Noncovalent bonds are key mechanisms for the cohesion of barnacle (Balanus crenatus) adhesive proteins

Cement of the barnacle species, Balanus crenatus, was isolated and separated by SDS-PAGE. Reductive and nonreductive conditions yielded the same result of six major proteins (in the range up to 100 kDa) occurring as two triplets. A third triplet of lower molecular mass was faintly visible. The presence of a reductive agent had only little impact on the solubility of B. crenatus cement. The strong effect of the denaturing conditions (the presence of SDS and the incubation at elevated temperature) on the solubility of the barnacle cement and the absence of disulfide signals in Raman spectra suggest a complex structure of the barnacle cement noncovalently bound. It can be speculated that this protein complex in its quaternary structure is formed by small subunits and is equivalent to the globular cement structures previously detected.     

Inhibition of attachment of larval barnacles,Balanus amphitrite,by bacterial surface films

Films of bacteria on solid substrata can positively or negatively influence the attachment of marine invertebrate larvae. Effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite Darwin were examined in the laboratory. Bacteria, grown to mid-exponential phase and allowed to adsorb irreversibly to polystyrene petri dishes, attached in densities of 10⁷ cells cm^-2. Assays (22h) were used to compare the effects of adsorbed cells of 18 different bacterial species on larval barnacle attachment. Most of the adsorbed bacteria either inhibited or had no effect on larval attachment compared to clean surfaces. Experiments testing the effect of larval age on barnacle attachment were conducted with six species of bacteria and showed that older larvae attached in higher percentages to clean surfaces and that bacterial films generally inhibited larval attaschment. Both the species of bacteria and the in situ age of the adsorbed bacteria affected barnacle attachment response: older films of Deleya (Pseudomonas) marina were more inhibitory. Bacterial extracellular materials may be involved in the inhibitory process.     

Physiological tolerance predicts species composition at different scales in a barnacle guild

This study examined how the species composition of an intertidal barnacle guild varied according to physical gradients in the environment at small scales governed by microclimates, medium scales of wave exposure and large scales of latitude. Barnacle distributions at small and medium scales were sampled in Ireland between 51°29′ and 52°44′N and 6°50′ and 10°08′W. Sampling on European shores spanned ~18° latitude from 37°05′ to 55°16′N. Barnacle surveys mainly took place in 2003–2004. An index of wave fetch was calculated along the wave exposure gradient using a digital coastline-based model that was supported by a biological exposure scale. A ‘dryness’ index was defined according to mean monthly wind speed, fetch along the average wind direction and mean monthly air or sea surface temperatures for 2 years (January 2001–December 2002) which is the period when the most recent adults in the barnacle community would have settled and grown to adulthood. The proportion of the dry-loving barnacle Chthamalus montagui Southward increased within the barnacle guild at all scales as the habitat became warmer and drier. Barnacle densities were high in all habitats, mean densities ranged from a minimum of 4.16 cm⁻² on moderately exposed shores to a maximum of 6.27 cm⁻² in sunlit or south-facing microclimates. Percentage cover of barnacles across the gradient of latitudes was usually >70%. The results suggest that the distribution and abundance of interacting barnacle species on European coasts is strongly controlled by abiotic factors, most likely temperature and desiccation.     

The effect of heavy metals on photosynthesis and loss of cell potassium in two species of marine algae,Dunaliella tertiolecta and Phaeodactylum tricornutum

Observations on sixth-stage nauplius (pre-cyprid) of the barnacle Balanus eberneus Gould treated with L-proline-3,4-H³ suggest that the cement gland in this stage is a functional organ with considerable biosynthetic activity; the activity of the cement glands in the cyprid similarly treated is relatively low, ceasing gradually during, and completely after, metamorphosis. In the early phases of this stage, the glands become highly vacuolated (degenerate), and disappear completely in 3 days. The origin of the cement apparatus in the newly metamorphosed barnacle is discussed.     

