The taxonomy of marine worms belonging to family Nereidae is still in an uncertain state. There are many species, like Nereis diversicolor Müller, N. japonica Izuka and N. limnicola Johnson, which are morphologically similar but have different reproductive habits. Clark (1977) reviewed many examples of reproductive isolation without morphological differentiation in polychaetes including members of the family Nereidae. He also stressed the need for detailed study in such polychaetes where taxonomic confusion exists.

Electrophoretic techniques have contributed a great deal in solving taxonomic problems (see Avise, 1975 and Burton, 1983). All electrophoretic methods have proved useful to varying degrees in characterizing specific organisms. In particular, acrylamide gel electrophoresis has seen extensive use because it has excellent resolving power (Brewer, 1970). Studies of the electrophoretic variation of nereid isozymes have not been reported, except by Jones (1970), who examined various polychaetous annelids for the presence of certain dehydrogenases. This present report contains preliminary observations concerning the applicability of isozyme electrophoresis to the study of nereid worms.

A new species of physonect siphonophore, Halistemma transliratum sp. nov., is described from two specimens collected at mesopelagic depths in Bahamian waters by the submersibles ‘Johnson-Sea-Link’ I and II, and comparisons are made with the established species of that genus.

The coastal prosobranch Hydrobia ulvae is known to occur in a wide range of marine and brackish habitats and to display great variation in its breeding and life-history characteristics. Several hypotheses have been advanced to account for the latter, including that the variation is environmentally induced and that the species can be divided into ecotypes. Comparison of two adjacent populations in Norfolk, U.K., one from the marine intertidal zone and the other from a non-tidal, landlocked, brackish coastal lagoon, however, disclosed that although shell form differed markedly (including a mean height ratio of 1:1.2), there was no difference in such otherwise variable features as numbers of eggs per capsule, size at hatching and larval type. In both, each capsule contained an average of 21-22 eggs, which hatched at a shell length of 152-154 μn to liberate relatyyively long-lived, free-swimming veligers. The two populations were also interfertile. In no respect had the isolated lagoonal population diverged away from the parent marine one towards the contrasting reproductive strategies characterizing the specifically lagoonal species of Hydrobia that occur nearby. The ‘displacement’ of shell size observed in the lagoon in the absence of sympatric hydrobiids is considered to cast further doubt on competitive character displacement in this genus.

During July 1984, large numbers of the sandy beach bivalve Donax vittatus (da Costa) were found either stranded in the intertidal, or washing to and fro in the surf on beaches at Dornoch, on the east coast of Scotland. The affected bivalves all carried large growths of several species of algae. The normal burrowing and recovery responses of the bivalves were unable to overcome the increased drag resulting from these epizoic algal colonies so that wave action caused dislodgement from the sand and eventually, stranding and death from dehydration. The resulting mortality affected mainly older individuals in the population; younger individuals had very small or no attached algae and were not dislodged.

The algal growths were complex and showed three stages in their development: primary settlements formed generally short tufts or mats attached to the posterior tip of die shell; secondary ‘dominant’ species were also attached to die shell but formed larger growths; tertiary species were attached as epiphytes to the primary and secondary growths. At least eight species of algae were involved. Juvenile mussels (Mytilus edulis L.) were also present in many cases attached to the weed, adding further to die drag.

During 1985, at Dornoch, secondary and tertiary algal species developed progressively from overwintering primary settlements, but the size of die algal colonies which developed was generally smaller dian in 1984 and diere was apparently little dislodgement and mortality.

Donax vittatus populations on other beaches in die Moray Firdi, and on most other Scottish beaches examined, had fewer individuals with attached algae, and diose affected carried only relatively small colonies which did not prevent normal burrowing. Complex algal colonies, showing even greater species diversity than those of Dornoch were, however, found on D. vittatus on beaches in South Harris, Outer Hebrides, during September 1984.

