Eight PCR primers to amplify EST‐linked microsatellites in the Eastern oyster,Crassostrea virginica genome

Twenty‐four microsatellite repeat sequences were identified by screening a total of 4446 eastern oyster, Crassostrea virginica, expressed sequence tags. Polymerase chain reaction primers were designed to amplify 12 of these loci. After optimizing reaction parameters, eight loci showed high variability with consistent amplification that could be scored unambiguously. Ninety two C. virginica from the James River, VA, were genotyped at these loci. Number of alleles per locus ranged from 11 to 53, expected and observed heterozygosities ranged from 0.69 to 0.97, and from 0.30 to 0.99, respectively. Discrepancies between expected and observed heterozygosities were common and likely caused by null alleles.     

The Distribution of Perkinsus marinus in Gulf Coast Oysters: Its Relationship with Temperature,Reproduction, and Pollutant Body Burden

Oysters from 48 Gulf of Mexico sites were examined for presence and infection intensity of the endoparasite, Perkinsus (= Dermocystidium) marinus (Mackin, Owen and Collier, 1950) as part of NOAA's Status and Trends Mussel Watch Program. Prevalence exceeded 75% at 25 sites. Infection intensity did not vary with sex or reproductive stage. Latitude, total polynuclear aromatic hydrocarbon (PAH) content and industrial and agricultural land use significantly affected the parasite's distribution. PAH and pesticide concentrations were latitudinally dependent, suggesting an impact of spawning frequency on uptake and depuration. P. marinus analysis complements the use of pollutant body burden for determining change in environmental quality because it responds differently than pollutant body burden to the biology and ecology of the oyster.     

A prodiginine pigment toxic to embryos and larvae of Crassostrea virginica

The red pigment produced by a marine Pseudomonas sp. which causes abnormal development and mortality in developing embryos of the American oyster, Crassostrea virginica, was analyzed. A comparative study of a nonpigmented and two pigmented mutants of the red parental strain indicated that virulence was associated and varied with pigmentation. The use of sonicated cells supported lysing of the pseudomonad cells as the most probable means of pigment release. Crude pigment extracted from the red parental strain and its yellow mutant was toxic to developing oyster embryos. Neither the “pigment” extracted from the white mutant nor dimethyl sulfoxide, used for dissolving the extract, was toxic. Three pigment fractions were demonstrated by thin-layer chromatography even after purification. Studies indicate that only the fraction corresponding to R₁ 0.41 was necessary for virulence. The virulent pigment fraction was identified as belonging to the prodiginine group.     

Co‐localized Crassostrea virginica and Crassostrea ariakensis Oysters differ in bioaccumulation,retention and depuration of microbial indicators and human enteropathogens

Aims: To evaluate the bioaccumulation, retention and depuration rates of nine pathogens and surrogates when two oyster species were co‐localized in tanks of seawater. Methods and Results: Crassostrea ariakensis (n = 52) and Crassostrea virginica (n = 52) were exposed to five virus types, two protozoan and two microsporidian species for 24 h. Oysters were then placed in depuration tanks, and subsets were removed and analysed for micro‐organisms at weekly intervals. The odds of C. ariakensis oysters harbouring mouse norovirus‐1 (MNV‐1), human norovirus (NoV) or haepatitis A virus (HAV) were significantly greater than the odds of C. virginica oysters harbouring the same viruses (MNV‐1 OR = 5·05, P = 0·03; NoV OR = 6·97, P = 0·01; HAV OR = 7·40, P < 0·001). Additionally, compared to C. virginica, C. ariakensis retained significantly higher numbers of transmissive stages of all protozoan and microsporidian species (P < 0·01). Crassostrea ariakensis oysters are also capable of retaining multiple human pathogens for at least 1 month. Conclusions: Crassostrea ariakensis oysters were statistically more likely to harbour enteropathogens and microbial indicators, compared to C. virginica. Individual C. ariakensis were also statistically more likely to retain multiple viruses, protozoa and microsporidia than C. virginica, highlighting the role the species may play in the transmission of multiple diseases. Significance and Impact of the Study: Nonnative Crassostrea ariakensis oysters are under review for their introduction into the Chesapeake Bay. The results of this study suggest that nonnative C. ariakensis oysters may present a serious public health threat to people consuming the oysters raw from contaminated sites.     

Reproduction of Blackchin Tilapia, Sarotherodon melanotheron, Within an Impounded Mangrove Ecosystem in East-central Florida

I investigated the reproductive biology of introduced blackchin tilapia, Sarotherodon melanotheron, over a twelve month period within a seasonally impounded mangrove ecosystem in east-central Florida, and compared the data to published accounts from native African habitats. Eggs and free embryos were collected from the buccal cavity of adult males from April to October indicating a protracted spawning season, however gonadosomatic indices suggested that most spawning occurred in April and May. The timing of reproduction was adjusted to occur immediately before temperatures reached optimal levels for juvenile growth and when increasing rainfall produced abundant food and shelter for the young. Temperatures below 24°C inhibited reproduction from November to March. The overall sex ratio was essentially 1:1. The minimum and maximum size at maturity were much larger in this study than those reported from Africa; the smallest mature male was 128mm standard length and 0.47 of the maximum size, while the smallest mature female was 145mm standard length and 0.54 the maximum size. However, because of the difficulty in aging this species and a lack of published information, it could not be determined whether the population in this study possessed a relatively early or delayed maturation compared to African populations.     

