Benthic assemblages of two Mediterranean submarine caves were compared. Species coverage and number of species were lower in internal (dark) communities than external. This feature was specially marked in the less illuminated cave. Ordination analyses performed on species coverage per community for each cave separately, distinguished several benthic communities from the outermost to the innermost zone of each cave. Cluster analyses on species coverage, taking into account all communities in both the caves, established similarities among communities: algal-dominated communities clustered according to the level of light received independently of the cave they inhabited, while animal-dominated communities were more similar within each cave than between the caves. Moreover, among the abiotic parameters measured irradiance was the only factor that clearly diminished from the entrance to the innermost zone in both the caves. In contrast, water movement and particulate organic matter varied differently in each cave. Results indicate that the different topography, depth and geographic location of the two caves determine water movement, light penetration and nutrient availability along the caves. These factors are responsible for determining species abundance and diversity, as well as species growth habit in each community.

In January and March, during the 1955 plaice spawning season, plankton samples were collected with a Heligoland larva net at stations on a grid around a floating radio buoy in the southern North Sea. There was a decided scarcity of suitable food for plaice larvae in the January patch, and this famine was reflected in the deteriorating physical condition of those larvae caught at the transition stage of development, when yolk reserves were becoming exhausted and an adequate external food supply essential. By March, the spring plankton outburst was in full swing. The condition of transitional larvae improved in this good food patch. Feeding started about the mid-yolk phase, mainly on plants. By the time most of the yolk had been resorbed, the appendicularians Oikopleura and Fritillaria had become the principal food items, and remained so throughout pelagic larval life.

Palaemon elegans Rathke on South Wales coasts, unlike P. serratus (Pennant), does not migrate offshore in winter but stays in intertidal pools throughout the year. Both species occur in rock pools in summer, with P. elegans extending farthest up the shore and often occurring in pools above M.H.W.N. Each shows a spontaneous but short-lived tidal rhythm of locomotor activity in constant laboratory conditions, the rhythm persisting longer in isolated prawns than in groups of animals recorded together. Peak activity occurred on the ‘expected’ ebb, and light/dark changes, including those associated with tidal rise and fall, appear to be important in synchronizing the rhythm. The tidal rhythm of Palaemon elegans above M.H.W.N. quickly rephases to a semi-diurnal dusk/dark rhythm during the period of neap tides, the rhythm again becoming tidal when spring tides return. The possible significance of ebb activity is discussed.

The feeding intensity and the diet of Merluccius merluccius were studied along a 1000 km latitudinal scale on the coasts of the Iberian Peninsula (western Mediterranean) in spring 2000. Merluccius merluccius was distributed along two bathymetric bands corresponding to the deep continental shelf (between 36 to 148 m), and the upper slope (between 215 to 310 m). At the shelf small crustaceans (mainly euphausiids and mysids) were dominant in the diet while fish (mainly Myctophidae) were the preferred prey on the slope. Feeding intensity of hake was significantly higher in areas with higher hake density suggesting feeding aggregations. Also, feeding intensity was significantly correlated with phytoplankton pigment concentrations (ppc), though only with ppc recorded one month before on the hake sampling stations. This delay between ppc and feeding intensity of hake may be a response to higher prey availability, because most hake prey were pelagic in origin (euphausiids, Clupeiformes) and they may reach high densities after exploiting local phytoplankton blooms. This delayed response seems to have more a local or spotted pattern. During three 8-h sampling cycles food consumed by hake ranged between 1·01 to 5·51% body wet weight (BWW), on average within the range of food consumption rates of other benthopelagic, active swimmer, fish.

the diet and feeding of the cutlassfish trichiurus lepturus were studied based on analyses of the stomach contents of larvae, juveniles, and adults collected along the continental shelf and shelf break off southern brazil, from the cape of santa marta grande (28°36′s) to chuí (34°45′s). the larvae and pre-juveniles with a total length of <5 cm were found to have fed almost exclusively on calanoid copepods, whereas juveniles (5 to 30 cm) fed on small zooplanktonic crustaceans such as lucifer faxoni and promysys atlantica. on the other hand, sub-adults (30 to 70 cm), fed on euphausiids, mainly euphausia similis, and small fish, mostly anchovy engraulis anchoita. adults (70 to 160 cm) fed on a wide range of larger prey, such as anchovy, sciaenid fish, cephalopods and coastal shrimps, as well as euphausiids. the juveniles and sub-adults fed more intensively than adults during the warm-water season whereas adults fed more intensively during the cold-water season. feeding activity was more intense at night, while cannibalism was more frequent during the warm season, when biological productivity was lower. finally, diet diversity was higher in coastal waters, during the warm season. the abundance of cutlassfish off southern brazil may be explained by the fact that it is adapted to feed on a wide size-range of both pelagic and demersal prey.

