In ovo metabolism of estradiol to estrone sulfate in chicken eggs: Implications for how yolk estradiol influences embryonic development

The steroid 17β-estradiol (herein "estradiol") is a potent regulator of sexual differentiation that exerts wide-ranging effects on the developing brain and other tissues. The developing gonads are an important source of estradiol but most, if not all, vertebrate embryos are also exposed to maternally derived estradiol during development. In birds, this maternally derived estradiol is present in the egg at the time of oviposition but very little is known about how this source of estradiol influences development. A critical aspect of understanding yolk estradiol effects is deciphering how steroid metabolism may regulate embryonic exposure to yolk estradiol. In this study, we examine the metabolic fate of estradiol during the first five days of incubation in chicken (Gallus gallus) eggs. Using tritiated estradiol to trace the movement and metabolism of estradiol, we demonstrate that estradiol is metabolized to estrone, which is subsequently conjugated to estrone sulfate as the primary metabolite. Estrone sulfate then accumulates in the albumen by day five of incubation. Overall, these findings have important implications for how yolk estradiol may influence development and alter offspring phenotype. Mechanisms through which estradiol, as well as estrone sulfate, might elicit effects are discussed.

Effects of high-intensity ultrasonic (HIU) treatment on the functional properties and assemblage structure of egg yolk

The effects of high-intensity ultrasonic (HIU) treatment on the functional properties of egg yolk were studied in the present work. After HIU treatment, the emulsifying, foaming and gel properties of the egg yolk solution significantly increased, but the foam stability decreased. SDS-PAGE results showed that there was no obvious change in the protein bands of egg yolk, indicating that the yolk proteins did not undergo covalent crosslinking or degradation. HIU treatment enhanced the zeta potential of egg yolk components in solution and increased the free sulfhydryl content of egg yolk proteins. Moreover, the particle size distribution of egg yolk components in solution changed markedly, and these changes demonstrated that HIU treatment caused the aggregation of yolk low-density lipoprotein and the partial dissociation of yolk granules. These results revealed that HIU treatment could change the aggregation of yolk components, which in turn could influence the solution characteristics of egg yolk, finally resulting in changes to the functional properties of egg yolk.

Sodium alginate potentiates antioxidants, cryoprotection and antibacterial activities of egg yolk extender during semen cryopreservation in buffalo

The study was conducted to determine effects of sodium alginate on sperm during cryopreservation. Each ejaculate (n = 20) of five buffalo bulls (3-5 years) were divided into six equal fractions and diluted using egg yolk based extender supplemented with different concentrations of sodium alginate and cryopreserved. Frozen-thawed semen samples were evaluated using the CASA, hypo-osmotic swelling test, cervical mucus penetration capacity test, and chlortetracycline fluorescence assay (CTC). Phosphorylation of tyrosine containing proteins and malondialdehyde concentration of sperm membrane were evaluated using immunoblotting and thiobarbituric acid reactive substance assay respectively. The semen extender's anioxidative capacities were estimated by conducting 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays, metal chelating capacity by assessing ferrozine and antibacterial capacity using agar plate methods. Supplementation of sodium alginate in extender improved sperm longevity, plasma membrane integrity as well as capacity to transit through the cervical mucus. Supplementation of extender with sodium alginate minimises the phase transition of sperm membranes and phosphorylation of tyrosine containing proteins during cryopreservation. Malondialdehyde concentration of sperm was less in sodium alginate-treated sperm as compared with control samples. The results indicated that sodium alginate increased antioxidant capacity of semen extender. Supplementation with sodium alginate also improved the metal chelating capacity and antibacterial properties of the extender. In conclusion, supplementation of extender with sodium alginate enhances free radical scavenging, metal reduction and chelating capacities to protect sperm during cryopreservation.

Liquid storage of dromedary camel semen in different extenders

This study was conducted to assess the effects of commercial extenders and storage temperature on dromedary camel sperm quality during liquid preservation. In Experiment 1, ejaculates (n = five males; replicated seven times) were split and diluted with synthetic (OPTIXcell, EquiPlus, INRA96, Bioxcell or AndroMed; Experiment 1a) or egg-yolk based (Biladyl, Green buffer or Triladyl; Experiment 1b) extenders and stored for 48 h at 4 °C. In Experiment 2, split ejaculates (n = five males; replicated six times) were used to directly compare Green buffer, OPTIXcell and Triladyl extenders over 48 h of storage at 4 °C. Ejaculates collected in Experiment 3 (n = five males; replicated five times) were diluted with Green buffer or Triladyl before chilled storage for 48 h at 4 or 15 °C. Sperm kinematics, viability and acrosome integrity were assessed during liquid storage. In Experiment 1a, there was the greatest total sperm motility (TM) in the OPTIXcell group following 24 and 48 h of storage, while in Experiment 1b, there was the greatest TM after 48 h of storage with Triladyl and Green buffer. In Experiment 2, there were greater TM and viable acrosome intact spermatozoa in the Triladyl and Green buffer than with OPTIXcell group. In Experiment 3, there was a greater TM in the Triladyl than Green buffer group at 24 and 48 h of storage regardless of storage temperature (which had no effect on sperm quality). In conclusion, camel sperm have greater viability when preserved in liquid form for 48 h following dilution with Triladyl and storage at either 4 or 15 °C.

Boat noise affects the early life history of two damselfishes

Anthropogenic noise can have a negative effect on the physiology and survival of marine fishes. Most research has focused on later life-stages, and few studies have investigated the effects of human-induced noise on embryogenesis. The current study investigated whether playback of motorboat noise affected the embryogenesis of the coral reef damselfishes, Amphiprion melanopus and Acanthochromis polyacanthus. Embryos reared under the playback of boat noise had faster heart rates compared to the ambient reef controls. The effects of noise on morphological development differed between species and the fundamental interrelationships between early life history characteristics changed dramatically under boat noise for Ac. polyacanthus. Noise treatments did not alter the survival rates of embryos under laboratory conditions. Although species specific, our findings suggest that anthropogenic noise causes physiological responses in fishes during embryogenesis and these changes have direct impacts on their development and these alterations may have carry-over effects to later life stages.

LC-MS/MS-Based Metabolome Analysis of Biochemical Pathways Altered by Food Limitation in Larvae of Ivory Shell, Babylonia areolata

Ivory shell, Babylonia areolata, is one of the commercially important mariculture species in China and South East Asia. Survival varies in the artificial hatching and larval rearing of B. areolata. Food deprivation may be involved in rearing mortality, and so, a better understanding of how larvae respond and adjust to starvation is needed. In this study, the metabolite profiles of newly hatched larvae with yolk (I), larvae with yolk exhaustion (II), larvae suffering 24 h starvation after yolk exhaustion (III), and larvae fed with exogenous nutrients after yolk exhaustion (IV) were analyzed by LC-MS/MS. Principal component and cluster analyses revealed differential abundance of metabolite profiles across groups. When compared to metabolite levels of the I group, significantly up-regulated metabolites included polyunsaturated fatty acids, phospholipids, nucleotide, amino acids, and their derivatives were found in the II group, indicating that organisms relied predominantly on glycerophospolipid metabolism and protein-based catabolism for energy production during this stage. During starvation after yolk exhaustion, the levels of all energy related metabolites were significantly reduced, but an increase in products of purine and pyrimidine metabolism indicated an insufficient energy supply and an increase in cellular disintegration. Larvae fed exogenous nutrients can have significantly improved metabolism compared to starved larvae. These findings suggest that metabolomics, using LC-MS/MS, can be used to assess the physiological status and food-affected metabolic changes affecting B. areolata larvae.

High post-thaw survival of ram sperm after partial freeze-drying

BACKGROUND

Recrystallization damages occur when a frozen sample is held at high subzero temperatures and when the warming process is too slow.

METHODS

In this work, ram semen diluted in two different concentrations of sugar solutions (Lyo A consisted of 0.4 M sorbitol and 0.25 M trehalose, and the second, Lyo B composed of 0.26 M sorbitol and 0.165 M trehalose) in egg yolk and Tris medium were compared after freezing 10 μL samples to: (1) - 10, - 25, and - 35 °C and thawing. (2) Freezing to - 10 and - 25 °C, holding for 1 h and then thawing, and (3) freezing to - 10 and - 25 °C and drying for 1 h at these temperatures at a vacuum of 80 mTorr, prior thawing. For drying, we used a new freeze-drying apparatus (Darya, FertileSafe, Israel) having a condensation temperature below - 110 °C and a vacuum pressure of 10-100 mTorr that is reached in less than 10s.

