Showing papers in "Journal of the Marine Biological Association of the United Kingdom in 1990"
TL;DR: In the south of the region (Spanish slopes, mooring 118), the upper-slope (water depth 1005 m) flow exhibited a strong vertical structure with the maximum surface inflow occurring in the winter period, and this effect may be wind induced as mentioned in this paper.
Abstract: Slope currents in the Bay of Biscay show a consistent poleward transport but seasonal
trends and vertical current structure appear more variable. Indeed more long term records are required to establish seasonal trends firmly.In the south of the region (Spanish slopes, mooring 118), the upper-slope (water depth 1005 m) flow exhibited a strong vertical structure with the maximum surface inflow
occurring in the winter period, and this effect may be wind induced. Satellite imagery
shows that this flow originates from the Iberian slope and that a decreasing along-slope
surface transport occurs along the north Spanish slopes at this time of year.In the north of the region (Porcupine Seabight slopes) vertical structure was again
evident in the upper slope (~1000–m depth) flow. At mooring 114 the flow at mid–depth showed a weakening along-slope flow and an on-slope tendency in the March/April period; a complete reversal in the slope current occurred at mid–depths at the position of mooring 112 during March.In the central region (Celtic and -Armorican slopes) seasonal variations in the upper
layers on the slopes were also present. In this region, the upper–slope transport (2500m depth) reached maximum values of 3–5 Sv in late summer. Upper flows at the rise (mooring 8002) were directed on-slope during the period of maximum upper–slope transport but changed direction in the March/April period.In this region on the Celtic shelf (DB1), the surface flow is in a counter–current sense and wind-induced and so the seasonal variations here reflect seasonality in the wind stress.
327 citations
TL;DR: Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.
Abstract: The swimbladder is recognized as responsible for a major part of the acoustic backscattering from fish. In most fishes it has the function of a buoyancy regulator but in others its main function is rather unclear. Based on methods for exact mapping of the swimbladder shape, observations of deviations from normal appearance and shape are discussed in relation to possible effects on target strength. Evidence for both periodic variations, as from uncompensated vertical migrations, and seasonal variations, caused by the fat cycle and gonad development, are presented.
257 citations
TL;DR: Responsiveness to attacks was very low in the smaller larvae but increased as the otic bulla filled with gas and the lateral line canal developed, and response distances were generally short, only 2–4 cm, with no substantial differences associated with sensory capability.
Abstract: Herring (Clupea harengus L) larvae, ranging from 8–35 mm TL were subjected to predation by juvenile herring and sprats (Sprattus sprattus L) ranging from 80–160 mm TL Responses to attacks and non-threatening encounters were recorded by a TV system operated with infra-red light, which was invisible to both predator and prey Records were made in both light and dark with larvae before and after the otic bullae filled with gas, before and after lateral line canal formation, and before and after chemical ablation of the neuromasts with streptomycinLarvae often responded with a C-start, turning away from the stimulus source, both in dark and light Attacks on larvae occurred only in the light Responsiveness to attacks was very low in the smaller larvae but increased as the otic bulla filled with gas and the lateral line canal developed Larger larvae responded more often to attacks than to non-threatening encounters with predators Vision seems to inhibit unnecessary responses since responsiveness was lower in the light than the dark for non-threatening encounters Response distances were generally short, only 2–4 cm, with no substantial differences associated with sensory capability
135 citations
TL;DR: Ocenebra erinacea females exhibit structural abnormalities of the oviduct as a result of advanced imposex, including absence of a genital papilla and a normal vulva, a deformed bursa copulatrix and the presence of a longitudinal split as discussed by the authors.