Feeding of laboratory-reared larvae of the sea bream Archosargus rhomboidalis (Sparidae)

Feeding by larvae of the sea bream Archosargus rhomboidalis (Linnaeus) was investigated from late September, 1972 to early May, 1973 using laboratory-reared larvae. Fertilized eggs were collected from plankton tows in Biscayne Bay, and the larvae were reared on zooplankton also collected in plankton nets. Techniques were developed to estimate feeding rate, food selection, gross growth efficiency, and daily ration. Daily estimates of these were obtained through 16 days after hatching at rearing temperatures of 23°, 26°, and 29°C. Feeding rate increased exponentially as the larvae grew, and increased as temperature was raised. At 23°C larvae began feeding on Day 3, at 26° and 29°C larvae began feeding on Day 2. Feeding rates at initiation of feeding and on Day 16 were, respectively: 23°C, 7.16 food organisms per larva per hour (flh) and 53.78 flh; 26°C, 7.90 flh and 168.80 flh; 29°C, 17.62 flh and 142.07 flh. Sea bream larvae selected food organisms by size. At initiation of feeding they selected organisms less than 100 m in width. As larvae grew they selected larger organisms and rejected smaller ones. The major food (more than85% of the organisms ingested) was copepod nauplii, copepodites, and copepod adults. Minor food items were barnacle nauplii, tintinnids, invertebrate eggs, and polychaete larvae. Mean values for gross growth efficiency of sea bream larvae ranged from 30.6% at 23°C to 23.9% at 29°C. Mean values for daily ration, expressed as a percentage of larval weight, ranged from 84% at 23°C to 151% at 29°C and tended to decline as the larvae grew.This paper is a contribution from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA     

Rearing Pandalus borealis larvae in the laboratory

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0°C to as high at 6°C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration (VO₂), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA–VO₂) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8°C), developmental stage (I–V at 3°C, I–VII at 5°C and 8°C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO₂ with body mass was faster at 5°C than at 3 or 8°C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5°C than at 3 and 8°C. However, MS did not limit growth in this study, since it explained only 39% of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q₁₀ of all three metabolic variables ranged from 1.6 and 2.2 for stages I–V larvae, except for VO₂ at stage I (3.9) and stage III (2.9).     

Changes in the timing of otolith zone formation in North Sea cod from otolith records: an early indicator of climate-induced temperature stress?

We examine the seasonal variation in otolith increment formation in southern North Sea cod as a means of monitoring how changes in sea temperature over the past 20 years have affected cod in the wild. Seasonal opaque zone formation was related to winter and early spring. Timing of opaque zone formation was not influenced by either temperature or fish length, but increasing age led to slightly earlier but slower opaque zone formation. In contrast, there was a clear shift in the timing of translucent zone formation with temperature. In warm years, translucent growth occurs up to 22 days earlier than in colder periods. Increasing age and smaller size-at-age resulted in an earlier transition from opaque to translucent edge formation. Translucent zone formation appears indicative of increasing metabolic stress, and the earlier onset provides direct evidence of the impact of increasing sea temperatures on wild North Sea cod stocks.     

Laboratory observations on spawning and embryonic development of a blue-ringed octopus

The infratidal zonation of animals in a 35 m deep fjord-like South African estuary is described. The barnacle Balanus amphitrite Darwin and the bivalve Musculus virgiliae Barnard form the uppermost zone and extend to a depth of 9 m. The oyster Crassostrea margaritacea (Lam.) forms a zone between 1 and 3 m depth while the sponge Grantessa ramosa (Haeckel) occurs between 3 and 7 m. The tubiculous polychaete Mercierella enigmatica Fauvel is the only species found below 10 m, and attains a depth of 33 m. In the wet season (summer) the surface salinity dropped to 2 and temperatures rose to 24°C. In the dry season (winter) surface salinity rose to 24 and temperatures dropped to 16°C. Salinity and temperature of deep water (6 to 33 m) were more stable and varied only between 32.5 and 35 and between 19.6° and 20.5°C, respectively. In June, water below 12 m was 50 to 60% saturated with oxygen but this declined to less than 5% saturation in January.     

