Showing papers on "Oyster published in 1993"

Vibrio infections on the Gulf Coast: results of first year of regional surveillance. Gulf Coast Vibrio Working Group.

Abstract: In 1989, the first year of coordinated Vibrio surveillance in four Gulf Coast states (Alabama, Florida, Louisiana, and Texas), 121 infections were reported. These included 34 V. parahaemolyticus, 30 V. cholerae non-O1, 18 V. vulnificus, 9 V. hollisae, 7 V. alginolyticus, and 7 V. fluvialis. Fourteen patients had primary septicemia, 71 had gastroenteritis, and 29 had wound infections; 7 had other or unknown illnesses. Sixty-six patients were hospitalized, and 9 died. All patients with primary septicemia, but only 17% of those with gastroenteritis, were known to have an underlying illness (P < .001). Among patients for whom data were available, 67% with primary septicemia and 74% with gastroenteritis ate raw oysters in the week before illness began. Of 50 patients with data on where oysters were obtained, 42 (84%) ate them at oyster bars or restaurants. These data provide evidence that in the Gulf Coast region raw oyster consumption is an important cause of Vibrio-associated gastroenteritis among adults without underlying illnesses.

The influence of irradiance on the biochemical composition of three phytoplankton species and their nutritional value for larvae of the Pacific Oyster (Crassostrea gigas)

Abstract: Three species of phytoplankton grown at high (HL) or low light (LL) were fed as saturating rations to laboratory-reared larval Crassostrea gigas. Larval C. gigas fed diets of HL grown Chaetoceros gracilis and HL grown Isochrysis aff. galbana grew faster than those fed LL grown cells of the same phytoplankton species. Faster growth of C. gigas larvae was consistently associated with increases in the percent composition of short chain saturated fatty acids (FA) 14:0+16:0 in the HL grown cells. There were no consistent and significant differences between HL and LL grown phytoplankton cells in their content of carbon, nitrogen, protein, lipid or carbohydrate. Intraspecific increases in percent composition of essential fatty acids (EFAs), 20:5ω3 and 22:6ω3, in the phytoplankton were not associated with improvements in the growth or survival of the oyster larvae. Oyster larvae fed diets of Phaeodactylum tricornutum with a relatively high proportion of EFAs grew more slowly than those fed C. gracilis. In this experiment the proportion of dietary EFA 20:5ω3 was negatively correlated with oyster growth rates. The faster growing oyster larvae contained relatively more of the FAs 14:0+16:0 which may be useful as measures of larval oyster condition. After a diet of one phytoplankton species for ca. 10 d, oyster larvae acquired distinctive FA profiles resembling that of their phytoplankton prey.

Indigenous bacteria in hemolymph and tissues of marine bivalves at low temperatures.

Abstract: Hemolymph and soft tissues of Pacific oysters (Crassostrea gigas) kept in sand-filtered seawater at temperatures between 1 and 8 degrees C were normally found to contain bacteria, with viable counts (CFU) in hemolymph in the range 1.4 x 10 to 5.6 x 10 bacteria per ml. Pseudomonas, Alteromonas, Vibrio, and Aeromonas organisms dominated, with a smaller variety of morphologically different unidentified strains. Hemolymph and soft tissues of horse mussels (Modiolus modiolus), locally collected from a 6- to 10-m depth in the sea at temperatures between 4 and 6 degrees C, also contained bacteria. The CFU in horse mussel hemolymph was of the same magnitude as that in oysters (mean, 2.6 x 10), and the bacterial flora was dominated by Pseudomonas (61.3%), Vibrio (27.0%), and Aeromonas (11.7%) organisms. In soft tissues of horse mussels, a mean CFU of 2.9 x 10 bacteria per g was found, with Vibrio (38.5%), Pseudomonas (33.0%), and Aeromonas (28.5%) constituting the major genera. After the challenge of oysters in seawater at 4 degrees C to the psychrotrophic fish pathogen Vibrio salmonicida (strains NCIMB 2245 from Scotland and TEO 84001 from Norway) and a commensal Aeromonas sp. isolated from oysters, the viable count in hemolymph increased 1,000-fold to about 10 bacteria per ml. In soft tissues, about a 1,000-fold increase in CFU to 6 x 10 was observed. V. salmonicida NCIMB 2245 invaded hemolymph and soft tissues after 14 days and dominated these compartments after 41 days, whereas strain TEO 84001 did not invade soft tissues to the same extent. Challenge with V. salmonicida NCIMB 2245 resulted in 100% mortality, whereas about 50% of the oysters survived challenge with the Norwegian strain, TEO 84001. The commensal Aeromonas sp. invaded hemolymph and soft tissues and caused 100% mortality. Oyster hemolymph contained agglutinins for Vibrio anguillarum but not for V. salmonicida, whereas we did not find agglutinins for either of these bacteria in horse mussels. Agglutinins for horse and human erythrocytes were found in hemolymph from both animals. We found no differences in agglutinin titers in oysters from different Norwegian locations, and long-term challenge with bacteria in seawater did not result in changes of agglutinin activity. These studies demonstrate that bacteria exist in hemolymph and soft tissues of marine bivalves at temperatures below 8 degrees C. Increased bacterial numbers in seawater at 4 degrees C result in augmented invasion of bacteria in hemolymph and soft tissues. V. salmonicida, a bacterium pathogenic for fish at low temperatures, invades bivalve hemolymph and soft tissues, and thus bivalves may serve as a reservoir for pathogens of fish at low seawater temperatures.