RESULTS

Results showed that samples in Lyo B solution frozen at - 25 °C had significantly higher sperm motility in partially freeze-dried samples than frozen samples (46.6 ± 2.8% vs 1.2 ± 2.5%, P < 0.001). Moreover, partially dried samples in Lyo B showed higher motility than Lyo A at - 25 °C (46.6 ± 2.8% vs 35 ± 4%). Cryomicroscopy and low-temperature/low-pressure environmental scanning electronic microscope demonstrated that the amount of the ice crystals present in partially dried samples was lower than in the frozen samples.

CONCLUSION

Holding the sperm at high subzero temperatures is necessary for the primary drying of cells during the freeze-drying process. Rapid freeze-drying can be achieved using this new device, which enables to reduce recrystallization damages.

Maternal corticosterone deposition in avian yolk: Influence of laying order and group size in a joint-nesting, cooperatively breeding species

Glucocorticoid hormones play a key role in day-to-day adjustments to fluctuating metabolic needs. These hormones also mediate physiological and behavioral responses to stressful events, allowing individuals to cope with stressors. Various environmental insults, such as a food shortages, predation attempts, and agonistic encounters often elevate plasma glucocorticoid levels in vertebrates. Because exposure to maternally-derived (via circulation or egg) glucocorticoids may be detrimental to the developing embryo, maternal stress can have negative carryover effects on offspring fitness. We examined corticosterone, the primary avian glucocorticoid, concentrations in egg yolk in a plural-breeding, joint-nesting species, the smooth-billed ani (Crotophaga ani), in which females compete among themselves to lay eggs in the final incubated clutch. We investigated whether yolk corticosterone levels varied with laying order and group size. Because egg-laying competition leads to physiological and social stress that is intensified with group size and laying order, we predicted that yolk corticosterone levels should increase from the early to the late egg-laying period and from single female to multi-female groups. In this two-year field study, we found that yolk corticosterone levels of late-laid eggs within the communal clutch were higher in multi-female groups than in single female groups. Results from this study suggest that laying females experience higher levels of stress in multi-female groups and that this maternal stress influences yolk corticosterone concentrations. This study identifies a novel cost of group-living in plural-breeding cooperatively breeding birds, namely an increase in yolk corticosterone levels with group size that may result in detrimental effects on offspring development.

A Survey of the Impact of Deyolking on Biological Processes Covered by Shotgun Proteomic Analyses of Zebrafish Embryos

Deyolking, the removal of the most abundant protein from the zebrafish (Danio rerio) embryo, is a common technique for in-depth exploration of proteome-level changes in vivo due to various environmental stressors or pharmacological impacts during embryonic stage of development. However, the effect of this procedure on the remaining proteome has not been fully studied. Here, we report a label-free shotgun proteomics survey on proteome coverage and biological processes that are enriched and depleted as a result of deyolking. Enriched proteins are involved in cellular energetics and development pathways, specifically implicating enrichment related to mitochondrial function. Although few proteins were removed completely by deyolking, depleted molecular pathways were associated with calcium signaling and signaling events implicating immune system response.

Promising Loci and Genes for Yolk and Ovary Weight in Chickens Revealed by a Genome-Wide Association Study

Because it serves as the cytoplasm of the oocyte and provides a large amount of reserves, the egg yolk has biological significance for developing embryos. The ovary and its hierarchy of follicles are the main reproductive organs responsible for yolk deposition in chickens. However, the genetic architecture underlying the yolk and ovarian follicle weights remains elusive. Here, we measured the yolk weight (YW) at 11 age points from onset of egg laying to 72 weeks of age and measured the follicle weight (FW) and ovary weight (OW) at 73 weeks as part of a comprehensive genome-wide association study (GWAS) in 1,534 F₂ hens derived from reciprocal crosses between White Leghorn (WL) and Dongxiang chickens (DX). For all ages, YWs exhibited moderate single nucleotide polymorphism (SNP)-based heritability estimates (0.25–0.38), while the estimates for FW (0.16) and OW (0.20) were relatively low. Independent univariate genome-wide screens for each trait identified 12, 3, and 31 novel significant associations with YW, FW, and OW, respectively. A list of candidate genes such as ZAR1, STARD13, ACER1b, ACSBG2, and DHRS12 were identified for having a plausible function in yolk and follicle development. These genes are important to the initiation of embryogenesis, lipid transport, lipoprotein synthesis, lipid droplet promotion, and steroid hormone metabolism, respectively. Our study provides for the first time a genome-wide association (GWA) analysis for follicle and ovary weight. Identification of the promising loci as well as potential candidate genes will greatly advance our understanding of the genetic basis underlying dynamic yolk weight and ovarian follicle development and has practical significance in breeding programs for the alteration of yolk weight at different age points.

Influence of mate preference and laying order on maternal allocation in a monogamous parrot species with extreme hatching asynchrony

It is well established that in many avian species, prenatal maternal resource allocation varies both between and within clutches and may affect offspring fitness. Differential allocation of maternal resources, in terms of egg weight and yolk composition, may therefore allow the female to adjust brood reduction and to fine-tune reproductive investment in accordance with the expected fitness returns. The adaptive value of such maternal resource allocation is thought to be context-dependent as well as species-specific. We investigated the effects of female preference for her mate on the allocation of prenatal maternal resources in the budgerigar, Melopsittacus undulatus, a monogamous species of parrot that shows an extreme hatching asynchrony. We assessed mate preferences in a two-way preference test and allowed females two breeding rounds: one with the preferred and one with the non-preferred partner. We found no effect of preference on either latency to lay or clutch size, but females mated with the preferred partner laid eggs that contained significantly more yolk. Their eggs also contained significantly more androstenedione but not testosterone. Our results suggest that in this species, female preference may influence maternal resource allocation, and that the functional roles of each androgen in the yolk should be considered separately. In addition, we found a significant effect of laying order on egg and yolk weight as well as on yolk testosterone and androstenedione levels. These measures, however, did not change linearly with the laying order and render it unlikely that female budgerigars compensate for the extreme hatching asynchrony by adjusting within-clutch allocation of prenatal maternal resources.

Experimental parameterisation of principal physics in buoyancy variations of marine teleost eggs

It is generally accepted that the high buoyancy of pelagic marine eggs is due to substantial influx of water across the cell membrane just before ovulation. Here we further develop the theoretical basis by applying laboratory observations of the various components of the fertilized egg in first-principle equations for egg specific gravity (ρ_egg) followed by statistical validation. We selected Atlantic cod as a model animal due to the affluent amount of literature on this species, but also undertook additional dedicated experimental works. We found that specific gravity of yolk plus embryo is central in influencing ρ_egg and thereby the buoyancy. However, our established framework documents the effect on ρ_egg of the initial deposition of the heavy chorion material in the gonad prior to spawning. Thereafter, we describe the temporal changes in ρ_egg during incubation: Generally, the eggs showed a slight rise in ρ_egg from fertilization to mid-gastrulation followed by a gradual decrease until full development of main embryonic organs just before hatching. Ontogenetic changes in ρ_egg were significantly associated with volume and mass changes of yolk plus embryo. The initial ρ_egg at fertilization appeared significantly influenced by the chorion volume fraction which is determined by the combination of the final chorion volume of the oocyte and of the degree of swelling (hydrolyzation) prior to spawning. The outlined principles and algorithms are universal in nature and should therefore be applicable to fish eggs in general.

Maternal diet influences offspring feeding behavior and fearfulness in the precocial chicken

Background

In chicken, oils in the maternal diet confer a specific scent to the yolk. Embryos are known to perceive and memorize chemosensory signals of the surrounding environment; however, the potential impact of the maternal diet has not previously been investigated. In the present study, we hypothesized that chicken embryos memorize the chemical signals of the maternal diet and that this perceptual learning may orient subsequent feeding behavior of the hatchlings.

Methodology/Principal Findings

Laying hens were fed standard food enriched with 2% menhaden oil (MH group) or 2% soybean oil (controls). The scent of menhaden was significantly more detected in MH egg yolks than in control yolks by a human panel. We analyzed the development and behavior of offspring towards different types of food, bearing or not bearing the menhaden scent. When chicks were exposed to a 3-min choice test between the familiar food bearing the menhaden scent and the familiar food without menhaden, no effect of treatment was observed. In a 3-min choice test with unfamiliar food (mashed cereals) MH chicks showed a clear positive orientation toward the unfamiliar food bearing the menhaden scent. By contrast, control chicks showed a preference for the non-odorized unfamiliar food. MH chicks expressed higher emotional reactivity level than control chicks as expressed by food neophobia and longer immobility in a restraint test.

Conclusion/Significance

Chicks exposed in ovo to menhaden oil via the maternal diet preferentially oriented their feeding behavior towards food containing menhaden oil, but only when the food was unfamiliar. We propose that oil in the maternal diet engenders maternal effects and contributes to the development of behavioral phenotype in the offspring. In ovo chemosensory learning may have evolved to prepare precocial offspring for their environment. This suggests a common principle of embryonic chemosensory learning across vertebrate taxa.