Role of wax esters in determining buoyancy inHoplostethus atlanticus (Beryciformes: Trachichthyidae)

Specimens of the orange roughyHoplostethus atlanticus were caught at the edge of the Chatham Rise, east of the South Island of New Zealand, in June 1988, during a commercial fishing voyage. Several tissues of the fish were found to contain large quantities of lipid almost entirely as wax esters. These tissues include a fat-invested swimbladder, the skin, skull and spine, and a fat-infiltrated tissue found in the neurocranial cavity. The physical properties of the wax esters have been examined relative to the temperatures that exist where the fish are found. Differential scanning calorimetry and NMR spectroscopy both suggest that at 6°C, the temperature at which the fish are located in the water column, the lipid is partially solid. However, at 14°C, the temperature at the surface where the fish are positively buoyant, the lipid is completely liquid. It is proposed that the increased density of the lipid at 6°C would make the fish neutrally buoyant in its normal habitat. The location of the lipidrich tissues has been examined relative to their possible buoyancy contribution, and a histological examination of the swimbladder has been performed.     

Mass mortality of Strongylocentrotus droebachiensis (Echinodermata: Echinoidea) off Nova Scotia,Canada

A mass mortality of Strongylocentrotus droebachiensis, attributed to disease, was monitored in an echinoiddominated barren ground at Eagle Head on the south-western coast of Nova Scotia, Canada, in 1982. Mortality was 70% in a shallow (3 m) nearshore area, resulting in a loss of echinoid biomass of 2 042 g fresh weight m^-2, and 6% in deeper (7 m, 10 m) offshore areas. Echinoid density, size and nutritional condition (gonad index) were highest in the nearshore area. Survivorship was higher in juveniles (<15 mm diameter) than in adults resulting in the formation of a bimodal size distribution in the nearshore area. Mortality began around early October, near the peak of the annual cycle of seawater temperature (15°C), and was arrested by early December (seawater temperature 7°C) when morbid echinoids appeared to recover. In laboratory experiments, time to morbidity of S. droebachiensis exposed to morbid conspecifics increased exponentially with decreasing temperature (20° to 8°C). There was no survival at 20° and 16°C, 20% survival at 12°C and 100% survival at 8°C after 60 d; suggesting a lower temperature limit (between 12° and 8°C) for possible transmission of a pathogenic agent. Morbid laboratory echinoids from experiments at 16°C, and recovering echinoids collected in the nearshore area in early December, showed 100 and 85% survival respectively at <=8°C, and 0 and 15% survival respectively at 16°C, after 30 d. Time to morbidity was not affected significantly by nutritional condition and was similar for juvenile and adult echinoids. Time to morbidity was greater in echinoids exposed to one or three morbid individuals continuously, or seven morbid individuals for 1 h, relative to higher levels of exposure (up to seven morbid individuals continuously). Recent mass mortalities in S. droebachiensis have occurred in years of record high sea surface temperatures. The extent of mortality is correlated with the magnitude and duration of temperatures above a lower limit.     

Scanning electron microscopy of metamorphosis in four species of barnacles (Cirripedia Thoracica Balanomorpha)

Metamorphosis and early juvenile development was followed in the laboratory in Balanus amphitrite and B. improvisus (family Balanidae) and in Semibalanus balanoides and Elminius modestus (family Archaeobalanidae) from cyprid settlement until 24 h after ecdysis. Stages of development were studied in vivo and with scanning electron microscopy. Events in metamorphosis and early juvenile development are very similar in all four species and can be interpreted in terms of a highly modified moult. Notably, there was no indication whatsoever of the amorphous decorticated settler previously described from metamorphosis of B. amphitrite. The shape of a juvenile barnacle with cirri and incipient shell plates is apparent immediately after the shedding of the cypris carapace, and rudimentary peduncle can be distinguished below the developing wall plates. A basal row of cuticular hairs encircles the peduncle in all species except S. balanoides. These hairs seem to serve a restraining function during early development, when the juvenile barnacle is only attached by the initially secreted cyprid cement. Similarly situated hairs are also present in very young juveniles of the lepadomorph Scalpellum scalpellum. In Semibalanus balanoides nothing indicates that the rostrum originates from the fusion of two latera as previously claimed, since this plate is single as soon as it can be distinguished.     

