Normal Sea Research Articles

Large-Scale Atmospheric Circulation Features of Warm and Cold Episodes in the Tropical Pacific

Ship observations of sea surface temperature (SST), sea level pressure and surface wind, and satellite measurements of outgoing longwave radiation (OLR) (an indicator of deep tropical convection) are used to describe the large-scale atmospheric circulation over the tropical Pacific during composite warm and cold episodes. Results are based on linear regression analysis between the circulation parameters and an index of SST in the tropical Pacific during the period 1946–85 (1974–89 for OLR). Warm episodes along the Peru coast (i.e., El Niño events) and basin-wide warmings associated with the Southern Oscillation are examined separately. Charts of the total as well as anomalous fields of SST, sea level pressure, surface wind and OLR for both warm and cold episodes are presented. SST and surface wind anomalies associated with warm episodes are consistent with the results of Rasmusson and Carpenter (1982). El Niño events are characterized by strong positive SST anomalies along the coasts of Ecuador and Peru and along the equator eastward of 130°W, and by an equatorward expansion and intensification of the Inter Tropical Convergence Zone (ITCZ) over the eastern Pacific. Basin-wide warm episodes exhibit positive SST anomalies along the equator eastward of 170°E, a southward expansion and intensification of the ITCZ, and an eastward shift and strengthening of the Indonesian convective zone. The movements of the precipitation zones are in good agreement with anomalous large scale surface wind convergence, Meridional wind anomalies dominate the anomalous surface convergence throughout the tropical Pacific. Surface winds are consistent with the sea level pressure distribution, with down-gradient flow near the equator, and with Ekman balance in the subtropics. A center of below normal sea level pressure over the equatorial eastern Pacific, distinct from the negative pressure anomalies over the subtropical southeast Pacific, is observed during basin-wide warm episodes. This equatorial feature is highly correlated with local SST and appears to be a boundary layer phenomenon. There is a net increase in deep convection over the tropical Pacific during warm episodes. Enhanced convection in the ITCZ during warm years is not accompanied by a net increase in surface wind convergence. A comparison between precipitation and surface wind convergence suggests that moisture convergence extends through a deeper layer in the equatorial western Pacific than in the ITCZ over the eastern Pacific. The contrasting distributions of surface relative humidity, total cloudiness and air-sea temperature difference over the eastern tropical Pacific during basin-wide warm and cold episodes are described in the context of boundary layer processes.

Variation in Pacific Hake (Merluccius productus) Summer Length-at-Age Near Southern Vancouver Island and Its Relationship to Fishing and Oceanography

Male and female Pacific hake (Merluccius productus) sampled in summer off southern Vancouver Island since 1976 show a general decline, plus marked variability, in mean lengths-at-age. Multiple regression analysis related the length-at-age pattern to von Bertalanffy and density-dependent growth, length-selective fishing mortalities, and a suite of oceanographic covariates (sea level height, temperature, and salinity anomalies). Because offshore Pacific hake migrate annually between southern California and British Columbia, with larger fish migrating further north, we deduce that the summer fishery in Canadian waters selectively removes the larger hake each year causing a decline over time in mean lengths-at-age. Apart from the general decline, oceanographic factors explained most interannual variability in mean lengths-at-age. Specifically, mean lengths-at-age were generally smaller in years of above normal sea level height and temperature, and below normal salinity. Sea level anomalies in particular have been associated with the relative strength of the alongshore currents within the coastal upwelling domain; thus, we argue that stronger northward (or weaker southward) flows assist the northward migration of hake. Consequently, in years of higher than normal sea level, such as during major El Niño–Southern Oscillation (ENSO) events, more smaller hake arrive off Vancouver Island in summer resulting in lower mean lengths-at-age.

