Layer Of Egg Research Articles

Increased nanosphere size in the cuticle layer of Japanese quail egg by mutation in the myostatin gene

Cuticle quality can affect food safety by protecting poultry eggs from bacterial infection in the modern poultry industry. However, genetic factors related to cuticle nanostructure are not much reported due to limited bird models. In the current study, the genome-edited quail targeting myostatin (MSTN) gene was used to investigate the effect of MSTN mutation on the cuticle nanostructure and quality. To analyze nanostructure of the cuticle layer of the MSTN mutant and wild-type (WT) quail eggs, scanning electron microscope (SEM) images was taken. Thickness of the cuticle layer did not differ between the MSTN mutant and WT groups, but the size of the nanospheres in the surface of the cuticle layer was increased by MSTN mutation. In addition, increased size of the nanospheres in the MSTN mutant group was also shown in the upper region of the cross-sectional cuticle layer. Notably, both groups showed similar small-sized nanospheres in the lower region of the cuticle layer and the size was increased as they ascended to the upper region. The data suggested that MSTN mutation increased the size of the nanosphere in the upper region of the cuticle layer at a late phase rather than increasing the size of nanospheres in the lower region of the cuticle layer at an early phase of cuticle formation. However, the number of Escherichia coli attached to the surface did not differ between the two groups indicating no association between nanosphere size and bacterial attachment in quail eggs. The current study demonstrated a new function of the MSTN gene on regulation of cuticle nanostructure, for the first time. These results advanced our knowledge on the association between genetic factors and cuticle nanostructure and can be served as a reference to study the mechanism of cuticle formation in the future study.

The shingled girl: Catherine Janet Hill and her contributions to embryology.

Catherine J. Hill is best remembered for her dedication to cataloguing the comprehensive embryological collection of her father J. P. Hill. Yet, her own research, during the interwar years, is little known. She made a significant contribution to interpreting the autonomic innervation of the gut, work that was presented to The Royal Society and earned her a PhD. Working in her father's laboratory, she then set about solving the sequence of secretions from the tubal epithelium and uterine glands that contributed the two layers of egg albumen and three shell layers of the monotreme egg. She was also the first to understand twinning in the marmoset and how two embryos came to share a single extraembryonic coelom, work that often is credited to J. P. Hill. Here. I explain how that happened and explore the context in which she and other female scientists worked at the time.

Inactivation of Salmonella Enteritidis on Hatchery and Table Eggs Using a Gas-phase Hydroxyl-Radical Process

Eggs represent a significant vehicle for Salmonella Enteritidis with the pathogen being transferred to chicks in the hatchery, or to consumers via table eggs. In the following, the efficacy of a gas-phase hydroxyl-radical process for decontaminating hatchery and table eggs was evaluated. Recovery of Salmonella was maximized through holding eggs in tryptic soy broth containing 20% w/v glycerol for 1 h prior to plating. By using this technique, it was possible to recover 63% of the theoretical Salmonella inoculated onto eggs. The continuous hydroxyl-radical reactor consisted of a bank of UV-C lamps (254 nm) that generated hydroxyl-radicals from the degradation of hydrogen peroxide (H2O2) mist and ozone gas. The optimal treatment was defined as that which supports a 5 log CFU/egg reduction of Salmonella without negatively affecting egg quality or leaving H2O2 residues. A process of 2% v/v H2O2 delivered at 30 mL/min with a UV-C dose of 19 mJ/cm2 and ozone (20 ppm) with a total treatment time of 10s was selected. The egg quality metrics (Haugh value, yolk index, albumin pH, yolk pH) did not negatively differ over a 35-day shelf-life at 4 or 25℃ compared to washed eggs or nontreated controls. The cuticle layer of eggs remained intact following hydroxyl-radical treatment. Fertilized eggs (n = 61) treated with the hydroxyl-radicals exhibited the same hatchery rate (75%) as nontreated controls (71–79%) with no defects (unhealed navels or red hocks) being observed. The same hydroxyl-radical treatment could be applied to table eggs to support >5 log CFU/egg reduction of Salmonella and was compatible with egg washing regimes practiced in industry. In comparison, the egg washing process based on sodium hydroxide and chlorine supported a 2.76 ± 0.38 log CFU/egg reduction of Salmonella. The hydroxyl-radical treatment represents a preventative control step to reduce the carriage of Salmonella on hatchery and table eggs.

