Telomere dynamics in the Sydney rock oyster (<Emphasis Type="Italic">Saccostrea glomerata</Emphasis>): an investigation into the effects of age,tissue type,location and time of sampling

Telomere length has been purported as a biomarker for age and could offer a non-lethal method for determining the age of wild-caught individuals. Molluscs, including oysters and abalone, are the basis of important fisheries globally and have been problematic to accurately age. To determine whether telomere length could provide an alternative means of ageing molluscs, we evaluated the relationship between telomere length and age using the commercially important Sydney rock oyster (Saccostrea glomerata). Telomere lengths were estimated from tissues of known age individuals from different age classes, locations and at different sampling times. Telomere length tended to decrease with age only in young oysters less than 18 months old, but no decrease was observed in older oysters aged 2–4 years. Regional and temporal differences in telomere attrition rates were also observed. The relationship between telomere length and age was weak, however, with individuals of identical age varying significantly in their telomere length making it an imprecise age biomarker in oysters.     

Mercury in a northeastern Brazilian mangrove area, a case study: potential of the mangrove oyster Crassostrea rhizophorae as bioindicator for mercury

The Channel of Santa Cruz is a mangrove area in northeastern Brasil 40 km north of Recife. Until 1991 a chlor-alkali factory discharged large amounts of mercury into the main tributary of the channel, the Rio Botafogo. The objective of this study was to assess the potential of the mangrove oyster Crassostrea rhizophorae as a bioindicator for mercury in this area and to examine the influence of condition on mercury concentrations in the oysters. The investigation was carried out in the late rainy season (July to September) 1993, in the rainy season (April to June) 1994 and in the dry season (November/December) 1994. At 11 stations in the channel, mangrove oysters, surface sediments and suspended matter were sampled, representing different compartments of the system. The distribution of mercury in the Channel of Santa Cruz exhibited for all compartments the same distinct spatial pattern with maxima in the Rio Botafogo. Seasonal variations were small and revealed no clear tendencies. In addition, mangrove oysters were transplanted from more contaminated stations to less contaminated stations and vice versa. These experiments were designed to study the oysters' capability to adjust their mercury concentrations to a changing bioavailability of mercury. The transplantation experiments suggest that the oysters are capable to adjust to changing ambient mercury availability within a few months. The transplantation experiments also revealed the importance of condition changes on the mercury concentration of the oysters. This factor should not be ignored during pollution studies. However, condition had apparently no strong influence on the spatial or seasonal mercury variations of the oysters. The mangrove oyster is a suitable bioindicator for long-term changes in mercury availability. Received: 20 August 1997 / Accepted: 15 January 1998     

The tidal rhythm of extracellular digestion and the response to feeding in Ostrea edulis

Under natural conditions, on the shore, there is a tidal rhythm for changes in pH, length, and protein and amylase content of the crystalline style of Ostrea edulis L. When oysters were kept immersed and fed continuously for 2 weeks, in the laboratory, the rhythm of extracellular digestion was lost. Oysters were fed discontinuously for 2 weeks, in the laboratory, with a 6 h-on, 6 h-off feeding regime. During the feeding period, the changes in pH, size, and protein content of the style were similar to the changes observed in the field over the period of high tide. It is our hypothesis that the tidal rhythm of extracellular digestion in Ostrea is not endogenous, but is controlled by feeding activity.     

Metal concentration changes in growing Pacific oysters,Crassostrea gigas,cultivated in Tasmania,Australia

Pacific oyster spat (Crassostrea gigas Thunberg) transferred from the Tamar Estuary to two growing areas in southern Tasmania were monitored for their metal contents over one growing season (1974–1975). Oysters at Pipeclay Lagoon were grown with stick and tray culture while those at Dart Island were cultured with the longline technique. Metal content of the oysters increased with time and the trend was similar to the weight growth curves. Mean dry weights of oysters increased from 0.07 to 1.19 g at Pipeclay Lagoon and from 0.25 to 1.47 g at Dart Island. Metal contents (g) increased at each site, respectively: Fe 57 to 326; 91 to 446; Zn 259 to 6 555; 755 to 5 335; Cd 1.5 to 13.3; 1.9 to 16.3; Cu 26 to 142; 9 to 116; Pb 1.9 to 11.9; 0.6 to 3.8. Concentration curves generally showed a downward trend with time. The relationships of metal concentrations with weight did not differ from sample to sample at a site nor did they differ at one site compared with the other. The only exception was lead, which showed no relationship of concentration with weight at Pipeclay Lagoon and a negative one at Dart Island. It is postulated that higher winter concentrations of metals in the oysters were linked with greater solubility of metal ions in lower salinity water.     