Effects of marine bacteria on the culture of axenic oyster Crassostrea gigas (Thunberg) larvae

Abstract: Bacteria-free oyster larvae (Crassostrea gigas) were cultured under aseptic conditions; they were fed axenic algae (Zsochrysis galbana), and the medium was inoculated with isolated strains of marine bacteria. Twenty-one bacterial strains were tested, and most were detrimental to larval survival and growth. However, ad- ditions of strain CA2 consistently enhanced larval survival (2 l-22%) and growth ( 16-2 1%) in comparison with con- trol cultures that were fed only algae. Size-frequency dis- tributions of populations of larvae cultured for 10 days on axenic algae were skewed due to the poor growth of many individuals; whereas size-frequencies from popu- lations of larvae fed axenic algae supplemented with CA2 bacteria were distributed normally. Strain CA2 may therefore make a nutritional contribution to the growth of oyster larvae. I. galbana did not grow under the light intensities used for larval culture; thus the improvement in larval growth cannot be attributed to bacterial en- hancement of algal growth and, consequently, food avail- ability. Naturally occurring microflora from Yaquina Bay, Oregon, depressed survival or growth of larvae-fed live algae.

In Vitro Propagation of the Protozoan Perkinsus Marinus, A Pathogen of the Eastern Oyster, Crassostrea Virginica

Abstract: .Perkinsus marinus, a pathogen of eastern oysters (Crassostrea virginica), has been successfully propagated in vitro. Cultures of the parasite were initiated from heart fragments of an infected oyster. the cultured protozoan (designated Parkinsus-1) was similar in morphology at both the light and transmission electron microscopy levels to histozoic stages of P. marinus in naturally infected oysters. In addition, cultured cells incubated in fluid thioglycollate medium produced enlarged cells (prezoosporangia) that stained blue-black in Lugol's solution, a response characteristic to Perkinsus spp. and used in routine diagnosis. Polyclonal antibodies raised against P. marinus prezoosporangia reacted positively to Perkinsus-1. Finally, the cultured cells infected susceptible oysters and reisolation of Perkinsus-1 cells was possible from the hearts of experimentally infected oysters. the culture medium contained most of the known constituents of cell-free hemolymph of oysters. the success achieved in culturing P. marinus will allow further investigations aimed at reducing mortalities caused by this important oyster pathogen and at addressing many unanswered questions about its biology and pathobiology.

Discrimination between closely related Pacific oyster species (Crassostrea) via mitochondrial DNA sequences coding for large subunit rRNA.

Abstract: Mitochondrial DNA sequence variation was characterized for the large subunit rRNA-coding gene (16SrDNA) in two closely related Pacific oyster species (Crassostrea gigas and C. sikamea) and an out group, the Olympia oyster (Ostrea lurida). Although each species was shown to have a single, fixed haplotype for the DNA sequence under study, 7 nucleotide differences were found between C. gigas and C. sikamea, and these two species differed from the O. lurida haplotype at 62 and 60 nucleotide sites, respectively. Nucleotide differences for the two Crassostrea species showed a notable transition bias (85.7%) in contrast to the marginal transversion bias (54.5%) in nucleotide differences between Crassostrea haplotypes and the more distantly related O. lurida. Conservation of primary sequence in all three oyster species as well as other published 16SrDNA sequences was noted for regions with apparent functional significance. We developed DNA sequence-specific discrimination techniques and employed sequence-specific PCR primers, dot-blot hybridization, and restriction digests as alternate techniques for rapid diagnosis of Crassostrea oyster larvae.