On the dip angle of subducting plates

An approximate analytic model to study the thermal structure of a subducting plate with finite length has been developed. The model is able to take into consideration the effects of a moving front edge and adiabatic compression of slab material. Based on this model, torque balance upon a descending slab is examined, and the resultant implications to the evolution of slab dip angles are investigated. Thermal structure within a descending slab of finite length is found to be similar to that predicted by a steady state assumption except near the slab tip. The effect of the leading edge is felt only within a distance equivalent to the slab thickness. Away from this region, slab temperature is largely dependent on the subduction velocity, the distance from the surface and the initial temperature profile of the plate. On the basis of this analytic thermal model, gravitational torques acting on subducting slabs can be evaluated for a complete range of dip angles. A comparison with field observations suggests that short slabs (i.e. slabs with penetration depth ≤ 400 km) are likely under torque equilibrium at present. For slabs that have penetrated the olivine-spinel phase boundary at about 400 km depth, the increase of gravitational torque due to the upward deformation of the phase boundary forces the slabs to move away from equilibrium. As a result, long slabs are speculated to be transient at present, rotating towards steeper dip angles. This transient behavior is likely to cause the mantle wedge to be pulled downward, and may explain the observed deeper bathymetry within many back-arc basins relative to normal sea floors of the same age.

The contractility of elongated microvilli in early sea urchin embryos.

Elongated microvilli attach the early sea urchin embryo to the fertilization envelope and support it in a concentric position within the perivitelline space. The contractility of the elongated microvilli was demonstrated in several ways. (1) During normal cleavage, these microvilli change their length to adapt to the change in shape and numbers of blastomeres. (2) When treated with calcium-free sea water, embryos become eccentrically located and the microvilli extend further than normal on one side; when returned to normal sea water, the embryos become centered again. (3) Several agents cause the fertilization envelope to become higher and thinner than normal and the elongated microvilli to extend correspondingly if treated within ten min after fertilization. In some cases, both elongated microvilli and fertilization envelope return to normal size when returned to normal sea water. (4) Fertilization in a papain solution causes the elongated microvilli and the fertilization envelope to contract to the surface of the embryo. (5) Refertilization after the papain-induced contraction can bring about the elongation of these microvilli and the elevation of the fertilization envelope a second time. It was also shown that elongated microvilli are extended immediately upon fertilization, at the same time as the short microvilli. The firm adherence of the tips of elongated microvilli to the fertilization envelope by means of extracellular matrix fibers is shown in a high voltage electron microscope stereoimage. This allows us to understand why it is that when the elongated microvilli extend or contract, the fertilization envelope also extends and contracts accordingly.

Geochemistry of lake waters of Pulicat, India

Pulicat Lake, which is a shallow depression bordering the E Coast of India, represents the coastal waters having transitional characters between terrestrial and deep sea waters. The geochemical characterisation of major elements in Pulicat lake is discussed. It has been observed that the concentrations of different constituents (physical and chemical) in Pulicat lake waters are much higher during dry season and lower in monsson season than the normal sea waters.

Model studies of the motion response of a damaged four column semisubmersible in regular and irregular waves

A brief review of the stability requirements of semisubmersibles is presented. Results of the dynamic response of a damaged, twin pontoon, four column semisubmersible at a scale of 1:100 are discussed. The tests involved both regular and irregular waves with the model oriented in head, beam and quartering directions for both intact as well as damage conditions. Four damage conditions representing partial damage to one column were simulated: two in windward (positive) direction and two in leeward (negative). The “light damage” condition represented about 9% flooding of the damaged column, while for the “moderate damage” the flooding was equivalent to about 18%. For moderate damage conditions, regular wave studies showed that the motions are essentially nonlinear, although for light damage conditions this cannot be said with certainty. Model tests showed certain asymmetry in the motions of the damage semisubmersible with respect to the position of the damaged column. Moderate damage conditions seemed to produce significant subharmonic response of the vessel in a frequency range which is twice the natural frequency of the vessel in heave. These observations were confirmed from the results of irregular wave studies. Irregular wave studies showed that the quartering sea pitch and roll motions in windward damage conditions are as significant as those in the leeward conditions which was not the case for regular wave studies. The energy due to the motion of the semisubmersible was concentrated in the frequency of 0.7–1.3 Hz, which corresponds to the energetic range of the normal sea state. The natural frequencies of the vessel in damaged condition in pitch, roll and heave are higher than the corresponding frequencies in the intact condition of the vessel. The natural frequency in heave, for both intact and damage conditions, is higher than either those of pitch and roll in similar conditions. These natural frequencies in pitch and roll begin to approach that of the natural frequency in heave as the damage condition increases. This is true irrespective of the position of the damaged column or the sea state. The value of the natural frequency in heave itself increased much more slowly with increase in damage condition. It was inferred that the nonlinear wave pressure term played only a minor role in the asymmetry of motions of the vessel, while the mooring characteristics had a more dominant influence.