Effects of food availability on yolk androgen deposition in the black-legged kittiwake (Rissa tridactyla), a seabird with facultative brood reduction

In birds with facultative brood reduction, survival of the junior chick is thought to be regulated primarily by food availability. In black-legged kittiwakes (Rissa tridactyla) where parents and chicks are provided with unlimited access to supplemental food during the breeding season, brood reduction still occurs and varies interannually. Survival of the junior chick is therefore affected by factors in addition to the amount of food directly available to them. Maternally deposited yolk androgens affect competitive dynamics within a brood, and may be one of the mechanisms by which mothers mediate brood reduction in response to a suite of environmental and physiological cues. The goal of this study was to determine whether food supplementation during the pre-lay period affected patterns of yolk androgen deposition in free-living kittiwakes in two years (2003 and 2004) that varied in natural food availability. Chick survival was measured concurrently in other nests where eggs were not collected. In both years, supplemental feeding increased female investment in eggs by increasing egg mass. First-laid ("A") eggs were heavier but contained less testosterone and androstenedione than second-laid ("B") eggs across years and treatments. Yolk testosterone was higher in 2003 (the year with higher B chick survival) across treatments. The difference in yolk testosterone levels between eggs within a clutch varied among years and treatments such that it was relatively small when B chick experienced the lowest and the highest survival probabilities, and increased with intermediate B chick survival probabilities. The magnitude of testosterone asymmetry in a clutch may allow females to optimize fitness by either predisposing a brood for reduction or facilitating survival of younger chicks.

Brood reduction via intra-clutch variation in testosterone--an experimental test in the great tit

In birds, yolk androgen concentrations in eggs can increase or decrease over the laying sequence and common hypotheses hold that this serves to favour the competitive ability of either first- or last-hatched chicks depending on the prevailing conditions, and thus promote brood reduction or maintenance of original brood size respectively. Intra-clutch variation of testosterone can shift relative competitive ability of siblings and hence competitive dynamics. In a natural population of great tits, we experimentally investigated the effects and function of maternal testosterone on offspring phenotype in relation to the laying position of the egg in a context of hatching asynchrony. To this end, we created three types of clutches where either the first three or the last three eggs of a clutch were injected with testosterone (T) dissolved in sesame oil, and the remaining eggs with sesame oil only, or where all eggs of a clutch were injected with sesame oil. Increased levels of yolk T in the last-laid eggs resulted in the last-hatched chicks being significantly lighter and smaller than their siblings, while increased levels of T in the first-laid eggs had no direct effect on the first-hatched chicks, but an indirect negative effect on their siblings. Our results suggest that females can potentially adjust offspring phenotype by modulating, over the laying sequence, the amounts of T deposited in the eggs. These results are in contradiction, however, with current hypotheses and previous findings, which suggest that under good conditions higher levels of maternally derived T in the last-laid eggs should mitigate the negative effects of hatching asynchrony.

Relative bioavailability to laying hens of indicator polychlorobiphenyls present in soil

Transfer of indicator polychlorobiphenyls (PCBs) from soil into hen eggs may occur in hens reared outdoor, which ingest significant amounts of soil. This transfer depends on the bioavailability of the ingested compounds. The impact of soil on the bioavailability of indicator PCBs was assessed by means by a relative bioavailability (RBA) trial, in which their deposition in egg yolk and in abdominal fat, in response to their ingestion through contaminated-soil and through spiked-oil were compared. A sandy soil (709 μg indicator PCBs kg(-1) dry matter) was collected in the vicinity of a former fire involving treated wood. Twenty-eight laying hens were individually housed and fed one of the seven experimental diets during 14 d. The seven experimental diets were an uncontaminated control diet, three diets in which contaminated soil was introduced at levels of 3%, 6% and 9% and three diets in which spiked oil was introduced to achieve similar levels and profile of contaminants. Yolk, abdominal fat and liver were collected at the end of exposure. Indicator PCBs were extracted by ASE (Accelerated Solvent Extraction) and analyzed by GC-HMRS. Within each ingested matrix, the concentration of indicator PCBs in yolk and in abdominal fat linearly increased with the amount of indicator PCB ingested (P<0.001). Except for PCB 28, the slopes of the responses to soil and to oil could not be differentiated (P>0.1). RBA estimates did not differ from 1 for all indicator PCBs except for PCB 28, for which it was 0.58-0.59. Measurements performed on liver confirm these conclusions.

Intra-clutch ratio of yolk progesterone level changes with laying date in rockhopper penguins: a strategy to influence brood reduction?

Hatching asynchrony in avian species generally leads to a size hierarchy among siblings, favouring the first-hatched chicks. Maternally deposited hormones affect the embryo and chick's physiology and behaviour. It has been observed that progesterone, a hormone present at higher levels than other steroid hormones in egg yolks, is negatively related to body mass in embryos, chicks and adults. A differential within-clutch progesterone deposition could therefore be linked to the size hierarchy between siblings and to the resulting brood reduction. We tested whether yolk progesterone levels differed between eggs according to future parental ability to feed the entire clutch in wild rockhopper penguins Eudyptes chrysocome. This species presents a unique reversed egg-size dimorphism and hatching asynchrony, with the larger second-laid egg (B-egg) hatching before the smaller first-laid egg (A-egg). Yolk progesterone levels increased only slightly with female body mass at laying. However, intra-clutch ratios were not related to female body mass. On the other hand, yolk progesterone levels increased significantly with the date of laying onset for A-eggs while they decreased for B-eggs. Early clutches therefore had proportionally more progesterone in the B-egg compared to the A-egg while late clutches had proportionally less progesterone in the B-egg. We propose that females could strategically regulate yolk progesterone deposition within clutches according to the expected food availability during chick growth, an adaptive strategy to adjust brood reduction to conditions. We also discuss these results, relating to yolk progesterone, in the broader context of other yolk steroids.

Nuclear accumulation of Smad complexes occurs only after the midblastula transition in Xenopus

Activin and the Nodal-related proteins induce mesendodermal tissues during Xenopus development. These signals act through specific receptors to cause the phosphorylation, at their carboxyl termini, of Smad2 and Smad3. The phosphorylated Smad proteins form heteromeric complexes with Smad4 and translocate into the nucleus to activate the transcription, after the midblastula transition, of target genes such as Xbra and goosecoid (gsc). In this paper we use bimolecular fluorescence complementation (BiFC) to study complex formation between Smad proteins both in vivo and in response to exogenous proteins. The technique has allowed us to detect Smad2-Smad4 heteromeric interactions during normal Xenopus development and Smad2 and Smad4 homo- and heteromers in isolated Xenopus blastomeres. Smad2-Smad2 and Smad2-Smad4 complexes accumulate rapidly in the nuclei of responding cells following Activin treatment, whereas Smad4 homomeric complexes remain cytoplasmic. When cells divide, Smad2-Smad4 complexes associate with chromatin, even in the absence of ligand. Our observation that Smad2-Smad4 complexes accumulate in the nucleus only after the midblastula transition, irrespective of the stage at which cells were treated with Activin, may shed light on the mechanisms of developmental timing.

Vertebrate Yolk Complexes and the Functional Implications of Phosvitins and Other Subdomains in Vitellogenins1

In nonplacental or nontrophotenic vertebrates, early development depends on the maternal provision of egg yolk, which is mainly derived from large multidomain vitellogenin (Vtg) precursors. To reveal the molecular nature of the protein pools in vertebrate oocytes, published data on the N-termini of yolk proteins has been mapped to the deduced primary structures of their parent Vtgs. The available evidence shows that the primary cleavage sites of Vtgs are conserved, whereas the cleavage products exist as multidomain variants in the yolk protein pool. The serine-rich phosvitin (Pv) domains are linearly related to the molecular masses of the lipovitellin heavy chain. The 3-D localization of Pv maps to the outer edges of the Vtg monomer, where it is proposed to form amphipathic structures that loop up over the lipid pocket. At this locus, it is proposed that Pv stabilizes the nascent Vtg while it receives its lipid cargo, thereby facilitating the hepatic loading and locking of lipid within the Vtg (C-sheet)-(A-sheet)-(LvL) cavity, and enhances its solubility following secretion to the circulating plasma. The C-terminal regions of Vtgs are homologous to human von Willebrand factor type D domains (Vwfd), which are conserved cysteine-rich molecules with homologous regions that are prevalent in Vtgs, lipophorins, mucins, integrins, and zonadhesins. Unlike human VWFD, lower vertebrate Vwfds do not contain RGD motifs, which are associated with extracellular matrix binding. Although its function in Vtg is unknown, the lubricant properties associated with mucins and the cell adhesion properties associated with integrins and zonadhesins implicate Vwfd in the genesis of hemostatic platelet aggregation. Similarly, the proteolytic inhibitory properties associated with the binding of factor VIII in humans suggest that Vwfd stabilizes Vtg during passage in the systemic circulation.

