[Chemical and physical studies on the eggshell of 4 species of running birds (Struthioniformes)].
Explore the source record for details and available documents.
Animals↗
SEARCH · PubMed Health
Results for “eggshell”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Sources and timing of calcium mobilization during embryonic development of the corn snake, Pantherophis guttatus.
Embryos of oviparous Reptilia (=turtles, lepidosaurs, crocodilians and birds) extract calcium for growth and development from reserves in the yolk and eggshell. Yolk provides most of the calcium to embryos of lizards and snakes. In contrast, the eggshell supplies most of the calcium for embryonic development of turtles, crocodilians and birds. The yolk sac and chorioallantoic membrane of birds recover and transport calcium from the yolk and eggshell and homologous membranes of squamates (lizards and snakes) probably transport calcium from these two sources as well. We studied calcium mobilization by embryos of the snake Pantherophis guttatus during the interval of greatest embryonic growth and found that the pattern of calcium transfer was similar to other snakes. Calcium recovery from the yolk is relatively low until the penultimate embryonic stage. Calcium removal from the eggshell begins during the same embryonic stage and total eggshell calcium drops in each of the final 2 weeks prior to hatching. The eggshell supplies 28% of the calcium of hatchlings. The timing of calcium transport from the yolk and eggshell is coincident with the timing of growth of the yolk sac and chorioallantoic membrane and expression of the calcium binding protein, calbindin-D28K, in these tissues as reported in previous studies. In the context of earlier work, our findings suggest that the timing and mechanism of calcium transport from the yolk sac of P. guttatus is similar to birds, but that both the timing and mechanism of calcium transport by the chorioallantoic membrane differs. Based on the coincident timing of eggshell calcium loss and embryonic calcium accumulation, we also conclude that recovery of eggshell calcium in P. guttatus is regulated by the embryo.
Animals↗
Influence of the microstructure on the shell strength of eggs laid by hens of different ages.
1. The eggshell is a bioceramic material constructed of columnar calcite crystals preferentially oriented with their c-axis perpendicular to the shell surface. 2. The influence of microstructure (crystal size, shape and crystallographic orientation of crystal grains) on the mechanical properties of eggshells (shell strength) was investigated using eggs from hens of different ages. 3. There was a strong correlation between crystallographic texture and the strength of the eggshell in the case of eggs laid by young hens. The strength of eggshells increased as the preferential orientation of the crystals constituting the eggshell decreased. 4. By comparing two age populations, the effect of hen age on eggshell properties was evaluated. In general, eggshells from aged hens had a lower breaking strength (less than half that of those laid by young hens) and showed a greater variability in their structural properties such as thickness, grain morphology and crystallographic texture. 5. Texture analysis revealed that shells from eggs laid by aged hens have two preferred crystal orientations, after (001) and (104), compared with mainly one, after (001), in eggs laid by young hens. 6. These observed changes in eggshell properties could be due to changes in the organic matrix of the eggshell associated with ageing of the hens.
Age Factors↗
Resistance of the shell membrane and mineral layer to diffusion of oxygen and water in flexible-shelled eggs of the snapping turtle (Chelydra serpentina).
At oviposition, flexible eggshells of many turtles have an outer mineral layer and an inner membrane layer of approximately equal thickness. We measured conductances of both layers to H2O and O2 at various levels of eggshell hydration. Both the mineral layer of the eggshell and the shell membrane offer significant resistance to diffusion of water vapor and oxygen in eggshells of the snapping turtle, Chelydra serpentina. Conductance to water vapor increases in both the membrane and mineral layer with increasing hydration of the eggshell, but conductance to oxygen decreases under similar conditions. Removal of the mineral layer increases conductance to oxygen in moist and dry eggshells, but decreases conductance at intermediate levels of dehydration. Removal of the mineral layer consistently increases conductance to water vapor. The eggshell membrane accounts for 24-76% of overall resistance to diffusion of water vapor. These results suggest that bulk flow of H2O or physical changes in the shell may interact with diffusion to limit gas exchange through the turtle eggshell.
Animals↗
Heritabilities and genetic and phenotypic correlations of egg quality traits in brown-egg dwarf layers.