Organization of a phyllobranchiate gill from the green shore crab Carcinus maenas (Crustacea, Decapoda)

The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated cells contain mitochondria and interdigitate with the bodies and processes of adjacent cells. Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.

Dermatan sulfate formation in gastrulae of the sea urchin Clypeaster japonicus.

Gastrullation of sea urchin embryos is arrested in sulfate-free sea water. This developmental arrest has been considered to be due to lack of sulfation of glycosaminoglycans in the extracellular matrix of the embryos. In the present study, we characterized a dermatan sulfate type component formed in gastrula-stage embryos of the sea urchin Clypeaster japonicus and examined the effects of sulfate deprivation on the formation. Glycosamino-glycans were prepared from gastrula-stage embryos incubated with [3H]acetate in normal and sulfate-free sea water. Enzymatic analyses indicated that embryos formed a glycosaminoglycan of the dermatan sulfate type which contained an N-acetylgalactosamine-6-sulfate-containing disaccharide as a major unit, plus a minor unidentified component. Under sulfate-free conditions, embryos formed an under-sulfated chondroitin/dermatan sulfate copolymer which mainly consisted of non-sulfate, glucuronic acid-containing (chondroitin) disaccharide units. These results suggest that sulfate deprivation diminishes not only the degree of sulfation but also the formation of L-iduronic acid-containing (dermatan) disaccharide units in dermatan sulfate in sea urchin embryos.

Physiological inducers of the acrosome reaction

This article reviews recent studies on physiological inducers of the acrosome reaction in starfish. Upon encountering the jelly coat of eggs, starfish sperm undergo the acrosome reaction in response to a cooperation of three jelly components: a sulfated glycoprotein named acrosome reaction-inducing substance (ARIS), a group of steroidal saponins named Co-ARIS, and an oligopeptide presumably having an activity to increase the intracellular pH of sperm. ARIS induces the acrosome reaction in high Ca 2+ or high pH sea water. In normal sea water, both ARIS and Co-ARIS are required for the induction. In addition to ARIS and Co-ARIS, a third jelly component, the oligopeptide, is necessary to mimic the full capacity of the jelly coat to induce the acrosome reaction. ARIS and Co-ARIS cooperatively increase the intracellular Ca 2+ by stimulating Ca 2+ channels, while the oligopeptide increases the intracellular pH by stimulating Na +/H + exchange systems. When sperm meet the eggs, both changes are simultaneously achieved in them and thus they undergo the acrosome reaction.

Fertilization envelope assembly in sea urchin eggs inseminated in Cl- deficient sea water: I. Morphological effects.

