The introduction of the Manila clam into British coastal waters in the 1980s was contested by conservation agencies. While recognizing the value of the clam for aquaculture, the government decided that it posed no invasive risk, as British sea temperatures would prevent naturalization. This proved incorrect. Here we establish the pattern of introduction and spread of the species over the first 30 years of its presence in Britain. We report archival research on the sequence of licensed introductions and examine their relationship in time and space to the appearance of wild populations as revealed in the literature and by field surveys. By 2010 the species had naturalized in at least 11 estuaries in southern England. These included estuaries with no history of licensed introduction. In these cases activities such as storage of catch before market or deliberate unlicensed introduction represent the probable mechanisms of dispersal. In any event naturalization is not an inevitable consequence of introduction and the chances of establishment over the period in question were finely balanced. Consequently in Britain the species is not currently aggressively invasive and appears not to present significant risk to indigenous diversity or ecosystem function. However it is likely to gradually continue its spread should sea surface temperatures rise as predicted.

Platymonas convolutae Parke et Manton is the natural algal partner of the symbiotic worm Convoluta roscoffensis Graff (Parke & Manton 1967). Recent work by Provasoli, Yamasu & Manton (1968) has shown that although several algae can form a symbiotic relationship with the worm if supplied in unialgal culture, the natural symbiont is the most effective and is able to eliminate competitors. The alga can be cultured in a denned medium away from its partner, and this paper presents some physiological characteristics of the alga in pure culture in comparison with some of its free-living relatives, in particular the type species of the genus Platymonas, P. tetrathele G. S. West. The present investigation has been concerned mainly with the uptake of carbohydrates and the utilization of organic nitrogen. Other aspects that are included are the excretion of metabolites into the medium and the soluble carbohydrates found within the algae. In addition, culturing the algae has revealed a difference in behaviour of possible relevance to the symbiotic relationship.

In past years during the study of the vertical distribution of macroplankton much information has been obtained on the abundance of the different animals in the catches at different times of the year. Results have already been published to show the seasonal distribution of pelagic young fish (4), and also on the abundance and composition of the Sagitta population (5, p. 565). In this latter study the change over from the predominance of Sagitta clcgans to that of S. sctosa during the years 1930 to 1932 is striking. During the examination of catches it has been noticed that each year has been characterised at some time by the abundance of a species which may occur only in small numbers, if at all, in other years. This has been especially noticeable in the composition of the medusa population. It is necessary to follow these changes through a number of years to see if the presence of certain plankton organisms cannot be used as an index of conditions that may lead to other fluctuations such as those of the fisheries.

The variable colour of Nereis diversicolor is due to variations in the proportion of green, orange and brown pigments. The orange and brown pigments are mainly carotenoids; the green colour is due to biliverdin.

Phaeophorbide-a and coproporphyrin III also occur, but both these pigments may be restricted to the gut wall; biliverdin occurs both in the wall of the gut, and in the epidermis and coelomic cells.

The biliverdin is formed by the breakdown of the haemoglobin of the blood.

Haemoglobin-breakdown takes place in the epidermis on the dorsal side of the body, in the epithelial tissue surrounding the proboscis and in the pygidium. Granules of biliverdin are probably removed by the coelomic cells and conveyed to the gut into which they are excreted.

In ripe males, and in females during and after spawning, phagocytosis of the tissues is accompanied by an increased haemoglobin-breakdown with a corresponding accumulation of biliverdin in the body. The green appearance is due not only to an increased amount of biliverdin, but also to a complete extraction of carotenoids from the body-wall.

The ecology and feeding behaviour of Antedon bifida bifida (Pennant) were studied in situ at five sites on the east and west coasts of Ireland. These encompassed a range of different habitats and hydrographic conditions, including currents of varying intensity, oscillations due to wave action, and multidirectional water movements.

Unlike other comatulids hitherto studied, this species was found to be relatively unspecialized in its choice of habitat and to display great flexibility of movement in its arms and pinnules which enable it to adapt to and feed in each of the different types of water movements described. Neither diurnal nor tidal feeding rhythms were observed, the animals being found to feed almost continuously. The relatively unspecialized nature of this species is discussed in relation to the almost cosmopolitan distribution of the genus Antedon.

Spirula spirula has stimulated considerable interest since it was first discovered.