Abstract: Imposex (the development of male sex organs on the female) has been studied in the European sting winkle, Ocenebra erinacea. In common with studies of other gonochoristic stenoglossan gastropods, the evidence gained from surveys of the south-west regions of England and Brittany (France) indicates that the phenomenon is a response to tributyltin (TBT) pollution. Close to sources of TBT, O. erinacea females exhibit structural abnormalities of the oviduct as a result of advanced imposex, including absence of a genital papilla and a normal vulva, a deformed bursa copulatrix and the presence of a longitudinal split. Copulation and capsule formation would appear to be inhibited in the worst-affected females. Such curtailment of breeding activity would result in population decline: direct evidence of the extinction of O. erinacea close to harbours, as is known for N. lapillus, is generally wanting for British shores, but the decline of the species in the Bay of Arcachon in France is attributable to TBT pollution.
119 citations
TL;DR: Summer outbreaks of Gyrodinium aureolum in European coastal waters have been described since 1966, with great differences in toxic effects found in in vitro studies, with critical cell densities varying from 6×10 5 cells 1 −1 to 3×10 7 cells 1−1.
Abstract: Summer outbreaks of Gyrodinium aureolum in European coastal waters have been described since 1966 (Braarud & Heimdal, 1970). The coincidence of G. aureolum blooms and observations of noxious effects on fauna (Widdows et al., 1979; Tangen, 1977; Jones et al., 1982; Southgate et al., 1984; Potts & Edwards, 1987; Thain & Watts, 1987) is well documented. However, great differences in toxic effects have been found in in vitro studies (Partensky & Sournia, 1986), with critical cell densities varying from 6×105 cells 1−1 to 3×107 cells 1−1. Production of a lethal agent has been suggested by Turner et al. (1987). More recently, the toxic principle has been identified by Yasumoto et al. (1989).
86 citations
TL;DR: The Plaice (Pleuronectes platessa L) in the southern North Sea use selective tidal stream transport to migrate between their summer feeding grounds and winter spawning grounds as discussed by the authors.
Abstract: Adult plaice (Pleuronectes platessa L.) in the southern North Sea use selective tidal stream transport to migrate between their summer feeding grounds and winter spawning grounds. The fish come up into midwater when the tidal stream is flowing in one direction, but remain on the bottom when it is flowing in the opposite direction. This behaviour can theoretically save energy, which can be used for growth or reproduction. Alternatively, it may provide a transport system by means of which fish that have no ability to navigate over long distances can be conveyed reliably between their feeding grounds and spawning grounds.
84 citations
TL;DR: Feeding tissues containing detoxified metals from a gastropod, bivalve and barnacle to carnivorous gastropods indicates that the food chain progression of material can result in the reduction of the bioavailability of metals.
Abstract: It has been observed previously that the digestive gland of the carnivorous gastropod mollusc, Murex trunculus , does not accumulate metals which occur in high concentration in the digestive gland of its prey, the detritus-feeding gastropod, Cerithium vulgatum It is proposed that mechanisms of metal detoxification which operate in C vulgatum render metals biologically unavailable to M trunculus In the present work, this scheme is tested by feeding tissues containing detoxified metals from a gastropod, bivalve and barnacle to carnivorous gastropods Metals in the prey are accumulated in insoluble granules in the digestive gland of the gastropod, kidney of the bivalve and gut connective tissue of the barnacle These tissues are fed to the carnivores and the granules pass through the entire length of the gut They are egested as clean preparations within the faecal pellets and they still contain the metals introduced by the tissues of the prey This transfer of detoxification between species indicates that the food chain progression of material can result in the reduction of the bioavailability of metals The observations are recorded by scanning electron microscopy and X-ray microanalysis
82 citations
TL;DR: A further 69 recaptures are reported from a tagging study of pelagic sharks initiated in 1970 in the north-east Atlantic, with growth rates of the tagged sharks close to the predicted values for G. galeus.
