Quantitative studies of the meiofauna of marine littoral sediments have been attempted only recently. Much of the work has been done in sheltered areas such as the Danish waddens (Muus, 1967), and in estuaries (Barnett, 1968; Capstick, 1959; Rees, 1940; Riemann, 1966), or in tideless areas such as the Baltic (Fenchel & Jansson, 1966; Fenchel, Jansson & von Thun, 1967; Jansson, 1968). Beaches exposed to tides and wave action have received less attention. Renaud-Debyser (1963) studied quantitative temporal variations in the meiofauna of beaches at the Bassin d'Arcachon, France, and Island of Bimini, Bahamas. Renaud-Debyser & Salvat (1963) have compared quantitatively the meio- and macrofauna of four beaches in the English Channel and six on the Atlantic coast of France. Schmidt (1968, 1969) has analysed quantitatively the distribution and population dynamics of the meiofauna of a number of beaches on the Island of Sylt off the German North Sea coast. Recently Mclntyre (1969) has reviewed the ecology of the meiobenthos. Subsequent to Mclntyre's review, in the U.S.A. quantitative investigations of the Gastrotricha (Hummon, unpublished) and Tardigrada (Pollock, 1970) of Massachusetts beaches have been made. Tropical beach meiofauna has been studied in India (Mclntyre, 1968), on the east coast of Malaya (Renaud-Mornant & Serene, 1967) and in Tuamotu, Polynesia (Salvat & Renaud-Mornant, 1969).

Gametogenesis has been studied in four cirratulid polychaetes: Caulleriella caput-esocis, Tharyx marioni, Cirriformia tentaculata and Cirratulus cirratus.

In all four species, sperm development follows a similar course of events, with the sperm cells being grouped in spheres and then platelets before developing tails to give rosettes which finally disintegrate to release the active spermatozoa. Except in Cirratulus, there is a well-defined annual cycle in the development of sperm.

Oogenesis in Caulleriella and Cirriformia is similar in that the growth curve of the oocytes is roughly sigmoid. In Tharyx the release of the oocytes to the coelom is delayed and discrete ovaries are formed, only the later stages of oocyte growth taking place within the coelom. In contrast to the above three species, oogenesis in Cirratulus does not show an annual cycle.

Maturation of the oocytes within the coelom prior to shedding has been established in Tharyx, Cirratulus and Cirriformia. In the former two species meiosis proceeds as far as the metaphase I stage and in the latter to the anaphase I stage, before the oocytes are released. Fertilizations were achieved only with oocytes which had matured in all three species. In the fourth species, Caulleriella, no fertile oocytes were discovered.

The diameters of the mature oocytes and the main spawning seasons of the four species at Plymouth are as follows: Caulleriella, about 110 μ (August to October); Tharyx, 200– 220 μ (late October to early November); Cirriformia, about 117 μ (late June to early July); Cirratulus, 135–150 μ (throughout the year).

Seven postlarvae and one juvenile of the golden mullet and two postlarvae of the thicklipped mullet, ranging from 60 to 27 mm and from 14-88 to 21-44 mm in length respectively, were found in plankton collections taken in the Plymouth area on 10 October and 14 November 1969. The morphological characters of these specimens are described and illustrated, and the presumptive spawning periods of the two species are briefly discussed in this paper.

Between May 1961 and November 1970 almost monthly visits were made to Duckpool, an exposed shore on the north coast of Cornwall, where Sabellaria alveolata (L.) is the dominant organism on low-level rocks uncovered only by spring tides. Massive colonies several feet across and up to some 2 ft thick, formed mainly of shell particles cemented together by the worms, as well as many smaller colonies and single tubes, here reach their maximum development in south-west England.

Selected sites and colonies were photographed and some measured at frequent intervals over long periods of time. comparative studies of long series of colour transparencies examined closely with a binocular microscope have proved invaluable in elucidating the manner and rate of growth of varied types of colonies, their lengths of life and the manner of their ultimate destruction. Detailed histories of these selected colonies are given in this paper and reveal much that was previously unknown or only guessed.

A short spawning period every year in July initiates each new generation. Experimental work, already published, had shown that individuals develop at different rates, the final stage with ability to settle being reached at any time from 6 weeks to 6 or more months, and when reached the ability can be retained for some weeks. This accords with observations on the shore, where settlement takes place in any month between late August and the following early May, or rarely June. The intensity of settlement varies enormously from year to year, there being none in some years, with slight or moderate or heavy settlements in others.

INTRODUCTION

It is well known that littoral teleosts, such as Blennius pholis, are on occasions subjected to considerable and abrupt variations in the salinity of their environment. Smith (1930) constructed a tentative model of the processes involved in the osmoregulation of teleosts; quantification of the various components of the Smith model has been extensive, but little attention has been paid to the respiratory stresses undergone by teleosts in fluctuating salinities.

