Prokaryote organisms, with characteristics of Gram-negative bacteria, occur intracellularly in Pogonophora, as described here for seven small species. The tissue containing the bacteria lies between the two longitudinal blood vessels in the posterior part of the trunk and has a special blood supply. This tissue is probably homologous with the so-called trophosome tissue of the much larger vestimentiferan pogonophores, which also contains bacteria, and the term can be applied to all pogonophores. The presence of such bacteria-containing trophosome tissue may be a characteristic of the phylum. In both large and small species examined the bacteria appear to be chemoautotrophs and probably assist the nutrition and/or metabolism of their hosts. It is not yet certain if the bacterium-containing cells do originate from mesoderm or endoderm, but, if the latter, then the trophosome represents the remains of the missing gut. The trophosome tissue situated internally, and transfer of bacteria must take place early in the life history, in the egg or embryo.

INTRODUCTION

Marine bivalve molluscs have in recent years attracted considerable attention for a variety of reasons, not least of which is their importance as a source of food for man. Much of this research has concentrated on studies of reproduction; Mytilus viridis (India: Nagabhushanam & Mane, 1975), M. edulis aoteanus and Aulacomya maoriana (New Zealand: Kennedy, 1977);Choromytilus meridionalis and Aulacomya ater (South Africa: Berry, 1978); Mytilus (= Perna) perna (Brazil: Lunetta, 1969); M. edulis planulatus (Australia: Wilson & Hodgkin, 1967); Mytilus californianus and M. edulis (U.S.A.: Hines, 1979); Mytilus galloprovincialis (France: Lubet, 1959) and M. edulis (U.K.: Chipperfield, 1953; Seed, 1975; Bayne et al. 1978). A review of the literature revealed that in the majority of studies cytology was used as a descriptive tool for the ‘staging’ (Chipperfield, 1953; Lubet, 1957; Seed, 1975, 1976) of the developing gametes and certain anomalies were apparent with regard to the nomenclature of the connective tissue matrix of the mantle lobes.

Until recently, the most detailed and widely quoted account of the life cycle and reproductive biology of Nereis diversicolor O. F. Müller was that of Dales (1950; 1951) for a population in the Thames Estuary followed for a single season. The study combined a periodic analysis of the population structure with assessment of reproductive maturity, by gamete analysis of individual worms, and a record of larval recruitment. The conclusions reached were that worms grew to maturity in one year, spawning in February, but that some survived up to a maximum life span of 18 months.

Chemostats were used to construct nutrient (vitamin B12) and energy budgets for the flagellate Monochrysis (Pavlova lutheri (Droop) Green) under varying conditions of nutrient and light limitation and luxury, the aim being to describe light limitation and luxury in terms analogous to those of the Cell Quota nutrient model. Measurements were made of steady-state dilution rate, biomass, cell quota, cell chlorophyll a, cell energy content, dark respiration and photosynthetic efficiency, under low irradiance (<13 W per m2).

Cell energy content was 0·54 joules per million cells and was not influenced by growth rate or nutrient/light status. Cell chlorophyll a was 25% less in the nutrient-limited cultures and did not show a clear trend with growth rate except in cultures receiving less than 4·3 W per m2. The effective specific extinction coefficient was 0·12 cm2 per μg chlorophyll. The photosynthesis/irradiance relation was linear. The mean slope (= efficiency) in samples from the light-limited chemostats was 0·225 and was independent of dilution rate. Samples from nutrient-limited chemostats showed a much lower slope, which decreased with decreasing dilution rate. These findings were confirmed by the chemostat kinetic data. Dark respiration varied with dilution rate in a hyperbolic manner and was greater in the nutrient- than the light-limited chemostat.

Light level had no effect on the subsistence quota when the nutrient was limiting, whereas under light-limiting conditions the subsistence quotas were enlarged in inverse proportion to the incident irradiance, thus showing a threshold rather than multiplicative interaction between light and the nutrient.

Energy absorption was very little reduced on nutrient limitation, the great reduction in overall efficiency being associated mainly with the reduction in photosynthetic efficiency.