Abstract: A further 69 recaptures are reported from a tagging study of pelagic sharks initiated in 1970 in the north-east Atlantic. Galeorhinus galeus tagged in England were recaptured in the eastern Atlantic from southern Spain to north-west of Iceland. Among the 42 G. galeus recaptured the longest time at liberty was about 12 years and the greatest distance travelled was 2461 km. Among the 21 Prionace glauca recaptured the l ongest time at liberty was 10.7 years, and seven sharks moved distances between 4362 and 7176 km. One shark tagged in south-west England was recaptured in the South Atlantic off South America. An Isurus oxyrinchus was at liberty for 4–6 years and a Lamna nasus for up to about 13 years. Lamna nasus were recaptured from northern Norway to northern Spain. The growth rates of the tagged sharks were close to the predicted values for G. galeus, were slower for P. glauca and faster for L. nasus.
82 citations
TL;DR: Analysis of evidence of epibiosis in the deep-water portunid crab Bathynectes piperitus in the Benguela upwelling region revealed that both sexes show different moulting patterns and burying behaviour appears to be not very widespread.
Abstract: Incidence of epibiosis has been studied in the deep-water portunid crab Bathynectes piperitus in the Benguela upwelling region. The serpulid polychaete Spirorbis cf. patagonicus, the hydroid Stegopoma plicatile and the stalked cirripede Poecilasma kaempferi were the commonest epizoitic species. Analysis revealed some biological and ecological features of the host population: the species does not have a terminal moult; both sexes show different moulting patterns; sexual maturity occurs at around 35 mm carapace length; there is asynchronous moulting among different sub-populations in different geographical areas; burying behaviour appears to be not very widespread.
74 citations
TL;DR: In early June 1988, an extensive bloom of Phaeocystis sp (29xlO6 cells 1−1) was observed in the eastern Irish Sea along the North Wales coast Chlorophylls, carotenoids, free amino acids, fatty acids, vitamin C, carbon and nitrogen were measured in particles from three size categories as discussed by the authors.
Abstract: In early June 1988, an extensive bloom of Phaeocystis sp (29xlO6 cells 1−1) was observed in the eastern Irish Sea along the North Wales coast Chlorophylls, carotenoids, free amino acids, fatty acids, vitamin C, carbon and nitrogen were measured in particles from three size categories (<22 μm, 22–100 μm and 100–200 μm) at a station 13 miles off the coast line Phaeocystis sp formed 99% of the total particle stock below 22 μm and was characterized by (1) the presence of chlorophyll c3, (2) the dominance of fucoxanthin over 19'- acyloxyfucoxanthins, (3) the presence of C18:5 fatty acid at trace levels and (4) different proportions of amino acids compared to those measured in particles greater than 22 μm These larger particles were dominated by diatoms, dinoflagellates and ciliates The poor nutritional value of Phaeocystis sp for herbivorous zooplankton was characterised by its low content of polyunsaturated fatty acids and vitamin C Comparison between the chemical composition of Phaeocystis sp and copepod faecal pellets showed that the copepods were feeding predominantly on other phytoplankton
71 citations
TL;DR: In Pagurus bernhardus it is suggested that two mechanisms have evolved: larval settlement is encouraged in the littoral zone where gastropod species are diverse and numerous and where the youngest hermits will find growth potentially unrestricted and ‘precocious’ breeding is suggested to be an adaptation enabling hermits to overcome the problems of shell-limitation.
Abstract: Hermit crabs use gastropod shells to protect their bodies and developing eggs; an inadequate supply of shells of the appropriate size will, therefore, adversely affect their growth, fecundity and longevity. Since the supply of shells is commonly limited, mechanisms that help to reduce these adverse effects will be selectively advantageous. In Pagurus bernhardus it is suggested that two mechanisms have evolved in this respect: larval settlement is encouraged in the littoral zone where gastropod species are diverse and numerous and where the youngest hermits will find growth potentially unrestricted; and females breed within their first year of life and at a size substantially below that which could be attained in the shells commonly available to them. This ‘precocious’ breeding is suggested to be an adaptation enabling hermits to overcome the problems of shell-limitation, since it frees females of the need to attain a specific age or size before reproducing - a situation which would be perilous when large shells are scarce. Males of a similar age are freed from competition for the larger shells as a result of this strategy, since the growth of the females is suppressed while they are ovigerous.