Farming the Sydney rock oyster (Saccostrea commercialis) in Australia

Abstract: Commercial production of Sydney rock oysters (Saccostrea commercialis) in Australia began simultaneously in New South Wales (NSW) and southern Queensland around 1870. It began with the exploitation of dredge beds, intertidal oyster beds, and with the placement of a range of catching and growing substrates such as sticks, slabs of rocks, and shell placed on intertidal mud flats. As dredge beds were depleted and problems with accumulation of silt and mudworm (Polydora sp.) increased, the industry progressively adopted the stick and tray culture on intertidal racks. However, the use of sticks for growing is now rapidly diminishing as farmers are learning to scrape small (4 to 8 mm) spat off sticks and grow them in specially adapted trays or other growing containers (single‐seed culture). At its peak in 1976–1977, the combined NSW and southern Queensland industry produced 9267 t (wet weight including shell) or 154,454 bags (1200 oysters per bag), but it has declined over the last decade to a producti...

Allozyme variation in European populations of the oyster Ostrea edulis

Abstract: Variations at 22 enzyme coding loci were surveyed in 11 populations of the oyster Ostrea edulis L, which were sampled between 1988 and 1990 along the Atlantic and Mediterranean coasts of Europe Atlantic oyster beds suffered a steady decline during the last century, and restocking of beds with oysters of foreign origin has probably resulted in a high degree of interbreeding of natural oyster stocks from all Atlantic Europe Our study confirms the low levels of genetic variability previously reported for the oyster populations from the Atlantic coasts, and extends it to the Mediterranean coasts The locus arginine-kinase (ARK *) exhibited a high degree of interpopulation differentiation (F ST=0289), resulting from extensive variation in gene frequencies along a geographical cline However, the overall genetic differentiation between populations was slight, and similar to that reported for other local populations of bivalves (mean genetic distance between populations is 0010, mean F ST=0062) A general pattern of increasing differentiation along the coastline in an Atlantic-mediterranean direction emerged; but genetic differentiation among the Atlantic populations was not significantly lower than that observed among the Mediterranean populations This and other results suggest that the effects of extensive transplantation of oysters among various areas in Europe are detectable only in some particular localities The geographical distribution of low-frequency alleles suggests a restriction to gene flow outwards from the Mediterranean Sea, across the Straits of Gibraltar

Vibrio vulnificus infections associated with raw oyster consumption-Florida, 1981-1992

Abstract: Vibrio vulnificus is a gram-negative bacterium that can cause serious illness and death in persons with preexisting liver disease or compromised immune systems. From 1981 through 1992, 125 persons with V. vulnificus infections, of whom 44 (35%) died, were reported to the Florida Department of Health and Rehabilitative Services (HRS). This report summarizes data on these cases and presents estimates of the at-risk population in Florida.

Detection of Salmonella spp. in Oysters Using Polymerase Chain Reactions (PCR) and Gene Probes

Abstract: The polymerase chain reaction (PCR) DNA amplification method was used to identify oligonucleotide primers from a target gene, hns, to specifically detect SulmonelIu spp. in contaminated oysters. The primers for PCR amplification and a hybridizing oligonucleotide probe to detect the amplified DNA were specific for all Salmonella spp. tested. Modification of a procedure for extracting DNA from oyster tissue matrices followed by PCR amplification, and coupled with gene-probe hybridization detected <40 cells of seeded or naturally occurring Sulmonella spp./g of oyster meat samples without any enrichment step. The detection of SaZmonella spp. was reliable, sensitive, and required considerably less time than conventional microbiological culture methods.

Abundance of Food Affects Relative Size of Larval and Postlarval Structures of a Molluscan Veliger.