During the last 3 years a survey of marine lipids has been in progress in this laboratory. Several classes of marine animals have been analysed for their fatty-acid composition. These results have shown a considerable species variation but no estimate could be made of the effect of season and environment. It was therefore decided to choose an inshore animal, which could be readily collected, and to examine its lipid composition with regard to seasonal and environmental changes.

The brackish-water, partly planktonic mysid, Neomysis integer (Leach), was selected. This species has already been the subject of much biochemical study (Raymont, Austin & Linford, 1964, 1966, 1968; Linford, 1965), in which the three major fractions protein, lipid and carbohydrate were examined. The lipid weight was found to be low in comparison with the protein content. Also, significant decreases in the lipid were found in November, January and March. It was concluded that N. integer stored little lipid as a metabolic energy reserve, and as the carbohydrate was low, protein may be catabolized. Only one sample analysis for fatty-acid composition was reported.

The marine species Neomysis nakazaviai has been investigated by Yamada (1961), but unfortunately an ether extract was taken from sun-dried material and so the results are not comparable with the present work on Neomysis integer.

In the present study the saponifiable fraction of the lipid is examined in more detail in an attempt to establish the relative importance of the factors of season, temperature and salinity upon the fatty-acid composition.

Proximate analyses of deep-frozen samples of Euphausia superba Dana obtained in December and January showed that protein was the major constituent, averaging just over 50% of the dry body weight. Lipid was much more variable; extreme limits of variation were from 6 to 33% dry weight, though the lipid content during January was distinctly higher than in December (means 27 and 13% dry weight respectively). This increase probably reflects a more intensive grazing by krill during the Antarctic summer. Increased lipid appears to be associated with some reduction in water content and in ash. Carbohydrate is low, the mean value for December being just under 5% dry body weight, but the content is slightly higher than that found for most zooplankton and may reflect the herbivorous habit of E. superba. The proximate biochemical composition of krill is similar to that of the boreal euphausiid, Meganyctiphanes norvegica.

The north-eastern Atlantic gobiid genus Lebetus Winther, 1877, was formerly believed to contain two species, Lebetus scorpioides (Collett, 1874) and L. orca (Collett, 1874). These have been subsequently shown to represent females (and immature fish) and males respectively of a single, sexually dimorphic species whose valid name is L. scorpioides. The discovery of two forms of Lebetus postlarvae, differing in meristic characters, fin growth, and pigmentation, is shown not to affect this conclusion but to suggest provisional recognition of another species, L. guilleti (Le Danois, 1913), with fewer anal fin-rays (A I/5–6) and vertebrae (25–26) than L. scorpioides (A I/7–8; vertebrae 27-29). A key and limited synonymy for the species is provided. As a possible alternative view it is suggested that relatively high summer sea-temperatures during early development of L. scorpioides in certain areas may produce the lower meristic features of L. guilleti.

Seventy-two holdfast samples of the kelp Laminaria hyperborea (Gunn.) Fosl., from fifteen approximately equidistant sites along the North-East coast of Britain, from St Abbs in Berwickshire to Flamborough Head, have been taken during the course of one spring-tide period. The nematode fauna of these samples (20,744 specimens of 61 species) has been examined and the data are presented in such a way as to facilitate comparison with previous work. The fauna in the North Sea is dominated by large enoploid species. Enoplus communis Bastian, Anticoma acuminata (Eberth), Thoracostoma coronatum (Eberth), Phanoderma albidum Bastian and Pontonema vulgaris (Bastian) are regularly abundant. The minor contribution of the family Monohysteridae indicates that silt is of little importance to the nematode fauna in exposed localities. The holdfast-dwelling nematodes are generally epigrowth feeders or omnivores, the latter exploiting the sediment-feeding niche apparently unavailable to specialized deposit feeders. Species with short body setae, body length above 1·5 mm, having smooth cuticles and possessing some visual mechanism are dominant. It is upheld that algal structure per se is of primary importance in determining the different nematode communities found to exist in algae of different growth forms, and to account for the similarity shown between the faunas inhabiting similar algal growth forms from widely separate geographical areas and differing levels on the shore. It is suggested that habitat-component generic keys might facilitate investigation of unknown regions.

INTRODUCTION

The occurrence of dense beds of the brittle-star Ophiothrix fragilis (Abildgaard) in certain localized areas around the British Isles has been reported by several authors (Allen, 1899; Vevers, 1952; Cabioch, 1961; Holme, 1961; Brun, 1969), with population densities varying from 340/m2 (Vevers, 1952) to 2196/m2 (Brun, 1969). These populations seem to be permanent features of the sea bed since the aggregation sampled by Allen was in the same position as that photographed by Vevers fifty years later.