Removal of Toxoplasma gondii Oocysts from Sea Water by Eastern Oysters (Crassostrea virginica)

SUMMARY. Toxoplasma gondii infections have been reported in a number of marine mammals. Presently it is not known how these animals acquire T. gondii from their aquatic environment. The eastern oyster, Crassostrea virginica , has been shown to remove Cryptosporidium oocysts from seawater and a similar phenomenon may be occurring with T. gondii oocysts and marine invertebrates. The present study was done to determine if eastern oysters could remove and retain T. gondii oocysts from seawater. Oocysts of the VEG strain of T. gondii (1 × 10⁶ oocysts) were placed in seawater (32 ppt NaCl) containing live eastern oysters. The infected seawater was removed one day postinoculation (PI) and replaced with fresh seawater. Selected oysters were removed at 1, 3 and 6 days PL Hemolymph, gill washes, and oyster tissue were collected separately at each observation time. The oyster tissue was homogenized and all 3 samples fed separately to mice. Toxoplasma gondii positive mice were observed at each time period. The results indicate that T. gondii oocysts can be removed from seawater by eastern oysters and retain their infectivity. Contaminated raw oysters may serve as a source of T. gondii infection for marine mammals and humans.     

Use of Competitive PCR to Detect and Quantify Haplosporidium nelsoni Infection (MSX disease) in the Eastern Oyster (Crassostrea virginica)

This study was undertaken to develop a quantitative polymerase chain reaction assay that would improve the utility of PCR for detecting Haplosporidium nelsoni (MSX), a serious parasite of the eastern oyster Crassostrea virginica. A competitive PCR sequence was generated from the H. nelsoni small subunit ribosomal DNA fragment, originally described by Stokes and colleagues, that was amplified by the same PCR primers and had similar amplification performance. Assays performed using competitor dilutions ranging from 0.05 to 500 pg/μl DNA were used to test oyster samples designated using histological techniques as having ``light' or ``heavy' MSX infections. Visual diagnoses were confirmed equally well with three methods: densitometry of ethidium-bromide-stained agarose, densitometry of SYBRGreen-stained polyacrylamide gels, and analysis by GeneScan 3.0 of fluorescent products detected in ultrathin gels. Oysters diagnosed as negative for MSX tested as negative or light by PCR. Oysters with light MSX infections generally had less than 5 pg/μl infectious DNA. Oysters with heavy infections generally corresponded to 5 pg/μl or greater competitor dilutions. Received September 3, 1999; accepted March 3, 2000.     

Diet of the killifish Rivulus marmoratus collected from land crab burrows,with further ecological notes

Synopsis One-hundred eleven specimens of the cyprinodont fish Rivulus marmoratus were trapped from burrows of the great land crab Cardisoma guanhumi in east central Florida and the entire alimentary tract removed for analysis of food items. Three categories of burrows (inactive, active and sealed) were sampled to examine possible relationships between burrow type and presence of R. marmoratus. Forty percent of the guts examined contained no food items, while the remaining 60% contained items of both terrestrial and aquatic origin. Capture rates among burrow categories did not vary significantly, and most collections consisted of 1 or 2 individuals per burrow. Mean standard length of fish within a burrow declined when more than 3 specimens were captured from a burrow. Supplemental observations on reproductive status and burrow water temperature are noted.     

Evaluating the Risk of Establishing a Self-Sustaining Population of Non-Native Oysters Through Large-Scale Aquaculture in Chesapeake Bay

A multistep invasive species methodology was used to evaluate the probability that the deployment of sterile non-native oysters (Crassostrea ariakensis, called Asian oyster) in field-based aquaculture could give rise to a reproductive population in Chesapeake Bay. Several pathways that could potentially lead to the unintentional release of reproductive C. ariakensis from aquaculture were identified. For the four quantifiable pathways, a probability was estimated for each step based on knowledge of ecological rates. A conservative estimate for the number of reproductive C. ariakensis that could arise over one spawning season at a hypothetical aquaculture site was estimated. A statistical expansion of this probability estimated that it is highly likely that the cultivation of putatively sterile C. ariakensis would initiate a reproductive population in Chesapeake Bay over a 10-year time span. The potential benefits of restoration actions involving non-native species in estuarine ecosystems must be weighed against potential ecological risks. A probabilistic approach can provide a useful method for summarizing the risk of an unintended introduction that may occur despite a reasonable and presumably “safe” approach for realizing benefits of a non-native species in aquaculture. The results presented here have important implications for future proposals involving the commercial use of non-native species in natural ecosystems.     

The occurrence of potentially toxic dinoflagellates and diatoms in a subtropical lagoon, the Indian River Lagoon, Florida, USA

The occurrence of potentially toxic phytoplankton species was examined over a 5-year period in a region of the Indian River Lagoon in Florida that has recently been subject to ecologically significant events, putatively related to algal toxins. The results of the study reveal a significant presence of two species of phytoplankton that have been shown to be toxic in Florida or other regions of world, the dinoflagellate Pyrodinium bahamense var. bahamense and the diatom Pseudo-nitzschia pseudodelicatissima. Concentrations of the former species reached 638,000 cells l⁻¹ and concentrations of the latter reached 23.9 million cells l⁻¹. In addition, the abundance of one of these species, P. bahamense var. bahamense appears to have increased over the 5-year study period from 1997 to 2002. It may be hypothesized that rainfall events following a regional drought period resulted in a flushing of bioavailable phosphorus and nitrogen into the Indian River Lagoon that stimulated P. bahamense var. bahamense blooms. The significance of these results is discussed within the context of the ecology of this flow-restricted lagoon.