A portable light-trap was designed and constructed to assist in Museum taxonomic studies on Crustacea. The trap was constructed throughout of transparent Perspex. The light-source was a chemoluminescent ampoule marketed under the name Cyalume® Lightstick. The present trap offers several advantages. It is inexpensive to construct, sturdy, readily portable, easy to operate, and safe to use. Field trials in Lough Hyne (Ine), Co. Cork, south west Ireland, have proved the apparatus to be most successful in attracting a wide variety of crustaceans.

The larval development of the parasitic barnacle, Sacculina carcini, has been closely followed. Size and volume measurements have been made for the four naupliar stages and cyprids of both male and female broods. Volume increases between naupliar stages are minimal (x 1.03–1.09) and in line with other barnacle species with lecithotrophic larvae. However, the large volume reduction between stage IV and cyprid for S. carcini, which is more acute for the female larvae, is a unique characteristic. The reduced setation formulae of the larval appendages of S. carcini and another rhizocephalan are compared to those of larvae, both lecithotrophic and planktotrophic, of a range of barnacles. Sex ratios and carapace length data for 184 S. carcini cypris populations are presented which reinforce the seasonal changes in sex ratios.

Spring and autumn phytoplankton blooms are characteristic of those temperate marine waters where thermal stratification occurs during the summer months (e.g. Raymont, 1976). However, in well-mixed coastal waters the phytoplankton production cycle may consist of a single peak of growth during the summer (Boalch, Harbour & Butler, 1978; Wafar, Le Carre & Birrien, 1983). In a recent paper, Brander & Dickson (1984) considered evidence from the Irish Sea continuous plankton recorder which reflects the phytoplankton growth cycle largely in the well-mixed areas of the sea. These data suggested a single late peak of production, in contrast to the bimodal blooms which are known to develop in the stratified areas of the Irish Sea (Burrows & Sharpies, 1973; Slinn, 1974). The purpose of the present work was to establish the production cycle for Belfast Lough, which lies adjacent to the North Channel, an area of strong tidal mixing which forms the northerly exit for water from the Irish Sea (Lee & Ramster, 1981; Howarth, 1984). There have been no previous measurements of primary production in Belfast Lough. There was considerable interest in this topic in the early years of this century when the Royal Commission on Sewage Treatment (1908) heard evidence that nutrient inputs from sewers into the lough resulted in excessive growth of the green alga Ulva, which caused a nuisance as it decayed around the shores. Although there have been no recent reports of this phenomenon, several sewage works continue to discharge partially treated effluent to the lough. An aim of this work was therefore to assess the role of anthropogenic nutrient inputs upon phytoplankton growth.

In direct-transfer temperature tolerance experiments, Lasaea rubra was found to have a median lethal low temperature of – 3.5°C and a median lethal high temperature of + 39°C. If introduced to temperatures slowly, survival at extreme temperatures was improved, particularly at freezing temperatures; > 92°0 of animals survived at – 10 °C and + 40 °C if introduction from a holding temperature of + 18 °C took place over at least 1 h.

Lasaea rubra are active at salinities between 15 and 60‰, indicating considerable tolerance of changes in body fluid osmolarity. In week-long exposure experiments more than 50 % of animals survived all salinities from 0 to 150‰; tight shell valve closure was maintained at extreme salinities.

When exposed to declining salinity, Lasaea rubra progressively isolates its tissues from the environment as salinities fall below 18–20‰, and maintains shell valve closure below 8‰. These responses are symmetrically reversed in response to rising salinity.

Salinity discrimination in Lasaea rubra is based upon sensing of external osmolarity, not external ionic concentrations.

Studies of the dispersal behaviour of marine and estuarine benthic invertebrates have concentrated on the majority of species where the individuals disperse as a planktonic larva. The view that seems to be prevalent, summarised by Crisp (1974, 1976), is that larvae are an adaptation to allow species to colonise transient habitats and for species with adults of limited mobility to colonise distant habitats. The spreading of the species over wide areas has the advantages of reducing competition and facilitating greater genetic diversity, leaving the species more adaptable to subsequent environmental changes. These advantages are greater with longer distances travelled, and are an explanation for larvae spending up to several weeks drifting in the plankton, despite the acknowledged high mortality rates associated with the pelagic existence.