Maternal effects and the evolution of brain size in birds: overlooked developmental constraints

A central dogma for the evolution of brain size posits that the maintenance of large brains incurs developmental costs, because they need prolonged periods to grow during the early ontogeny. Such constraints are supported by the interspecific relationship between ontological differences and relative brain size in birds and mammals. Given that mothers can strongly influence the development of the offspring via maternal effects that potentially involve substances essential for growing brains, we argue that such effects may represent an important but overlooked component of developmental constraints on brain size. To demonstrate the importance of maternal effect on the evolution of brains, we investigated the interspecific relationship between relative brain size and maternal effects, as reflected by yolk testosterone, carotenoids, and vitamins A and E in a phylogenetic study of birds. Females of species with relatively large brains invested more in eggs in terms of testosterone and vitamin E than females of species with small brains. The effects of carotenoid and vitamin A levels on the evolution of relative brain size were weaker and non-significant. The association between relative brain size and yolk testosterone was curvilinear, suggesting that very high testosterone levels can be suppressive. However, at least in moderate physiological ranges, the positive relationship between components of maternal effects and relative brain size may imply one aspect of developmental costs of large brains. The relationship between vitamin E and relative brain size was weakened when we controlled for developmental mode, and thus the effect of this antioxidant may be indirect. Testosterone-enhanced neurogenesis and vitamin E-mediated defence against oxidative stress may have key functions when the brain of the embryo develops, with evolutionary consequences for relative brain size.

Effects of carotenoids from lucerne, marigold and tomato on egg yolk pigmentation and carotenoid composition

1. The effects of various sources of natural carotenoids (Px alfalfa concentrate, tomato powder and marigold extract) as feed additives in quail diets on egg yolk pigmentation and carotenoid composition were investigated. 2. Adult Japanese quail were fed one of 5 different diets for 23 d: three diets each contained Px alfalfa concentrate (PX) or tomato powder (TP) or marigold extract (MG), one diet contained marigold extract and tomato powder (MG + TP) and a control diet (wheat/barley based) was low in carotenoid. All products were added at a rate of 2%, apart from marigold extract which was added at a rate of 0.2%. 3. Visual assessment of yolk colour (Roche colour fan) showed a stabilised yolk colour of 1.6, 7.7, 8.5, 8.8 and 10.6 for the control, PX, TP, MG and MG + TP treatments, respectively. 4. The total carotenoid concentration of the egg yolks were 2.2, 22.4, 4.1, 39.0 and 37.7 microg/g for the experimental groups fed the following diets: control, PX, TP, MG and MG + TP, respectively. Deposition of retinol, alpha-tocopherol and gamma-tocopherol in the egg yolk was unaffected by treatments. 5. Lutein was shown to be the major carotenoid in the egg yolk, comprising 1.65, 17.97, 2.03, 31.14 and 28.57 microg/g in control, PX, TP, MG and MG + TP, respectively. Inclusion of TP in the quail diet resulted in lycopene transfer to the egg. 6. It was concluded that, in comparison with the control group, there was an increase in the yolk concentrations of lutein, zeaxanthin, lycopene and beta-carotene in eggs produced by female quail fed diets supplemented with natural carotenoids.

Influence of the Nest Environment on Bone Mineral Content in Hatchling Painted Turtles (Chrysemys picta)

We performed an experiment at a field site in north-central Nebraska to assess the role of the nest environment in inducing variation in bone mineral content in hatchling painted turtles Chrysemys picta (Schneider 1783). The contents of several newly constructed nests were manipulated by reciprocal transplant, after which the eggs were allowed to incubate for 8 wk under natural conditions. The nests were then excavated, and the eggs were brought into the laboratory to complete incubation and hatch under standard conditions of temperature and moisture. The hatchlings were killed, and their carcasses and residual yolks were analyzed separately for calcium and phosphorus. More of the random variation in carcass calcium and phosphorus was related to the nest in which eggs incubated (37% and 42%, respectively) than was associated with the clutch of origin (21% and 37%). Moreover, hatchlings from some nests contained substantially more calcium and phosphorus than did hatchlings from other nests, both in terms of the absolute amounts of the elements in their carcasses (pointing to variation in body size) and in terms of the concentrations of those elements (pointing to variation in bone density). The amounts of calcium and phosphorus in carcasses of hatchlings were positively correlated with changes in mass of their eggs during the 8 wk that the eggs incubated in nests in the field, thereby indicating that the influence of the nest environment on developing embryos probably was mediated by water exchanges experienced by the eggs. These findings indicate that developmental plasticity underlies a major fraction of the variation in mineral content of hatchling painted turtles emerging from nests in the field. Phenotypic variation attributable to plasticity consequently needs to be addressed in models for life-history evolution of painted turtles and other chelonians producing eggs with soft, flexible shells.

Effects of elevated yolk androgens on perinatal begging behavior in yellow-legged gull (Larus michahellis) chicks

Maternal hormones may represent an important pathway by which mothers can adaptively adjust offspring traits and performance to suit the prevailing environmental conditions. Earlier studies of birds have shown that egg androgens of maternal origin may enhance post-natal offspring 'begging' displays, functioning to solicit parental care. Here we investigate the effects of elevated egg androgen levels on the prenatal begging behavior of yellow-legged gull (Larus michahellis) chicks. At laying, we experimentally increased the concentration of yolk testosterone (T) within the natural range of variation, and, shortly before hatching, we compared the structural properties, rate, and loudness of vocalizations of embryos developing in T- and oil-injected (control) eggs. In addition, we compared the early post-hatch begging rate (measured as the pecking rate towards a dummy gull head) in chicks of the two experimental groups. We found that T embryos produced louder embryonic vocalizations than controls, whereas structural properties and the calling rate did not differ between T and control embryos. The post-hatch begging rate was unaffected by T treatment, but strongly decreased with increasing chick body mass, suggesting that intensity of the begging display was sensitive to chick state and may therefore reliably indicate the need of food in this species. Therefore, the results of this study show for the first time that prenatal T exposure modulates the quality of embryonic vocalizations, but are not in accordance with previous findings reporting increased post-hatching begging intensity following increased prenatal exposure to androgens.

Incubation temperature and hemoglobin dielectric of chicken embryos incubated under the influence of electric field

Eggs from a layer-type breeder flock (Baladi, King Saud University) between 61 and 63 weeks of age were used in 3 trials to study the effects of electric field (EF) during incubation on the internal temperature of incubation, and eggs and hemoglobin (Hb) dielectric of chicken embryos at 18 days of age. Dielectric relative permittivity (epsilon') and conductivity (sigma) of Hb were examined in the range of frequency from 20 to 100 kHz. The values of dielectric increment (Deltaepsilon') and the relaxation times (tau) of Hb molecules were calculated. The internal temperature of eggs was measured in empty (following the removal of egg contents) and fertilized eggs in trials 1 and 2, respectively. The level of the EF was 30 kV/m, 60 Hz. EF incubation of embryos influenced the temperature of incubation and electrical properties of Hb molecules and did not influence the temperature of incubation and internal environment of eggs when empty eggs were incubated. EF incubation of fertilized eggs significantly raised the temperature of incubation, egg air cell, and at the surface of the egg yolk by approximately 0.09, 0.60, and 0.61 degrees F, respectively and Hb epsilon', sigma, Deltaepsilon', and tau as a function of the range of frequency of 20 to 100 kHz when compared with their counterparts of the control group. It was concluded that the exposure of fertilized chicken eggs to EF of 30 kV/m, 60 Hz, during incubation altered dielectric properties of Hb and that probably affected cell to cell communication and created the right environment for enhancing the growing process and heat production of embryos consequently increasing the temperature of the internal environment of the egg, and incubation.

Reorganization of cytoplasm in the zebrafish oocyte and egg during early steps of ooplasmic segregation

The aim of this work is to determine when and how ooplasmic segregation is initiated in the zebrafish egg. To this end, the organization of the ooplasm and vitelloplasm were examined in oocytes and eggs shortly after activation. Ooplasmic segregation, initiated in the stage V oocyte, led to the formation of ooplasmic domains rich in organelles, and ribonucleoproteins. A linear array of closely arranged peripheral yolk globules separated an outer domain of ectoplasm from an inner domain of interconnected endoplasmic lacunae. The structure of this yolk array and the distribution of microinjected labeled tracers suggests that it may provide a barrier limiting ooplasm transit. Loosely arranged yolk globules at the animal hemisphere allow wide connections between the endoplasm and a preblastodisc domain. Activation caused further segregation of ooplasm, reorganization of endoplasmic lacunae, and blastodisc growth. The presence of an endoplasmic cytoskeleton suggests that these changes may be driven by microtubules and microfilaments.

