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| 文件类型： | 文章 |
|---|---|
| 所有的著者/提供者： | Glen A Fox |
| ISSN: | 0043-5643 |
| OCLC号码： | 481764970 |
| 语言注释： | English |
| 注意： | Fig. 2. Structure of Common Tern eggshells collected during this study. A, Inner surface of a viable egg with membranes removed (168×). Note the densely packed, evenly distributed mammillae and prominent pores (arrows). B and D, Inner surface of a non-viable egg with membrane removed (168×). Mammillae are larger, unevenly distributed, and less densely packed. Pores are fewer and less prominent. C, Outer surface of a viable egg with cuticle removed showing a normal pore (1690×). Fig. 3. Structure of Common Tern eggshells collected during this study. A, Radial view of broken edge of a viable egg (770×). Note tightly packed mammillae and even, spongy appearance. B, Same view of a non-viable egg (420×). The mammillae are less densely packed, and the palisade layer is disorganized and cavitated. C, Tangential view of the outer surface of a viable egg with cuticle removed (1680×). Note the close-fitting, regular-shaped junctions between columns. D, Same view of a non-viable egg (840×). Junctions between columns are irregular in shape and widely separated with prominent "plugs" of material showing varied crystalline orientation. Fig. 4. Structural abnormalities in Common Tern eggshells collected during this study. A, Oblique view of outer surface of a shell which collapsed on laying (1680×). Note the prominent fissures between mammillae and absence of palisade layer. B, Oblique view of outer surface of a shell whose apex dented inward upon laying (840×). Note the poorly developed palisade layer, disorganized structure, and poor fusion. C and D, Views of the outer surface of two non-viable eggs (1680×) showing abundant globular projections which have been associated by other authors with organochlorine contamination. Fig. 5. The mechanisms and interrelationships by which organochlorines are thought to affect reproductive success in the Common Tern. Solid arrows indicate mechanisms which were observed in this study and shaded arrows represent postulated outcomes. |
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摘要：
A portable beta-backscatter gauge was used to measure the shell quality of 416 eggs laid in a colony of Common Terns located on Buffalo Lake, Alberta, Canada (52° 20′ N, 112° 50′ W) in 1972. Eggshell quality as measured by beta-backscatter (a composite response to thickness, chemical composition and ultrastructure) was an important determinant of hatching success. Abnormalities in shell structure and chemical composition were responsible for shell damage, which resulted in egg disappearance, and for death through hypoxia. There were also indications that low levels of DDE contamination had detrimental effects on the visual perception of chicks. No difference in intensity of incubation instinct could be detected between parents who produced eggs with high and low quality shells. Eggshells had a mean thickness index which was 3.8% lower than the pre-1945 mean for this geographical population. Denting of shells accompanied a 13.3% decrease in the thickness index which was not accompanied by a significant decrease in calcium content, but by increased molar Mg:Ca ratio. Both dented shells and shells of eggs in which the embryo died had significantly increased phosphorus contents when compared to shells surrounding viable embryos. Although small size of the pre-1945 sample prevented statistical comparisons, the chemical and physical characteristics of shells surrounding viable embryos were very similar to pre-1945 shells. Scanning electron microscopy revealed that shells of eggs in which embryos died had 44% fewer pores, and 21% fewer mammillae which were larger and more irregular in their distribution than those of shells of eggs which hatched. Evaporative water loss from eggs which were incubated but failed to hatch was 39% less than that from eggs which hatched, reflecting the reduction in pore numbers. The mean DDE content of 39 eggs with nondented shells was 3.42 ppm wet weight, while 5 eggs with dented shells contained a mean of 6.77 ppm. PCB's were present at about 1/10 the concentration of DDE. Food fish from Buffalo Lake contained a mean DDE content of 0.02 ppm wet weight basis. Hence, contamination is assumed to occur on the wintering grounds.
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添加标签 目的是为 "Eggshell Quality: Its Ecological and Physiological Significance in a DDE-Contaminated Common Tern Population".
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