Physiological features of development and options for technology for obtaining pluripotent stem cells

Topical issues related to the technology of isolation and mechanisms of development of pluripotent stem cells and their application in medicine are considered. The isolation, as well as the subsequent use of stem cells, still remains an unsolved problem both from a scientific point of view and especially in practical health care. There are three ways to produce pluripotent stem cells. First, they can be obtained in vitro from cell culture of the inner layer of early eggs. These are embryonic stem cells. Second, they can be obtained from somatic cells, as a result of the introduction of a group of genes that induce pluripotency. These are induced pluripotent stem cells. Finally, they can be obtained by transplanting the nucleus of somatic cells into an enucleated secondary egg. The microenvironment of the egg contributes to the reprogramming of the nucleus to a state close to the zygote. Mouse embryonic stem cells have many embryonic markers on their surface: carbohydrate receptors CD15, alkaline phosphatase, factor 4 like Kruppel, estrogen-bound receptor, transcription factor CP2 like 1, T-box transcription factor and gastrulation homeobox brain 2. Embryonic mouse stem cells differentiate from the internal mass of cells at the stage of preimplantation, epiblast. This is established by comparing gene expression profiles and directly isolating embryonic stem cells from epiblasts of 4.5-day-old fertilized eggs. Embryonic stem cells derived from mouse embryos of later stages of development lose markers of pluripotency. Approximately 3 days after the elimination of the leukemia inhibition factor, the expression of the Oct4 gene leads to the loss of specificity markers by cells of the early embryo. Currently, the reprogramming of pluripotency is an active area of research in which significant technological progress has been made. So, the original gene cocktail consisting of four genes is used: Oct4, Sox2, Klf4 and cMyc. The obtained types of embryonic stem cells of mouse and human, from fertilized blastocysts, induced pluripotent stem cells undoubtedly exist. However, this does not apply to pluripotent stem cells derived from postnatal animals, humans, or from extraembryonic sources such as amniotic fluid or cord blood. Despite the fact that many laboratories are working to obtain stem cells from these objects, unfortunately, there is little reproducibility in this work, and the properties of the resulting cells and even their existence are still the subject of controversy.

Effects of Urtica dioica agglutinin on glycotargeting of the vasculature: an in ovo study on chicken embryo.

The angiogenesis process is a pivotal cellular process involved in both developmental and pathological circumstances. In this study we investigated effect of Urtica dioica agglutinin (UDA), as an unusual phyto-lectin from the chitin-binding protein family, on the angiogenesis of chicken embryos. The UDA was extracted from plant rhizomes and purified by affinity chromatography column. The activity of this lectin was assayed by hemagglutination test on the human RBCs. Anti-angiogenic effect of UDA on the extra-embryonic layer of the chick egg was studied in the different concentrations. Our results showed that the minimum concentration of UDA for agglutination were 48.00 and 15.00 µg mL-1 in macro- and microscopic studies, respectively. Because the number and length of the vessels were dramatically decreased at 100 µg kg-1 of UDA, the lectin had an inhibitory effect on angiogenesis of the embryonic vasculature of the chick. We concluded that UDA might target the vascularization events through binding to GlcNAc-conjugates. More investigations are needed to clarify the angiogenesis-related therapeutic roles of this interesting biomolecule.

Vitelline Membrane Protein 26 Mutagenesis, Using CRISPR/Cas9, Results in Egg Collapse in Plutella xylostella.

