) in the rock shell, Thais clavigera and T. bronni (Mollusca: Gastropoda) were investigated at 32 sites in Japan from May 1990 to October 1992. The rate of occurrence of imposex was 100% in both species, at almost all sites surveyed. Degrees of imposex indicated by relative penis length (RPL) index reflected the pollution levels not only of TBT, but also TPT. In heavily polluted areas, many individuals were found with oviducts which were blocked by vas deferens development, and capsule glands which were filled with aborted egg masses. These organisms were thought to be sterile.

This work presents the description of an intracoelomic parasite of the genus Dendrogaster (Crustacea: Ascothoracida), the largest ever reported, collected for the first time from the starfish Hippasteria phrygiana in the deep waters of the St Lawrence Estuary (eastern Canada). The parasite bears a close resemblance to only one previously described species, D. arbusculus from the west American coast, suggesting a bicoastal and possibly circumpolar distribution. Female growth is concurrent with embryo development and the parasite may have a negative impact on host starfish densities through gonad atrophy. This research also demystifies the old and persistent description of a supposed parasite in H. phrygiana 70 years ago, Laocoön paradoxus, and finally concludes that this parasite never existed and in fact represents the water vascular system found in all starfish.

Tolerance and behaviour to hypoxia and anoxia by the annelid Loimia medusa (Savigny) (Polychaeta: Terebellidae), a common species in estuarine habitats where summer hypoxic events often occur, were examined in the laboratory. The worm can tolerate anoxia or severe hypoxia (7% air saturation at 26°C) for 3 to 5 d. Under low dissolved oxygen (<14% air saturation) feeding stops, although tube irrigation continues and periodic protrusions from the tube are common. Most worms come out to the sediment surface, but the number of worms dead on the surface is higher in anoxia than in hypoxia. The prevalence of L. medusa in deep estuarine channels may be partially explained by its tolerance to prolonged periods of hypoxia (14 d at 14% air saturation). Our data, however, suggest that subtle changes in oxygen concentrations may be important in the control of populations of L. medusa in habitats affected by low oxygen disturbances.

Members of the Haptophyta from British waters have been listed in a number of check-lists between 1953 and 1976 (Parke, 1953; Parke & Dixon, 1964, 1968, 1976), but there has been no attempt to draw the records together on a world-wide basis. However, a recent review of the classification system of the coccolithophorids included a check-list of all species thought to be extant from marine, coastal and freshwater habitats (Jordan & Kleijne, 1994). At the same time, two ambitious projects, the Encyclopaedia of Algal Genera (ed. B.C. Parker, in preparation) and the preparation of a CD-ROM retrieval system for information on algal and protist groups by the Expert-Centre for Taxonomic Identification (ETI), have required further collation of the available records (see Note 1), and, as a result, we have now extended the scheme of Jordan & Kleijne (1994) to include a global list of all extant haptophytes.

Shell growth of the razor clam Ensis siliqua (Mollusca: Bivalvia) from southern Portugal has been analysed using both surface growth rings and internal shell microgrowth patterns. The growth rate estimated from an analysis of the growth rings is slower (von Bertalanffy growth, constant K=0·27) than that determined from the annual narrowing of the internal microgrowth patterns present in shell sections (K=0·65), although both methods predict a similar asymptotic length, L∞, of 144·8 and 139·6 mm, respectively.

The Barrinha razor clam population occurs in a heavily dredged area and an analysis of shell sections reveals the presence of a series of shell margin breaks consisting of deep clefts in the outer shell layer in which sand grains are embedded. It is suggested that these disturbances to shell growth are the result of repeated dredge damage. The frequency of the clefts increases with the size and age of the razor clams, and thus the shells provide a record of the intensity and frequency of unsuccessful capture or retrieval attempts. Cleft formation also occurred seasonally with the deposition of a small cleft during June, but these annual clefts were much less pronounced than those caused by dredge damage.

A procedure for accurately determining age and growth of the sea urchin Sphaerechinus granularis (Lamarck) (Echinodermata: Echinoidea) in the Bay of Brest (France) is described. Readings of growth lines were made from the longitudinal cross-section of interambulacral oral plates of sea urchins collected in February 1993. These results agree with age estimates calculated using the ELEFAN I programme based on diameter-frequency distributions of sea urchins collected from February 1992 to March 1993. A non-linear regression (monomolecular equation) best describes the relationship between test diameter and plate thickness. The diameter-at-age data can be increased by back-calculation, assuming a constant proportional deviation from the mean size of the test. Although von Bertalanffy growth curves fitted to actual observations were similar to those fitted to back-calculated diameter-at-age data, the latter produced a more adequate curve and increased the quality of the growth parameter estimators. The von Bertalanffy growth curve estimated by ELEFAN I shows a pattern similar to the back-calculated von Bertalanffy growth curve.