Albumen height, albumen weight (AW), eggshell color (ESC), eggshell index, eggshell strength, eggshell thickness, eggshell weight (ESW), egg weight (EW), Haugh units, and yolk weight (YW) were measured in 2,272 eggs collected 3 d sequentially from 920 brown-egg dwarf layers caged individually. The restricted maximum likelihood procedure was applied to estimate heritabilities and genotypic and phenotypic correlations for these egg quality traits. Heritabilities of albumen height, AW, ESC, eggshell index, eggshell strength, eggshell thickness, ESW, EW, Haugh units, and YW were 0.51, 0.59, 0.46, 0.40, 0.24, 0.34, 0.64, 0.63, 0.41, and 0.45, respectively. The genetic correlations between EW and AW, YW, and ESW were high ranging from 0.67 to 0.97, whereas those for ESC with external and internal egg quality traits were low ranging from -0.23 to 0.13. Thus although heritabilities for these traits were moderate to high, genetic correlations with ESC were low, suggesting a minor relationship between shell color and physical attributes of the shell as well as internal egg quality in brown-egg dwarf layers.
Animals↗
[Enrichment characteristics of heavy metals in heron eggs].
In this study, the eggs and tissues of black-crowned night heron, little egret, Chinese pond heron and cattle egret were sampled from the Dashu, Yuantong and Taizi mountains in Hefei areas of Anhui Province in April to June 2004, and the residual amounts of Cd, Pb and Cr in the samples were determined by atomic absorption spectrophotometry. The results showed that the test heavy metals could be detected at high levels in the eggshell, egg contents, and tissues of most samples. Eggshell and bone were the two main sites for heavy metals enrichment. Eggshell had significantly higher residues of the heavy metals than egg contents, implying that heavy metals could be excreted by eggshells. The residues of heavy metals in eggshell ranked as Cr > Pb > Cd, and had significant differences among species. Of the three heavy metals, Cr showed the most variation among species, being the highest in eggshell of Chinese pond heron and the lowest in that of cattle egret, but in egg contents, there was no significant difference among species. The variation of Cr residues among species was the second, being the highest in the egg contents of Chinese pond heron but not detected in that of cattle egret. The residues of Pb among species varied little. Since eggshell was easy to collect, it was practical to use it as the indicator to assess the pollution status of wetlands.
Animals↗
Eosinophil chemotactic factor release from neutrophils induced by stimulation with Schistosoma japonicum eggs.
The neutrophil is one of the sources of eosinophil chemotactic factor (ECF) in the presence of some stimulants. In the present study we showed that guinea-pig neutrophils could release ECF upon stimulation with Schistosoma japonicum eggs. ECF release from neutrophils began as early as 5 min after the stimulation and reached a peak at 20 min. When homogenate of the eggs was separated into a water-soluble fraction as soluble egg antigen (SEA) and a water-insoluble fraction (eggshell), both preparations possessed a potent neutrophil-stimulating activity to release ECF. The ECF release was dependent on the concentration of eggshells or SEA or on the number of neutrophils. The neutrophil-stimulating activity of eggshells was stable to heat, HCl, or pronase treatment but sensitive to NaOH treatment. When the eggs or eggshells were washed with acetone or Tween-20, they lost the neutrophil-stimulating activity to release ECF, indicating that the neutrophil-stimulating factor (NSF) possesses a lipid nature. The molecular weight of NSF extracted from the eggshells was estimated to be about 1000 Da by gel chromatography on Sephadex G25. The possible role of eggshells in the formation of eosinophil-rich granulomatous lesions in schistosomiasis japonica is discussed.
Animals↗
Calcium metabolism in olive ridley turtle eggs during embryonic development.
Analyses of calcium, magnesium, sulphur, potassium and phosphorus content of the eggshell, yolk-albumen and embryos of olive ridley turtle, Lepidochelys olivacea, have been carried out at various stages of embryonic development. Calcium is the major inorganic constituent in the egg (shell and yolk-albumen) and embryos. Other elements are present either in trace or in minute trace amounts. The egg contents (yolk and albumen) provide only 40% of the embryonic calcium requirement of the hatchling. The remaining 60% is provided by the eggshell. The eggshell also undergoes a similar reduction in its calcium content from laying to hatching. Elements other than calcium present in the yolk-albumen are sufficient for normal embryonic development. The movement of calcium from the eggshell to the embryo starts at about the 40th day of development at 29.5 degrees C. Birds, turtles and crocodiles use their eggshell as the secondary source of embryonic calcium requirement. This dependence on the eggshell varies in different groups which is highest in birds and lowest in crocodiles.