The haemolymph of balanomorph barnacles contained very few haemocytes. The hyaline cell was the main haemocyte type found and this cell is capable of phagocytosing foreign bodies. A few semi-granular cells were also found, but granulocytes never occurred. Haemocytes were not found within haemolymph clots.

The spatial and vertical distributions of alkaline phosphatase activity (APA) in the western English Channel in July 1987 were determined using 2 μM 3-O-methylfluorescein phosphate as substrate. The response of APA to increases in substrate concentration followed Michaelis-Menten kinetics but differences in Ks values between stations suggested a species dependency of the half-saturation constant. Phosphate inhibition of APA was, however, similar at 3 locations. The chlorophyll specific APA (SAPA) in surface waters ranged from 0.004 to 0.57 nMPO43- μg chla-1 min-1 and was inversely exponentially related to the chlorophyll a concentration reflecting the fact that phytoplankton populations are largest where inorganic nutrient availability is greatest and synthesis of the enzyme is not derepressed. SAPA values were found to be low in the bloom of Gyrodinium aureolum in the Ushant front and in the sub-surface chlorophyll maximum in the stratified region. Vertical distributions of SAPA are discussed in terms of the hydrographic characteristics of the water column and an attempt has been made to distinguish between APA associated with phytoplankton and with bacteria.

The littoral prawn Palaetnon elegans Rathke regulates the body concentration of zinc at higher external zinc concentrations in the presence of EDTA. The dissolved zinc concentration in artificial sea water corresponding to the threshold of regulation breakdown changed from ca. 100 μg Zn 1-1 (ca. 1.53 μmol Zn 1-1) without EDTA, to ca. 316 μg Zn 1-1 (ca. 4.8 μmo1 Zn 1-1) in the presence of 8.6μmol EDTA 1-1 at 10 °C. The regulated body Zn concentration remained unchanged at 77–79 μg Zn g-1 dry wt with or without EDTA. Increased levels of EDTA in the medium decreased the rate of uptake of labelled zinc by P. elegans. The presence of 3 μmol EDTA 1-1 decreased the mean Zn uptake rate of prawns in 100 fig Zn 1-1 (ca. 1.53 μmol Zn 1-1) from 2.9 to 0.25% of total body Zn g-1 day"1 at 10 °C. The increased ability of P. elegans to regulate zinc in the presence of EDTA may be explained by the reduced bioavailability of the zinc-EDTA complex for uptake. There is marked individual variation in the rate of uptake of labelled zinc in prawns, even in the presence of the same concentration of zinc or zinc-EDTA.

Ostrea puelchana is a larviparous oyster from the S.W. Atlantic coasts. This species is not being commercially exploited at present. Because of its high food qualities, however, it may constitute a resource of economic interest in the future.

Until now larval development and characteristics of the incubation period have been poorly known. This study describes the characteristics of the mode of brooding under laboratory rearing conditions and, using scanning electron microscopy, the morphogenesis of the hinge until larval release from the parents.

The larva develops two anterior and two posterior denticles during brooding. A comparison with larvae of other species of the genus Ostrea reveals that the main differences among them do not lie so much in the pattern of hinge dentition as in the rate of evolution of the hinge components, which is faster in Ostrea puelchana. This species has fully developed denticles at the time of release, which places the larva of this oyster as particularly evolved within the genus Ostrea.

The paragnaths are soft outgrowths of the crustacean exoskeleton lying close to the mandibles on the aboral side. They are sometimes termed the metastoma, for instance in Pike (1947) in Galathea squamifera Leach, or the hypopharynx by Wägele (1987) in the isopod Antarcturus Schultz. It should be noted however that Manton (1964) stated that the crustacean paragnath was not the same structure as the insect hypopharynx.

Two hundred Chlamys varia (L.) from Roskeeda Bay (W. Ireland) and Lough Hyne (S. Ireland) were collected and labelled in December 1979. One hundred individuals from the L. Hyne sample were then transferred to Roskeeda; similarly, 100 Roskeeda scallops were transferred to L. Hyne. At each site 100 indigenous scallops were held as controls.