Vitelline membrane proteins (VMPs) are the main proteins that form the inner shell (vitelline membrane layer) of insect eggs and are an integral part of egg formation and embryo development. Here, we characterized the molecular structure and expression patterns of the VMP26 gene and analyzed its reproductive functions in diamondback moth, Plutella xylostella (L.), a worldwide migratory pest of cruciferous plants. The PxVMP26 gene was shown to be a single exon gene that contained an open reading frame of 852 base pairs (bp) encoding 283 amino acids. Both qPCR and western blot analyses showed that PxVMP26 was specifically expressed in female adults and was significantly highly expressed in the ovary. Further anatomical analysis indicated that the expression level of PxVMP26 in the ovarian tube with an incomplete yolk was significantly higher than that in the ovarian tube with a complete yolk. CRISPR/Cas9-induced PxVMP26 knockout successfully created two homozygous strains with 8- and 46-bp frameshift mutations. The expression deficiency of the PxVMP26 protein was detected in the mutant strains using immunofluorescence and western blot. No significant difference was found in the number of eggs laid within three days between wild and mutant individuals, but there was a lower egg hatchability. The loss of the PxVMP26 gene changed the mean egg size, damaged the structure of the vitelline membrane, and increased the proportion of abnormal eggs due to water loss, resulting in egg collapse. This first analysis of the roles of the VMP gene in the oocyte formation and embryonic development of P. xylostella, using CRISPR/Cas9 technology, provides a basis for screening new genetic control targets of P. xylostella.

Effects of Dithiothreitol on Fertilization and Early Development in Sea Urchin.

The vitelline layer (VL) of a sea urchin egg is an intricate meshwork of glycoproteins that intimately ensheathes the plasma membrane. During fertilization, the VL plays important roles. Firstly, the receptors for sperm reside on the VL. Secondly, following cortical granule exocytosis, the VL is elevated and transformed into the fertilization envelope (FE), owing to the assembly and crosslinking of the extruded materials. As these two crucial stages involve the VL, its alteration was expected to affect the fertilization process. In the present study, we addressed this question by mildly treating the eggs with a reducing agent, dithiothreitol (DTT). A brief pretreatment with DTT resulted in partial disruption of the VL, as judged by electron microscopy and by a novel fluorescent polyamine probe that selectively labelled the VL. The DTT-pretreated eggs did not elevate the FE but were mostly monospermic at fertilization. These eggs also manifested certain anomalies at fertilization: (i) compromised Ca2+ signaling, (ii) blocked translocation of cortical actin filaments, and (iii) impaired cleavage. Some of these phenotypic changes were reversed by restoring the DTT-exposed eggs in normal seawater prior to fertilization. Our findings suggest that the FE is not the decisive factor preventing polyspermy and that the integrity of the VL is nonetheless crucial to the egg’s fertilization response.

PRELIMINARY STUDY ON THE EFFECT OF WATERMELON JUICE AND MILK SOLUTION ON DE-ADHESION, DEVELOPMENTAL STAGES AND HATCHING RATE OF EGGS AND SURVIVAL OF FRY OF CLARIAS GARIEPINUS

Sticky layer of Clarias gariepinus eggs cause the clumping of eggs immediately after fertilization, this create low oxygen, and increase pathogenic infection, thereby reducing fertilization and hatching rate hence reduces in mass production of C. gariepinus seed. Although various substances are use in the removal of the sticky layer, no information is available about the use of watermelon. Therefore, the present study, aim in exploring the potential of using watermelon in removing the sticky layer of C. gariepinus to enhance production. Fertilized eggs were treated with watermelon juice (T1) for comparison with 14 g L-1 milk solution (T2 as de-adhesion reference) and water as control (T0 as adhesion reference). The treatments were agitated with aeration for 30 minutes, rinsed with water, and poured on respective netted hatching trough, with water recirculation for incubation at 27 0C for 24 h period. Except for T0, no clumping of eggs was observed in the remaining groups. Slight variation in attaining a developmental stage among eggs was observed in eggs treated with watermelon. Hatching and survival rate in T2 are higher than T1 and T0 (P<0.05). However, watermelon indicated the potential, as it removed the sticky layer while maintaining hatching and survival rate as in the control (T0) (P>0.05), more should be explored before adoption of watermelon for de-adhesion and incubation of C. gariepinus eggs.

New morphological and molecular perspectives about Macracanthorhynchus hirudinaceus (Acanthocephala: Oligacanthorhynchidae) from wild boar, Sus scrofa Linn., in Ukraine.

