Diet and sexual maturation were examined in the winter–spring cohort of the neon flying squid, Ommastrephes bartramii, during its southward migration through the Kuroshio–Oyashio transition region of the western North Pacific. The main prey items are micronektonic animals and small pelagic fish, which were abundantly distributed throughout the study area. Among the prey species, O. bartramii was dependent on the Japanese anchovy Engraulis japonicus, which also migrate from the northern to southern transition region during the winter, and the micronektonic squid Watasenia scintillans throughout the study period. Other common prey items were Gonatopsis borealis, Diaphus theta, and Ceratoscopelus warmingii from October to November or December, and Tarletonbeania taylori after December. These dietary changes can be explained by the difference in the seasonal north–south migration patterns of the predator and prey species. Male sexual maturation progressed throughout the season, and most individuals were fully mature in January. In contrast, most of the females were immature throughout the study period. The feeding strategy of the squid in relation to their seasonal north to south migration and sexual maturation was discussed.

The identification of magelonids with mucronate chaetae on chaetiger 9 has long been confused. Until 1977 all corresponding European specimens were erroneously referred to Magelona papillicornis; a Brazilian species. Since then, but without any detailed study, the name M. mirabilis (originally given to a species from Scotland) has been widely employed. However, in recent years, it has become clear that two morphologically similar species coexist in European waters. Magelona mirabilis is redescribed and a neotype designated, and M. johnstoni sp. nov. is formally distinguished. Following re-examination of the other five species present in the region, a dichotomous key and a synoptic table of characters is provided for all seven European species.

INTRODUCTION

Balanus balanoides (L.) is a cross-fertilizing hermaphrodite. Insemination takes place in November in North Wales. Spermatozoa are deposited in the mantle cavity of a receptive individual by the extended penis of a neighbouring ‘acting male’. If a receptive individual – that is one that will accept insemination – is examined before oviposition takes place, the oviducal glands are found to be distended by a clear fluid (Walley, 1965). Oviposition follows insemination and fertilization is external, taking place within the confined space of the mantle cavity. The oocytes enter the mantle cavity, via the paired oviducal glands, and become enclosed in a pair of thin membranes. These membranes, enveloping the egg masses, are formed by distension of the elastic sacs secreted by the oviducal glands (Walley, 1965) and the spermatozoa have to pass through them in order to fertilize the eggs. If spermatozoa which have been deposited in the mantle cavity of a receptive individual are removed and examined before oviposition begins, they are immotile. If, however, they are examined several minutes later, during oviposition, they are found to be swimming vigorously (Barnes & Crisp, 1956): they have apparently been activated. The work described in this paper yields some information on the activation of the spermatozoa in B. balanoides, supplements recent work on the structure of cirripede spermatozoa (Brown, unpublished2; Turquier & Pochon-Masson, 1969; Bocquet-Vedrine & Pochon-Masson 1969; Munn & Barnes, 1970), and fixes the time within the sequence of maturation divisions of the oocyte at which fertilization takes place.

Belize contains important habitat for Antillean manatees (Trichechus manatus manatus) and provides refuge for the highest known population density of this subspecies. As these animals face impending threats, knowledge of their dietary habits can be used to interpret resource utilization. The contents of 13 mouth, six digestive tract (stomach, duodenum and colon) and 124 faecal samples were microscopically examined using a modified point technique detection protocol to identify key plant species consumed by manatees at two important aggregation sites in Belize: Southern Lagoon and the Drowned Cayes. Overall, 15 different items were identified in samples from manatees in Belize. Five species of seagrasses (Halodule wrightii, Thalassia testudinum, Ruppia maritima, Syringodium filiforme and Halophila sp.) made up the highest percentage of items. The red mangrove (Rhizophora mangle) was also identified as an important food item. Algae (Ulva sp., Chara sp., Lyngbya sp.) and invertebrates (sponges and diatoms) were also consumed. Variation in the percentage of seagrasses, other vascular plants and algae consumption was analysed as a 4-factor analysis of variance (ANOVA) with main effects and interactions for locality, sex, size classification and season. While sex and season did not influence diet composition, differences for locality and size classification were observed. These results suggest that analysis of diet composition of Antillean manatees may help to determine critical habitat and use of associated food resources which, in turn, can be used to aid conservation efforts in Belize.

During a parasitological survey of the brown mussel Perna perna from highly productive culture fields in the southern sector of Brazil, monstrilloid copepods were discovered in the mantle of this mytilid bivalve. Numerous specimens of endoparasitic copepods were found within nodules in the mantle of the host; they belong to an undetermined species of Monstrilla. Monstrilloid copepods were known to be endoparasitic in polychaetes and in one species of prosobranch mollusc only; their occurrence as parasites of bivalve molluscs has not been previously documented. This is also the first record of these crustaceans infecting commercial molluscs. The prevalence of Monstrilla sp. infecting the brown mussel was 25.6%. At the histological level, it was observed that the larvae induced a strong haemocytic infiltration resulting from the complete larval encapsulation within the host mantle. The effect of this monstrilloid in the cultured populations of P. perna deserves further study.