TL;DR: Dried Nannochloris sp.
Abstract: Spray-dried Nannochloris sp. and Tetraselmis suecica were fed to larvae of the Manila clam (Tapes philippinarum).These dried diets supported growth equal to, or greater than, their live algal counter-parts, but less than a control diet, a mixture of two algae species of known high nutritional value (Chaetocems calcitrans and T-ISO).Larvae were grown through to metamorphosis on the dried Nannochloris sp. diet in 21 days, compared with 8–11 days with the control diet. Using dried Nannochloris, it was shown that T. philippinarum larvae do not have an essential requirement for long-chain (20 and 22C) polyunsaturated fatty acids, but are able to synthesize them from shorter chain (18C) fatty acids present in the diet. The higher total carbohydrate content of the dried algae was reflected in the larvae feeding on this diet.
TL;DR: In this paper, the age and growth rate of Modiolus modiolus have been studied from acetate peel replicas of polished and etched shell sections, and it was shown that the inner nacreous layer of the shell is a potentially long-lived member of the subtidal benthos.
Abstract: The age and growth rate of Modiolus modiolus have been studied from acetate peel replicas of polished and etched shell sections. Age estimates could be reliably obtained from the alternating patterns of light (summer) and dark (winter) growth lines present in the middle nacreous layer of the shell. Growth lines in the inner nacreous layer, however, generally converged to form blocks of nacre such that the identity of individual lines was lost, whilst in the umbones growth lines were often tightly compressed and difficult to resolve. Data obtained from analyses of the internal growth lines in the middle nacreous layer were used to construct growth curves for several subtidal populations using the von Bertalanffy growth equation. The fastest growth rate was recorded for mussels growing epifaunally on the legs of a drilling platform in the North Sea; these mussels achieved a maximum shell length of 110 mm within ten years. The oldest mussel (from Ling Bank in the northern North Sea) was 48 years old and measured 133 mm in length whilst the largest mussel (from Loch Spelve in western Scotland) was 147 mm long and 38 years old. With the exception of the relatively young population (maximum age 10 years) from the drilling platform, most of the benthic populations studied included mussels in excess of 35 years of age. It is clear, therefore, that M. modiolus is a potentially long-lived member of the subtidal benthos.
TL;DR: Results from the study show that mussels of primary settlement size, 250–400 im shell length, were available to colonise newly deployed pads throughout the investigation, and cohorts of larger mussels recruited to the pads during much of the year.
Abstract: Artificial substrates were used to monitor Mytilus edulis L. settlement on an exposed rocky shore at Ballynahown, on the west coast of Ireland, from August 1984 to September 1985. Flat nylon domestic pan scourers proved to be good collectors of mussel recruits. The appearance of new modes of 300 µn shell length at times of increasing density of colonising mussels indicated direct settlement of mussel larvae from the plankton onto the pads. These modes appeared in September 1984, May 1985 and August 1985. Direct settlement periods followed the known main spawning times of adult mussels at the study site, March-April and July-August, and are consistent with settlement times ob-served on filamentous algae and adult beds on the same shore. Results from the study show that mussels of primary settlement size, 250–400 im shell length, were available to colonise newly deployed pads throughout the investigation. Furthermore, cohorts of larger mussels recruited to the pads during much of the year. The possible source of these recruiting mussels is discussed.
TL;DR: In this article, the authors compared the effectiveness of different chlorophyll extraction techniques and concluded that air drying was the most appropriate preparation method for SEM observation and provided reasonable estimates of microbial composition and abundance.