Elevation and hardening of the fertilization envelope (FE) occur within 15 min following insemination of the sea urchin egg. When chloride ions were replaced in the media with various anion substitutes, including methyl sulfonate, nitrates, bromide, and isethionate, the fertilization envelope failed to harden and collapsed back to the surface of the egg of Lytechinus variegatus, L. pictus, and Strongylocentrotus purpuratus. At the light microscopy level, the collapse of the envelope was accompanied by a decrease in birefringence, compared with controls. When examined with electron microscopy, the FEs of eggs inseminated in reduced Cl- solutions failed to transform from an amorphous layer into the more robust laminar structure observed around eggs incubated in normal sea water. Furthermore, in the case of S. purpuratus, the I-T transformation of the FE did not occur. When transfer of the inseminated eggs from the Cl- -deficient sea water to normal sea water was carried out before 10 min elapsed, the envelope did not collapse, and the birefringence of the envelope was similar to that of controls. Partial envelope collapse was also observed in a dose-dependent manner, varying with the concentration of the Cl- in the sea water solution. The results suggest that lack of Cl- in the media may interfere with proper fertilization envelope assembly. Possible mechanisms, including proper incorporation of the cortical granule exudate into the nascent envelope structure, are discussed.

Significance of an Increase of Intracellular Adenosine Concentration for Dormancy in Starfish Blastulae: (starfish embryos/blastula/adenosine/dormancy).

Adenosine at concentrations greater than 6 μg/ml halted embryonic development of the starfish Asterina pectinifera specifically at the 256-cell stage which corresponds to the onset of blastulation. When a fertilized egg was cultured continuously in sea water containing adenosine from fertilization, a gradual increase in intracellular concentrations of free adenosine was observed before a cessation of development took place. On the other hand, intracellular concentrations of ATP, ADP and AMP in the embryo cultured in sea water containing adenosine were nearly the same as those of an embryo cultured in sea water without adenosine. By returning the development-arrested embryo to normal sea water the embyro developed normally to the bipinnaria stage accompanied by a gradual decrease in the intracellular cencentration of adenosine. Treatment of fertilized eggs with 9-β-d-arabinofuranosyl-9H-purine-6-amine (25 μg/ml) or 2'-deoxyadenosine (10 μg/ml) halted development specifically before the onset of blastulation in an irreversible manner. Embryos treated with 3'-deoxyadenosine (50 μg/ml) shortly after fertilization developed to healthy blastulae but hatching never occurred. These results exclude the possibilities that the action of adenosine is mediated by the inhibition of DNA synthesis or RNA polyadenylylation.

Adenosine induces dormancy in starfish blastulae

External application of 50 micrograms ml-1 adenosine inhibits development of the starfish Asterina pectinifera at the 256-cell stage when all the embryonic cells differentiate to epithelial cells. Intracellular concentration of adenosine in the adenosine-treated embryo is 2.7 times higher than those of the normal embryo whereas the contents of ATP, ADP, AMP and adenosine 3',5'-monophosphate are the same for both embryos. Adenosine causes more than 95% reduction in the rate of protein, DNA and RNA syntheses. By returning the embryo to normal sea water, macromolecular synthesis restarts and the embryo develops to the bipinnaria stage.

Isolation and Characterization of Marine Caulobacters and Assessment of Their Potential for Genetic Experimentation

A total of 25 marine caulobacters were isolated from littoral marine sources. Several aspects of their physiology and morphology were examined, as well as their suitability for genetic manipulation in laboratory cultivation. Caulobacters were readily isolated from all sources, including samples from areas containing pollution-related organic compounds. All isolates grew best in media containing seawater, but eight strains grew if sea salts were replaced with NaCl alone, three strains grew at 1/10 the normal sea salt concentration, and one isolate grew, albeit poorly, in freshwater medium. Of the marine isolates, 12 strains grew under anaerobic conditions, indicating that some caulobacters are not obligately aerobic bacteria, as they are currently categorized. Although some freshwater caulobacters are able to oxidize manganese, this capability was not found in these marine caulobacters. Of the marine isolates, 10 strains were resistant to mercury chloride concentrations 10- to 20-fold greater than that tolerated by sensitive bacteria. However, a mercury reductase gene comparable with that found in R100-type plasmids was not detected by gene hybridization. With respect to the potential for genetic experimentation, most strains grew rapidly (3- to 4-h generation time at 30 degrees C), producing colonies on solid media in 2 to 3 days. The isolates were sensitive to antibiotics commonly used in recombinant DNA experiments, and spontaneous drug-resistant mutants were selectable. Conjugal transfer of plasmids from Escherichia coli to several marine caulobacters was demonstrated for four broad-host-range plasmid incompatibility groups, by using both self-transmissible plasmids and cloning-oriented plasmids that require a helper plasmid. Conjugal transfer of broad-host-range plasmids between freshwater and marine caulobacters was also demonstrated in both directions. Native plasmids of approximately 100- to 150-kilobase sizes were found in 2 of the 25 marine Caulobacter strains. The native plasmids were present in relatively high copy number and appeared stable in laboratory culture. In short, the marine caulobacters appeared appropriate as candidates for genetic manipulation and the expression of selected genes in the marine environment.