The reciprocal of photosynthetic efficiency was shown to be analogous to a standardized nutrient cell quota, and an analogous coefficient of luxury could be defined as the ratio of the light-limited to nutrient-limited photosynthetic efficiency at the same growth rate. Thus, light limitation and luxury could be described in terms compatible with the nutrient model without having to introduce new concepts, and a practical criterion between light- and nutrient-limitation could be provided.

INTRODUCTION

The common mussel Mytilus edulis L. is one of the most successful shore molluscs. It is widely distributed in the northern hemisphere and is abundant not only in the most sheltered bays and loughs but also in conditions of extreme exposure (Lewis, 1964; Seed, 1976). Attachment to the substratum is by means of the proteinaceous byssus complex, the strength of which has been shown to vary seasonally (Price, 1980b). This variation could be a response to seasonal fluctuations in wave action, as suggested by Pieters et al. (1978), or may result from the seasonality of other environmental variables. Some of these, e.g. salinity and sea temperature, have been shown to influence byssus production (Glaus, 1968; Van Winkle, 1970; Allen et al. 1976), Phytoplankton density, spawning and the reduced ‘scope for growth’ during winter months (Bayne & Widdows, 1978) may also play a role in determining byssus strength.

In the present study, the relationships between byssal attachment strength and environmental and other variables are examined in a population of mussels on the South Wales coast.

A fixed bottom net was used to study the relationship between the horizontal and vertical density distribution of polychaete and cirripede larvae over an inshore rock platform.

Strong horizontal density distributions were obtained close to the bottom in many species from both groups, while the vertical samples showed larvae to be distributed towards the bottom both during the day and at night. It is suggested that the concentration of larvae within the slow-moving bottom water was responsible for the observed limited lateral larval dispersal.

The results are discussed in relation to their bearing upon a number of problems within the field of meroplanktonic ecology.

The planktonic foraminifer Globigerinoides sacculifer (Brady) was cultured under two different light intensities and in continuous darkness. High light intensity (HLI = 400–500 μeinsteins/m2/s) resulted in a longer lifespan, a greater number of chambers formed, and a larger final shell size compared with individuals cultured under low light intensity (LLI = 20–50 μeinsteins/m2/s) or in continuous darkness. Shell growth rates were unaffected by increasing light intensity, but gametogenesis was delayed. Continuous darkness induced a rapid onset of gametogenesis in organisms with shell lengths larger than 250 μm. Feeding frequency had a greater effect on growth and reproduction than light intensity under conditions of LLI and HLI, but continuous darkness had an overriding effect on growth and reproduction owing to the rapid onset of gametogenesis which terminated the life of the mother cell. Our previous data indicated that the longevity of G. sacculifer was dependent on feeding frequency, and that G. sacculifer cultured under LLI had a lifespan of approximately 2–4 weeks. Present results suggest that the lifespan can vary from a minimum of 8 days for organisms fed daily in continuous darkness to a maximum of 54 days for organisms fed once every 7 days and maintained in HLI. It is concluded that individual G. sacculifer attain a shell size greater than 600 μm only if they maintain their position in the euphotic zone. Prolonged existence below the euphotic zone would result in premature death or gametogenesis following stunted shell growth.

Little is known about the life history of the species of Gaidropsaurus Rafinesque, 1810. Two species of this genus, G. mediterraneus (Linnaeus, 1758) and G. biscayensis (Collett, 1890) = Antonogadus megalokynodon Kolombotovic, 1894 occur in the Sea of Marmara. The egg, larvae and pelagic juveniles of G. biscayensis have never been described. Egg, prelarval and early postlarval stages attributed to G. mediterraneus have been described and illustrated by many workers, but there has been confusion in their identifications.

Three species of Gaidropsaurus, G. mediterraneus, G. biscayensis and G. vulgaris (Cloquet, 1824) are recorded from the Mediterranean. Raffaele (1888) made artificial fertilizations of eggs of Naples specimens that he identified as Motella tricirrata Nilsson, 1832 = G. vulgaris. Holt (1899) found some eggs which are similar to those described and figured by Raffaele in the plankton off Marseille, but he considered it impossible to distinguish whether the larvae which hatched out from those eggs were Motella tricirrata i.e. G. vulgaris or Motella mediterranea Lütken, 1882 i.e. G. mediterraneus. Ehrenbaum (1905–9) who re-examined the various records of eggs and larval stages of Gaidropsaurus believes that those figured by RafFaele (1888) and Holt (1899) as well as the larvae referred to Phycis Artedi, 1792 and a pleuronectid by Emery (1886) and Marion (1894) respectively probably belong to Onos (Gaidropsaurus) mediterraneus. Aboussouan (1964) who worked on ichthyoplankton of the Gulf of Marseille also attributed some eggs and larvae to G. mediterraneus and figured one of those postlarvae which is 2·65 mm in standard length.