INTRODUCTION

In the central regions of the English Channel surface tidal streams are strong, often exceeding 160 cm s−1 at peak springs, with maximum values of over 250 cm s−1 off the headlands of Portland Bill and Cap de la Hague (Sager & Sammler, 1975). Correspondingly high values for bottom stress (Pingree & Griffiths, 1979) result in a scoured sea-bed covered with a minimum of sediment, the underlying bedrock being exposed in places. Study of current-generated bedforms in relation to the prevailing tidal currents has indicated the presence of a bed-load parting zone across the Channel from the Isle of Wight to Cap de la Hague (Stride, 1963; Johnson et al. 1982).

The main purpose of the work described in this paper was to find a humane way of killing crabs for eating, but the method that resulted from the investigation is applicable also in the biological laboratory, unless it is necessary that the nerve ganglia should be intact.

The importance of Meganyctiphanes norvegica (M. Sars) as a source of vitamin A for its predators has been demonstrated by Fisher, Kon & Thompson (1955). Basing their conclusions on the observations of Macdonald (1927) on the feeding of M. norvegica in Loch Fyne, Fisher, Kon & Thompson (1954) and Kon (1954) suggested a possible scheme of accumulation of vitamin A in the animal. They also made cursory examinations of the stomach contents from animals caught in the same area and their findings appeared to agree fairly well with those of Macdonald, except that from his results he concluded that phytoplankton was a major item in the diet. This conclusion has been disputed by Einarsson (1945) who called for more detailed investigation of fresh material in order to obtain a clearer picture of the feeding of north Atlantic euphausiids. Such information would be of great value in the study of the vitamin A chain in the plankton. We have, therefore, examined the stomach contents of M. norvegica over nearly two years to try to detect every type of food that might be eaten. In addition to our own survey, Dr J. Mauchline (1959) of the Marine Station, Millport, made a more intensive study of the food in relation to the diurnal migrations in July and November.

Growth in ophiuroids is highly variable, and with increasing size and age of an ophiuroid specimen more and more of the innermost growth rings on the vertebral ossicles become overgrown and hence invisible. Two approaches to estimate individual age of slow growing brittle stars using the high Antarctic species Ophionotus victoriae are compared. One method interprets natural growth ring readings as size-increment data, whereas the second method compensates for growth ring overgrowth by means of an iterative corrective approach. Preconditions as well as advantages and disadvantages of both methods are discussed.

Present knowledge of the nutritional requirements of fish is limited to certain species of salmon and trout (e.g. Halver, DeLong & Mertz, 1957; Shanks, Gahimer & Halver, 1962). In view of the current interest in the cultivation of marine flatfish (Shelbourne, 1964) information on their dietary needs is equally desirable. Experience with salmon (DeLong, Halver & Mertz, 1958) has indicated that protein is the largest and most expensive constituent of fish diets and studies on the nutritional value of different food proteins for fish are necessary if the fish are to be reared economically and successfully. A desirable prerequisite to such studies is a knowledge of those amino acids for which the fish has an absolute dietary requirement, i.e. which it cannot itself synthesize from other substances normally available. With most animals these requirements have been identified by growth trials using partially (or wholly) defined diets. The rearing of fish on defined diets is not easy and it seemed in the first instance that an indirect but valid approach might be utilized. If animals are given a radioactively labelled carbon source, such as uniformly labelled [U-14C]glucose a significant amount of the radioactive carbon will be incorporated only into those compounds which the animal can itself synthesize. By isolating the amino acids from the tissue proteins following such a dose the essential amino acids are identified as those which are not radioactive. The amino acids containing radioactivity correspond with the so-called non-essential amino acids.

The stenophagous ascoglossan (=sacoglossan) opisthobranch Elysia viridis has long been a model organism for the study of endosymbiosis or kleptoplasty as well as one of the few herbivores to consume the introduced green macroalga Codium fragile on European shores. Larval and post-larval dynamics of the ascoglossan were investigated. Planktotrophic larvae of E. viridis grew at 5–10 μm d−1 (shell length) at 15°C on a unicellular algal diet (the cryptophyte Rhodomonas baltica); larvae became competent one month post-hatching. Effective feeding and chloroplast acquisition typically started within 2–3 d of metamorphosis. Slugs grew about 8 mm in the first month of post-larval life. During this period, juveniles held in the light did not grow faster or survive better than conspecifics held in the dark; thus, functional kleptoplasty did not occur during first three weeks of benthic life. While larval growth rates and the nature of metamorphic cues are consistent with those of many other opisthobranch species with planktotrophic larvae, measures of post-larval growth—particularly as it pertains to kleptoplasty—is a new contribution to opisthobranch biology.