Messinian Paleomorphological and Sedimentological Characteristics from a 3-D Survey in Tarraco Concession Area (Spanish Mediterranean Sea): ABSTRACT

Characteristics of the Messinian unconformity have been extracted with great detail from a 3-D seismic survey shot in the Tarraco concession area, offshore the Ebro delta. Paleomorphological features in combination with well data confirm that, during the Messinian, sea level dropped rapidly and substantially the magnitude of which is estimated as being at least 2,000 m. The sea level drop resulted in a marked relief cut into the sub-Messinian shelf-and-slope sequence under subaerial conditions. In thalweg positions of paleovalleys, a residual deposit of cemented conglomerates has been observed. Outstanding high reflection amplitudes are associated with these sediments. The distribution pattern of the amplitude anomaly clearly shows fluvial patterns. The final return to normal global sea level, as well as sea level fluctuations during the Messinian, must have been very rapid, as indicated by the apparent lack of intermediate sedimentation between Messinian deposits and overlying deep marine strata.

Calcium‐activated inward spike after‐currents in bursting neurone R15 of Aplysia.

1. Slow inward and outward after-currents follow action potentials in the bursting pacemaker neurone, R 15, of Aplysia californica. These experiments were performed to examine the role of axo-dendritic calcium influx in activating these after currents. 2. Depolarizing voltage-clamp commands issued at the soma were used to elicit the after-currents. The earlier inward depolarizing after-current of DAC was followed by the hyperpolarizing after-current or HAC. The DAC and HAC appeared at a threshold following depolarizing commands in normal sea water, presumably due to triggering of action potentials in inadequately space-clamped axon. In 100 microM-tetrodotoxin (TTX), the after-currents were graded, increasing gradually in amplitude with increasing voltage or duration of the command. 3. After-current amplitudes varied with the holding potential through the range tested, -40 to -80 mV. DACs were maximum at -40 to -50 mV and decreased in amplitude with hyperpolarization. HACs were maximum at -40 mV and decreased with hyperpolarization to disappear between -70 and -80 mV. 4. The dependence of after-currents upon intracellular calcium accumulation during the depolarizing command was tested in several ways. Bathing R15 in 0 Ca2+-2 mM-EGTA (ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid) sea water eliminated the after-currents. Bathing in 1 mM-Ca2+ sea water reduced the DAC by 76% and the HAC by 87% following 10 ms long depolarizations to +40 mV. Application of Mn2+ (25 mM) or La3+ (5 mM) blocked the after-currents. Injection of EGTA intracellularly practically eliminated after-currents. Greatly prolonged depolarizations were required to elicit them after EGTA injection. Substitution of Ba2+ for Ca2+ also eliminated after-currents. 5. Sodium-free sea water eliminated the DAC. The HAC following brief (less than 30 ms) depolarizing commands was also eliminated in zero sodium, although longer commands were followed by an outward tail current. 6. Although the after-currents seemed dependent upon calcium influx, they were not suppressed by depolarizing commands whose voltage exceeded the calcium equilibrium potential at the soma as indicated by suppression of the calcium-activated potassium current, or IK(Ca), observed during the depolarization. However, if the extracellular calcium was lowered to 1 mM, large depolarizations did suppress the DAC. 7. Dopamine blocked the after-currents when applied to the axo-dendritic area but not when applied to the soma. Similarly, synaptic inhibition of long duration blocked the after-currents.(ABSTRACT TRUNCATED AT 400 WORDS)