Abstract: Chlorophyll analysis and methods of direct observation of rock surfaces under the SEM were used to estimate composition and abundance of epilithic microbial taxa. Effectiveness of different chlorophyll extraction techniques was assessed. Extraction from ground and intact rock was compared using both hot methanol and acetone extraction methods. Hot methanol extraction from intact rock provided the most accurate and precise estimates of chlorophyll content. SEM preparation methods were compared. Microbial taxa were counted under the SEM from cryostage, critically point dried and air-dried material. It was concluded that air drying was the most appropriate preparation method for SEM observation. Air drying provides reasonable estimates of microbial composition and abundance and was less time consuming so allowing an adequate number of samples to be analysed. Cumulative species number with sampling effort curves were used to establish minimal sample sizes with respect to estimates of species number. Sequential estimates of mean abundance with increasing sample size were used to determine the effects of increasing sample size on estimates of abundance of the dominant taxa. These estimates were compared at different times of the year and for two different locations. Microbial communities were found to be extremely patchy in distribution. However, sample sizes required to give good estimates of taxa number and abundance were established. These estimates were found to be similar for the main taxa at different times of the year and at different locations.
TL;DR: In this paper, the distribution of doliolids in CPR samples taken in the North Sea in the last three months of 1989 is shown in Figure 1.Doliolid densities were estimated at >100 m−3 for about 112 km of tow between Newcastle and Esbjerg.
Abstract: Doliolids were found in samples taken with a Continuous Plankton Recorder (CPR) in October 1989 between 55°14'N 03°32'E and 55°20'N 06°13'E during a tow between Newcastle and Esbjerg. Densities were estimated at >100 m−3 for about 112 km of tow. A sub-sample of specimens in sufficiently good condition to be reliably identified were referred to Doliolum nationalis Borgert. Substantial numbers of doliolids were found on a CPR tow between Harwich and Gothenburg which passed through the same area in that month and specimens were found nearer to the Danish coast in November and south-west of Helgoland in December. The distribution of doliolids in CPR samples taken in the North Sea in the last three months of 1989 is shown in Figure 1.
TL;DR: An account is given of a flagellated protist isolated from Atlantic sediments at a depth of 1500 m, which forms part of the microbial food web by consuming suspended bacteria.
Abstract: An account is given of a flagellated protist isolated from Atlantic sediments at a depth of 1500 m. The organism forms part of the microbial food web by consuming suspended bacteria. The organism was originally described by Ruinen as Cryptobia libera. On the basis of its ultrastructure, assignment to the genus Cryptobia is regarded as inappropriate, and Jakoba is proposed as a new generic vehicle.
TL;DR: Unusually high densities of juvenile flatfish in some areas of a nursery ground, and complete absences from other areas, were associated with a dense bloom of the colonial alga Phaeocystis pouchetii along the coast of North Wales.
Abstract: Unusually high densities of juvenile flatfish in some areas of a nursery ground, and complete absences from other areas, were associated with a dense bloom of the colonial alga Phaeocystis pouchetii along the coast of North Wales. A possible explanation for these movements, and for the presence of patches of anoxic sediments, is proposed.
TL;DR: The leatherback turtle studied was a male, weighing 916 kg, with a total dorsal length of 291 cm, and is currently the largest leatherback ever recorded, suggesting that arachidonic acid assumes more importance in food chain relationships involving leatherbacks than in other marine food webs such as those involving fish.