In continuation of the study of the vertical distribution of the pelagic young of Teleostean fishes, already reported on for 1924 and 1925 (1), a further fifteen stations were made with the two-metre stramin net in the daytime between April and September in 1926. The collections were made in a manner exactly similar to that for those of the previous years, hauls of ten minutes' duration being made almost always at six different depths with the net towed horizontally as near as possible at the same speed on each occasion. The Admiralty depth-recording instrument was used at every station, and the results for each haul are given in Figures 6 and 7 on pages 666 and 667, which show the graphic records of the path of the net through the water for each haul. (That for June 25th is not included, an unsatisfactory record being obtained on that day owing to the drum of the recorder not having been fully screwed down, see 4, p. 431.)

The feeding habits of the Rio skate, Rioraja agassizi, from off Uruguay and north Argentina were evaluated using a multiple-hypothesis modelling approach. Relationships between number of preys and sex, maturity stage, body size, season and region were assessed by building generalized linear models. Rioraja agassizi fed mainly upon crustaceans (shrimps, crabs and amphipods) and teleosts, but also upon isopods, cumaceans, lancelets and polychaetes. Ontogenetic diet shifts were found: small R. agassizi consumed amphipods, cumaceans and isopods and large individuals on shrimps, crabs and teleosts. The consumption of crustaceans (amphipods, shrimps, crabs, isopods and cumaceans) was higher in the northern (34°–38°S) than in the southern area (38°–41°S). Rioraja agassizi consumed more teleosts in the cold season and preyed more on lancelets in the warm season. Prey size increased with increasing body size of R. agassizi, but large individuals also consumed small prey. Ontogenetic shifts may be related to body size rather than other life-history traits. Rioraja agassizi adapts its feeding habits in response to regional and seasonal changes.

During the last sixty years many attempts have been made to take photographs underwater at depths varying from just below low-water to many thousands of feet. The pioneer work of Boutan (1893) showed clearly that the essential requirements were a relatively light apparatus fitted with a good source of illumination. Ewing, Vine & Worzel (1946) gave a list of workers who have obtained underwater photographs at wading or diving depths. In their own work Ewing, Vine & Worzel have designed a number of underwater cameras with which they have taken some thousands of pictures of the sea-bottom. In their free-floating cameras the apparatus is allowed to sink to the bottom with a ballast weight. On touching the bottom a trigger sets off the camera which takes two pictures with a time interval of 30 sec. After this the ballast is released and a float brings the apparatus to the surface. In their suspended cameras the component parts are mounted, as in the free-floating cameras, on a vertical pole, with the camera near the top and a trigger at the base. Activation of the camera occurs when the trigger touches the bottom. Their most satisfactory light source proved to be the photoflash bulb. With one or other of these cameras they have obtained large numbers of clear photographs in depths ranging from 10 to 2400 ft., and have used these in studies of bottom deposits, sand ripples, and the distribution of animal life. (See also Ewing, Woolard, et al, 1946.)

Possible effects of ‘El Niño’ Southern Oscillation (ENSO) components ‘El Niño’ and ‘La Niña’ on populations of southern elephant seals, Mirounga leonina, were analysed. Changes in the cephalopod diet composition of moulting females at King George Island, Antarctic Peninsula were considered. The diet of female elephant seals sampled in 1991–1992 and 1992–1993 (El Niño years) were compared with those taken in 1995–1996 (La Niña year) at the same site and employing the same methodology. The squid Psychroteuthis glacialis constituted the main cephalopod prey of the seals. A reduction in the ‘Index of Biomass Ingested’ by female elephant seals (IBIF) of this prey species was observed in ‘El Niño’ years (1992, 1993) compared with the ‘La Niña’ year (1996). This reduction in biomass applied to all squid species in the seals' prey with the exception of Galiteuthis glacialis, which occurred in low numbers, but was more abundant during El Niño years than in the La Niña year.

Direct observations of egg masses on the shore indicates that Lipophrys pholis is a winter and spring spawner in Portuguese waters. The results are compared with those published for the British Isles.

Lipophrys pholis, Linnaeus, 1758, is a very common intertidal fish in the north-eastern Atlantic and in the North Sea. Considerable work has been published concerning its breeding season in British waters (Lebour, 1927; Qasim, 1957; Shackley & King, 1977). The breeding season of the species at the southern limit of its range is almost unknown, and Zander (1986) mentions the period from April to August for the whole species. Based on dates of first appearance of larvae in plankton collected in the Bay of Biscay, Villegas (1981) concluded that breeding should have begun as early as the end of December.