We make new morphological observations not previously reported for the old acanthocephalan Macracanthorhynchus hirudinaceus (Pallas, 1781) Travassos, 1917, described for the first time about 240 years ago. Our specimens were collected from the wild boar, Sus scrofa Linn., in Ukraine in 2005. We provide comparative morphometrics with other populations from Ukraine, Union of Soviet Socialist Republics, Europe, Brazil and the United States of America. Our specimens from the Ukraine had the smallest trunk (110-120 mm long), longest and thickest hooks, with the third hook being the largest, largest eggs, and a proboscis wider than long. We document the morphology of the proboscis, apical organ, hooks, hook roots, sensory pores, micropores, and eggs with scanning electron microscopy for the first time. We also provide chemical analysis of hooks and eggs using energy-dispersive X-ray analysis, discuss its micropores, and provide a new molecular profile based on 18S rDNA from a European population for the first time. Edge of hook tips feature high levels of calcium and phosphorous but the high level of sulphur is mostly found in the cortical layer of eggs. One new partial 18S rDNA sequence (482 nt length) was generated from an adult specimen of M. hirudinaceus. We present the first 18S rDNA published sequence for this cosmopolitan acanthocephalan obtained from Europe. The amplified region corresponded to the approximate middle region of the small subunit ribosomal ribonucleic acid gene, which is ~1800 nt in length. This molecular contribution is especially valuable in light of the extreme scarcity of genetic information about species of Macracanthorhynchus and of the family Oligacanthorhynchidae as a whole.

Host Specificity of the Parasitic Wasp Anaphes flavipes (Hymenoptera: Mymaridae) and a New Defence in Its Hosts (Coleoptera: Chrysomelidae: Oulema spp.)

The parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae) is an important egg parasitoid of cereal leaf beetles. Some species of cereal leaf beetle co-occur in the same localities, but the host specificity of the wasp to these crop pests has not yet been examined in detail. A lack of knowledge of host specificity can have a negative effect on the use of this wasps in biological control programs addressed to specific pest species or genus. In this study, laboratory experiments were conducted to assess the host specificity of A. flavipes for three species of cereal leaf beetles (Oulema duftschmidi Redtenbacher, 1874, Oulema gallaeciana Heyden, 1879 and Oulema melanopus Linnaeus, 1758) in central Europe. For the first time, a new host defence against egg parasitoids occurring in O. gallaeciana from localities in the Czech Republic, a strong dark sticky layer on the egg surface, was found and described. The host specificity of A. flavipes was studied in the locality with the presence of this defence on O. gallaeciana eggs (the dark sticky layer) (Czech Republic) and in a control locality (Germany), where no such host defence was observed. Contrary to the idea that a host defence mechanism can change the host specificity of parasitoids, the wasps from these two localities did not display any differences in that. Respectively, even though it has been observed that eggs with sticky dark layer can prevent parasitization, the overall rate of parasitization of the three species of cereal beetles has not been affected. However, in our view, new host defence can influence the effects of biological control, as eggs of all Oulema spp. in the locality are protected against parasitization from the wasps stuck on the sticky layer of the host eggs of O. gallaeciana.

Origin, differentiation and functional ultrastructure of egg envelopes in the cestode Echinococcus multilocularis Leuckart, 1863 (Cyclophyllidea: Taeniidae)

The origin, differentiation and functional ultrastructure of oncospheral or egg envelopes in Echinococcus multilocularis Leuckart, 1863 were studied by transmission electron microscopy (TEM) and cytochemistry. The purpose of our study is to describe the formation of the four primary embryonic envelopes, namely vitelline capsule, outer envelope, inner envelope and oncospheral membrane, and their transformation into the oncospheral or egg envelopes surrounding the mature hexacanth. This transformation takes place in the preoncospheral phase of embryonic development. The vitelline capsule and oncospheral membrane are thin membranes, while the outer and inner envelopes are thick cytoplasmic layers formed by two specific types of blastomeres: the outer envelope by cytoplasmic fusion of two macromeres and the inner envelope by cytoplasmic fusion of three mesomeres. Both outer and inner envelopes are therefore cellular in origin and syncytial in nature. During the advanced phase of embryonic development, the outer and inner envelopes undergo great modifications. The outer envelope remains as a metabolically active layer involved in the storage of glycogen and lipids for the final stages of egg development and survival. The inner envelope is the most important protective layer because of its thick layer of embryophoric blocks that assures oncospheral protection and survival. This embryophore is the principal layer of mature eggs, affording physical and physiological protection for the differentiated embryo or oncosphere, since the outer envelope is stripped from the egg before it is liberated. The embryophore is very thick and impermeable, consisting of polygonal blocks of an inert keratin-like protein held together by a cementing substance. The embryophore therefore assures extreme resistance of eggs, enabling them to withstand a wide range of environmental temperatures and physicochemical conditions.