The eggs and prelarval stage of G. mediterraneus have more precisely been described and illustrated by Soviet investigators (Vodyanitskii & Kazanova, 1954; Duka, 1958; Dekhnik, 1973)> from the Black Sea.

INTRODUCTION

Estimations of the growth of bivalves have traditionally been determined from measurements of animals collected on a regular basis from natural populations. Generally size frequency distributions have been analysed or growth rates estimated from measurements of the distances separating the annual rings (Hughes, 1970; Seed & Brown, 1978; Taylor & Venn, 1978). While both methods provide valuable information on shell growth, a more direct approach is to investigate experimentally the growth of individual animals held in cages and to follow the seasonal changes in the dimensions of their shells.

The queen scallop Chlamys opercularis (L.) is found in large numbers in areas around Great Cumbrae Island in the Firth of Clyde where they form the basis for a small local fishery. In 1979 the British Steel Corporation started operating a deep-water terminal at Hunterston unloading and loading iron ore and coal. It was envisaged that accidental spillage of material during transfer from the vessels to the shore might affect the queen scallop populations in the area.

The recognition that non-essential metals, such as mercury, cadmium and lead, could, upon entering aquatic environments, produce harmful effects to man, directly or through food chains, has resulted in studies directed towards the identification of potentially hazardous levels.

The life histories of Gracilaria verrucosa from England and from Vancouver Island, Canada, were completed in culture. Although representatives of the two populations were morphologically and anatomically indistinguishable, their chromosome numbers differed markedly, being n = 32 for British material and n = 24 for western Canadian plants. It is propounded that the Vancouver Island plants are not authentic G. verrucosa and, moreover, that this name may have been applied erroneously in other reports of the species from localities distant from the British Isles (type locality).

The physiological response of ammonium-limited continuous cultures of Skeletonema costatum (Grev.)Cleve to steady-state and transient conditions was tested and compared to simulations with a Droop-type quota model and a four-state variable model (internal amino acid pool added to the quota model). External ammonium, free internal amino acids, protein, silicate and culture-cell volume were measured.

All cultures showed reproducible changes in growth and uptake kinetics due to spontaneous cell-cycle synchronization of the populations. Under steady-state conditions protein decreased with increasinggrowth rate from 82%; cell-nitrogen to 52% and free internal amino acids increased from 2·5% cell-nitrogen to 8%. Under transient conditions amino acids could reach 25% of cell-nitrogen.

A comparison of model and culture results yielded the following information: Both models could simulate steady-state and most transient conditions. The dependence of the quota on steady-state growth rate is not the result of changes in amino acid or protein pool size. The amino acid pool, an intermediary step in the nitrogen assimilation, does not serve to increase the time lag in growth response significantly. The four-state variable model reproduced under most conditions the behaviour of theamino acid pool without the use of feedback control mechanisms on the rate of uptake. The models could simulate a strong increase in growth rate except when it was initiated by impulse dilution of the culture. Then growth response was controlled by epigenetic mechanisms induction of enzyme synthesis). (6) The maximum nutrient uptake rate per culture cell volume of Skeletonema is inversely related to cell size.

Variation in the abundance of Barleeia unifasciata is compared in several red algal species between June 1978 and June 1980 at Cooskeen Cove, Bantry Bay, Ireland. Population abundance in all algae varied seasonally, exhibiting a cycle of late-summer to autumn maxima, with winter to early summer minima. Greatest abundance was recorded in those algae which formed compact turf-like growths suitable for the entrapment of diatoms and detrital material and provided greatest shelter from wave-crash. Length frequency data showed the main recruitment period to be late June-October with a peak in August with juveniles present in all months of the year. Maximum life span was shown to be 2 years or more with only 15 % of the population surviving into the second year. Sexual development and reproductive cycle was determined for 0 + and 1 + animals. Mature males produced sperm continuously throughout the year. Not all 0 + females spawned in their first year. Summer spawning 0 + females exhibited reduced sexual activity in October and spawned again in the following summer. Some 1 + females spawned in winter and spring. Delayed sexual development in some individuals of both sexes was related to late hatching.