It is a member of one of the two genera of sepioids to frequent oceanic water (the other being Heteroteuthis); it has a unique spiral shell which acts as a buoyancy mechanism and can withstand considerable pressure (Denton, Gilpin-Brown & Howarth, 1967); and, until the capture by the Danish Oceanographical expeditions it was considered very rare, only 12 specimens having been captured. The Dana expeditions caught 193 individuals from 1909 to 1931 and these were described by Kerr (1931) and Bruun (1943,1955). Most of these were caught in the waters around the Canary Islands of the North Atlantic. Bruun (1943) arranged the specimens according to month and size and claimed that two size groups could be distinguished. The specimens were taken over a wide geographical area, in several years and during the months of February (1 specimen), March (40), April (3), May (8), June (1), August (1) and October (23). His conclusion concerning growth depends entirely upon his decision to split the March sample into two year-groups; those above 1.9 cm in ventral mantle length he put in a separate year-class to those below 1.9 cm in ventral mantle length. This division was arbitrary and, one suspects, based on a belief that a one-year life-span was likely.

Clearly the growth of Spirula requires further study based on a larger collection and the present paper is an attempt to fulfil this need.

MATERIAL AND METHODS

This work is based upon 256 specimens collected to the south-east of Fuerteventura in the Canary Islands by R.R.S. ‘Discovery’ during 1965–68.

On October 28th, 1920, a conjoint meeting was held by representatives of the Development Commission, the Ministry of Agriculture and Fisheries and the Oyster Merchants and Planters Association to institute investigations into the cause of the abnormal mortality which had occurred among oysters in the oyster beds in the Thames Estuary during the summer of 1920. As a result of this meeting investigations were begun under the general direction of the writer. On the completion of the work a full report of the results obtained was forwarded to the Fisheries Department, Ministry of Agriculture and Fisheries. The more important parts of that report will be published as follows: Part I, Main Report, Fishery Investigations, Ministry of Agriculture and Fisheries, London, Series II, Vol. VI, No. 3, 1923; Part II. containing the more important Appendices, will appear later.

The hypothesis that vital functions of one of the most successful macroinvertebrates of sandy beaches of Chile, the mole crab Emerita analoga are negatively affected by the environmental conditions of reflective beaches was tested. Twelve exposed sandy beaches distributed along 200 km of coast of central Chile, and selected to cover a wide morphodynamic spectrum were sampled every two months from April 1997 to November 1998. Significant phenotypic differences among local populations of the sand crab were detected. Important life history traits of the sand crab, linked to growth pattern, reproductive biology and burrowing capacity, were negatively affected by the environmental conditions of reflective beaches. The present results reinforce the view that environmental variations associated with beach morphodynamics, play a critical role in the life history patterns of sandy beach organisms.

The 1947 records of the seasonal abundance of the pelagic young stages of teleosteans in the plankton of Plymouth off-shore waters are a continuation of the series of observations made by Mr F. S. Russell (1930–47). The form of the previous reports is retained. The dates on which collections were made are given in Table I, and the monthly average catches of young fish in Table II. The fortnightly averages of all young fish less clupeids are shown in Fig. I, together with the corresponding curve for the period 1930–34.

Cucutnaria elongata Düben & Koren, collected from the Northumberland coast in January 1968, was induced to spawn in the laboratory by raising the temperature. At spawning, the animal waved its pharyngeal bulb back and forth while a thin string of gametes was discharged. The freshly spawned eggs, surrounded by a jelly coat, were at the end of the second meiotic division and the size varies from 250 to 350 μ in diameter. Oocytes in the ovarian tubules can be grouped into three stages according to their size and other morphological features. Insemination of artificially recovered eggs resulted in only a very low frequency of abnormal development up to 8-cell stage. However, over 90% fertilization was achieved by insemination of the naturally shed eggs and the development was normal. The cleavage was holoblastic and radial type. The larva hatched at post blastula stage and swam freely with its animal pole upward. A doliolaria stage with four ciliary bands and pentactula stage with five primary tentacles subsequently developed. The planktonic life at temperature 9–11 °C ended on the ninth day after fertilization. Pentactula, up to 4 months old, live underneath the mud where they are deposit feeders. The primary tentacles bearing mucus glands in the form of papillae are important in both locomotion and feeding. An outline of chronology from fertilization up to 5 months old is presented.