Environmental stress,competition and dominance of Crassostrea virginica near Beaufort,North Carolina,USA

Observations and experiments were made at 2 intertidal areas near Beaufort, North Carolina, USA from May 1977 to July 1978 to determine why the oyster Crassostrea virginica dominated the community in areas protected from wave action but not in areas directly exposed to waves. Barnacles, oysters, the green alga Enteromorpha sp. and the mussel Brachiodontes exustus were the main occupiers of primary space at the mid and low intertidal levels of exposed areas. The intertidal community at the protected site consisted of a mid intertidal occupied by the barnacles Balanus amphitrite and Chthamalus fragilis, and the oyster C. virginica, and a low intertidal dominated by C. virginica. The exposed area was highly variable with high colonization and mortality for all species producing large seasonal changes in structure. The protected site remained constant throughout the year; there was no evidence of further colonization of either barnacles or oysters and mortality was very low. Recolonization experiments, selective removal of species, and growth and survival data demonstrated that C. virginica does not become dominant at exposed locations because (1) the constant wave shock at the ocean site reduces growth and increases mortality of young and adult oysters and (2) oysters are outcompeted by the mussel B. exustus. The monopolization of space by C. virginica at protected sites contrasts with studies north of Cape Hatteras where the abundance of predators produces a more diverse and heterogeneous community. Predation was unimportant in Beaufort because predators were absent at the exposed areas and the oyster drill Urosalpinx cinerea was restricted to the subtidal zone at the protected site. This absence of predators indicates a higher level of environmental stress near Beaufort compared to areas farther north.     

Effects of the polychlorinated biphenyl Aroclor® 1254 on the American oyster Crassostrea virginica

Young oysters (Crassostrea virginica) were continuously exposed to Aroclor^® 1254, a polychlorinated biphenyl (PCB), in flowing, unfiltered seawater. Growth rate (height and in-water weight) was significantly reduced (=0.05) in oysters exposed to 5 g/l (ppb) for 24 weeks. Growth rate was not affected in oysters exposed to 1 ppb for 30 weeks. Mortality was not significant in exposed and control groups. In oysters exposed to 5 ppb, greatest PCB residue (whole body) was 425 mg/kg (ppm), 85,000x the concentration in the water, and less than 0.3 ppm was retained after 28 weeks depuration in PCB-free water. In oysters exposed to 1 ppb, greatest residue was 101 ppm, 101,000x the concentration in the water, and less than 0.2 ppm was retained after 12 weeks depuration. Examination of oysters exposed to 5 ppb of this PCB for pathogenesis revealed atrophy of digestive diverticular epithelium and degeneration of vesicular connective tissues concomitant with leukocytic infiltration, but tissue recovery seemed excellent after 12 weeks depuration.Registered trademark, Monsanto Company, St. Louis, Missouri, USA. Mention of commercial products or trade names does not constitute endorsement by the Environmental Protection Agency.Contribution No. 146, Gulf Breeze Laboratory.     

The ecological energies of growth,respiration and assimilation in the intertidal American oyster Crassostrea virginica

Seasonal variations in the growth, respiration and assimilation of the intertidal oyster Crassostrea virginica (Gmelin) of different sizes were determined. The instantaneous growth rates for intertidal oysters decreased with increasing size and with lower temperatures. Q₁₀ values computed from instantaneous growth rates were approximately 2 during the warm growing season, but were higher in the colder months. Oxygen consumption increased with temperature and body size. A model was developed to predict oxygen consumption at any environmental temperature from 10° to 30°C for oysters ranging in weight from 0.1 to 100.0 g. Q₁₀ values computed from oxygen-consumption rates decreased with increasing temperature and increasing body size. Intertidal oysters utilize a large proportion of their assimilated energy in growth.Supported by a Belle W. Baruch Fellowship in Marine Ecology.     

