Incubated embryos are here recorded from the Sabellinae Amphiglena mediterranea, Potamilla neglecta and Perkinsiana antarctica, and the Fabriciinae Fabricia sabella, Fabriciola chilensis, Oriopsis alata and Oriopsis ehlersi, but incubation has not been observed in most species of Sabellinae, nor in any Myxicolinae. Natural fission (as opposed to regeneration following damage or autotomy) is also rare in Sabellidae, but a Scilly Isles tube worm identified as Sabella variabilis Langerhans, multiplies by fission from the posterior end, like the Filograninae amongst serpulids.

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.

Guanine and hypoxanthine were excellent sole nitrogen sources for several microalgal species grown in axenic culture. Of the algae studied only Chlorella stigmatophora grew well on pyrimidines. Freshly harvested nitrate or ammonium-grown organisms generally lacked ability to take up guanine or hypoxanthine but this ability developed during several hours of photosynthesis in nitrogen-free medium. Nitrate-grown (but not ammonium-grown)Tetraselmis subcordiformis and Chlorella fusca could take up guanine, the initial rate of uptake increasing when the cells were also nitrogen-deprived. Of the algae studied only Chlorella vulgarisand Attheya decora required prior incubation with guanine before being able to take it up. Porphyridium purpureum did not take up guanine. Factors affecting the development of ability to take up guanine and the characteristics of guanine transport were studied. The transport systems showed Michaelis-Menten type kinetics with K s values ranging from 05 to 3–7/IM guanine. In marine species, guanine uptake was dependent on the presence of Nations in the medium but Chlorella stigmatophora showed less dependence on Na+ than other species.

A multinucleate, monopodial, lobose amoeba from a Cornish rock pool was identified as Amoeba flavescens Gruber, 1889, originally described from the Mediterranean. It is the type species of a genus Gruberella. Although its locomotive form and activity resemble those of the uninucleate Vahlkampfiidae and its Golgi system, like that of the vahlkampfiids, is not organized into dictyosomes, its mitotic pattern differs from that of the vahlkampfiids. The presence of mitochondria and other characters distinguish it from Pelomyxa. The only other similar marine amoeba is Hyperamoeba fallax Seravin & Goodkov, 1982, from the Far East. The process of ‘paracopulation’ reported for H. fallax was not observed in the Cornish isolates. Pending more evidence of familial relationships, Gruberella remains incertae sedis within the suborder Gymnamoebia Haeckel, 1862.

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.

Light and electron microscopical reinvestigation of Polyoeca dichotoma Kent revealed that Acanthoecopsis spiculifera Norris, the type species of the genus, is a synonym for Polyoeca dichotoma. Since this step invalidates the use of the name Acanthoecopsis, a new genus Acanthocorbis was established for the three species formerly included in Acanthoecopsis.

The three dimensional arrangement of costal strips forming the loricae of Polyoeca dichotoma and Acanthoeca spectabilis Ellis were examined by scanning electron microscopy. The arrangement of costal strips were similar in both species. The longitudinal costal strips and those forming the spines were arranged outside the supplementary costae and those of the transverse bonds.

By means of capillary gas chromatography (GC) and capillary gas chromatography'mass spectrometry (GC/MS), the aliphatic hydrocarbons, fatty acids, fatty alcohols and 3ß-sterols were identified in saponified lipid extracts of the green alga, Dunaliella primolecta, the copepod, Calanus helgolandicus, and faecal pellets released by the animal when fed in the laboratory on the algal diet. Comparison of the lipid data for faecal pellets with those for the plant showed that marked changes to dietary lipids occur during passage through the gut of the copepod: (1) 17:2, 17:1, and 17:0 hydrocarbons are completely eliminated; (2) polyunsaturated fatty acids (e.g. 16:4 and 18:3) are significantly reduced relative to total fatty acids; (3) evidence of the conversion of phytol to dihydrophytol is observed; (4) C28 and C29 sterols with Δ and Δ nuclear unsaturation are selectively removed from the diet relative to Δ components. The Δ sterols are released unchanged as faecal lipids. Cholest-5-enol, absent from the original diet, is also released in the faecal pellets. These observations illuminate the fate of specific dietary lipids in Calanus and the contribution copepod faecal pellets can make to the overall lipid composition of bottom sediment in many marine environments.