Sedimentary Mounds and Washout Depressions from the Middle Ordovician Limestone, Ottawa Valley, Canada

ABSTRACT Small elliptical mounds and depressions (about 1 m long) occur on and within a bed of fine-grained Middle Ordovician limestone in the Ottawa Valley, Canada. Both the mounds and the bottoms of the depressions contain abundant fossils in contrast to the surrounding bed, which is essentially barren. The mounds and depressions formed in the outer and deepest part of a quiet tropical marine lagoon, behind a carbonate bank, where bottom conditions were normally anoxic. An unusually diverse and abundant fauna lived on the bottom just prior to deposition of the bed containing the mounds and depressions, indicating an abnormally high oxygen concentration at the sediment/water interface at the time. As bottom conditions deteriorated, many of the species survived only on the mounds, which had fo med by the trapping and holding of sediment by large branching bryozoans. The suspension-feeding fauna that flourished on the mounds, slightly above the barren sea floor, implies a location at the interface between the oxygenated normal sea water and a bottom lens of anoxic water of somewhat higher salinity. The depressions are washout features that formed when sediment was eroded from the mounds.

Paleoenvironmental and Source Rock Assessment of Black Shales of Pennsylvanian Age, Powder River and Northern Denver Basins: ABSTRACT

Thin Middle Pennsylvanian (Desmoinesian) organic-rich black shales (cumulative thickness < 50 ft) underlie much of the northern Denver basin and southeastern Powder River basin. In the Powder River basin, these shales are part of the middle member of the Minnelusa Formation. During Desmoinesian time, the present area of the southeastern Powder River basin and Nebraska was a shallow, at times highly saline, restricted sea. In contrast, in the present area of northeastern Colorado, black shales were deposited in a marine environment with normal salinity that was probably continuous with the Mid-Continent Pennsylvanian sea. Assessment of the paleoenvironment has been carried out using organic geochemical parameters. Shales deposited in the restricted basin setting contain abundant porphyrins (25,000-30,000 ppm relative to total extractable organic matter) and significant quantities of aryl isoprenoids. The aryl isoprenoid compounds (1) are evidence for the presence of the sulfur bacteria families Chlorobiaceae and possibly Chromatiaceae and (2) indicate that euxinic conditions existed in the water column. High ratios of sulfur to carbon in the shales support this interpretation. In contrast, extracts from black shale in the normal sea to the south contain lower porphyrin concentrations (generally less than 1000 ppm) and aryl isoprenoids are minor constituents ormore » are absent. Sulfur/carbon ratios in these latter shales are similar to those observed for normal marine shales (that is, not euxinic conditions). Other paleoenvironmental indicators (sterane composition, alkane distribution) are consistent with these observations. Bulk organic matter in the black shales from both environments is type II and has good source potential for generation of liquid hydrocarbons during catagenesis. Pyrolysis yields of 50 kg/MT (50,000 ppm) are common, and in some shales, yield is 100 kg/MT (100,000 ppm).« less