ERK/MAPK regulates ecdysteroid and sorbitol metabolism for embryonic diapause termination in the silkworm, Bombyx mori

The eggs of the silkworm Bombyx mori undergo a state of suspended overt development and diminished metabolism called "diapause" to escape adverse environmental conditions. Termination of Bombyx embryonic diapause requires 2-3 months of low temperature (5 degrees C), but the molecular mechanisms underlying diapause termination are unknown. Diapause termination requires a decrease in the sorbitol concentration, which arrests embryonic development, and the secretion factors from yolk cells that promote embryonic development. In the present study, we report that 20-hydroxyecdysone promoted the development of denuded embryos and that ecdysteroid-phosphate phosphatase (EPPase), which is a key enzyme for active ecdysteroid production, was induced by incubation of diapausing eggs at 5 degrees C. In dechorionated egg cultures, extracellular signal-regulated kinase (ERK), which is activated by incubating diapausing eggs at 5 degrees C, regulated sorbitol-glycogen conversion, ecdysteroid secretion via gene transcription of key enzymes, sorbitol dehydrogenase-2, and EPPase, suggesting that ERK has a key role in diapause termination.

Yolk Testosterone Stimulates Growth and Immunity in House Finch Chicks

Female birds deposit variable amounts of androgens, such as testosterone, into the yolks of their eggs. Evidence suggests that yolk androgens play an important role in the determination of offspring phenotype. While androgens are generally regarded as anabolic and immunosuppressive, studies of the behavioral and physiological effects of yolk androgens on offspring of several avian species have been conflicting, leaving the adaptive significance associated with deposition patterns of yolk androgens unclear. We injected either a physiological dose of testosterone or a control vehicle into house finch (Carpodacus mexicanus) eggs and examined the effects of these injections on offspring growth and immunity. Two days after hatching, nestlings from eggs treated with testosterone were significantly larger than nestlings from eggs treated with a control injection, suggesting a stimulatory effect of yolk androgens in early development. By 8 d after hatching, however, this effect disappeared, and chicks from the two treatment groups were similar in size. Nestlings in the testosterone treatment group showed a significantly larger swelling response to phytohemagglutinin than control nestlings 15 d after hatching, which is close to fledging. Overall, our observations show that when food resources are abundant, testosterone stimulates both early growth and immunity in developing house finches.

Effects of Egg Yolk and Cooling Rate on the Survival of Refrigerated Red Deer (Cervus elaphus hispanicus) Epididymal Spermatozoa

Egg yolk is a common component to sperm refrigeration for most of the deer species, the role of which is to protect sperm membranes against cold shock. In addition, there have been many studies of conservation of ejaculated semen from stags, but few have been reported for epididymal spermatozoa. This work was designed to investigate the combined effects of cooling rates (slow: 0.23 degrees C/min vs rapid: 4.2 degrees C/min) from room temperature to 5 degrees C, and egg-yolk concentration (0, 5 or 20%) in the extender on the survival of Iberian red deer epididymal spermatozoa refrigerated at 5 degrees C. Heterospermic sperm samples were diluted to a final sperm concentration approximately 400x10(6) sperm/ml with a Tris-citrate-fructose (TCF)-egg-yolk diluent. Sperm quality was in vitro judged by microscopic assessments of individual sperm motility [sperm motility index (SMI)], and of plasma membrane (hypo-osmotic swelling test) and acrosome (NAR) integrities. Our results first showed that the presence of egg yolk in the extender significantly improves (p=0.01) the viability and sperm motility after sperm dilution. In addition, acrosome and plasma membrane integrities post-refrigeration did not differ significantly between cooling procedures; however, the SMI differed significantly between cooling procedures (slow: 46.6% vs rapid: 50.0%; p=0.01). Our results also showed that sperm quality was significantly (p<0.01) affected by the combined effects of egg-yolk concentration and cooling procedure, being rapid cooling with 20% of egg yolk the most suitable combination for epididymal sperm refrigeration. In conclusion, egg-yolk improved red deer epididymal spermatozoa characteristics after dilution. Rapid cooling protocol using TCF with 20% egg-yolk significantly improved sperm motility of red deer epididymal spermatozoa after cooling.

A Study on the Interaction of Xylanase and Phytase Enzymes in Wheat-Based Diets Fed to Commercial White and Brown Egg Laying Hens

A trial was conducted to investigate potential interactions between phytase and xylanase enzymes in wheat-based laying diets. Hens (480 ISA-White and 480 ISA-Brown) were distributed into 160 experimental units and fed one of 10 diets containing 75 to 77% wheat from 33 to 64 wk of age with a diet change at 49 wk. Two diets were adequate in P content (0.3 and 0.25% available P in the 2 phases) with or without xylanase (0 or 2,000 U/kg; Avizyme 2300, Danisco Animal Nutrition, Marlborough, Wiltshire, United Kingdom), and 8 diets had reduced P (0.2 and 0.15% available P) with or without xylanase and phytase (0, 300, 500, and 700 ppu/kg; Phyzyme 5000G, Danisco Animal Nutrition). Egg production was higher for ISA-Brown than for ISA-White hens, and ISA-Brown hens were larger. Eggs from ISA-Brown hens had lower albumen height; higher egg, shell, and albumen weights; and lower yolk weight than those from ISA-White hens. Egg production was not affected by the diet. In P-reduced diets without xylanase, phytase significantly increased BW gain in the first period with no change in feed intake or feed efficiency. In P-adequate diets, xylanase increased egg and albumen weight and albumen height. In P-reduced diets with xylanase, increasing levels of phytase increased egg and albumen weight. This trial demonstrated no negative interactions between these enzymes for production traits and no interactions between the diet and strain of hen. These data suggest that poultry producers can use these enzymes individually or together in feed for the Brown and White egg layers used in this study without concern for the strain of hen.

Calcium-regulated fusion of yolk granules during early embryogenesis ofPeriplaneta americana

This work reported membrane fusion of yolk granules (YGs) during early embryogenesis of the insect Periplaneta americana (P. americana). We showed that eggs from Day 5 of embryogenesis possess a greater amount of enlarged YGs in comparison with Day 1. Day 5 is also the period when the largest amount of free calcium is found (approximately 17 mM) within the oothecae from early embryogenesis. Treatment of Day 1-YGs fraction with 17 mM Ca2+ resulted in a YG size pattern very similar to the one observed in Day 5 eggs, where enlarged YGs were formed. YG membrane fusion was observed by fluorescent membrane dye transfer from previously labeled small YGs to larger ones and was also visualized by electron microscopy. We also showed that the small "in fusion" YGs seemed to be acidic, suggesting that acidification is correlated with YG membrane fusion. Hence, it was shown that YGs are capable of membrane fusion in a calcium-dependent manner and this process probably occurs in vivo during early embryogenesis of P. americana.

Experimental manipulation of yolk testosterone affects digit length ratios in the ring-necked pheasant (Phasianus colchicus)

In humans, most of the mammals and one bird species studied so far, the relative length of individual digits is sexually dimorphic. Most studies of humans have been concerned with the ratio between second (2D) and fourth digits (4D), whereas some studies of humans and other mammals have also investigated other digit ratios. Inter- and intra-sexual variation in 2D:4D may depend on differential exposure to androgens during embryonic life, and the genetic mechanisms linking 2D:4D to androgens may be mediated by Hox genes. Because Hox genes are conserved in vertebrates, similar patterns of variation in digit ratios might be expected across vertebrate classes. The observation of correlations between digit ratios and physiological, psychological and performance traits in humans has generated interest in exploring the possibility that digit ratios are a marker of embryonic exposure to androgens, which have diverse consequences on several phenotypic traits. However, the hypothesis that digit ratios depend on androgen effects during development has never been tested experimentally. In this study, we increased testosterone concentration in ring-necked pheasant eggs and measured length ratios between the second, third and fourth digits of both feet in fully grown offspring. Females from testosterone-injected eggs had larger 2D:3D in the left foot, whereas this was not the case in males. The other digit ratios were unaffected by hormone treatment in both sexes. However, digit ratios showed no sexual dimorphism among controls. Thus, present results are consistent with the hypothesis that variation in testosterone levels during development affects digit ratios.