High- and low-shore populations of Bathyporeia pilosa LindstrÖm, kept in the laboratory under natural day-night illumination and constant dark conditions, show distinct swimming rhythms of tidal frequency (12–4 h) with activity maxima on the early ebb tide. A diurnal component is evident, activity during thenight being greater than during the day. The tidal rhythm deteriorates under laboratory conditions, but swimming activity recurs after a semi-lunar period. Under natural illumination, both populations show a night tide swimming rhythm of semi-lunar frequency, activity occurring mainly over the 'falling' spring tides. Plankton sampling on night tides over the area of the beach occupied by high-shore B. pilosa shows that the animals emerge and swim on ebb tides which are in phase with darkness. The importance of exogenous factors such as wave action, pressure, temperature and light is discussed. Ecological implications and the possible function of the swimming rhythm are considered.

During recent cruises of R.R.S. ‘Discovery’ in the eastern North Atlantic an investigation has been made of the depth distribution and diurnal migration of the pelagic fauna in selected oceanic areas. This continuing programme has entailed intensive mid-water sampling with opening-closing nets, fishing discrete depth horizons mainly within the upper 1000 m but also on occasion at greater depths. Hauls made during the cruise of January-April 1968 in a position 11°N, 20°W, south-east of the Cape Verde Islands, yielded 43 specimens of an apparently new species of the genus Acanthephyra. A further 113 specimens were taken during a subsequent cruise to the same area and the species has also been recorded in a sample collected in the Indian Ocean during the International Indian Ocean Expedition.

Having examined the literature and concluded that the species was undescribed the author referred to the large collection of decapod Crustacea that had been amassed as a result of cruises of ships of the Discovery Committee made prior to 1939. This material, together with that taken on the Dana Expeditions, had formed the subject of Dr Stanley W. Kemp's extensive studies on the Oplophoridae (Kemp, 1939), consequently the carefully preserved, labelled, and identified specimens represent a unique reference collection. It proved to contain five specimens identical to those taken at 11°N in 1968. Not unexpectedly Kemp had realized their uniqueness and had not only designated the type but named it. A description, however, was never published although it was prepared and has in part survived.

Using 14C as a tracer in experiments of 2–3 h duration it has been demonstrated, both with individual species in culture and natural populations, that marine phytoplankton from tropical inshore waters releases products of photosynthesis insoluble extracellular form. The relative extent of this excretion varied between 1% and 20% of the total carbon fixed but on any particular occasion the amount of extracellular products was approximately proportional to the amount ofphotosynthesis which had taken place. An inverse relation-ship between relative extent of excretion and phytoplankton abundance as measured by chlorophyllα concentration was found, in agreement with the results of previous workers. The relative extent of excretion did not appear to be greatly different in brackish water of 12–3% salinity from that in ordinary sea water.

INTRODUCTION

Various authors during the last century (Johnston, 1847; Hincks, 1868, 1880) and more recently (D. Eggleston, unpublished†) have recorded a number of species as epizoites on the perennial bryozoan Flustra foliacea (L.) (Table 1); but the ecology of the ‘community’ (Hedgpeth, 1957) of epizoites and their interaction with the living substratum has never been studied. The sessile fauna of Flustra fronds includes species of seven different phyla, but it can be said of only a few that the fronds provide their typical habitat. For example, the barnacles are never very numerous and the lamellibranchs rarely reach adult size. This paper is concerned mainly with the most common epizoites: the hydroids and bryozoans. The distribution and orientation of some of these species on the fronds are of ecological interest.

The reproductive cycles of the two cockles Cerastoderma edule (L.) and C.glaucum (Poiret) (= Cardium lamarcki Reeve) from a mixed population in the Crouch estuary, Essex, have been investigated. Reproductive maturity was estimated by assessment of gonad condition. A difference in maturity related to shore level was noted. The reproductive cycles of the two cockles were found to be essentially similar. Rapid gametogenesis occurred in both cockles in spring, C. edule then spawned in May, whereas C. glaucum did not spawn until July. The difference in time of spawning appears to be responsible for the maintenance of the two genotypes in a sympatric association, as hybridization experiments showed an absence of isolation at the gamete level. The relationship between C. edule and C. glaucum is discussed.

When beginning research into the cultivation of marine shrimps and prawns, it is usually the most worth while of the local species that is chosen for study. From this it follows that in tropical regions the penaeids tend to be favoured, especially following the pioneering work of Hudinaga (1942) with Penaeus japonicus (Bate), whereas in the temperate regions of Europe and Canada it is the carideans that are receiving most attention, particularly the palaemonids. One notable exception is the advanced study of the Asiatic Giant Prawn Macrobrachium rosenbergii (de Man), which was initiated in Malaysia and subsequently taken up in Hawaii and Great Britain (Ling, 1962).