An exploratory study with the proton microprobe of the ontogenetic distribution of 16 elements in the shell of living oysters (Crassostrea virginica)

Study of the chemical composition of shell of exoskeletonous organisms in the past has required the sacrifice of the organism. Because the beam of the proton microprobe is relatively nondestructive and analyzes the surface layer of the shell, organisms do not have to be killed. The present paper presents results of a preliminary experiment in which distribution of elements (Na to Sr) in shell of living juvenile oysters, Crassostrea virginica (Gmelin), was studied in situ with a proton microprobe at monthly intervals for four months. The relative concentration of 16 elements was measured in the newly deposited prismatic edge of the right valve of three oysters reared in controlled laboratory conditions. Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, and Sr were detected in concentrations as low as a few parts per million relative to the concentration of standards added to pure CaCO₃. Concentration of elements varied nominally among shells of the three individual oysters and in their successive ontogenetic stages. Fluctuations in concentration of Na, Mg, S, Cl, Ca, Mn, Fe, Cu, and Zn were generally similar in the two normally growing oysters, but differed from those in the oyster that stopped growing. Trends in concentration of Al, Si, and Sr were similar in the three oysters: those of Br were variable. Relative concentrations of Na, Cl, S, Mn, Fe, and Zn increased slightly with age of oysters, that of the other elements stayed relatively constant. Concentration of most elements was higher in shell than in seawater. Variable concentrations, especially of Na, Cl, and Si in valve edges, tend to support the hypothesis of earlier workers that separate mineral phases are present as impurities entrapped within the shell during calcification.     

Occurrence of the Kumamoto oyster Crassostrea sikamea in the Ariake Sea, Japan

The Kumamoto oyster Crassostrea sikamea is distinguished from the closely related Pacific oyster C. gigas by concordant differences in 16S rDNA, allozymes, and a one-way gametic incompatibility. After repeated failures to find this oyster in its native habitat, we speculated in 1994 that “the Kumamoto oyster may be extinct in Japan”. In September 1996, we sampled small, deep-cupped oysters from the Ariake Sea and typed these for 16S rDNA and ITS-1 DNA markers previously shown to be diagnostic for the three most common oysters in the Ariake Sea, C. gigas, C. sikamea and  C. ariakensis. Our earlier suggestion of the demise of  C. sikamea proved incorrect. Of the 256 oysters sampled, 181 (71%) were  C. gigas, 53 (21%) were C. sikamea, and 22 (9%) were  C. ariakensis; no interspecific hybrids were observed. The distributions of C. sikamea and  C. ariakensis are clumped in the Ariake Sea:  C. sikamea occurs on the eastern and northern shores,  C. ariakensis occurs only in the northern part. These results emphasize the value of molecular markers for discriminating these morphologically plastic species both in the field and in aquaculture. Received 6 July 1998 / Accepted 8 October 1998     

Depuration of twelve trace metals in tissues of the oysters Crassostrea gigas and C. virginica

The depuration of 12 trace metals in the mantle, gill, digestive gland, and kidney of Crassostrea gigas and C. virginica was investigated under natural field conditions; oysters from a relatively contaminated environment (Redwood Creek in south San Francisco Bay) were transplanted to a relatively clean environment (Tomales Bay). In the transplanted oysters, the digestive gland and kidney depurated Cd, Cu, Hg, Ag, and Zn more readily than the mantle and gill. Other trace metals As, Fe, Mn, Ni and Se showed varying depuration patterns. The results for Cr and Pb were inconclusive, since initial concentrations were too low to follow any losses. Interspecific differences in trace metal depuration were observed. Biological half-lives for most trace metals were on the order of 23 to 60 d for C. gigas and on the order of 70 to 180 d for C. virginica.     