The effect of removal of seminal plasma, egg yolk level and season on sperm freezability of canary buck (Capra hircus)

Goat semen is different from that of other domestic species in its limited tolerance to the inclusion of egg yolk in the freezing medium, and this tolerance depends on the presence of enzymes in the seminal plasma that react with egg yolk, producing toxic compounds to the spermatozoa. Moreover, the goat is a seasonal breeder that shows variations in semen quality throughout the year, and those variations may affect semen freezability; hence in freezing protocols, for instance, removal of seminal plasma (washing) yields varying results. This work was designed to study this problem in Canary goats: semen from six males was collected in spring, autumn or winter, washed or non-washed, diluted in a freezing extender with 1.5, 6 or 12% egg yolk, frozen, and thawed after 2 days, 2 or 6 months of cryopreservation. The effect of egg yolk concentration in the freezing extender was far more important than the effect of washing or season on sperm cryosurvival. The quality of frozen-thawed semen tended to improve as egg yolk concentration increased regardless of the effects of season, washing or period of cryopreservation. Washing produced a positive effect on frozen-thawed semen collected during spring or autumn, but the difference decreased as the concentration of yolk increased. However, washing produced a negative effect on frozen-thawed semen collected during winter, diluted with either 6 or 12% egg yolk. There was no apparent seasonal effect on gross measures of sperm production but the seasonal effect was ever present and was reinforced by freezing.

Feed allowance-genotype interactions in broiler breeder hens

Ad libitum feeding reduces livability and reproductive fitness in broiler breeder hens. Two genotypes, a standard (S) and an experimental dwarf broiler breeder (E), were fed ad libitum (SA and EA, respectively), restricted at 55% of ad libitum feed intake (intermediate restriction) from 6 to 15 wk of age (SI and EI, respectively), or restricted (SR and ER, respectively) to match a standard growth curve with a diluted mash feed (2,400 kcal/kg). The experiment was repeated at 2 locations (experiment 1 = 672 hens in pens from 0 to 40 wk; experiment 2 = 420 hens in pens and cages from 0 to 53 wk). Feed restriction reduced adult BW by 20% compared with ad libitum feeding, delayed sexual maturity by 2 to 4 wk, and improved livability. Hens fed the intermediate diet immediately compensated after 15 wk of age to reach BW, sexual maturity, and livability close to those of ad libitum-fed hens. The E genotype exhibited better tolerance to ad libitum feeding than the S genotype in all measured aspects. Average laying rate during the first 24 wk of lay was 66.4, 77.4, 69.9, 47.2, 57.9, and 72.4% for EA, EI, ER, SA, SI, and SR respectively in experiment 2. Egg abnormalities (double yolk, shell problems) decreased after the peak of lay but remained consistently higher for S compared with E, and for ad libitum and intermediate diets compared with the restricted diet. Yolk deposition rate was measured by a double dye technique. Duration of yolk rapid growth was 8.8 d in E and 9.3 d in S hens (P < 0.001), but this difference did not explain the observed variations in laying rate. The potential to increase feed allowances even with a diluted diet in broiler breeder hens requires adapted genotypes.

[Altricial and precocial developmental features in modern meat-type chicks]

Variability of egg weight, egg yolk content, neonatal growth rate and relationships of these parameters were studied in meat-type chicks. As it had been established the level of variability in neonatal growth traits was greater than variability of the egg morphology parameters. Egg weight had stronger influence on the chicks' neonatal growth rate than egg yolk content did. Low egg size was associated with limited neonatal growth rate variability, declined chick weight at hatching and increased relative growth rate throughout four days post hatch. Comparison of egg morphological parameters in two species having the same female definitive body weight--meat-type domestic fowl (precocial type) and brown pelican (altricial type) has shown, that, in contrary to predicted on the basis of avian developmental typology, egg weight to female body ratio was greater in brown pelican, egg yolk content was equal in both species.

Enhanced yolk testosterone influences behavioral phenotype independent of sex in Japanese quail chicks Coturnix japonica

Studies have demonstrated an effect of yolk testosterone levels on the physiology and behavior of nestling birds. In order to investigate this phenomenon experimentally in a precocial bird, we enhanced yolk testosterone, but within the physiological range, by injecting 50 ng testosterone in ethanol into Japanese quail Coturnix japonica eggs prior to incubation. The chicks hatching from these as well as from control eggs that had received the carrier-only or were left unmanipulated were subject to a number of behavioral tests from hatching to the age of 3 weeks. In addition, fecal samples were taken during a 90-min isolation period to determine a physiological response to a stressor. Experimental chicks performed a detour task faster and approached novel objects sooner than did the controls. Chicks from treated eggs took a longer time to start distress vocalizing and also produced less distress calls during open-field trials, took on average a larger number of trials for them to show tonic immobility and also excreted lower levels of corticosterone metabolites (BM) than did the controls. In response to a stressor, excreted BM was initially higher in the control chicks, as compared to the experimental birds. Induced behavioral effects were independent of sex with no sex treatment interactions found. In sum, experimentally enhanced testosterone levels in the eggs shifted individual behavioral phenotype towards "bold" or "proactive", irrespective of sex. We conclude that testosterone in the yolk influences the coping style of hatchlings and may be a potential means of maternal influence on offspring phenotype.

Effect of meiotic maturation on yolk platelet lipids fromBufo arenarum oocytes

Progesterone induces the resumption of meiosis in Bufo arenarum full-grown arrested oocytes through a nongenomic mechanism called meiotic maturation. Growing evidence indicates that lipids are involved in the maturation process. They are mainly located in yolk platelets, the principal organelles of amphibian oocytes. The aim of the present study was to analyze the effect of progesterone-induced maturation on lipids from B. arenarum yolk platelets. Ovarian oocytes, manually obtained, were incubated with progesterone to induce maturation. Yolk platelets were isolated by centrifugation at low velocity. Lipids were separated by thin-layer chromatography. For compositional analysis, they were derivatized by methanolysis, and were identified and quantified in a gas-liquid chromatograph. Phospholipid content decreased in progesterone-treated oocytes, mainly as a result of a decrease at the level of phosphatidylcholine (PC). The turnover of this lipid is considered crucial for the completion of meiosis. Sphingomyelin also underwent a decrease that could be related to the important role of ceramide as an inducer of germinal vesicle breakdown. Maturation effect on fatty acid composition registered significant changes in PC whose saturated fatty acids increased. A net increase in arachidonic acid was observed in phosphatidylserine after progesterone treatment. The contents of total triacylglycerols and diacylglycerols were not significantly modified by hormone effect while free fatty acids underwent a significant increase as a result of polyunsaturated fatty acids increase. Altogether, our results demonstrate that yolk platelet lipids are involved in the resumption of the meiotic cell cycle, thus suggesting that these organelles participate in a dynamic role during amphibian development.

Oogenesis in the viviparous matrotrophic lizardMabuya brachypoda

Oogenesis in the lizard Mabuya brachypoda is seasonal, with oogenesis initiated during May-June and ovulation occurring during July-August. This species ovulates an egg that is microlecithal, having very small yolk stores. The preovulatory oocyte attains a maximum diameter of 0.9-1.3 mm. Two elongated germinal beds, formed by germinal epithelia containing oogonia, early oocytes, and somatic cells, are found on the dorsal surface of each ovary. Although microlecithal eggs are ovulated in this species, oogenesis is characterized by both previtellogenic and vitellogenic stages. During early previtellogenesis, the nucleus of the oocyte contains lampbrush chromosomes, whereas the ooplasm stains lightly with a perinuclear yolk nucleus. During late previtellogenesis the ooplasm displays basophilic staining with fine granular material composed of irregularly distributed bundles of thin fibers. A well-defined zona pellucida is also observed. The granulosa, initially composed of a single layer of squamous cells during early previtellogenesis, becomes multilayered and polymorphic. As with other squamate reptiles, the granulosa at this stage is formed by three cell types: small, intermediate, and large or pyriform cells. As vitellogenesis progresses the oocyte displays abundant vacuoles and small, but scarce, yolk platelets at the periphery of the oocyte. The zona pellucida attains its maximum thickness during late oogenesis, a period when the granulosa is again reduced to a single layer of squamous cells. The vitellogenic process observed in M. brachypoda corresponds with the earliest vitellogenic stages seen in other viviparous lizard species with larger oocytes. The various species of the genus Mabuya provided us with important models to understand a major transition in the evolution of viviparity, the development of a microlecithal egg.