Complex mesoscale eddy interactions are characteristic of the North Atlantic, resulting in a mosaic of water masses with different physical, chemical and biological properties. Observations of protist assemblages during spring 1989 and 1990 in the vicinity of 47°N 18°W indicate that timing, composition, and further development of the spring bloom community are highly variable between years. During 1989 a microbial community, dominated by small photosynthetic nanoplankton and protist grazers, was observed after the main diatom bloom in the transition zone between two cyclonic eddies. This community was characterized by a high ratio of ‘protozoan’ to ‘phytoplankton’ carbon, and dominance of the microzooplankton by mixotrophic ciliates. A nanodiatom/prymnesiophyte bloom was observed to replace the typical ‘microdiatom’ bloom in a front between a cyclonic and anticyclonic eddy during 1990. After the demise of the diatoms, high standing stocks of nanophytoplankton persisted until early June. In this post-diatom-bloom period, the ‘protozoan’ biomass was lower and the ‘nanophytoplankton’ stocks higher than in 1989. Very high stocks of heterotrophic nanodinoflagellates were observed in 1990. The factors responsible for the development of these quite different microbial food-webs in two consecutive years and the consequences thereof for ecosystem function remain to be more fully explored.

Two razor clam populations from two shores in North Wales were identified on morphological grounds as Ensis siliqua (L.) and E. ensis (L.). Ensis siliqua occurs in fine sand on the exposed south-westerly facing shore of Newborough beach, whilst E. ensis inhabits the coarser sediment of Penmon beach, a sheltered north-easterly facing shore in the Menai Strait. At Penmon smaller E. ensis (<100 mm) inhabited sediments at mean low water of spring fides, whereas larger individuals (>100 mm) occurred almost subtidally at extreme low water springs. No small E. siliqua (<110 mm) were found on Newborough beach, where there has been a noticeable decline between 1990 and 1992 in the number of individuals larger than 175 mm. Growth of the two species was different. The von Bertalanffy growth constant, k, was similar in the two species, but E. siliqua had a larger asymptotic length than E. ensis.

The global distribution of the 12 described, deep-living megacalanid species is presented in a report on collections made in the Southern Ocean during the United States Antarctic Research Program. Included are four species and one subspecies described in 1967 from samples obtained early in the program. In the material lent to the author by the Smithsonian Oceanographic Sorting Center, only six of the described species were found. Bathycalanus bradyi, common in those samples and elsewhere, is made a synonym of B. richardi. The predominant forms are, in order, B. richardi, Megacalanus princeps, and B. princeps, with Bradycalanus sarsi, B. typicus and B. gigas also present. Knowledge of their distribution and ecology is discussed.

The serendipitous detection of a rare hermaphrodite individual of Mytilus galloprovincialis during the process of spawning in the laboratory enabled self- and cross-fertilization to be achieved. Self-fertilized larvae exhibited significantly higher percentages of morphological abnormality at 3 d, lower survival at 9 d and decreased size at 31 d of age compared with cross-fertilized larvae. These results are discussed in the light of equivocal evidence for inbreeding depression in larvae derived from self-fertilization, full-sib matings and gynogenesis in other bivalves.

The capacity for oxygen uptake of a respiratory organ can be estimated using morpho-metric techniques, the two essential measurements being respiratory surface-area and thickness of the tissue barrier across which oxygen diffuses. In cephalopods, the gills are the main site of respiratory exchange and this study was designed to estimate oxygen uptake capacity of the gills of four different genera of cephalopods. A preliminary study was required to determine the form and structure of the gills. Light microscopy showed the surface of the gills to be highly folded, particularly in Octopus. A level of microscopy was chosen at which the outline of the smallest folds of the epithelium and the blood vessels of the gills could be easily resolved. Stereological techniques were then employed to obtain values for the respiratory surface-area related to body weight (cm2 g-1), tissue barrier thickness (μm) and oxygen-diffusing capacity (ml O2 min1 Torr·1 kg1). Values for these three variables obtained for the different species were as follows: Octopus vulgaris 2·9 cm2 g-1, 10 μm, 0·05 ml O2 min-1 Torr-1 kg1; Alloteuthis subulata 10·6 cm2 g1,6 μm, 0·27 ml O2 min-1 Torr-1 kg-1; Nautilus sp. 4·9 cm2 g-1,15 μm, 0·05 ml O2 min-1 Torr1 kg-1; Sepia hatchlings 13·3 cm2 g-1, 4 μm, 0·52 ml O2 min-1 Torr-1 kg-1.