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  • 1990-1994  (2)
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  • 1
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As part of NOAA's Status and Trends Program, oysters were sampled from 43 sites throughout the Gulf of Mexico from Brownsville, Texas, to the Florida Everglades from 1986 to 1989. Oysters were analysed for body burden of a suite of metals and petroleum aromatic hydrocarbons (PAHs), the prevalence and intensity of the oyster pathogen,Perkinsus marinus, and condition index. The contaminants fell into two groups based on the spatial distribution of body burden throughout the Gulf. Arsenic, selenium, mercury and cadmium were characterized by clinal reduction in similarity with distance reminiscent of that followed by mean monthly temperature and precipitation. Zinc, copper, PAHs and silver showed no consistent geographic trend. Within local regions, industrial and agricultural and use andP. marinus prevalence and infection intensity frequently correlated with body burden. Contaminants and biological attributes followed one of three temporal trends. Zinc, copper and PAHs showed concordant shifts over 4 years throughout the eastern and southern Gulf. Mercury and cadmium showed concordant shifts in the northwestern Gulf. Selenium, arsenic, length, condition index andP. marinus prevalence and infection intensity showed concordant shifts throughout most of the entire Gulf. Concordant shifts suggest that climatic factors, the El Niño/Southern Oscillation being one example, exert a strong influence on biological attributes and contaminant body burdens in the Gulf. Correlative factors are those that probably affect or indicate the rate of tissue turnover and the frequency of reproduction; namely, temperature, disease intensity, condition index and length.
    Type of Medium: Electronic Resource
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