Abstract: The leatherback turtle, Dermochelys coriacea (L.) studied was a male, weighing 916 kg, with a total dorsal length of 291 cm. It was beached on the Welsh coast, UK in September 1988 and is currently the largest leatherback ever recorded.Total lipid formed between 87.5 and 95.4% of the dry weight of representative samples of the blubber and 43.0% and 4.9% of the liver and pectoral muscle respectively. High levels of neutral lipid in the liver (79.0% of the total lipid) as well as the blubber (87.6–99.9% of the total lipid) suggest an important energy storage function for these tissues.Overall, with the notable exception of 22:lwll, fatty acids which are found in a putative jellyfish diet of Rhizostoma, Amelia, Cyanea and Chrysaora are also present in the leatherback liver and muscle, blubber and other fatty tissues. Fatty acid 22:lwll is present in the jellyfish samples, but is absent or at trace levels only in the leatherback tissues (0.1–0.3% of the total fatty acids).The polyunsaturated fatty acids of the w3 series 20:5w3, 22:5w3 and 22:6w3 are well represented in leatherback adipose tissues, muscle and liver as well as in the jellyfish examined. The leatherback and jellyfish lipids are therefore marine in character, but are also similar to terrestrial animal lipid in having a high proportion of fatty acids of the w6 series, principally arachidonic acid, 20:4w6. The significant levels of 20:4w6 in jellyfish total lipid (9.7–20.0% of the total fatty acids) and in the leatherback neutral lipid (1.0–10.9% of the total fatty acids) and phospholipid (0.6–15.5% of total fatty acids) fractions of all tissues sampled suggests that arachidonic acid assumes more importance in food chain relationships involving leatherbacks than in other marine food webs such as those involving fish.
TL;DR: In this paper, the authors used scanning electron microscopy to document the relationship of larval shell morphology to development and successfully reared four species with planktotrophic larvae, Crepidula convexa, Littorina obtusata, Busycon canaliculatum and Urosalpinx cinerea.
Abstract: The larval shell of molluscs contains a preserved record of the organism's growth and developmental history. Many investigators have utilized the information recorded in the larval shell morphology to infer mode of development.Marine prosobranch gastropods were collected from intertidal sites from Maine to Florida and were cultured in the laboratory. Scanning electron microscopy was used to document the relationship of larval shell morphology to development. Four species with planktotrophic larvae, Crepidula fornicata, Crepidula plana, Cerithium atratum and Ilyanassa obsoleta, and four species with non-planktotrophic development, Crepidula convexa, Littorina obtusata, Busycon canaliculatum and Urosalpinx cinerea, were successfully reared through metamorphosis.
TL;DR: The reproductive biology of the abyssal seastar Dytaster grandis has been studied in this article, which suggests seasonal reproduction that is related to the seasonal pulse of phytodetritus to the deep-sea floor.
Abstract: Examination of the reproductive biology of the abyssal seastar Dytaster grandis taken at different times of the year in the NE Atlantic suggests seasonal reproduction that is related to the seasonal pulse of phytodetritus to the deep-sea floor. Although this seastar is an omnivore, the availability of this labile organic material may fuel vitellogenesis during the summer and autumn months. The egg size suggests planktotrophic larval development. Spawning occurs in the early part of each year to allow the zygote to develop into a feeding larva to coincide with the downward flux of phytodetritus. Thus the flux of detritus may constitute an environmental forcing pressure at least at two points in the life history of D. grandis.
TL;DR: In this article, it was shown that zinc levels in Anemonia viridis increased markedly at sea-water concentrations exceeding 200 μg I 1, while A. equina exhibited only slightly enhanced tissue levels.
Abstract: Field and experimental observations on sea anemones (Actinaria) Ammonia viridis (Forskal) and Actinia equina (L.) indicated that in both species body zinc concentrations usually ranged between 100 and 200 ug (g dry wt)1 in waters containing up to 200 μg I1 of the metal. At higher dissolved concentrations, as observed in Restronguet Creek, A. equina exhibited only slightly enhanced tissue levels. However, in the laboratory, zinc levels in Anemonia viridis increased markedly at sea-water concentrations exceeding 200 μg I”1. Studies on the uptake of 65Zn-labelled zinc showed that, when the sea-water concentration was increased from 2 to 52 μg 11, both species absorbed the metal and new equilibria appeared to be reached in about a week. At equilibrium, the concentration of zinc in Actinia equina had risen by up to 11%, and in Anemon ia viridis, by up to 28%. About one third of the difference between the amounts absorbed by the two species may be accounted for by zinc accumulated in the symbiotic algae (zooxanthellae) of A. viridis. Short-term (12 h) experiments showed that, although A. viridis absorbed a significant amount of labelled zinc when the concentration increased from 2 to 52 μg I1, uptake was not much greater when the concentration increased from 2 to 202 μg I1. It is postulated that, up to a sea-water concentration of 202 μg I1, the absorption of zinc is dependent on the amount adsorbed at the body surface: saturation of the surface at higher concentrations leads to more direct dependence on the level of dissolved zinc.