INTRODUCTION

In the Bivalvia the two valves and connecting ligament are parts of a single shell each composed of three layers secreted by continuous surfaces of pallial epithelium as shown in Fig. 1. The superficial periostracum is formed in a groove at the base of the inner side of the outer (secretory) fold of the mantle margin and is continuous around the pallial lobes and within the embayments at each end of the ligament. The outer calcareous (prismatic) layer of the valves and the anterior and posterior outer (lamellar) ligament layers are formed by the outer surface of this outer fold which hypertrophies in the depths of the embayments where ligamental material is secreted. The inner calcareous (usually nacreous or porcellanous) layer of the valves is produced by the general pallial surface except along a mid-dorsal strip, the mantle isthmus (Owen, Trueman & Yonge, 1953; Yonge, 1953) which secretes the inner (fibrillar) ligament layer.

Actinians are equipped with cnidae which function in food capture, defence and aggression (Mariscal, 1974). Cnidae cannot be renewed and after discharge they are extruded from the epithelium. Regulation of the spirocyst and nematocyst population must be important, but as yet no quantitative data about this are available for actinians (Picken & Skaer, 1966).

Freshly captured Nautilus macromphalus were observed to place new cameral liquid into emptied or partially emptied chambers, both at the surface and at 250 m, in response to sudden buoyancy increase. The sudden addition of buoyancy was accomplished either through removal of cameral liquid from chambers, removal of shell material from the apertural region of the body chamber, or by cementing buoyant corks on the sides of the shell. A maximal refilling rate of 100 μl/h was observed. The osmolality of refilled cameral liquid was observed to match closely the osmolality of the original cameral liquid. The refilling mechanism allows Nautilus to regain neutral buoyancy after sudden buoyancy gain, such as could be expected to occur from shell loss due to predatory attack on the Nautilus, or from shell breakage.

INTRODUCTION

Cephalopods are among the most active and agile animals in the oceans. They are all predators and many pelagic species are capable of high swimming speeds.

The morphology of the gills (ctenidia) and heart and vascular systems in cephalopods are suggestive of a high efficiency in respiratory gas exchange and internal blood gas transport.

The present study reports on resting (standard) values of O2-uptake in relation to body size and ambient water O2-tension in the common cuttlefish, Sepia officinalis.

In his recent monograph on British Marine Amphipoda, Lincoln (1979) reported that three species of Leucothoe Leach had been recorded from the British Isles previous to his work and added a fourth species, L. richiardii Lessona. This fourth species he added after examining material collected in 1935, from the Eddystone grounds, by G. I. Crawford. The species had previously been recorded from the same area (Marine Biological Association, 1957) as ‘Leucothoe sp. nov. (allied to L. richiardii Lessona)’.

We have recently had the opportunity to examine more material of the above species from Ireland, together with Crawford's original material kindly loaned to us by Dr Lincoln. Females of this species closely resemble L. richiardii, and only the presence of males in the Irish material (unavailable to Dr Lincoln prior to the publication of his monograph), which differ significantly from those of L. richiardii, alerted us to the distinctness of this species.

Bate (1857) described a new species of Leucothoe from Banff, Scotland under the name L. procera Bate. His three line description however, is insufficiently precise to determine to which species he was referring. Later (Bate, 1862) he redescribed and figured the species under the name L. furina Savigny, and his description and figures agree well with present material except in the shape of epimeron 3 (quadrate) and the telson which is terminally narrow. Bate & Westwood (1862) again figure and describe the species under the name L. furina and re-emphasize the peculiar telson. The epimera are figured as rounded lobes. Unfortunately, Bate's type material is no longer extant, but there seems little doubt, when one considers the perfect agreement in the structure of the male gnathopod 2 between Bate's figured material and present material, that the two are conspecific.