Various biological and environmental changes that have been observed during the present century in the area of the western English Channel are briefly described, and then theories that have been put forward to account for them discussed and compared critically with one another.

At the moment, the rise in sea temperature and a possible accompanying change in emphasis of water movements offers the best explanation of all the changes. Such a theory is obviously applicable to the replacement of coldwater northern forms by warmer-water species that has taken place in many habitats (e.g. demersal fishes, pelagic fishes, intertidal zone). A decline in number of macroplankton animals, including the pelagic young of some demersal fish, can be regarded as another aspect of the temperature change, in part related to a shift in distributional boundaries, but also influenced by the replacement of herring by pilchard, which has apparently led to increased stocks of pelagic fish, and perhaps a higher level of predation throughout the year. It is suggested that the plankton production cycle may have become slightly smoother, and possibly a little more efficient, with less' wastage' to the bottom-fauna, the biomass of which may also have suffered indirectly from the increased stocks of pelagic fish.

A new species provisionally attributed to the genus Nephroselmis has been described with the aid of light- and electron-microscopy. Significant features include the presence of a single layer of scales over the flagellar and cell surfaces as in Micromonas squamata Manton & Parke, though the morphology of the flagellar scales is as in the outer scale layer of Pyramimonas and Halosphaera. Reasons are given for rejection of Thalassomonas on the grounds of nomen confusum and for homologizing various representatives of it with Micromonas squamata.

Some additional facts about the latter include details of the imbrication of the flagellar scales and demonstration, made possible by the use of lead staining of sections, of a close association between golgi bodies and the scale-producing vesicles.

The hydrographic conditions in the two sea-lochs is briefly described where relevant to the survey of the benthos. Seasonal changes in temperature and salinity in Loch Etive appear to follow roughly the local coastal pattern but usually with a lag in timing that is considered to be because of the restricting effect of the twin sills. Replenishment of deep-basin water by ventilation over the sills is spasmodic and controlled by surface stratification; the latter being due primarily to freshwater runoff. This situation contrasts with Loch Creran which has only a small catchment and where the seasonal hydrography closely follows the pattern outside. Other possible reasons for the differences observed between the two lochs are discussed.

The bottom fauna of both lochs was sampled semi-quantitatively with an anchor dredge at 22 stations in Loch Etive and 8 in Loch Creran at depths from 7–117 m. A detailed list of the fully marine fauna present is given. The species occurrences in the single-haul samples are compared objectively using a coefficient of similarity of the presence/absence records. An attempt is made to relate the groupings shown up to the classical ‘bottom community’ concept, to the feeding-type categories of the bottom animals and to analysis of particle size of sediment samples taken at the same stations. A correlation to sediment type was apparent. This is considered to owe as much to local hydrographic conditions which the sediment reflect as to the sediment itself.

A Corophium-bed characterized by a mosaic of emerged areas and tidal pools during low water was established on an intertidal flat in the southern part of the Danish Wadden Sea. In spring 1990, the plateaux harboured relatively high densities of the amphipod Corophium volutator, whereas the amphipods were almost absent in the pools. Following a parasite-induced mass-mortality in the population of Corophium, summer 1990, the plateaux of the bed were subjected to sediment erosion. The heterogeneous plateau-pool structure disappeared, accompanied by increased median particle diameter and decreased silt content in the former plateau sediment. These events were accompanied by increased chlorophyll-a concentrations in the sediment of both plateau and pool areas.

The results suggest Corophium volutator to be the single most important organism stabilizing the plateau sediment, and hence, the heterogeneous topographic structure of the Corophium-bed. It is proposed that the stabilizing effect of Corophium burrows also in deeper sediment strata may outweigh the surface stabilizing influence of epipelic diatoms, as well as the negative effect of amphipods eating the diatoms, in non-cohesive coarser sediments.