Albumins↗
Timing of the calcium intake and effect of calcium deficiency on behaviour and egg laying in captive great tits, Parus major.
The calcium demand of egg-laying birds is much higher than in other vertebrates during reproduction. We showed elsewhere that a low level of calcium availability can greatly affect the eggshell quality and reproduction of free-living passerines. However, there are few data on calcium demand and calcium intake in relation to egg laying and behaviour and egg-laying performance under conditions of calcium shortage in nondomesticated birds. We examined these aspects in an experiment with captive great tits, Parus major, on a diet deficient in calcium, with or without snail shells as an additional calcium source. More than 90% of the calcium intake for egg production took place during the egg-laying period. Females ingested about 1.7 times as much calcium as they deposited in eggshells. Removing the snail shells after the first egg resulted in eggshell defects and interruptions of laying after 1-3 d. Females without snail shells doubled their searching effort and started to burrow in the soil and to eat sand, small stones, and their own eggs. Most calcium was consumed in the evening, probably to supplement the calcium available from the medullary bone with an additional calcium source in the gut during eggshell formation. The results demonstrated that eggshell formation requires accurate timing of the calcium intake and that obtaining sufficient calcium is time-consuming, even in calcium-rich environments. These factors pertaining to calcium intake greatly affect the ability of birds to collect sufficient calcium for eggshell formation in calcium-poor areas.
Animals↗
The effect of a commercial UV disinfection system on the bacterial load of shell eggs.
AIMS: To study the effect of UV irradiation on the bacterial load of shell eggs and of a roller conveyor belt. METHODS AND RESULTS: The natural bacterial load on the eggshell of clean eggs was significantly reduced by a standard UV treatment of 4.7 s; from 4.47 to 3.57 log CFU per eggshell. For very dirty eggs no significant reduction was observed. Eggs inoculated with Escherichia coli and Staphylococcus aureus (4.74 and 4.64 log CFU per eggshell respectively) passed the conveyor belt and were exposed to UV for 4.7 and 18.8 s. The reduction of both inoculated bacteria on the eggshell was comparable and significant for both exposure times (3 and 4 log CFU per eggshell). Escherichia coli was reduced but still detectable on the conveyor rollers. The internal bacterial contamination of eggs filled up with diluent containing E. coli or S. aureus was not influenced by UV irradiation. CONCLUSIONS: There is a significant lethal effect of UV irradiation on the bacterial contamination of clean eggshells and recent shell contamination, contamination of rollers can be controlled and the internal contamination of eggs is not reduced. SIGNIFICANCE AND IMPACT OF THE STUDY: The penetration of UV into organic material appears to be poor and UV disinfection can be used as an alternative for egg washing.
Animals↗
Regional and developmental variations of blood vessel morphometry in the chick embryo chorioallantoic membrane.
Avian eggs contain all the necessary materials for embryonic development except for oxygen, which diffuses in from the environment via pores in the hard, calcified eggshell to the chorioallantoic membrane (CAM), the respiratory organ, which is rich in blood vessels. An air cell is formed at the blunt pole of the egg between the two membranes of the eggshell and enlarges during incubation due to water vapor loss. In this study of the CAM of chicken eggs, we compared blood vessel numerical density [N(A(v))], area fraction of blood vessels [A(A(v))], CAM thickness (D(CAM)), total length of blood vessels (L) and surface area of the CAM attached to the eggshell (CAMre) with those under the air cell (CAMac) during incubation. We found that N(A(v)), A(A(v)), D(CAM) and L of the CAM increase with embryonic age and development. The N(A(v)), A(A(v)) and L under the air cell were higher in relation to the rest of the CAM at all ages tested, while the D(CAM) under the air cell was always lower than around the rest of the egg. Since the eggshell over the air cell has a relatively greater porosity, and the respiratory gas exchange ratio there is higher than at other areas of the egg, there is a correlation between all the above morphometric data and the eggshell porosity. This suggests optimization of embryonic gas exchange in the chicken egg. We would like to propose that, during natural incubation, an increased gas diffusion under the air cell, together with increased blood vessel numerical density, may compensate for covering of the central part of the eggshell by the incubating parent.
Age Factors↗
Vital gas exchange and hatchability of turkey eggs at high altitude.