TL;DR: It is shown that gastropod muscle proteins can be digested by Gastropod salivary gland enzymes to generate peptides attractive to the hermit crab, Clibanarius vittatus, in field assays.
Abstract: Gastropod shells are essential to most hermit crabs. Shell availability limits hermit crab populations. Shells provide protection and the degree of shell-fit controls crab growth and fecundity. Crabs locate new gastropod shells from a distance under water by molecules released from gastropod flesh during predation events. Here we test the hypothesis that the salivary glands of the predatory gastropod are the source of enzymes that digest muscle proteins and release peptide attractants. We describe the anatomy of both the acinous salivary glands and the tubular accessory salivary glands of Busycon contrarium which are similar to those of B. carica. The salivary gland ducts empty at the mouth, suggesting a role in the primary digestion of food. We show that gastropod muscle proteins, extracted by salt solutions with the ionic strength of sea water and purified by precipitation in low ionic strength can be digested by gastropod salivary gland enzymes to generate peptides attractive to the hermit crab, Clibanarius vittatus, in field assays.
TL;DR: Growth curves fitted to growth ring measurements indicate three contrasting growth strategies amongst the species examined, which generally support recent interpretations of demographic structure reached from studies of size frequencies in samples collected from other areas in the NE Atlantic range of these species.
Abstract: Skeletal growth banding has been studied in the vertebral arm ossicles of the shallowwater brittle stars Ophiothrix fragilis, Amphiura filiformis, A. chiajei, Ophiura ophiura and O.albida collected from near Oban. Scanning electron microscopy of ossicle microstructure show the bands reflect differences in stereom porosity and surface relief on the surface of the wing-like fossae of the ossicle. The evidence supports the interpretation of the bands as annual growth markers, with coarse-pored stereom laid down during periods of active growth in summer/autumn whilst finer-pored stereom, that often forms ‘breaking wave’- like ridges, is formed during periods of slow or negligible skeletal growth during the rest of the year. Growth curves fitted to growth ring measurements indicate three contrasting growth strategies amongst the species examined. These data generally support recent interpretations of demographic structure reached from studies of size frequencies in samples collected from other areas in the NE Atlantic range of these species.
TL;DR: The lipids of leatherbacks exhibit features which are consistent with maintenance of a core temperature above ambient levels when in cool waters, and leatherback adipose tissues show levels of unsaturation in neutral lipid fractions intermediate between those of seals and sheep.
Abstract: Unlike other sea turtles, the leatherback Dermochelys coriacea forages widely in temperate waters during summer and dives to abyssal depths (>1000 m) where temperatures are low. There is strong anatomical plus limited physiological evidence in favour of at least facultative endothermy. The lipids of leatherbacks exhibit features which are consistent with maintenance of a core temperature above ambient levels when in cool waters. The lipid of flipper adipose tissue freezes at a lower temperature than lipids extracted from the blubber lining carapace and plastron. Lipid freezing points in leatherbacks are lower than for tropical caimans or terrestrial sheep, but higher than for lipids taken from the blubber of a grey seal. Leatherback adipose tissues show levels of unsaturation in neutral lipid fractions intermediate between those of seals and sheep.
TL;DR: The mobility and quantity of retinula cell proximal screening pigment, and the liability of the eyes to light-induced damage, were investigated in the Norway lobster, Nephrops norvegicus, obtained from three separate populations from depths of 18, 75, and 135 m.