Cell-free extracts of Phaeodactylum tricornutum contained a methyltransferase which catalysed the methylation of guanine or hypoxanthine by 5–adenosyl-methionine. The product ofthe reaction appeared to be a methylhypoxanthine irrespective of whether guanine or hypoxanthine was substrate. This enzyme activity (per unit protein) trebled during 6 h of nitrogen deprivation. It is suggested that this enzyme is responsible for the methylation of guanine and hypoxanthine when these are taken up by nitrogen-deprived intact cells. Uricase, allantoinase and allantoicase were present in cells incubated with guanine, hypoxanthine, uric acid or allantoin;these activities did not appear during nitrogen-deprivation. Crude cell-free extracts containedaninhibitor of uricase and activity could be demonstrated only after ammonium sulphate precipitation of protein. When these three enzymes were induced by incubation with guanine, their order of appearance was identical to the order in which they operate in purine catabolism, namely (i) uricase (ii) allantoinase (iii) allantoicase. Guanine deaminase, xanthine oxidase and xanthine dehydrogenase activities were not detected irrespective of whether cells were nitrogen-deprivedor incubated with purine.

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 vertical distribution of Decapoda (Crustacea) at deep-water stations in the Rockall Trough and the Porcupine Seabight is discussed and compared to the near-bottom distribution of Decapoda on the continental slope of the Seabight. The vertical distribution of some species is unaffected by the shallowing of the sea floor in the slope area. Other species are found in much higher concentrations near-bottom over the slope than at similar depths at the adjacent deep-water stations and at least one species extends its lower vertical range. It is suggested that the increased food availability near-bottom may be the principal factor influencing aggregation.

Four squid species from around Scotland and in the northern North Sea were examined for larval ascaridoid nematodes maturing in warm-blooded vertebrates. A larval contracaecinean (possibly Contracaecum osculatum) in Loligo forbesi, and Anisakis simplex L in L. forbesi, Alloteuthis media and Todaropsis eblanae are recorded, apparently for the first time. Neither of the inshore neritic myopsids L. forbesi and A. media appears to be an important host of Anisakis simplex L3. The oceanic oegopsid Todarodes sagittatus showed the highest A. simplex L3 burdens; whilst the general pattern of infection in this species was similar to that of teleost fish in the northern North Sea, the density of infection was lower. The possible significance of L3 in squid for the population dynamics of A. simplex is discussed. Larval ascaridoid nematodes in squid may have no public health significance in the U.K.

A further series of North Sea demersal fish surveys was carried out during the summers of 1981 and 1982. The remote headline camera was used and the benthos trawled was recorded. At stations of special biological interest the camera was adjusted to take from one to three frames per minute throughout the 1 h duration of the trawl. A successful series of underwater photographs were obtained at 95 stations throughout the North Sea.

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).

Available data on the size distribution of particles captured by Mytilus indicates that a somewhat leaky, but non-sticky, filter with a minimum mesh size of a little over 1.0 μm is present. The side branches of the latero-frontal cirri have such a mesh and are positioned so as to filter water passing between the gill filaments. Information on the pressure distribution within the water circulation, and calculations of the pressure required to pass watet ihrough the latero-frontal filter at observed speeds, suggest that a little more than half the pressure generated by the lateral ciliary pump is required to overcome resistance in the latero-frontal filter and the remainder is required to circulate water in through the inhalant opening and out in an exhalant jet. The lateral cilia appear theoretically capable of generating sufficient power to produce the required pressures. Calculations indicate that although hydro-mechanical shear forces are unlikely to provide a significant contribution to particle capture, they may provide a means of keeping particles within the frontal current without a need for mucus, after filtration and transfer of particles to the frontal surface by the latero-frontal cirri.