Time-course uptake and elimination of benzo(a)pyrene and its damage to reproduction and ensuing reproductive outputs of Pacific oyster, <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

The time-course of uptake and elimination of benzo(a)pyrene (BaP) for the Pacific oyster, Crassostrea gigas and reproduction damage and reproductive outputs were studied. Sexually immature C. gigas broodstock were fed for 28 days with live algae grown in four BaP solutions of 0, 50, 500, and 5,000 μg L⁻¹ (hereafter, control, 50, 500, and 5,000 oysters) and were subsequently conditioned to maturation by a feeding with BaP-free live algae under temperature manipulation for another 28 days. The 5,000 μg L⁻¹ oysters gained a steady state concentration, around 30,000 ng g⁻¹ d.w. for digestive gland, a week earlier compared to the 500 μg L⁻¹ oysters. The earlier gain or longer persistence of the steady state concentration influenced elimination of BaP, with an eliminating trend for 500 μg L⁻¹ oysters, while no elimination for 5,000 μg L⁻¹ oysters. The maternal persistence of the steady state concentration resulted in significant damages in the reproductive success and their reproductive outputs in terms of the hatching rate and larval growth, survival, and settlement. The 50 μg L⁻¹ oysters remained far below the steady state concentration, and showed a manifest eliminating behavior during the subsequent BaP-free 28 day maturation period. The reproductive success and initial larval events of 50 μg L⁻¹ oysters were comparable to those of control. However, the damage potential of the 50 μg L⁻¹ oysters might be more significant if their maternal exposure continued beyond 28 days, since the accumulation profile at this dose was linear.     

Toxic dinoflagellates (Alexandrium fundyense and A. catenella) have minimal apparent effects on oyster hemocytes

The possible effect of Alexandrium spp. containing paralytic shellfish poisoning (PSP) toxins on the hemocytes of oysters was tested experimentally. In one trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoflagellate, Alexandrium fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissflogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed Pacific oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissflogii. Measurements of numbers of oyster hemocytes, percentages of different cell types, and functions (phagocytosis, reactive oxygen species (ROS) production, and mortality) were made using flow-cytometry. During and after exposure, almost no significant effects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in C. virginica and measured toxin accumulation in C. gigas. The only significant correlation found was between toxin accumulation at one temperature and higher numbers of circulating live and dead hemocytes in C. gigas. The PSP toxins are known to interfere specifically with sodium-channel function; therefore, the finding that the toxins had no effect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions. Finally, because oysters were exposed to the living algae, not purified toxins, there was no evidence of bioactive compounds other than PSP toxins affecting hemocytes in the two species of Alexandrium studied.     

Karyotype, nucleolus organiser regions and constitutive heterochromatin in Ostrea angasi (Molluscae: Bivalvia): evidence of taxonomic relationships within the Ostreidae

Chromosome preparations from gill tissue of the Australian flat oyster Ostrea angasi Sowerby were studied with conventional Giemsa staining, C-banding and silver staining techniques. A diploid complement of 2n = 20 was observed, consisting of five metacentric, three submetacentric and two subtelocentric pairs. Constitutive heterochromatin was distributed as large centromeric blocks in Chromosome Pairs 3, 6, 8, 9 and 10. The nucleolus organizer regions (NORs) were located terminally on long arms of Chromosome Pairs 9 and 10. This allowed the identification of homologous chromosomes in submetacentric and subtelocentric pairs. Intraspecific variability in NOR pattern as revealed by differences in the number of silver-stained NORs (Ag-NORs) per cell was found to be very common. Comparison of the patterns of karyotype, C-band and Ag-NORs between species of the larviparous oysters for which data have been published demonstrate that the chromosomal structure of the endemic Australian and New Zealand species O. angasi shows little similarity to the Southern Hemisphere oysters O. (Eostrea)puelchana Orbigny and Tiostrea chilensis (Philippi) and the Indo-West Pacific oyster O. denselamellosa, but very high resemblance to the European species O. edulis. Received: 12 August 1996 / Accepted: 16 September 1996     

Metabolism of palmitic,linoleic, and linolenic acids in adult oysters,Crassostrea virginica

This study investigated incorporation and metabolism of saturated [(1-¹⁴C) 16:0] and unsaturated [(1-¹⁴C) 18:26 and (1-¹⁴C) 18:33] fatty acids in adult eastern oysters,Crassostrea virginica Gmelin (spawned from parents obtained in 1986 from Mobjack Bay, Virginia, USA), and the influence of temperature on these processes. InC. virginica, incorporation of injected palmitic (16:0) and linolenic (18:33) acids was increased when oysters which had been grown in warm water (22 to 23°C) were transfered to cold water (5 to 7°C) for 8 to 18 d. Incorporation of linoleic acid (18:26) was unchanged under these conditions. The changes in concentration may have been linked to depression of metabolism in these oysters, in particular that of 16:0, which was reduced by 90%. Oxidation of incorporated fatty acids was much higher in warm than in cold water. Cold-temperature conditioning ofC. virginica altered the distribution of fatty acids among the neutral and polar lipid fractions. Long-term exposure to cold water increased the proportion of fatty acids in the polar fraction, which may be related to maintenance of membrane fluidity. Short-term exposure to cold water had the opposite effect, which may be due to increased energy requirements as the oyster adapts to new conditions. Reutilization of¹⁴C-acyl groups demonstrated de novo synthesis of 16:0 and 18:0 fatty acids. Only limited elongation and no desaturation of the administered fatty acids was observed.     