Abstract: Veliger larvae of mollusks were predicted to develop a larger velum relative to the larval shell when reared with scarce food. The functional consequences of such developmental plasticity would be (1) greater max- imum capacity for capturing particles when food is scarce and (2) greater growth of structures retained in the post- larva when food is abundant. The hypothesis was tested by rearing veligers of the oyster Crassostrea gigas at high (near satiating) and low (growth limiting) concentrations of food. Veligers at the measured shell lengths (>200 ,m) had significantly larger velar lobes and longer prototrochal cilia than veligers reared in low concentrations of food. An analogous response to food levels (relatively longer ciliated band when food is scarce) has now been found for larvae as disparate as oyster veligers and sea urchin plutei. These observations suggest that functionally similar examples of developmental plasticity in the growth of lar- val parts have evolved more than once and may be wide- spread. An alternative interpretation is that differential mortality or growth in a genetically heterogeneous batch of oyster larvae results in advanced veligers of different forms at different concentrations of food. Both interpre- tations suggest an adaptive advantage to growing a larger

Quantitative measurement of reproductive output in the American oyster, Crassostrea virginica (Gmelin), using an enzyme‐linked immunosorbent assay (ELISA)

Abstract: . A quantitative gonadal index was developed for oysters, Crassostrea virginica (Gmelin. 1791), using polyclonal antibodies from eggs and sperm. Percoll used in the purification of oyster eggs and sperm greatly improved the purity of antigens compared to filtering the egg or sperm through a fine mesh only. The antigen-antibody reaction was tested with indirect sandwich ELISA using alkaline phosphatase-conjugated goat anti-rabbit igG as a secondary antibody. Rabbit anti-oyster egg IgG and anti-oyster sperm IgG initially exhibited a weak cross-reactivity over somatic tissue. Absoring with acetone-dried oyster tissue powder removed this cross-reactivity. Both antisera exhibited strong specific immunological reactions to oyster eggs or sperm respectively. The quantity of eggs or sperm was measured using ELISA and a quantitative gonadosomatic index (dry wt of egg or sperm/dry wt oyster) (GSI) calculated. GSI from ELISA correlated with gonadal stage measured histologically. Monthly mean GSI of female oysters was highest during late spring to early summer (0·157–0·201) and lowest during early winter to early spring (0·002-0·000). Maximum GSI observed during the study was 0·422 for female oysters and 0·446 for male oysters. Female oysters produce 3·7–65·4 million eggs, with an average of 21·1 million during each spawning. A positive correlation was observed between the number of eggs produced and oyster size; the number of eggs in the gonad increased as oyster size (i.e. total dry wt) increased (r= 0·67); however, the relationship was non-linear. Large oysters contained proportionally fewer eggs. Prevalence of Perkinsus marinus parasitism was high, 90–100%, during the study, as was weighted incidence, 1·33 to 2·67, No statistically significant correlation was observed between infection intensity and the per cent weight of oyster eggs or egg number.

History and Impact of MSX and Dermo Diseases on Oyster Stocks In the Northeast Region

Abstract: Two other infectious oyster diseases, however, commonly known to oyster growers as “MSX” and “Dermo”, have had a much more significant and chronic effect on oyster populations in the northeastern region of the United States. The combined impact of both diseases has caused hundreds of millions of dollars in losses over the last 35–45 years in mid-Atlantic states (especially Chesapeake and Delaware Bays) and seriously threatens both natural and cultivated oyster populations in the New England states. Although both parasites are lethal to eastern oysters, they are not harmful to humans. This publication provides a current overview of both diseases by summarizing information on their natural history and distribution, methods of transmission, diagnostic techniques, environmental influences, control measures, and recommended management practices. MSX Disease Natural History and Distribution MSX disease was first recognized as the cause of massive oyster mortalities (90–95%) in lower Delaware Bay in 1957. Two years later, the disease was discovered in the lower Chesapeake Bay. The causative agent, a singlecelled parasite, Haplosporidium nelsoni, was originally given the acronym “MSX” because it was observed as a Multinucleated Sphere with unknown affinity (“X”).

Sterols ofChaetoceros andSkeletonema

Abstract: Dietary sterol is required by the oyster for growth, and sterol is believed to be obtained primarily from dietary phytoplankton Seven isolates ofChaetoceros and one ofSkeletonema, which are of potential use as oyster food, were analyzed for sterol composition using gas chromatography, high-performance liquid chromatography and gas chromatography/mass spectrometrySkeletonema and five isolates ofChaetoceros contained cholesterol as their major sterol Two other isolates ofChaetoceros also contained cholesterol, but 24-methylenecholesterol was the principal sterol Cholesterol has rarely been reported as the major sterol from phytoplankton In view of the widespread occurrence ofSkeletonema andChaetoceros in the marine environment, these algae could be an important source of the oyster's cholesterol