The discovery thirty years ago of daily growth increments in squid statoliths and the development of statolith ageing techniques gave new insight into squid age, growth and metabolism. The techniques have shown that the majority of recent coleoid cephalopods live in the ‘fast lane’, growing rapidly and completing their life cycles in a year or less. Surprisingly, these useful approaches to the study of age and growth in squid have not gained much momentum. Only approximately an eighth of more than 300 squid species have had their basic age assessed and described. Two dozen species are subject to continuing arguments about which increments to consider as daily growth increments. This paper outlines major problems encountered during age determination of squid and suggests ways to improve the techniques and make them applicable to a wider spectrum of species.

In previous papers (Southward, 1950, 1951 Southward & Crisp, 1952, 1954 a, b: see also Kitching, 1950 Moore & Kitching, 1939) it has been shown that the geographical distribution of several common intertidal animals in Britain is related to the temperatures prevailing in the different regions. Species of generally southern distribution in Europe are commonest on, or restricted to, the south and west coasts of Britain, where temperatures are higher, while those species of essentially northern character are commoner in the north and east where the temperatures are lower. Where species of northern and southern distribution occur side by side in the same habitat, and are in competition, it seems important to know the range of temperatures over which processes such as feeding and respiration can be carried out, as well as the often narrower range of temperatures within which breeding can take place (cf. Orton, 1920). For example, the two common intertidal barnacles of the European coasts, Chthamalus stellatus (Poli) and Balanus balanoides (L.), occur side by side only in Britain and Northern France, where they reach the northern and southern limits respectively of their distributions. From the distributions it can be inferred that the vital activities of the two species are keyed to different temperature ranges. This implies that for each species there is an optimum range of temperature, above or below which the species becomes less efficient at feeding, respiring or reproducing. Where the two species occur side by side, there may be periods of the year when one of them is living outside its optimum range, and is at a disadvantage compared with the other species.

This study of the genus Pterosperma followed on from our work on the genus Halosphaera (Parke & Adams, 1961; Parke & Hartog-Adams, 1965; Boalch & Mommaerts, 1969) since while studying the latter we found abundant pterospermatacean material. In recent books on algae the family Pterospermataceae Ostenfeld (1902) is placed in the class Chrysophyceae (Papenfuss, 1955; Bourrelly, 1957, 1968; Fott, 1959, 1971; Prescott, 1969). The family, however, rightfully belongs in the class Prasinophyceae (Parke in Parke & Dixon, 1964, 1968; Christensen, 1966) in the order Pterospermatales (Parke & Green in Parke & Dixon, 1976).

The external and internal structure of the spines of Squalus acanthias are described. Internally the spines consist of a series of dentine cones laid down one within the other. This series is reflected in the external structure by bands of pigment associated with ridges of enamel. The latter are proved to be annual.

The use of the spines for age determination is discussed and the growth parameters and growth curves calculated. The results obtained differ from those of previous authors, whose work is critically discussed.

Seasonal changes in the gonads of both sexes of Venus striatula were followed by macroscopic and microscopic examination, in over 700 animals from a population consisting mainly of one year-group. The sex ratio was approximately equal, and no hermaphrodite adults were found.

The requirement for thiamine was examined in eleven marine protists of littoral, supra-littoral or neritic origin. Six were found to have an absolute requirement for the vitamin.

The thiamine-requiring Chrysophyta responded to the pyrimidine half of the vitamin, whereas the two thiamine-requiring Pyrrophyta responded to the thiazole half.

All the species requiring thiamine were auxotrophic with respect to at least one other factor (usually vitamin B12).

For half-maximal growth, species responding to pyrimidine required 100–300 mμg/1. pyrimidine or thiamine and species responding to thiazole 2000 mμg/1. thiazole or thiamine.

A quantitative study of macrobenthos was carried out on three transects on the shelf and continental slope off Chile (22° to 42°S; from 100 to 2000 m water depth) within and beneath the oxygen minimum zone (OMZ). Macrobenthos mean densities ranged from 104 to 13 808 ind m−2, with highest values off Concepción (∼36°S), where highest chloroplastic pigment equivalents were also measured. Polychaetes were the numerically dominant group in all transects and depths, followed by peracarid crustaceans. Species richness and diversity correlated with observed changes in bottom-water oxygen concentrations and sediment-bound pigments. Our results show that the shelf macrobenthic communities were negatively affected by low oxygen. The non-metric multidimensional scaling (nMDS) analysis evidenced depth-related station groups which may be related to the different environments provided by the water masses involved. Indeed, the depth ranges of stations groups with their specific species inventories coincide quite well with the boundaries of the three important water masses in the region, the Equatorial Subsurface Water (∼50 m to ∼400 m depth), the Antarctic Intermediate Water (∼400 to ∼1200 m depth), and the Pacific Deep Water (>1200 m depth).