A technique is described for the in vitro culture of the eggs and embryos of amphipod crustaceans. The technique was used, with mixed success, to culture the eggs of four species of amphipod (Gammarus duebeni, Orchestia gammarellus, Gammarus pulex and Echinogammarus pirloti) through to hatching. Eggs of the brackish water G. duebeni showed good hatching success in culture (70–75%) over a wide range of experimental salinities (75–1250 mOsm kg1). The eggs of O. gammarellus showed higher mortality rates in culture (compared with G. duebeni), especially in more dilute salinities (300 mOsm kg1) in which they swelled greatly prior to disintegration. Survival and true growth (as distinct from osmotic swelling) of O. gammarellus embryos in dilute salinities were significantly im-proved by introducing embryos into culture at a later stage of development. Antibiotic treatment had no demonstrable effect on embryo survival or growth. Whilst difficult to culture using this method, the eggs of the fresh water G. pulex showed best hatching success on a very dilute saline medium (~40 mOsm kg1). The results are discussed in relation to the development of embryonic osmoregulation, the implications for brood pouch function and the potential for female control of the embryonic environment, especially in semi-terrestrial species.

Cytokinesis is described for the first time in a pelliculate dinoflagellate that retains its thecal plates during cell division. In Heterocapsa niei cytokinesis proceeded in a manner that differed from that described for other dinoflagellates. The thecal plates separated along the fission line before the development of a cleavage furrow. A distinct cleavage furrow developed as cytokinesis progressed. The outer membrane and the outer plate membrane expanded during division to enclose the enlarging cell undergoing cytokinesis; however, as the cleavage furrow deepened, these membranes were not continuous with the cytoplasm. The pellicle was occasionally intermittent in the region of the cleavage furrow, possibly facilitating movement of material from the cytoplasm to the developing outer membranes. Thecal plate formation occurred within the thecal vesicle from unrecognizable precursors.

The component acids of the fats of the following marine algae have been investigated by gas-liquid chromatography:Rhodymenia palmata, Laurencia pinnatifida, Laminaria digitata, L. saccharina, Fucus vesiculosus, F. serratus, Pelvetia canaliculata, Ascophyllum nodosum. The principal saturated acids are palmitic and myristic acids, some contain ca. 2–5% of stearic acid; traces of C8 and C10 saturated acids are present, but C12 (and in all but one) C 20saturated acids are absent. The major unsaturated acids are octadecenoic and octadecadienoic acids (probably oleic and linoleic acids), but some species also contain appreciable amounts (up to 12%) of hexadecenoic acid. All the oils contain significant amounts of an eicosatetraenoic acid (probably arachidonic acid) and in some eicosatrienoic and/or eicosapentaenoic acids are also present in small quantities. Two acids of unknown constitution (possibly branched chain acids) are also present in minor amounts. No C22 unsaturated acids could be detected.

INTRODUCTION

Very little is known about the component fatty acids of marine algae. Lovern (1936) examined the fatty acids from the fats of Fucus vesiculosus, Laminaria digitata and Rhodymenia palmata using lead salt crystallization and fractional distillation techniques (Table 2). With these methods, however, it was not possible to separate individual unsaturated acids having the same number of carbon atoms from one another. The mean unsaturation values of these fractions were therefore evaluated from their iodine values and expressed as the number of hydrogen atoms necessary to convert the fraction to the corresponding fully saturated state; thus ( — 4–0H) indicates an average unsaturation corresponding with two double bonds.

We describe an experiment where Ascophyllym nodosum was removed from two 1 x 1 m plots in south-western Iceland in August 1985. The plots were studied regularly until 2005. Recovery of the Ascophyllum canopy took 7–8 years. The understorey algae in one of the plots consisted mostly of extensive growth of Cladophora rupestris, which died within a year of Ascophyllum clearance. No Cladophora had reappeared by 2005, although it was healthy and abundant in control plots throughout the study period. Thus even after 20 years the community had not recovered from disturbance.