Mortality of newly metamorphosed eastern oysters (Crassostrea virginica) in mesohaline Chesapeake Bay

 Stocks of eastern oysters, Crassostrea virginica (Gmelin), in mesohaline Chesapeake Bay, USA, exhibit a high degree of inter-annual and spatial variability in recruitment. We found that cumulative oyster spatfall on off-bottom collector plates, measured throughout the summer in 14 years over a span of three decades, was highly positively correlated (r ² = 0.8) with juvenile oyster recruitment on adjacent oyster bars. Total abundances of juvenile oysters on these bars were, however, generally 99.7% lower than predicted from cumulative seasonal larval settlement on collector plates. We propose that although the number of larvae metamorphosing was the key factor in determining the gross annual pattern of recruitment to these mesohaline oyster bars, the actual magnitude of recruitment was governed by post-settlement processes, such as competition for limited resources and predation. We tested the hypothesis that predation may be partly responsible for high post-settlement juvenile oyster mortality. We performed a series of 3-d field investigations over two summers (1989, 1990) at a mesohaline site, employing cages of various mesh sizes (400, 800, 1500 μm) to protect hatchery-reared spat of 0.5 to 4.0 mm shell height. Mortality rates for spat held for 3 d in the estuary (17.8%) were significantly higher (P = 0.0001) for the smallest spat (0.5 to 2.0 mm) compared with those of 2.01 to 4.0 mm (4.2%). In 1990, but not in 1989, enclosure within 400 and 800 μm mesh cages significantly (P = 0.004) increased survival during 3-d deployments (9.4 and 10.1%, respectively) compared with spat unprotected by mesh cages (21.9%). In a series of laboratory predation studies that used the entire community of invertebrates that could penetrate the cages, microscopic juvenile polyclad flatworms, Stylochus ellipticus, were the only organisms that we observed crawling into living oysters and feeding on oyster tissue. Large flatworms (50 to 200 mm²) are known to be important predators on oysters, but this ability of flatworms that were so small (<ca. 5 mm²) and translucent as to be almost invisible without magnification to feed on immediate post-metamorphic oysters has not been documented previously. Our results suggest that the rate of mortality due to predation in mesohaline Chesapeake Bay is much reduced once spat survive for 2 to 3 weeks post-metamorphosis. Thus, it is likely that predation in the 1 to 2 week period immediately after settlement may be a crucial factor in the structuring of eastern oyster populations. Received: 21 December 1998 / Accepted: 2 December 1999     

Effects of temporary starvation on the survival,and on subsequent feeding and growth,of oyster (Crassostrea gigas) larvae

Larvae of oysters, Crassostrea gigas, were maintained without food for 1 to 8 d after fertilization, and fed daily thereafter. There was little difference in survival and growth between controls and larvae kept without food for 2 or 3 d. Survival and growth rates were depressed in larvae starved for 4 or 5 d. For larvae starved for 6 to 8 d, survival was negligible or nil; even those larvae which survived the starvation period died later in the presence of food, apparently because of impaired digestion. Therefore, food availability in the first few days after spawning appears to be of paramount importance to the successful recruitment of Pacific oysters.     