Bacterivory in Pacific oyster Crassostrea gigas larvae

Abstract: A bacterium (Strain CA2) that enhances sunrival and growth of larvae of the oyster Crassostrea gigas (Thunberg) was used in a series of experiments to determine the occurrence of bacterivory in straight-hinged bivalve larvae. Size and carbon content of this bacterium was found to be within the range reported for naturally occurnng marine bacteria. Unattached, motile, DAPI-stained CA2 cells were readily captured and ingested by oyster larvae and were seen to accumulate in larval digestive systems. Ingestion of 14C-labelled bacteria occurred at all bacterial concentrations tested from 1 X 105 to 1 X 10' cells m]-'. Retention of carbon by axenic oyster larvae, fed either 14C-labelled live or heat-killed bacteria in 'pulse-chase' feeding experiments, demonstrates the endogenous ability of larvae to digest and assirmlate bacterial carbon.

Selecting flat oysters, Ostrea edulis, for survival against the parasite Bonamia ostreae : assessment of the resistance of a first selected generation

Abstract: In 1989, a selected strain of flat oyster. Ostrea edulis, was produced from breeders that survived Bonamia ostreae and that were over selected by injection of purified parasites. This generation (G 1) was compared to native oysters which had settled during the same year. After a growing period of 21 months, the oysters were tested according to three procedures: exposure to natural infection in an intertidal area, maintenance at the laboratory in tanks near heavily infested oysters, injection of parasites. The test lasted 7 months. In each procedure, oysters of the first generation (G1) showed a better survival rate than control oysters (72 to 94% versus 48 to 66%). On the other hand, the highest mortalities were observed among injected oysters (G1 and controls). In the laboratory tests, however, infestation rates of surviving oysters were equal or even higher in Gl than in the controls. This reduces the gain of resistance, regarding the number of non infested survivors. Neverthe1ess, the difference remains significant between oysters over selected by inoculation and their controls (49% versus 32%). This confirms that the injection technique may provide faster assessment of disease resistance and also may be used for over selection. Survivors of the over selected first generation have been kept to produce a second generation (G2).

Effects of Physicochemical Factors and Bacterial Colony Morphotype on Association of Vibrio vulnificus with Hemocytes of Crassostrea virginica.

Abstract: Vibrio vulnificus is a naturally occurring marine bacterium that causes invasive disease of immunocompromised humans following the consumption of raw oysters. It is a component of the natural microbiota of Gulf Coast estuaries and has been found to inhabit tissues of oysters, Crassostrea virginica (Gmelin 1791). The interaction of V. vulnificus with oyster host defenses has not been reported in detail. We examined the interaction of V. vulnificus with phagocytic oyster hemocytes as a function of time, temperature, bacterial concentration, pretreatment with hemolymph, and V. vulnificus translucent and opaque colony morphotypes. Within these experimental parameters, the results showed that the association of V. vulnificus with hemocytes increased with time, temperature, and initial V. vulnificus/hemocyte ratio. Pretreatment of V. vulnificus with serum or an increased serum concentration did not enhance V. vulnificus-hemocyte associations, a result suggesting the absence of opsonic activity. More than 50% of hemocytes bound the translucent, avirulent morphotype, whereas 10 to 20% were associated with the opaque, virulent form, a result indicating that the degree of encapsulation was related to resistance to phagocytosis, as previously described for mammalian phagocytes. Understanding these cellular interactions may, in part, explain the persistence of V. vulnificus in oyster tissues and the ecology of V. vulnificus in estuarine environments.

Small subunit ribosomal RNA gene sequence of the oyster parasite Perkinsus marinus.

Abstract: The small subunit rRNA gene of the oyster pathogen Perkinsus marinus was characterized from cells of infected oyster hemolymph by polymerase chain reaction and molecular cloning. The gene, 1,793 nucleotides in size, has 77.2% sequence similarity to that of its host, the eastern oyster Crassostrea virginica. The sequence was confirmed using recently available in vitro cultures of P. marinus. DNA from pure P. marinus culture was amplified with specific primers synthesized according to the sequence from infected oyster hemolymph, and predicted size fragments were obtained. Furthermore, restriction digests yielded fragments of expected size in amplified rDNA from in vitro cultures. The P. marinus sequence has 97.5% similarity to the Perkinsus sp. sequence from the Australian mollusc Anadara trapezia.