In this report we present data on the spawning season of this blenny based on direct observation of the presence of eggs and/or parental guarding males on the shore.

Data were collected at a site located at Arrábida (38°28′N, 8°59′W), near Senibal, 50 km south of Lisbon, Portugal. In the course of behavioural observations on the breeding males of L. pholis, the area was visited at various intervals during the period 1986 to 1989. The nests were located intertidally in holes in vertical walls. On each visit, the presence of eggs and/or black males inside the nests was registered. Each nest was mapped for inspection in subsequent visits. The results are summarized in Figure 1.

It is clear that in our study area breeding begins as early as December, and has virtually ended in June.

Spatial distribution patterns of black anglerfish, Lophius budegassa were examined in relation to size category, bathymetry, locational covariates, and season. Data were collected during a 2-y period (1998–1999) of quasi-synoptic seasonal sampling using demersal trawl surveys in the Aegean Sea. Generalized additive models (GAMs) were used to test the hypotheses that there was size-related variation in species' habitat associations and that the study area might serve as a nursery ground for black anglerfish. The current results supported these hypotheses. Data are presented that reveal size-dependent aggregation patterns of black anglerfish and an important habitat utilization of the north-eastern Aegean area. The modelled anglerfish abundances showed a strongly non-linear dependence on the explanatory covariates. The different size-classes exhibited significant seasonal effects and preferences for specific regions and distinct water depths. The present results also suggested that 1-y-old fish and potential spawners appeared to concentrate in the vicinity of the same areas. Two main areas of juvenile aggregations were detected in the deeper water regions of the study area on a seabed of around 300 m depth; both emerged in the proximity of the locations of larger fish. The bathymetric distribution of intermediate size anglerfish followed an inverse trend, with fish captured mainly in shallower waters. Results indicated a preferential aggregation of 1-y-old L. budegassa in the study area that is hypothesized to influence the supply of recruits to distant regions of the Aegean Sea.

The myotomes in yolk-sac larvae of the Atlantic herring (Clupea harengus: Teleostei) contain a single layer of small-diameter superficial muscle fibres surrounding an inner mass of around 280 larger-diameter muscle fibres. The fraction of muscle fibre volume occupied by mitochondria is dependent on temperature, and in larvae reared at 8°C was 41% for the superficial fibres, and 25% for the inner muscle fibres. The inner muscle fibres of larvae share some myofibrillar proteins with adult white muscle, but contain unique isoforms of myosin heavy chains, troponin T, troponin I and myosin light chain 2. A monoclonal antibody has been produced which is specific to myosin light chain 3 (MLC3). Immunocytochemical studies have shown that the expression of MLC3 is switched off in the superficial muscle fibres at the start of metamorphosis when larvae reach 28–30 mm total length (TL). Metamorphosis to the juvenile stage is complete in fish 35–40 mm TL and is also associated with the development of gill filaments and the production of presumptive slow muscle fibres which form externally to the larval superficial muscle fibres in the region of the lateral line nerve.

the strontium (sr) and calcium (ca) concentrations in the otoliths of the skipjack tuna katsuwonus pelamis collected in the western pacific ocean were examined by wavelength dispersive x-ray spectrometry on an electron microprobe. otolith sr:ca ratios of the tunas collected off the marshall islands in the tropical waters were constant over the life history transect of the otolith. in contrast, ratios in most tunas collected off sanriku in the temperate waters in october fluctuated from low to high at 1100–1800 μm from the core. a similar fluctuation of otolith sr:ca ratio from low to high was found in a skipjack tuna that was tagged and released off sanriku, and then recaptured off the palau islands. therefore, at least two life history patterns of the skipjack tunas, of global migration toward northern temperate regions and local residence in tropical spawning grounds, are suggested by specimens collected in the western pacific ocean.

The distribution of Laminaria ochroleuca along the south-west coast of England and the Isles of Stilly is brought up to date. The pattern of distribution is discussed with reference to certain factors controlling the ‘ performance’ and success of the species on the northernmost edge of its range. The performance of individuals of the species (measured as net stipe production) sampled from populations growing on the coast of south-west England is compared with populations from north-west Spain, where it is growing in the centre of its geographical range.

The degree of exposure to direct onshore wave action appears to govern the upper limit of its bathymetric range as well as its distribution along the south-west coast of England.

It was found possible to age this species using the method and precautions described by Kain for Laminaria hyperborea.

The stipe material sampled from the English populations had a higher ash content per gram dry weight and a higher calorific content per gram of organic material than that from the Spanish populations.

Individuals from the English population had a lower weight per unit length of stipe in all age-classes than those from Spain.

It is suggested that incident radiation may be a more important factor than temperature in controlling the northward limit of the species.