A comparative morphological study was performed on the otolith growth patterns of 11 species of the genus Merluccius. The otolith growth pattern, based on the radius of the first eight growth increments (GI) from the otolith core, was determined from transverse sections of sagitta otoliths. The structure and periodicity of the GI were identified based on previous knowledge. Two cluster analyses were performed using GI width as a proxy for otolith growth. The first cluster analysis corresponded to the juvenile (immature) period of the fish including the mean width of the first four GI. The second analysis compared the mean width of the next four GI, i.e. those corresponding to mature fish. The results showed an important environmental influence in immature fish; while after maturation, the GI pattern was also related to an endogenous influence depending on the phylogenetic line.

INTRODUCTION

Recent experiments with symbiosis in the flatworm Convoluta roscqffensis Graff (Provasoli, Yamasu & Manton, 1968; Provasoli, Yamasu & Mabuchi, 1969) reveal an important area in the investigation of algal-invertebrate associations, demonstrating the potential of studies based on the principle of cross-infections using various experimental symbionts. The studies which these authors describe are feasible only if detailed taxonomic data are available to facilitate rapid identification of symbionts in situ. This kind of experimentation is impossible in symbiotic systems involving ‘zooxanthellae’, because of the general failure to provide adequate descriptions of the genera and species included in this ill-defined group. Admittedly, the situation shows signs of improvement. We now know that the ‘zooxanthella’ associated with C. convoluta Abildgaard is a diatom belonging to the genus Licmophora (Ax & Apelt, 1965; Apelt, 1969), the morphological criteria for the identification of Symbiodinium microadriaticum Freudenthal have been redefined (Taylor, 1969 a) and a revised taxonomic description of this species is now available (Kevin, Hall, McLaughlin & Zahl, 1969). Nevertheless, we are still a long way from achieving a representative collection of well known experimental symbionts for use in comparative studies. It therefore seems worthwhile (not merely an exercise in micro-taxonomy and micro-horticulture) to continue to collect, identify and describe the range of genera and species that may be hidden among the ‘zooxanthellae’. The present paper is one in a series (see Taylor, 1969 a, b, c) intended to explore the potential variety of these organisms.

1. Vegetable detritus of land and coastal origin is of notable importance as a source of food, especially to those specimens measuring 21-29 mm., which is the most abundant size found in the Clyde Sea Area.

2. Meganyctiphanes in the Clyde Sea Area for the most part lives and feeds between 10 and 20 fathoms above a muddy bottom, usually in waters about 60-80 fathoms deep.

3. Meganyctiphanes feeds by selecting from the surrounding water the suspended micro-organisms and detritus, and would thus come under the category of a “suspension feeder.”

4. The larger specimens measuring 29-31 mm. are found chiefly in Upper Loch Fyne. The largest specimens measuring 37 mm. are found exclusively in Upper Loch Fyne.

5. Adult specimens tend to decrease in numbers from May till September. During these months they appear to live during the day immediately above or on the muddy bottom.

6. The association of Meganyctijihanes norvegica, Thysanoessa raschii, Euchceta norvegica, and Calanus finmarchicus, in large numbers in Upper Loch Fyne would indicate that conditions there are specially favourable to all these species.

7. In Upper Loch Fyne M. norvegica, T. raschii, E. norvegica, and C. finmarchicus, make partial vertical diurnal migrations, specimens being found a few fathoms from the bottom during both day and night.

8. Under certain circumstances light appears to have a harmful effect on M. norvegica.

Marine algae supply good examples of the difference between ‘ecological’ and ‘non-environmental constitutional’ resistance of the protoplasm of their cells to variations in the environment. The resistance to ecological factors such as diluted or concentrated sea water, to desiccation, or to light exposure is very similar among algae occupying the same habitat. On the basis of the degree of resistance shown, three ecological groups can be distinguished: (1) algae from the intertidal zone; (2) algae from the low-water level and tide-pools; and (3) sublittoral algae.

On the other hand, there is no similarity in the resistance to chemical substances (H3BO3, ZnSO4, MnSO4, VOSO4) of algae within a given ecological group. It is characteristic for a given species.