Temperature tolerance of the estuarine prawn Upogebia africana (Anomura,Crustacea)

Continuous temperature measurements were made in a typical South East African estuary. Mean summer (November to March) temperatures were in the range 19° to 24°C, and in winter (June to August) from 13° to 16°C. Large daily temperature fluctuations of 6° to 10°C occurred in summer; these appear to result from tidal movement of cool sea water into the estuary. In winter, temperature fluctuations were much smaller (3° to 5°C). The burrowing prawn Upogebia africana (Obtmann) was found to have an upper lethal temperature of 29°C in both winter and summer. The resistance time of prawns to temperatures above 30°C was much greater in summer than in winter. It was possible to acclimate winter prawns and increase their resistance time to a level comparable to that of summer individuals. A latent period of 40 h occurred before acclimation effects were detectable. Long-term exposure of prawns to high temperatures did not increase their resistance above that of summer prawns. Water at a temperature above this upper lethal temperature is not pumped through the burrows. This avoidance behaviour considerably increases the ability of U. africana to withstand short-lived temperature extremes.     

Molecular genetic structure suggests limited larval dispersal in grass rockfish,<Emphasis Type="Italic"> Sebastes rastrelliger</Emphasis>

The grass rockfish (Sebastes rastrelliger Jordan and Gilbert, 1880) is a non-migratory, benthic, near shore species distributed along rocky reefs and sea grass beds. It occurs from Baja California, Mexico, to Oregon, USA, spanning the Oregonian and Californian biogeographic provinces. In California this fish receives intense fishing pressure from an expanding and loosely regulated live-fish fishery. It is not known whether or by what mechanism larvae and juveniles are retained locally or dispersed widely during the early life-history phase. Tissue samples of S. rastrelliger were collected between 1996 and 2001 from 405 adult fish at eight sites (42.70°N; 124.50°W to 32.67°N; 117.25°W) spanning the species range. Individuals were surveyed for polymorphism at six microsatellite loci. Allele frequency heterogeneity was not significant among all sites (F_ST=0.001; P=0.18), nor in pairwise comparisons, but a clear correlation of genetic and geographic distance was detected (P=0.019). Fit of genetic and geographic distance was stronger within biogeographic provinces than at a range-wide scale, suggesting that populations north and south of the Point Conception biogeographic boundary are not in equilibrium with respect to migration and genetic drift. Estimates of mean coastal dispersal distances associated with the isolation-by-distance relationship are on the order of 10 km generation^–1. Such limited dispersal in a species with a pelagic early life history suggests active retention mechanisms near the shore. This has important implications for coastal management zones and design of marine reserves.Communicated by J.P. Grassle, New Brunswick     

Are barnacle larvae able to escape from the threat of UV?

Earlier laboratory experiments suggested that environmental levels of UV-B radiation can damage the eyes of barnacle naupliar larvae and impair their phototactic behaviors. However, since barnacle larvae may avoid UV by migrating to deeper waters, it is not known whether such impairment would actually occur under field conditions. For the first time, this study provides both field and laboratory evidences to show that prevailing UV-B in the natural habitat of barnacle larvae could be an important environmental factor affecting natural barnacle populations. We here showed that although barnacle nauplii may avoid UV-B irradiation by downward migration, the amount of UV energy (9.8 × 10⁻⁶ J) received by a naupliar eye during downward migration in the natural water column is within the same order of magnitude as the total energy (7.5 × 10⁻⁶ J) sufficient to cause damages to naupliar eye and impair their phototactic responses. It is possible that solar UV-B prevailing at shallow waters would pose a similar threat to other zooplankton species over large geographic scale.     