Samples of the deep-sea holothurian Ypsilothuria talismani were collected in a time series sampling programme from April 1978 to August 1981 at a 2200 m station in the northern Rockall Trough. The gonad of Ypsilothuria talismani lies beneath the dorsal body wall and the gonad tubules ramify throughout the body cavity close to the gut. In the female, there is no synchrony of gamete development between tubules although macroscopic observation suggests oocyte development is synchronous within each tubule. Maximum fecundity at any time is less than 50 oocytes per individual. The developing oocyte grows to a maximum size of 350 μm and is lined with accessory cells. Spermato-genesis is initiated at several nodes along the tubule with maximum sperm production at the periphery of each node. As spermatogenesis proceeds more of the tubule becomes active until, at maximum development, the tubule is a long digitate structure. We have found no evidence of seasonal reproduction throughout the time series samples. From the egg size, and fecundity we infer lecithotrophic development, with a reduced larval stage, for this species.

Frontal horns are prominent structures, characteristic of the nauplii of most cirripedes. Such horns are more prominent amongst the Lepadomorpha, i.e. Lepas (see Groom, 1894).

Reference is made to frontal horns in those papers concerned with the identification of nauplii (Nilsson-Cantell, 1921; Herz, 1933; Bassindale, 1936; Batham, 1946; Pyefinch, 1948; Buchholz, 1951; Barnes and Barnes, 1959a, b), but more detailed descriptions of horns and associated gland cells are limited to the studies of Groom (1894), Kaufmann (1965) and Walley (1969).

In the present study, the morphology of the frontal horns and the cytology of associated frontal horn gland cells of three barnacle species - Balanus hameri (Ascanius), Balanus balanoides (L.) and Elminius modestus Darwin were investigated.

While collecting acanthocotylid monogeneans for various investigations (Kearn, 1967; Lyons, 1972; Macdonald, 1974) Mr J. E. Green of the Laboratory of the M.B.A. at Plymouth has very occasionally found specimens of what each of these authors has suspected may be a new species. In July 1978 nine more living worms were collected, the material was indeed found to require the erection of a new species and we propose to call the parasite Acanthocotyle greeni.

The climbing behaviour of the gastropod Hydrobia ulvae (Pennant) and its relationship with flotation/dispersal were investigated by field observations and experiments in Norfolk, U.K. and by laboratory experiments. Field experiments of the type used by previous authors were discontinued when it was observed that counts at low tide of snails which had climbed objects the previous high tide did not reflect adequately climbing activity during that period of tidal cover. Both field and laboratory studies yielded five general results: (i) snails climbed only when covered by tidal water; (ii) climbing activity was not related to population density; (iii) climbing activity, under conditions of constant population density, varied markedly during the cycle of spring tidal cover, reaching a peak after the first few tides and declining rapidly thereafter; (iv) maximum numbers of snails were present on submerged structures relatively early in any given period of cover and declined (snails crawled downwards off the structure) as the period of cover continued; and (v) rarely were large proportions of climbed Hydrobia floated off their support by the incoming tide; this was associated only with conditions of extreme calm.

discards represent a significant percentage of the total catches (up to 35%) in the north of spain trawl fishery. in the cantabrian sea (southern area of the bay of biscay), the estimated average total annual catch of small-spotted catshark (scyliorhinus canicula) is approximately 1500 tn, from which 80% is discarded. several experiments have been carried out in order to estimate the survival-rate of the small-spotted catshark caught by commercial trawlers in this area. the estimate of mean survival-rate from tagging surveys was 90% while from commercial trawlers it was 78%. several factors potentially influencing the survival-rate (sex, length, maximum depth fished, sorting time and trawl duration) were examined. no significant differences in survival-rates were found between males and females, and no strong relationships between survival-rate and depth fished, sorting time or trawl duration were evident. in commercial trawlers survival-rate was not dependent on the fish length.

During my stay at the Plymouth Laboratory in 1931 I had an opportunity of investigating the innervation of the heart of Ligia oceanica, and of making some experiments on the function of the ganglionic trunk which constitutes the main element of its innervation. In a short note describing these experiments (Alexandrowicz, 1931) it was stated that a description of the arrangement of the nerve elements would appear in a short time. However, on later examination of the preparations it seemed to be desirable to verify some of the findings, but the same animal was no longer available. Another isopod, Mesidotea entomon, with which I tried to continue the work during my visit to the Marine Biological Laboratory in Hel, proved to be much less suitable for this kind of investigation despite its larger size. Later events, unfavourable for scientific work, caused the loss of all my preparations and a further delay. It is only now, thanks to the chance of working again at the Plymouth Laboratory, that I have been able to resume my investigations.