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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Branching heads of symbiotic corals were pulse labeled with either 14C-acetate or 14C-bicarbonate for 1.33 h and the distribution and loss of label was then followed for 16d. The patterns of incorporation and washout were similar for both tracers. Non-solvent-extractable radioactivity (1/3 of the total) was divided into a CaCO3 and an organic fraction, both of which exhibited small if any decrease in radioactivity over 16d. In contrast, total solvent extractable (lipid) radioactivity (2/3 of the total) decreased during the washout period with the first half-life for bicarbonate at 2 d, the second at 4 d and the third could not be measured because of the persistence of a constant amount of radioactivity (18% of Day 1 value) from Day 8 to 16. Of the total retained activity, the zooxanthellae fraction contained between 8–18% from Day 1 to 5. The percentage of total animal (host) radioactivity in lipids rose from 35–40% at 0 time after tracer exposure to 70–90% at 60 min. The majority of 14C fixed into lipids was recovered in the fatty acyl moieties and not in the glycerol moiety as had been previously reported a number of times. These studies suggest that photosynthetically fixed carbon is immediately synthesized into lipid, which is translocated to the host. Analyses of the fatty acid compositions of triacylglycerols (TG) and wax esters (WE) of 40 species of coral from a small patch reef were made. In aposymbiotic species the absence of zooxanthellae appeared to be correlated with higher levels of total lipid, lower percentages of saturated fatty acids and lower TG/WE ratios than in species with symbionts.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 94 (1987), S. 451-458 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dinoflagellate symbionts (zooxanthellae) present in many reef corals aid in the survival of the symbiotic unit in nitrogen deficient tropical waters by providing additional routes of nitrogen uptake and metabolism. The enzymatic pathway of ammonia assimilation from seawater and the re-assimilation of coral ammonium waste by zooxanthellae was studied by examining the affinity of glutamine synthetase for one of its substrates, ammonia. Glutamine synthetase activity was measured in dinoflagellates of the species Symbiodinium microadriaticum found in symbiotic association with various marine coelenterates. Michaelis-Menten kinetics for the substrate ammonia were determined for freshly isolated dinoflagellates from Condylactis gigantea (apparent NH3 Km=33 μM) and for cultured dinoflagellates from Zoanthus sociatus (apparent NH3 Km=60 μM). On the basis of the low apparent Kms for NH3, it appears that ammonia assimilation by these symbiotic dinoflagellates occurs via the glutamine synthetase/glutamate synthase pathway. Additionally, the uptake of exogenous ammonium by an intact coelenterate-dinoflagellate symbiosis was strongly inhibited by 0.5 mM methionine sulfoximine, and inhibitor of glutamine synthetase.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 39 (1977), S. 371-379 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rates of photosynthesis and dark respiration for 7 marine algae and 1 fresh-water alga were measured and compared. The dinoflagellates Glenodinium sp. and zooxanthellae have high dark respiration rates relative to photosynthetic rates, which may decrease their net growth rates. Photorespiration in the 8 algal species was studied by examining the effects of the concentration of oxygen on the rates of photosynthesis, on the incorporation of 14CO2 into the photorespiratory pathway intermediates glycine and serine, and on the postillumination burst of carbon dioxide production and oxygen consumption. A combination of these results indicates that all the algae tested can photorespire, but that Glenodinium sp., Thalassiosira pseudonana, and zooxanthellae either have a photorespiratory pathway different from that proposed for freshwater algae (Tolbert, 1974), or an additional pathway for glycolate metabolism.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 65 (1981), S. 215-219 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic quotients of the marine prymnesiophyte Pavlova lutheri and the marine dinoflagellate Glenodinum sp. were measured at different concentrations of dissolved oxygen and inorganic carbon. Dissolved oxygen concentration appeared to be the most important factor controlling the photosynthetic quotient. Photosynthetic quotients generally were between 1.0 and 1.8 at oxygen concentrations less than saturation, were approximately 1.0 at oxygen saturation, and generally were from 0.1 to 1.0 at oxygen concentrations greater than saturation. The photosynthetic quotients greater than 1.0 were not caused by lipid synthesis. They may have been partially caused by the presence of KNO3 rather than an ammonium salt in the growth media. The lowered photosynthetic quotients at higher oxygen concentrations were probably caused by algal photorespiration.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 75 (1983), S. 113-116 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of inorganic carbon concentrations on photosynthetic oxygen evolution of isolated zooxanthellae and coral tips from the hermatypic coral Seriatopora hystrix were measured in the laboratory using an oxygen electrode. Whole coral colonies of Stylophora pistillata were examined in situ, using a bioassay respirometer. Inorganic carbon concentrations above 2.3 mM, the ambient concentration of reef water, generally did not stimulate photosynthesis. These results indicate that inorganic carbon is not limiting to coral photosynthesis and that respiratory carbon dioxide production by the coral host probably has little effect on the photosynthetic rates of its symbiotic zooxanthellae.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 75 (1983), S. 131-136 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooxanthellae (symbiotic algae) from the same head of Stylophora pistillata were isolated at different times of the day over a period of 5 d and examined by phase contrast light microscopy. The percentage of isolated algal cells with extruding (blebbing) triglyceride droplets reached a maximum value of 11–13% between 14:00 and 19:00 hrs and exhibited a minimum value of 5–7% in the early morning. Wax esters were not synthesized by isolated algae. The diameter of the fat droplets varied from 〈1 μm to over 5 μm. Droplets appeared to originate within and were held next to the algal cell by the limiting outer membrane of the algal cell. Various stages of extrusion or sloughing of outer limiting membrane vesicles by the algal cells were observed. Although these spherical vesicles often contained fat droplets, their density was high enough that they often sedimented with the algal cells during gentle (1 000 g's) centrifugation. The percentage of freshly isolated cells undergoing division averaged 2% with a slightly higher value of 4% observed in the early morning. Microscopic evidence suggests that fat droplets and vesicles of outer limiting membrane from zooxanthellae are translocated into animal cells during coelenterate symbiosis.
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  • 7
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At various times throughout the light period of a day, freshly harvested Seriatopora hystrix colonies in seawater were labeled with H14CO 3 - for 20 min and then washed thoroughly with fresh seawater. The labeled colonies were left in fresh seawater, and at time intervals (some as long as 27h) samples were removed, separated into zooxanthellae and coral animal tissue, and the radioactivity in the two fractions determined. In 30 to 60 min after initiating the experiments, the zooxanthellae retained 75 to 82% of the total label. Zooxanthellae labeled early in a day lose label throughout the day and near sunset retain about 55% of the total label in the colony. Colonies labeled in the last 1 to 2 h of daylight retain 65 to 73% of the label in the zooxanthellae. At night the zooxanthellae retain almost all of their 14C-labeled materials regardless of the labeling hour of the previous day. A loss of carbon at night from the zooxanthellae occurred only when the colonies were labeled in the last 1 to 2 h of daylight; the loss was approximately 5% over the night period. The next day, after several hours of light, 14C-labeled material again moved from the zooxanthellae to the animal tissue. We conclude that in the intact coral as much as 45% of the newly fixed carbon moves from the zooxanthellae to the animal tissue each day, but that little net carbon movement between these two organisms occurs at night.
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  • 8
    Publication Date: 1983-01-01
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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  • 9
  • 10
    Publication Date: 1977-01-01
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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