Conductance of turkey eggshells was observed to be significantly (P less than .01) greater at 2000 than at 200 m elevation. It was concluded that the increased conductance may have been due to the Chapman-Enskog relation. Eggshells of nonhatching eggs from the high altitude were examined, and it was determined that despite the increased conductance rate, eggshells with significantly (P less than .05) less functional pore area hatched poorly in both oxygenated and nonoxygenated environments. When oxygen was not supplemented to the incubators at high altitudes, eggshells required significantly (P less than .01) fewer pore concentrations to allow embryos to survive to late stages of embryonic development than eggs in oxygen supplemented environments. However, greater pore concentrations on the air space were required in both environments to complete hatching. Cuticle removal from eggshells incubated in oxygen supplemented incubators at high altitudes significantly (P less than .05) reduced late embryonic mortality. It was concluded that eggshell cuticle removal may be more advantageous to hatchability at high altitude than oxygen supplementation.
Altitude↗
The hatching mechanism in Atlantic halibut (Hippoglossus hippoglossus).
In general fish larvae emerge from the protective egg after secreting a hatching enzyme (HE) from diffusely located hatching gland cells (HGCs). This proteolytic enzyme is distributed over the entire inner part of the eggshell (zona radiata). In a marine flatfish halibut, (Hippoglossus hippoglossus), we have found a more specialized hatching process. A strategic location of the HGCs in a narrow belt on the anterior part of the yolk sac leads to restricted degradation of the eggshell resulting in cleavage of the eggshell into two distinct rigid parts. This hatching process--termed "rim-hatching"--results in an empty eggshell with a lid approximately 1/4 the size of the bottom shell. During the hatching process the yolk sac is reshaped. The posterior part of the yolk sac contracts and the yolk mass is squeezed forward before hatching. This mechanism ensures close contact between the HGCs and the eggshell during the release of the hatching enzyme, which is a prerequisite for restricted degradation of the eggshell.
Animals↗
Histology and functional morphology of the female reproductive tract of the tortoise Gopherus polyphemus.
The oviducts of 25 tortoises (Gopherus polyphemus) were examined by using histology and scanning electron microscopy to determine oviductal functional morphology. Oviductal formation of albumen and eggshell was of particular interest. The oviduct is composed of 5 morphologically distinct regions; infundibulum, uterine tube, isthmus, uterus, and vagina. The epithelium consists of ciliated cells and microvillous secretory cells throughout the oviduct, whereas bleb secretory cells are unique to the infundibulum. The epithelium and endometrial glands of the uterine tube histologically resemble those of the avian magnum which produce egg albumen and may be functionally homologous. The isthmus is a short, nonglandular region of the oviduct and appears to contribute little to either albumen or eggshell formation. The uterus retains the eggs until oviposition and may form both the fibrous and calcareous eggshell. The endometrial glands are histologically similar to the endometrial glands of the isthmus of birds, which are known to secrete the fibers of the eggshell. These glands hypertrophy during vitellogenesis but become depleted during gravidity. The uterine epithelium may supply "plumping water" to the egg albumen as well as transport calcium ions for eggshell formation. The vagina is extremely muscular and serves as a sphincter to retain the eggs until oviposition. Sperm are found within the oviductal lumen and endometrial glands from the posterior tube to the anterior uterus throughout the reproductive cycle. This indicates sperm storage within the female tract, although the viability and reproductive significance of these sperm are unknown.
Animals↗
In vitro hatching of the tapeworm Moniezia expansa (Cestoda: Anoplocephalidae) and some properties of the egg membranes.
In vitro studies revealed that the hatching of oncospheres of Moniezia expansa requires the mechanical breakage of the eggshell and subshell membrane and enzymic digestion of the pyriform apparatus. Removal of the outer two egg membranes elicits the activation of most oncospheres. Between pH 5.0-7.8, there is no significant difference in numbers of oncospheres activated by eggshell removal and the addition of sodium bicarbonate has no effect. Solutions of more extreme pH values (2.0 and 10.0) are harmful and render oncospheres immobile. The subshell membrane forms a barrier to the passage of water in an osmotic gradient and to several molecular and ionic substances. Between the eggshell and subshell membrane is a layer of droplets which have a strong affinity for Sudan stains and which are partially removed by lipase. The eggshell is resistant to a variety of proteolytic enzymes, amylases and lipase. The pyriform apparatus is digested by chymotrypsin and pepsin, though not by trypsin. Both eggshell and pyriform apparatus are dissolved by solutions of sodium sulphide and sodium hypochlorite, indicating that their structures are stabilized by disulphide bonds and other covalent linkages.