Effect of high temperatures on the ultrastructure of Leydig cells in Mytilus galloprovincialis

Individuals of the mussel Mytilus galloprovincialis (L), collected from the Black Sea, were subjected to relatively high temperatures (25°, 28° and 30°C) for 60 h Ultrastructural studies on Leydig cells of the mantle indicated progressive modifications in their structure. Mainly, we established that a continuous decrease of glycogen quantity in the cells took place as the temperature raised, while the lipid content increased, up to 28°C. Between 28° and 30°C the lipid content decreased as a result of a pronounced degradation process. An increase of membrane permeability and the disturbance in the synthesis of mucoproteic secretory granules were observed. It is concluded that for Mytilus galloprovincialis the thermal adaptation zone ranges between 25° and 28°C. 28°C is the upper tolerable limit temperature, while 30°C acts as a lethal temperature.     

Release of zooxanthellae with intact photosynthetic activity by the coral<Emphasis Type="Italic"> Galaxea fascicularis</Emphasis> in response to high temperature stress

Damage to zooxanthellae photosynthetic apparatus has been proposed to be the underlying mechanism of coral bleaching, but how the expulsion of zooxanthellae is triggered is still not understood. The present study compared the photosystem II (PSII) functioning and overall photosynthesis of retained and released zooxanthellae from the reef-building coral Galaxea fascicularis exposed to high temperature stress. The use of pulse-amplitude-modulated (PAM) fluorometry for isolated zooxanthellae was validated and used to measure photosynthesis. There was no significant difference in PSII functioning and the overall photosynthesis between retained zooxanthellae, which were isolated immediately after stress treatment, and those released from the coral exposed to either 30 or 32°C, while the zooxanthellae population released at 28°C showed significantly lower PSII functioning than those retained in the polyps. The release of healthy-looking zooxanthellae by polyps exposed to elevated temperatures was significantly higher than those in the control (28°C). Higher release of undischarged cnidae, indicative of host cell necrosis or detachment, was observed in 32°C treatments. These findings indicate that the zooxanthellae released in 30 or 32°C treatments exhibited normal morphology and intact photosynthetic activity. The present results strongly suggest that the release of zooxanthellae from G. fascicularis at 30 or 32°C is a non-selective process with respect to the zooxanthellar PSII functioning and thus the host seems to be the first partner to be physiologically affected in temperature-induced bleaching.Communicated by T. Ikeda, Hakodate     

Autecological investigation on marine diatoms 3. Thalassiosira nordenskioeldii and Chaetoceros diadema

The temperature range for the best competitive position by growth of Thalassiosira nordenskioeldii Cleve has been determined by comparing generation times. It ranges from-1.5° to 6°C. At these temperatures, especially at lower light intensities, it was one of the fastest growing species, whereas above 6°C many other species grew faster. High light intensities at increasing temperatures became damaging. A flowering of the cold oligo-eurytherm diatom T. nordenskioeldii occurs not only in the upper layers, but can also occur at greater depth simultaneously, because decreasing daylengths at 6°C had the least influence on its growth. Continuous light at 6°C had a positive influence on its growth. The start of the T. nordenskioeldii spring flowering under the Arctic Sea Ice is discussed in connection with the occurrence of enclosed marine diatoms in Polar Sea Ice. The influence of the winter temperature on the spring flowering of the North Sea, the southern border for flowerings of T. nordenskioeldii, is discussed. For Chaetoceros diadema (Ehrenberg) Gran the best competitive position by growth is reached at-1.5° to about 6°C. It has the best opportunity of reaching high cell numbers at the lowest temperatures of the range. The occurrence of the cold oligo-eurytherm diatom Ch. diadema in plankton samples at temperatures above 10°C need not be incorret, for the species did grow in cultures at 12° and 16°C. The wrong interpretation of the experimentally determined optimum temperature of e.g. T. nordenskioeldii caused a discrepancy between experimental results and field data that does not exist. The question is discussed whether ecologically it is relevant to talk about a temperature optimum. On account of the results of T. nordenskioeldii the question of the adaptation of diatom cultures for the start of the real experiments is discussed.     