After a period of approximately 1 year, survivors at each site were scored at 13 enzyme/protein loci using starch gel electrophoresis. Significant genetic differences were observed at the Pgm and Lap loci between native L. Hyne and native Roskeeda scallops. These differences persisted between surviving Roskeeda scallops (92% of the original sample) transferred to L. Hyne. However, after one year L. Hyne scallops transferred to Roskeeda (61% of original sample) did not differ significantly from indigenous Roskeeda scallops. Possible reasons for the observed selective mortality at this site are discussed.

The starfish Anseropoda placenta (Pennant) is abundant in the gravelly sands of the Bay of Brest (Finistere, France). The size, distribution and density of this animal were evaluated along a transect perpendicular to the River Aulne in the southern part of the Bay. The spawning phases, the recruitment and growth processes were defined. When the entire population was considered, three plurimodal year classes were visible from the length frequency histograms. Year-class segregations were observed. Their density varied in space and time in a manner which suggests a pattern of migration from the southern part of the transect towards the northern part. Juveniles were recruited mainly during the autumn on the gravelly bottom of the southern shallow part. By late winter, they had migrated to the deeper parts of the channel. Feeding preferences do not seem to be the main factor controlling these migrations which are discussed in relation to environmental factors and the intra- and inter-specific competition.

The hermit crab Clibanarius erythropus first reported from Britain in 1961 is no longer present. There appears to have been no further recruitment since the late 1950s when there was a favourable combination of climate and hydrographical factors that led to successful invasion of Devon and Cornwall.

The population appears to have succumbed to the combined effect of age and declining temperatures. Additional contributory factors in the decline could be the mortalities resulting from the ‘Torrey Canyon’ disaster; the reduction in numbers of the dog-whelk (whose empty shells are the favoured home of the crab in Britain) as a result of organotin antifouling paints; and increased public pressure on the habitat.

Ten species of marine strombidiid ciliates were identified after protargol staining plankton samples. The taxonomic redescriptions include a diagnosis for Tontonia gracillima Faure-Fremiet, 1924, Strombidium wulffi (Wulff, 1919) Kahl, 1932, Strombidium acutum Leegaard, 1915, Strombidium constrictum (Meunier, 1910) Wulff, 1919, Strombidium compressum (Leegaard, 1915) Kahl, 1932, and Strombidium sulcatum Claparede & Lachmann, 1858. Four new species, Strombidium dalum n.sp., Strombidium epidemum n.sp., Strombidium rhynchum n.sp., and Strombidium tressum n.sp., are defined based primarily on the characteristics of the anterior oral polykinetids, numbers of oral polykinetids, and presence of anterior protuberance.

The paper presents preliminary data on the response of Pectinaria koreni to light and on the effect of light and temperature on its rate of sediment reworking. Pectinaria at the ‘settling in’ stage reacted to light by burying themselves completely under the sediment. There was indication that vertical movement of Pectinaria in the sediment followed a diurnal rhythm probably associated with feeding activity. Pectinaria was most active at higher temperatures and in the dark. At 7 °C the rate of sediment reworking was significantly less than that at 10 and 15 °C and was not affected by light. At 10 and 15 °C the amount of sediment reworked in the dark was significantly greater than that reworked in the light.

The population dynamics of rock barnacles, Semibalanus balanoides (L.), residing in low and high intertidal zones are affected by conspicuously different factors. The barnacle population in the high intertidal zone tends to show longterm stability due to a low incidence of both predation and interspecific competition. Wave exposure, desiccation and intraspecific competition are more important factors affecting abundance and size distribution in this zone (Menge, 1976). In the low intertidal zone, barnacle predation by the dogwhelk, Nucella lapillus (L.) is intense (Menge, 1976) and both the adults and larvae are smaller than in the high intertidal zone (Barnes, 1953). The growth form of S. balanoides is density dependent with taller, more columnar individuals predominating at high densities and short conical barnacles at low densities. Lower fecundity of conical individuals may be due to lower internal shell volume compared with columnar forms (Wethey, 1984). Fecundity increases both with increasing age and base length (Arnold, 1977) and is positively density dependent (Wethey, 1984).