Calcium activation of macrocilia in the ctenophoreBero�

1. Macrocilia on the lips of the ctenophore Beroë are usually quiescent, but can be activated to beat rapidly and continuously by various stimuli. 2. During feeding, macrocilia beat actively and serve to spread the lips of Beroë over its prey. 3. Vigorous, repetitive mechanical stimulation of the lips evokes widespread activation of macrocilia via a pathway that is probably neural. 4. Extracellular electrical stimulation (DC or bipolar pulse-trains) elicits immediate activation of macrocilia on lip pieces, but not on dissociated cells. 5. Macrocilia on lip pieces are activated to beat by high KCl artificial sea water (ASW), but not by high KCl Ca-free ASW. Continuous beating for long periods is also elicited by high Ca ASW or Mg-free ASW, but not by Ca-Mg-free ASW. Addition of La, Cd, Co or Mn (10 mM) to high KCl ASW reversibly blocks activation. Verapamil, D-600, nifedipine, or BAY K 8644 (10 microM) has no effect on KC1-induced activation, but the anticalmodulin drug W-7 (10 microM) reversibly inhibits beating. 6. Mild heat treatment dissociates macrociliary cells from lip tissue. Such isolated macrociliary cells usually beat continuously in normal sea water, and swim in circular paths. Ca-free ASW, or addition of Co or Mn to ASW, inhibits beating of dissociated cells. High KCl ASW activates beating of quiescent, isolated macrociliary cells. 7. Ca-Mg-free ASW inhibits beating of dissociated macrociliary cells, and return to Mg-free ASW activates motility, allowing one to activate macrocilia on isolated cells simply by addition of Ca.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of heavy metals in soft bodies and shell cavity fluids of Crassostrea gigas.

A number of oysters were collected at the intertidal zone and kept in ice boxes, from which the specimens were serially picked up over 17 times at the interval of 6 hours for 96 hours. Copper, Zn Fe, Mn and Cd contents in soft bodies and shell cavity fluids were determined. At the same time, nitrogen contents in shell cavity fluids were also determined. Regression and correlation coefficients between the metal and nitrogen contents and the serial times were not significant. Namely, the contents fluctuated independently without regard to the elapsed time. This proved that the preserving method was adequate to confine the metabolic activity of the specimen oysters. Of the total absolute amounts of Cu and Zn in soft bodies and shell cavity fluids, more than 94% distributed in soft bodies, and consequently, less than 1% of the two metals existed in the fluids. Cadmium more than 98%, Mn more than 97% and Fe more than 96% distributed in soft bodies. Although the levels of metal contents in shell cavity fluid were clearly less than those in soft bodies, the levels in the fluids were surprisingly higher than those in normal sea waters. Taking into account the fluctuations of the heavy metal and the nitrogen contents in the shell cavity fluids mentioned above: it was suggested that the pre-concentration in shell cavity fluid through the uptake process of heavy metals is the main factor for the high heavy metal contents in the fluids. Since, for specimens frozen deeply with shell valves, heavy metal contents in shell cavity fluid have been determined for a long time together with those in soft bodies, heavy metal contents of lamellibranchs are estimated somewhat higher than those obtained from fresh specimens.

Development of Sea Urchin Embryos in Artificial Sea Water Containing Br- in Place of Cl- : (sea urchin/spicule formation/Cl- -deficient sea water/Br- ).

In artificial sea water in which the Cl- concentration was reduced to less than 10% of that in normal sea water by its replacement with Br- , sea urchin eggs were fertilized and developed into abnormal plutei following almost the same time schedule as in natural sea water. These embryos had poorly developed spicules, short pluteus arms, somewhat jagged embryo-walls and quasi-normal archenterons. Similar embryos were obtained in another artificial sea water in which 90% of the Cl- concentration in normal sea water was reduced by Br- and 10% by acetate. In artificial sea water, in which either 90% of the Cl- was replaced by Br- or 10% was replaced by acetate, embryos developed into plutei with quasi-normal spicules, pluteus arms and archenterons. These findings indicate that deficiency of Cl- results in somewhat abnormal sea urchin embryos. When cells derived from isolated micromeres, were cultured in these Cl- -deficient artificial sea waters, containing Br- in place of more than 70% of the normal Cl- concentration in sea water, spicule formation was strongly inhibited, but pseudopodial cables were well developed. Thus, external Cl- seems to be necessary for at least normal formation of spicule rods.