Mitochondrial DNA markers allow monitoring of oyster stock enhancement in the Chesapeake Bay

Overharvesting, habitat degradation, and disease have resulted in a century of decline for Atlantic Coast populations of the eastern oyster Crassostrea virginica (Gmelin). The introduction of oysters with superior disease resistance (e.g. oysters from different geographical areas, or genetically improved strains) may be useful in restoration efforts. In 1997 the Oyster Recovery Partnership and the University of Maryland Center for Environmental Science planted more than four million Louisiana oysters in the Choptank River, which flows into the Chesapeake Bay, Maryland, USA. These oysters, which may be distinguished from Atlantic oysters by diagnostic single-nucleotide polymorphisms (SNPs) in their mitochondrial DNA, were expected to display enhanced survival and reproduction as a result of their superior resistance to Dermo disease. A high-throughput, synthesis-by-sequencing technique (Pyrosequencing) was used to determine the mitochondrial haplotypes of spat collected in the Choptank River and nearby regions of the bay. Of 3,545 spat collected in 1999, 2000, and 2001, 3,349 (94.47%) possessed the North Atlantic haplotype, 176 (4.68%) had the South Atlantic haplotype, and 3 individuals (0.08%) had the Gulf Coast haplotype. Detection of newly recruited oysters possessing the Gulf Coast haplotype in the Choptank River confirmed the survival and reproduction of the outplanted Louisiana oysters. If appropriate genetic tags are available, effective monitoring of stock-enhancement projects can be achieved with high-throughput molecular genotyping techniques.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J.P. Grassle, New Brunswick     

Accumulation,release and retention of petroleum hydrocarbons by the oyster Crassostrea virginica

Two Crassostrea virginica populations, differing in fat content, were experimentally exposed to a complex petroleum-hydrocarbon fraction. The hydrocarbons in this mixture were accumulated by both groups of oysters, and their lipid content, as well as the concentration of hydrocarbon in the water, were found to affect the rate and extent of accumulation. Hydrocarbons accumulated were rapidly, although incompletely, discharged when the oysters were transferred to an uncontaminated system. Amounts of hydrocarbons discharged and amounts retained after discharge are probably related to the level of contamination. The data can be interpreted as indicating that equilibration and the occurrence of multiple compartments where hydrocarbons can reside are factors involved in the uptake and retention of nonbiogenic hydrocarbons by oysters. The petroleum hydrocarbons contained in the oysters differed from the contaminating oil by displaying a greater aromatic content. In addition, gas-liquid chromatograms of aliphatic fractions of the hydrocarbons in the oysters rapidly showed a degraded appearance; the possibility that the oysters themselves are modifying the oil cannot be excluded.Contribution No. 3098 from the Woods Hole Oceanographic Institution.     

Mitochondrial DNA analysis of native and selectively inbred Chesapeake Bay oysters,Crassostrea virginica

Mitochondrial DNA (mtDNA) genotypes were examined in 1989 in threeCrassostrea virginica (Gmelin) populations native to Chesapeake Bay, USA, and in one population selectively inbred for rapid growth for ten generations. We wished to determine whether this character would be useful as a genetic marker for distinguishing between the inbred line and the native oysters and to determine whether detectable genetic differences exist among present-day native populations ofC. virginica. Thirty mtDNA haplotypes were identified. The average percentage nucleotide difference between native haplotypes was 1.8%. Inbred oysters were characterized by mtDNA haplotypes distinctly different from ancestral native oysters, indicating a high degree of genetic differentiation between the two groups (average percentage mtDNA nucleotide sequence divergence,=21.8%). The common native haplotype was not present in the selectively inbred sample, and six of the seven haplotypes detected in the inbred oysters were not found in the survey of native oysters. Chi-square tests on haplotype frequencies indicated that the native populations were not significantly different from one another. However, the distribution and relatedness of haplotypes suggest that significant change in the oyster gene pool may have occurred over the past few decades.     

Effects of temperature,nutritional factors and salinity on the uptake of L-methionine by the Sydney rock oyster Saccostrea commercialis

The effects of physiological and nutritional factors and of temperature on the uptake of L-methionine by Saccostrea commercialis were investigated on cultured rock oysters from Port Stephens, New South Wales, Australia, in 1983. Optimum conditions for L-methionine accumulation were 30°C, 18 h exposure and concentrations of other amino acids less than that of L-methionine. The uptake of L-glycine was inhibited by L-methionine in a reciprocal manner. There was no effect of salinity on the accumulation of L-methionine by acclimated oysters. During the latter investigations the range of osmoconformity was found to be 15 to 45 S. Oysters take 2 d to conform to new media osmolarities after salinity changes of 15. Amino acid supplements in oyster diets should be kept within the same order of magnitude to reduce inhibition of uptake.