Doubtless each chosen species has its merits, but overriding importance must be attached to ease of mating, for this imposes an immediate limit on the reliability of the whole process and holds the key to the selective breeding of improved strains. Indeed, it has been pointed out that reliance on wild-spawned animals is a major obstacle to commercial development (Tabb et al., 1969) and such vagaries in the supply of young shrimps has already limited some research (Cook & Murphy, 1969).

Under captive conditions it has proved a great deal easier to mate carideans than penaeids, but the continuing part played by caridean females in incubating the eggs over a contracted period is a disadvantage. Relieving the ovigerous females of this task would allow the eggs to be incubated at greatly increased densities in conditions no longer dictated by the females. Further, it would lead to the more effective use of the female during the period she would otherwise be incubating.

INTRODUCTION

Algal-invertebrate symbiosis is common among species of acoelus Turbellaria in both marine and freshwater environments (Droop, 1963; Buchner, 1965; McLaughlin & Zahl, 1966). Associations involving these organisms exhibit broad variations in the amount of integration achieved through the reciprocal relations of hosts and symbionts. In the symbiosis involving Convoluta roscqffensis Graff, the maximum degree of intimacy is achieved, and the host appears totally dependent on its symbiont for its nutritional requirements (Keeble & Gamble, 1907; Keeble, 1910). This type of closed symbiosis is unknown in other invertebrate phyla and may even be unique among turbellarians. Similarly, the association between Amphiscolops langerhansi (Graff) and a unicellular alga is a typical example of the more common, open or facultative symbiosis. Both species (with their algal partners) are potentially useful as investigative tools in the study of cellular interaction in algal-invertebrate symbiosis, and may provide the basis for understanding the broader aspects of cellular integration in metazoan tissues. Recent studies of C. roscqffensis provide a basis for understanding the biology of the symbiosis which it sustains (Parke & Manton, 1967; Provasoli, Yamasu & Manton, 1968; Provasoli, Yamasu & Mabuchi, 1969). The present communication is intended to provide similar information on the association found in A. langerhansi.

Information on the population structure and breeding of the following species is presented: Siriella armata (Milne-Edwards), 5. clausii G. O. Sars, S.jaltensis (Czerniavsky),Gastrosaccus spinifer (Goës), Anchialina agilis (G. O. Sars),Psendomma affine G. O. Sars and Hemimysis latnornae (Couch). There is no previously published information on the biology of these species in British waters except notes on 5. armata and A. agilis. Notes on the occurrence of the following species on the west coast of Scotland are also given: Siriella norvegica G. O. Sars, Gastrosaccus sanctus (van Beneden), G. normani G. O. Sars, Leptomysis mediterranea G. O. Sars, Mesopodopsis slabberi (van Beneden), Heteromysis formosa S. I. Smith and Acanthomysis longicornis (Milne-Edwards).

The formation of ‘teeth’ in immature Nucella lapillus (L.) is indicative of a stoppage in growth. Along the western coasts of southern Britain the proportion of individuals showing these growth disturbances is predictably related to the exposure of the shore to wave action. Farther east the proportion is much higher but not obviously so related. Sharp discontinuities separate eastern and western populations. Possible reasons for the differences are discussed and it is concluded that great care must be exercised when applying information about this species derived from the one coast to situations on the other. The potential value of this species as an indicator of environmental change is considered.

Growth of shells of larvae of Nassarius reticulatus (L.) and Crepidula fornicata (L.) reared in the laboratory under constant temperature (14 °C) and illumination (155 lx) occurs by the addition of successive strips secreted at the mantle edge. Growth lines on the embryonic teloconch also indicate intermittent growth; the protoconch secreted by the shell gland has no such lines. There is evidence that growth periods are short and pauses separating them prolonged. The diameter of the older whorls of the shells of these and six other species examined increase with the volume of the viscera. This change in diameter is made possible by the flexibility of the organic matrix, the funda-mental constituent of the shell. The matrix, secreted as fibres at the mantle edge, forms sheets, and provides sites for the deposition of calcareous concretions; at metamorphosis the concretions apparently initiate the formation of crystals. The concretions also sculpture the surface of the shell producing a pattern sufficiently conspicuous to allow identification of some species with the aid of only the stereomicroscope. For example, large concretions form longitudinal rows over the protoconch and teloconch of Littorina neritoides (L.) and smaller ones combine to form a more decorative pattern in Rissoa sarsi Loven. In other species details of the surface design require a scanning electron micro-scope. Interspecific differences in the arrangement of concretions may be traceable to differences in the pallial glands which secrete the matrix.