Animals↗
Speckled eggs: water-loss and incubation behaviour in the great tit Parus major.
Many small passerine birds worldwide lay white eggs speckled with red, brown and black protoporphyrin pigment spots (maculation). Unlike some patterns of avian eggshell pigmentation which clearly serve a crypsis or signalling function, the ubiquity of maculation among passerines suggests that its origins lie in another function, not specific to any particular ecological or behavioural group. Elsewhere, we have presented evidence that protoporphyrin pigments serve a structural function related to eggshell thickness and calcium availability: eggshell maculation in the great tit Parus major increases with decreasing soil calcium levels, pigments demarcate thinner areas of shell, and both the pigment intensity and distribution are related to shell thickness. Here we show that maculation also affects the rate of water loss from the egg during incubation (approximately Mass Loss per Day or MLD, which is critical to egg viability), but not that of unincubated eggs. We also demonstrate, both by observation and experiment, that the effect of female incubation behaviour on MLD compensates in some way for variation in egg characteristics, and that differences between females in the degree of such compensation are related to differences in clutch maculation. Our results suggest that, while a principal function of maculation in this species may be to strengthen the eggshell, it may also reduce eggshell permeability when large amounts of pigment are used, and that this necessitates a behavioural adjustment from the female during incubation. We discuss these findings and make further testable predictions from our model.
Animals↗
Clarification of effects of DDE on shell thickness, size, mass, and shape of avian eggs.
Moriarty et al. (1986) used field data to conclude that DDE decreased the size or altered the shape of avian eggs; therefore, they postulated that decreased eggshell thickness was a secondary effect because, as a general rule, thickness and egg size are positively correlated. To further test this relationship, the present authors analyzed data from eggs of captive American kestrels. Falco sparverius given DDT- or DDE-contaminated or clean diets and from wild brown pelicans Pelecanus occidentalis collected both before (pre-1946) and after (post-1945) DDT was introduced into the environment. Pertinent data from other field and laboratory studies were also summarized. DDE was not related to and did not affect size, mass, or shape of eggs of the brown pelican or American kestrel; but the relationship of DDE to eggshell thinning held true. Size and shape of eggs of brown pelicans from the post-1945 era and those of kestrels, on DDT-contaminated diets showed some significant, but inconsistent, changes compared to brown pelican data from the pre-1946 era or kestrels on clean diets. In contrast, nearly all samples of eggs of experimental kestrels given DDT-contaminated diets and those of wild brown pelicans from the post-1945 era exhibited significant eggshell thinning. Pertinent experimental studies with other sensitive avian species indicated no effects of DDE on the size or shape of eggs, even though the high dietary concentrations caused extreme eggshell thinning and mortality of some adult mallards (Anas platyrhynchos) in one study. These findings essentially controvert the argument that decreased eggshell thickness is a secondary effect resulting from the primary effect of DDE-induced changes in the size or shape of eggs.
Journal Article↗
Effects of some egg characteristics on the mass loss and hatchability of ostrich (Struthio camelus) eggs.
1. This study was conducted to examine some egg characteristics and determine the effects of eggshell thickness and eggshell porosity on water loss and hatchability of eggs in ostriches. 2. Shell thickness did not correlate significantly with hatchability. However, eggs of low shell thickness lost more mass (13.03%) than those with intermediate (11.22%) and high (10.36%) shell thickness. Mass loss during incubation was higher in hatched (11.98%) than unhatched eggs (11.09%). Shell thickness was negatively correlated to egg mass loss (r = -0.65). 3. The pore density was correlated with hatchability. Hatchability was 50% lower in eggs with low pore densities (40.93%) than with high densities (80.94%). Pore density was positively correlated with egg mass loss (r = 0.63). Incubation mass losses of hatched and unhatched eggs were not significantly different. 4. Mean eggshell water vapour conductance (G) value and shell conductance constant (k) were 87.77 +/- 4.21 mg H2O/d/Torr and 2.44 respectively (n = 15). 5. Because of eggshell functional properties and resulting low egg mass loss hatchability is low when ostrich eggs are artificially incubated. The mass of eggs used in the experiment was relatively high and their eggshell water vapour conductance was low. As a result, egg incubation mass loss was lower than it should be. It is concluded that incubator humidity should be low (25%) to allow enough mass loss during incubation from the eggs.
Animals↗