Abstract: The mobility and quantity of retinula cell proximal screening pigment, and the liability of the eyes to light-induced damage, were investigated in the Norway lobster, Nephrops norvegicus (L.), obtained from three separate populations from depths of 18, 75, and 135 m.During the morning after capture, the migration of the proximal pigment in response to the onset of illumination below the threshold for damage varied between the three populations. In the eyes of deep water N. norvegicus, the proximal screening pigment was located close to or below the basement membrane when dark-adapted and rose to a position midway up the rhabdoms when light-adapted. In the dark-adapted N. norvegicus from shallow water the proximal pigment was located more distally than in eyes of deep water animals. After the onset of illumination, the pigment migrated distally to completely cover the rhabdoms. The amount of retinula cell proximal screening pigment was found to decrease linearly with depth.When dark-adapted individuals from each depth were exposed to light a positive correlation was obtained between the photon fluence rate (PER) and the proportion of the retina damaged. For a given light exposure the amount of damage was highest in animals from deeper water. The PFR causing 25% damage was approximately 1 log unit higher in animals from 18 m compared to those from 135 m.The amount of damage varied with the delay between capture of the animals and exposure to light. When exposed 2 h after capture significant differences between depths were seen but the results were influenced by the incomplete dark adaptation of some specimens.
TL;DR: Ovaries of the common sole were collected prior to, or at the beginning of, spawning from the spawning grounds in the Bristol Channel, indicating that the sole is a determinate spawner and that, at least for this population, an annual potential fecundity can be measured.
Abstract: Ovaries of the common sole (Solea solea (Linnaeus)) were collected prior to, or at the beginning of, spawning from the spawning grounds in the Bristol Channel. Size frequency distributions of oocytes over 100 μm are presented. They clearly show a break in the size frequency distributions, at about 170 μm, indicating that the production of new oocytes to be spawned that season had ceased. It indicates that the sole is a determinate spawner and that, at least for this population, an annual potential fecundity can be measured. Estimated annual fecundity at length of Bristol Channel sole is calculated, and values are compared with those found for sole from the North Sea, eastern English Channel and the Bay of Biscay.
TL;DR: In this article, the authors 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 in Portuguese waters.
Abstract: 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 Arrabida (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.
TL;DR: Thirty-four adult individuals of Loligo forbesi were observed in captivity in a 3 m diameter closed sea-water system on Faial Island, Azores and body patterns in relation to relaxation, stress, shock, feeding, locomotion and aggression were observed.
Abstract: Thirty-four adult individuals of Loligo forbesi (males and females with dorsal mantle lengths from 27–77 cm) were observed in captivity in a 3 m diameter closed sea-water system on Faial Island, Azores. Squids were caught by jigging and were fed with horse mackerel (Trachurus picturatus) and chub mackerel (Scomber japonicus), either alive or dead. The maximum survival was 73 days. Feeding behaviour was dependent upon both the size of prey and its state of preservation;e.g. the squid would eat the head of small fish ( about 35 cm) or a fish poorly preserved.
Seventeen chromatic, 9 postural and 6 movement components of body patterns were observed and described. Conspecific interactions considered to be aggression and dominance were observed among males; no such interactions occurred when one male and two females were kept together. Body patterns in relation to relaxation, stress, shock, feeding, locomotion and aggression are also described.
TL;DR: The net decrease in total lipid in both modes of feeding with this species suggests that annelids, where present, are as important as other invertebrate groups in affecting the flux of lipids through marine food chains.
Abstract: Changes in dietary lipids (fatty acids, sterols and fatty alcohols) during herbivory and coprophagy by the annelid worm Hediste (Nereis) diversicolor (O.F. Muller) were modelled in laboratory feeding experiments. The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory; faeces from the crustacean Neomysis integer (Leach) after feeding on this same alga, were used as the food in coprophagy. Nereis is extremely efficient in its assimilation of dietary lipids and produces faeces with very low fatty acid:sterol (FAST) ratios in both herbivory and coprophagy. The net decrease in total lipid in both modes of feeding with this species suggests that annelids, where present, are as important as other invertebrate groups in affecting the flux of lipids through marine food chains.