Experimentally increased testosterone affects social rank and primary sex ratio in the spotless starling

It has been suggested that the amount of maternal testosterone allocated into the eggs might be implicated in the process of sex determination. However, recent findings on the effect that female social rank has on the level of egg testosterone suggest that reported associations between male-biased sex ratios and yolk testosterone may represent an indirect hormonal effect mediated by the interdependence among maternal hormones, female social rank, and sex ratio. Here, we report the results of a field experiment in which we manipulated the circulating levels of testosterone in female spotless starlings (Sturnus unicolor) before egg formation. Focal females were controlled in subsequent years to explore possible delayed effects of hormone manipulation on primary sex ratio and social status that could persist because of permanent hormonal change or through hormone-dominance interactions. The results indicate that testosterone-implanted females (T-females) produced significantly more sons than control females (C-females) in the year in which they were manipulated. These differences in offspring sex ratio between T- and C-females persisted in the next 3 years, although no additional hormone treatments were given. These results were not mediated by an eventual effect of testosterone treatment on the quality of the females' mates. A similar proportion of T- and C-females acquired a nest box and bred either in the manipulation year or in Year 1 after manipulation, but T-females tended to be more successful in acquiring a nest box than C-females in Years 2 and 3 after manipulation. These results suggest that added testosterone had a direct role on the acquisition and maintenance of high social rank. Delayed effects of testosterone on primary sex ratio might have been caused by altered endogenous production of T-females. Alternatively, the maintenance of sex ratio differences between T- and C-females long after having being implanted might be attributed to the positive effect that enhanced social rank of T-females has on their circulating testosterone levels.

The influence of dietary boron supplementation on egg quality and serum calcium, inorganic phosphorus, magnesium levels and alkaline phosphatase activity in laying hens

This study was performed to investigate the influence of dietary boron (B) supplementation on egg production, interior and exterior egg quality and serum parameters related to egg formation in laying hens. Two hundred and twenty four, 18 week old, Hyline Brown 98 strain hens were assigned to 7 groups with 4 replicates. After 10 days of adaptation the hens were fed for 8 weeks on diets supplemented with 0, 5, 10, 50, 100, 200 and 400 mg/kg (diet) B (H(3)BO(3)). Live weight, feed consumption and egg production were reduced in the 400 mg/kg B supplemented group. Increases were determined in serum Ca, inorganic P and Mg levels and serum ALP activity was not influenced by supplemental B. Boron changed the interior and exterior quality of eggs. In particular, high level of B supplementation reduced live weight, feed consumption and egg production and changed some blood metabolites.

[Eggs fertilizability in domestic hens Gallus gallus domesticus as a function of the yolk surface area]

The increase of egg mass and reliable decrease of egg fertilizability were observed when the mass surface area of yolk (egg) increased. The results obtained suggest that, in addition to the number of viable spermatozoa penetrating across the perivitelline membrane within 15-20 min after ovulation, the probability of fertilization depends on the area of egg surface, which approximately corresponds to the area of perivitelline membrane. Apparently, the ratio of receptors' numbers and spermatozoa, which contact with them on the germ disc surface, to their number on the rest part of perivitelline membrane decreases with the increase of yolk size. The decreased egg fertilizability concomitant with the increased area of perivitelline membrane suggests that the egg size is one of the factors of fertility of the female gametes as concerns both variability of the egg composition and age.

Ovarian histology of the placentotrophicMabuya mabouya(Squamata, Scincidae)

Ovarian structure and folliculogenesis of females at different reproductive stages are described for the viviparous placentotrophic lizard Mabuya mabouya. The small ovaries have a thin wall formed by the ovarian epithelium and a thin tunica albuginea. One to two germinal beds that contain numerous oogonia and developing primordial follicles are derived from the ovarian epithelium and are next to the ovarian hilum. The ovarian cortex contains follicles at different stages of development, corpora lutea, and atretic follicles. The yolk nucleus and Balbiani complex were not evident in the ooplasm of previtellogenic follicles. The follicular epithelium of these follicles is polymorphic, as in other species of Squamata, but the larger cells are spherical and monolayered rather than pyriform. The zona radiata of the preovulatory follicles is less developed than in lecithotrophic species. These features suggest a decrease in metabolic and absorptive processes during follicular growth. In preovulatory follicles (1.5-1.8 mm diameter), primordial yolk vacuoles and small cortical granules are deposited in the ooplasm instead of fatty yolk platelets, so that only one stage of vitellogenesis is observed. Polyovular atretic follicles occur in some females. Follicular atresia is minimal for preovulatory follicles, but is more frequent in follicles with polymorphic epithelia. In the corpus luteum, the luteal tissue is formed from granulosa cells and luteolysis occurs during the late gastrula -- late neurula embryonic stages. Thus, the maintenance of gestation from the pharyngula to preparturition stages seems to be related to secretion of extraluteal progesterone, possibly of placental origin. These observed ovarian features are related to the high degree of placental complexity of this species and show that the evolution of advanced placentotrophy in species of this lineage has been accompanied by concomitant changes in ovarian function.

Resource Allocation in Offspring Provisioning: An Evaluation of the Conditions Favoring the Evolution of Matrotrophy

We used analytic and simulation models to determine the ecological conditions favoring evolution of a matrotrophic fish from a lecithotrophic ancestor given a complex set of trade-offs. Matrotrophy is the nourishment of viviparous embryos by resources provided between fertilization and parturition, while lecithotrophy describes embryo nourishment provided before fertilization. In fishes and reptiles, embryo nourishment encompasses a continuum from solely lecithotrophic to primarily matrotrophic. Matrotrophy has evolved independently from lecithotrophic ancestors many times in many groups. We assumed matrotrophy increased the number of offspring a viviparous female could gestate and evaluated conditions of food availability favoring lecithotrophy or matrotrophy. The matrotrophic strategy was superior when food resources exceeded demand during gestation but at a risk of overproduction and reproductive failure if food intake was limited. Matrotrophic females were leaner during gestation than lecithotrophic females, yielding shorter life spans. Our models suggest that matrotrophic embryo nourishment evolved in environments with high food availability, consistently exceeding energy requirements for maintaining relatively large broods. Embryo abortion with some resorption of invested energy is a necessary preadaptation to the evolution of matrotrophy. Future work should explore trade-offs of age-specific mortality and reproductive output for females maintaining different levels of fat storage during gestation.

Genetic relations of yolk proportion and chick weight with production traits in a White Leghorn line

1. The main purpose of this study was to estimate genetic correlations between yolk proportion, chick weight and production traits using an animal model. 2. Direct-direct genetic correlations were estimated between yolk proportion and age at first egg (-0.34), body weight at 20 (0.10), 40 (0.58) and 60 (0.52) weeks of age, egg number (0.56), egg mass (0.59), feed intake (0.64) and feed conversion (-0.25). 3. Maternal-direct genetic correlations were estimated between chick weight and age at first egg (0.40), body weight at 20 (0.57), 40 (0.66) and 60 (0.56) weeks of age, egg number (-0.50), egg mass (0.21), feed intake (0.45) and feed conversion (0.17), respectively. 4. In conclusion, the results suggest that selection on a higher yolk proportion would not have any unfavourable effects on egg production. Maternal-direct genetic correlations between chick weight and production traits resembled direct-direct genetic correlations between egg weight and production traits found in other studies.

Assembly of yolk spindles in the early Drosophila embryo

The development of the early Drosophila embryo is marked by the separation of two nuclear lineages, yolk and somatic nuclei, each having its own division program despite residing in a common cytoplasm. We show that the failure of nuclear division of the yolk nuclei is a consequence of dysfunction in bipolar spindle organization during mitosis 10 and 11. Yolk spindle organization defects are directly correlated to centrosome behaviour, which is abnormal in at least three sequential aspects. First, the yolk centrosomes do not migrate properly along the nuclear envelope during nuclear cycles 10 and 11 and give rise to non-functional monopolar spindles. Second, the centrosomes detached from the poles spindle at the end of nuclear cycle 11, leaving the spindles anastral. Third, the free centrosomes duplicate in the absence of nuclear division during last mitoses and early gastrulation, but do not separate properly. In spite of their reduced nucleating properties, beyond the nuclear cycle 12, the yolk centrosomes contain typical centrosomal antigens, suggesting that their structural organization has not been changed after they disperse in the cytoplasm. Our findings also demonstrate that the centrosome dynamics are spatially and temporally regulated in the yolk region. This observation is consistent with the presence of rate-limiting levels of maternally provided key molecular components, needed for centrosome duplication and positioning. The presence of normal and abnormal centrosomes in the same cytoplasm provides an useful model for investigating the common regulators of the nucleus and centrosome cycle which ensure precise spindle pole duplication.