Thraustochytrid protists as a component of marine microbial films

Although ubiquitous in the marine environment, the presence and importance of thraustochytrid fungoid protists in primary film formation of freshly immersed surfaces in the sea have not been investigated. We isolated thraustochytrids from surfaces of glass, aluminium, mild steel and fibre glass panels immersed in sea water for 1 to 4 d, but not from those of copper and cupro-nickel. Microscopic examination of the primary film on glass surfaces revealed the presence of thraustochytrids. Thraustochytrids grew to varying population densities on surfaces of glass, aluminium and fibre glass in the laboratory. Scanning electron microscopy of the growth of Ulkenia profunda Gaertner, isolated from the primary film, on surfaces of glass and aluminium suggested that cells of the thraustochytrid attached directly to the surfaces, without producing copious extracellular polysaccharides. The presence of ectoplasmic net elements was not a prerequisite for attachment of cells to surfaces. Cell surface hydrophobicity of the thraustochytrid, as estimated by the MATH assay, might play an important role in adhesion. The presence of thraustochytrid cells on a polystyrene surface markedly induced settlement of barnacle larvae (Balanus amphitrite), as compared to barnacle extract and a control. Received: 26 July 1999 / Accepted: 21 January 2000     

A dispersal model for larvae of the deep sea red crab Geryon quinquedens based upon behavioral regulation of vertical migration in the hatching stage

Behavioral responses to gravity, hydrostatic pressure, and thermoclines are described for Stage I zoeae of the deep sea red crab Geryon quinquedens Smith. Survival and rate of development as a function of temperature is presented for all larval stages. Although temperatures between 10° and 25°C have no direct effect upon survival, development time is five times longer at 10°C than at 25°C. Stage I larvae show strong negative response to gravity. Swimming rate increases with an increase in pressure up to 20 atm above ambient at 11°C, but not at 15°C. Swimming rates at 15°C are higher than those measured at 11°C at each pressure tested. Stage I larvae readily penetrate sharp thermoclines. Potential dispersal ranges of G. quinquedens larvae in the Mid-Atlantic Bight are suggested based on larval behavior, development time, and coastal hydrography. A testable recruitment model is proposed for G. quinquedens.Contribution no. 1365 of the Center for Environmental and Estuarine Studies     

Role of form vision in habitat selection of the grass shrimp Hippolyte californiensis

The caridean shrimp Hippolyte californiensis Holmes locates its host plant, the eel grass Zostera marina, visually, discriminating it on the basis of its form. Using models of the plant, the form-specific sign stimuli optimally releasing the host-selection response were investigated. Shrimps preferentially approached dark forms presented against a lighter background. The more a form contrasted with the background, the higher was its stimulatory value. Shrimps showed differential responses to solid forms of varying shape, preferring a stripe-like rectangle in a vertical orientation. Rectangular forms 50° (visual angle) or more in height and between 12° and 20° in width were maximally stimulating. Patterns of several vertical stripes had a greater releasing value for the approach response than a solid rectangle form of optimal dimensions. The greater the spatial frequency of a striped pattern, the reater was its attractiveness. Shrimps discriminated patterns of stripes whose elements were as small as 2° wide, giving an estimate of their visual acuity. Along with the relative contrast, the most important stimulus parameters of striped patterns are the continuous, straight form of the edges and their vertical orientation. It is postulated that the scototactic response of H. californiensis to relatively large, dark, solid forms is involved in the distant detection of clumps of eel grass. At closer range, the eel grass plants are then discriminated on the basis of the stripelike pattern of the leaves.This study was supported by the Marine Life Research Group of Scripps Institution of Oceanography and represents a portion of a dissertation submitted in partial satisfaction of requirements for the Ph.D. at the University of California, San Diego.