Males of Eledone cirrhosa grow to a size little over 600 g and normally have well-developed, and presumably active, reproductive organs from about 200 g upwards. Total weight of the genital bag is well correlated with total body weight (r= 0·906). Growth of the testis precedes that of the spermatophoric sac, and the size of neither of these reproductive components is predictable from body weight. The sizes of these organs and the estimated number and length of stored spermatophores are given for 100 g intervals of total body weight. No evidence was obtained for a seasonal trend in male maturity.

Three species of salps (Pegea confoederata, Salpa maxima, and S.fusiformis) from the Western Mediterranean have been analysed for their general biochemical composition and their detailed sterol chemistry. In particular the distribution of saturated sterols in various tissues of the salps has been studied. The results suggests that dietary phytoplankton exerts a major influence on the tissue sterol composition of the salps, although the presence of occelesterol and saturated sterols in the salps cannot be explained on the basis of diet. Possible explanations for the occurrence and distribution of the saturated sterols are considered.

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.

The Plymouth Marine Fauna (Marine Biological Association, 1957) list of monogenean parasites of fishes has been increased from 39 to 58 species and in addition 2 species have been recorded from a cephalopod host. The increase in listed species represents an increased ‘parasitological effort’ rather than an influx of new species into Plymouth waters.

The brittle-star Ophiothrix fragilis forms dense aggregations on the sea bed off Plymouth, as well as in other parts of the English Channel. From about 1970 there was a marked decline in populations off Plymouth, and study of previous records suggests that there have from time to time been considerable fluctuations in abundance of this species — since beds were first reported by E. J. Allen in the 1890s. The decline did not extend to populations in the southern and eastern parts of the Channel. The distribution of Ophiocomina nigra, which sometimes occurs in mixed populations with Ophiothrix, is also described. This species is more or less limited to the western Channel, and populations, which are nowhere very dense, showed no decline comparable to that of Ophiothrix.

Predation by the starfish Luidia ciliaris and L. sarsi is thought to be a likely cause of the disappearance of Ophiothrix. Luidia spp. are active predators on ophiuroids and other echinoderms, and numbers of L. ciliaris were observed in the vicinity of the Ophiothrix beds at the time of the decline. Both species of Luidia have a ’western’ distribution in the Channel, and showed an increase in density off Plymouth after the late 1960s, which is probably related to a changeover from a Sagitta setosa to a 5. elegans plankton community from 1968 on. The distribution of these Luidia is confined to stratified waters in the western Channel, surviving stocks of Ophiothrix being limited to mixed waters in the southern and eastern Channel where Luidia does not occur.

Female Eledone cirrhosa held in aquarium conditions for periods of time of five daysand over show relatively enlarged ovary sizes. Values for ovary index considerably exceed thoseof freshly caught animals and the incidence of the final stage of maturity, in which eggs pack the oviducts, is greater. A comparison of maturity indices for fresh and aquarium males was inconclusive. The range of factors associated with aquarium conditions is briefly reviewed and it is concluded that studies of cephalopod reproductive maturation must distinguish fresh and aquarium animals.

Introduction

External factors effective in inducing sexual maturation in cephalopods have been suggested several times. The influence of the absence of light has been implicated since the experiments of Wells & Wells (1959) showed that blinded Octopus vulgar is matured precociously. An effect of short day length in stimulating the optic glands of Sepia has been found by Defretin & Richard (1967) and Richard (1967) but this is not clearly the case for Octopus (Buckley, 1977). Octopuses kept in aquarium conditions for lengthy periods are said to have larger relative gonad sizes than those fresh from the sea (Wells & Wells, 1975). One of the factors associated with aquarium conditions is often a degree of starvation, and this circumstance alone is held to be a factor in inducing precocious sexual maturation in Eledone (Mangold & Boucher-Rodoni, 1973).

In the course of recent studies on the growth and reproduction of Eledone cirrhosa from the North Sea (Boyle & Knobloch, 1982,1983,1984) animals which had remained in aquarium conditions for 5 days or over were separated from the analysis.