Effect of sperm coating on the survival and penetrating ability of in vitro stored bovine spermatozoa

The aim of this study was to examine the effect of sperm coating on the survival and penetrating ability of in vitro stored diluted spermatozoa. Bovine semen was collected by means of an artificial vagina connected with a tube containing 5 ml of the commercial Triladyl diluent supplemented with 20% egg yolk and 6.7% glycerol (EYTG). Both EYTG and seminal plasma were removed by centrifugation and the spermatozoa were stored under different in vitro storage conditions. In the first and second experiment, "control" and "coated" spermatozoa were stored in Hepes-TALP (pH 6 and 7) at room temperature. After 4 days of storage, the progressive motility, membrane integrity, mitochondrial membrane potential or DNA integrity of the spermatozoa were evaluated before and after Percoll centrifugation. The in vitro penetration rate of the spermatozoa was examined only after Percoll centrifugation. A significantly (P<0.05) positive influence of sperm coating was observed on the tested sperm characteristics and penetration rate of spermatozoa when they were stored in Hepes-TALP at pH 7, but not at pH 6. In the last experiment, the influence of the storage medium Hepes-TALP (pH 7) or EYTG was investigated on motility, membrane integrity, mitochondrial membrane potential and in vitro penetration potential of "coated" spermatozoa stored at room temperature or at 4 degrees C during 4, 5 and 6 days. After 6 days of storage, a significantly (P<0.05) higher percentage of motile and membrane intact spermatozoa with high mitochondrial membrane potential was obtained in EYTG at both temperatures leading to a significantly higher in vitro penetration rate. These results indicate that sperm coating could preserve sperm characteristics and penetrating capacity of fresh bovine spermatozoa stored in egg yolk containing diluent for up to 6 days.

Influence of extender, temperature, and addition of glycerol on post-thaw sperm parameters in ram semen

Using a two-step extension methodology, two experiments were conducted using a split-sample design to compare the effect on post-thaw ram sperm parameters of a milk-based extender (Experiment 1) containing four different egg yolk concentrations (5% [M5], 10% [M10], 15% [M15], and 20% [M20]), and a commercially available extender (Bioexcell); IMV, L'Aigle, France) free from additives of animal origin, containing two different final glycerol concentrations (3.2% [B] and 6.4% [BB]) (Experiment 2). In both experiments, glycerol was added either at 5 degrees C or at 15 degrees C together with the second fraction of each extender. The sperm characteristics assessed were motility (measured subjectively [SM] and by means of cell motion analysis (CASA), membrane integrity (SYBR-14/PI), and capacitation status (chlortetracycline (CTC)/EthD-1). Results of Experiment 1 showed no significant positive effect of increasing the concentration of egg yolk above 10% on post-thaw motility, membrane integrity, or induction of sperm capacitation-like changes. In Experiment 2, Bioexcell (BB) yielded similar post-thaw results as did the milk extender (control). In both experiments, post-thaw sperm parameters were better preserved when glycerol was added at 5 degrees C, although the results were not always statistically significant for all variables studied. In conclusion, when using milk-based extenders for freezing ram semen, low (5-10%) concentrations of egg yolk and the addition of glycerol at 5 degrees C are recommended. Furthermore, the results indicate that when freezing ram semen, Bioexcell containing 6.4% glycerol may be used as an alternative extender to the conventional milk extender containing 5% egg yolk.

Dietary levels of chia: influence on hen weight, egg production and sensory quality, for two strains of hens

1. Laying hens, 225 white and 225 brown, were fed for 90 d to compare a control diet with diets containing 70, 140, 210 and 280 g/kg chia (Salvia hispanica L.) seed. 2. Hen weight was not significantly affected by diet; however, manure production was less for the hens fed on chia. 3. Egg weight and production, yolk weight, and yolk percentage were determined at d 0, 30, 43, 58, 72 and 90. 4. A sensory evaluation was conducted on eggs produced during the last week of the trial. 5. No significant differences in egg production were found among treatments for the brown hens. 6. With the 280 g/kg chia diet, the white hens produced fewer and lighter eggs than did the hens fed on the control diet. 7. No significant differences were detected in yolk weight until d 90. 8. On this date the yolks produced by the white hens fed on the 70 g/kg chia diet were significantly lighter in weight, whereas the brown hens produced significantly heavier yolks, compared with the hens fed on the control diet. 9. Yolk weight as a percentage of egg weight was lower for white hens throughout the trial except on d 58 with the 140 g/kg chia diet. Significant differences, however, were detected only with the 70 g/ kg chia diet on d 90 and with the 210 g/kg chia diet on d 58, 72 and 90. 10. No significant differences in taste preference or flavour were found among any of the chia treatments and the control.

Advances in cryopreservation of stallion semen in modified INRA82

In the procedure used in this paper, semen was first diluted in INRA82+2% egg yolk (E1) at 37 degrees C. Before or after cooling to 4 degrees C, semen was centrifuged and diluted in E1+2.5% glycerol (E2). Cooled semen was frozen in 0.5-ml straws. Straws were thawed at 37 degrees C for 30s. For fertility trials, frozen ejaculates were used only if total post-thaw motility was above 35%. Most mares were inseminated two times before ovulation with 400 x 10(6) total spermatozoa every 24h. This paper presents post-thaw motility (CASA) and fertility results obtained when some steps of the procedure were evaluated. Use of the first three jets of ejaculate before the centrifugation did not improve post-thaw motility compared to use of the whole semen (25% versus 25%, 2 stallions x 12 ejaculates, P>0.80). When the first dilution was performed in E2 at 22 degrees C instead of in E1 at 37 degrees C, motility was slightly improved (38% versus 36%, n>283 ejaculates per group, P<0.04) but fertility was similar (51% versus 58%, n>196 cycles per group, P>0.10). Coating the spermatozoa with 0.5, 1, 2, 4 and 8mM of Concanavalin A resulted in unchanged post-thaw motility (6 stallions x 3 ejaculates, P>0.05). The extender E2 was modified or supplemented with different substances. Increasing egg yolk concentration from 2 to 4% (v/v) did not increase post-thaw motility (42% versus 34%, 6 stallions x 2 ejaculates, P>0.05). Different glycerol concentrations (range: 1.7-3.7%) had no significant effect on post-thaw motility even though 2.4-2.8% resulted in a nonsignificant higher motility (7 stallions x 2 ejaculates, P>0.05). Glutamine at 50mM in E2 improved post-thaw motility compared with no glutamine (49% versus 46%, n>584 ejaculates per group, P<0.0001) but not fertility (53% versus 54%, n>451 cycles per group, P>0.80). Thawing at 75 degrees C for 10s slightly increased motility after 120 min at 37 degrees C (6 stallions x 1 ejaculate, P<0.05) but no effect on per-cycle fertility was noted (32% (19 cycles) versus 41% (17 cycles), P>0.50). When post-thaw dilution was performed using a fixed molarity multi-step system (25 mOsm per step) from various osmolarities (900-690 mOsm) to 365 mOsm, motility was unaffected compared with dilution in one step (36% versus 38%, 6 stallions x 1 ejaculate, P>0.20).

A gene expression screen in zebrafish embryogenesis

A screen for developmentally regulated genes was conducted in the zebrafish, a system offering substantial advantages for the study of the molecular genetics of vertebrate embryogenesis. Clones from a normalized cDNA library from early somitogenesis stages were picked randomly and tested by high-throughput in situ hybridization for restricted expression in at least one of four stages of development. Among 2765 clones that were screened, a total of 347 genes with patterns judged to be restricted were selected. These clones were subjected to partial sequence analysis, allowing recognition of functional motifs in 163 among them. In addition, a portion of the clones were mapped with the aid of the LN54 radiation hybrid panel. The usefulness of the in situ hybridization screening approach is illustrated by describing several new markers for the characteristic structure in the fish embryo named the yolk syncytial layer, and for different regions of the developing brain.

Transfer of Vitamins E and A from yolk to embryo during development of the king penguin (Aptenodytes patagonicus)

Since the yolk lipids of the king penguin (Aptenodytes patagonicus) are rich in n-3 fatty acids, which are potentially susceptible to peroxidative damage, the yolk contents and yolk-to-embryo transfer of antioxidants and lipid-soluble vitamins were investigated under conditions of natural incubation in the wild. The concentration of vitamin E in the unincubated egg was 155 microg/g wet yolk, of which 88% was alpha-tocopherol and the rest was gamma-tocopherol. Vitamin A (2.9 microg/g) was present in the yolk entirely as retinol; no retinyl esters were detected. Throughout the latter half of the incubation period, vitamins E and A were taken up from the yolk into the yolk sac membrane (YSM) and later accumulated in the liver, with vitamin A being transferred in advance of vitamin E. In the YSM, vitamin A was present almost entirely as retinyl ester, indicating that the free retinol of the yolk is rapidly esterified following uptake. Retinyl esters were also the predominant form in the liver. The retinyl esters of the liver and YSM displayed different fatty acid profiles. At hatching, the brain contained relatively little vitamin E (4.7 microg/g) compared to the much higher concentration in the liver (482.9 microg/g) at this stage. Ascorbic acid was not detected in the yolk but was present at a high concentration in the brain at day 27 (404.6 microg/g), decreasing to less than half this value by the time of hatching. This report is the first to delineate the yolk-to-embryo transfer of lipid-soluble vitamins for a free-living avian species. The yolk fatty acids of the king penguin provide an extreme example of potential oxidative susceptibility, forming a basis for comparative studies on embryonic antioxidant requirements among species of birds whose yolk lipids differ in their degree of unsaturation.