Temperature Effects on Development and Phenotype in a Free-Living Population of Western Pond Turtles (Emys marmorata).

Changes in temperature regimes are occurring globally due to climate change as well as habitat alterations. Temperatures are expected to continue to rise in the future, along with a greater degree of climatic instability. Such changes could have potentially serious consequences for oviparous ectotherms, especially those with temperature-dependent sex determination. To investigate the effects of temperature on a range of developmental phenomena in a population of western pond turtles (Emys marmorata), we placed temperature sensors on top of each layer of eggs within nests and recorded temperatures hourly through the first 2-3 mo of incubation. These methods allowed us to look at in situ nest temperatures with high resolution. We found that mean incubation temperatures were similar between different nests and at different levels within nests but that incubation temperature fluctuations and maximum incubation temperatures differed greatly in both cases. The hatchling turtles were more likely to be female if they spent 30% or more of their sex-determining period of incubation above 29°C. Hatching success was best predicted by the maximum incubation temperature. We also found that incubation duration tended to be shorter as the mean temperature increased. However, exposure to either extremely high or low temperatures extended incubation times.

FRET analysis using sperm-activating peptides tagged with fluorescent proteins reveals that ligand-binding sites exist as clusters.

Long-range cellular communication between the sperm and egg is critical for external fertilization. Sperm-activating peptides (SAPs) are diffusible components of the outer layer of eggs in echinoderms, and function as chemoattractants for spermatozoa. The decapeptide named speract is the best-characterized sea urchin SAP. Biochemical and physiological actions of speract have been studied with purified or chemically synthesized peptides. In this work, we prepared recombinant speract fused to a fluorescent protein (FP; FP-speract) using three color variants: a cyan (eCFP), a yellow (mVenus) and a large Stokes shift yellow (mAmetrine) FP. Although these fluorescence tags are 20 times larger than speract, competitive binding experiments using mAmetrine-speract revealed that this FP-speract has binding affinity to the receptor that is comparable (7.6-fold less) to that of non-labeled speract. Indeed, 10 nmol l(-1) eCFP-speract induces physiological sperm responses such as membrane potential changes and increases in intracellular pH and Ca(2+) concentrations similar to those triggered by 10 nmol l(-1) speract. Furthermore, FP-speract maintains its fluorescence upon binding to its receptor. Using this property, we performed fluorescence resonance energy transfer (FRET) measurements with eCFP-speract and mVenus-speract as probes and obtained a positive FRET signal upon binding to the receptor, which suggests that the speract receptor exists as an oligomer, at least as a dimer, or alternatively that a single speract receptor protein possesses multiple binding sites. This property could partially account for the positive and/or negative cooperative binding of speract to the receptor.

Fret Analysis using Sperm-Activating Peptides Tagged with Fluorescent Proteins Reveals that Ligand-Binding Sites Exist as Clusters

Cells can communicate even when they're far from each other; this is critical for gametes from species that reproduce through external fertilization. In sea urchins, the molecules used by egg to attract sperm are the sperm-activating peptides (SAPs), which diffuse from the external layer of eggs into the sea water. The decapeptide speract was the first SAP described and its function has been studied by purified speract or using chemically synthesized analogues. This work attempts to prepare a recombinant speract analogue with new characteristics that could allow us to investigate unknown aspects about the speract-induced signaling pathway and the interaction with its receptor. To this end, speract was fused to three fluorescent proteins (FP; FP-speract) differing in color: cyan (eCFP), yellow (mVenus) and a large Stokes shift yellow (mAmetrine) and its activity was evaluated. First, using mAmetrine-speract for competitive binding assays, we determined that the affinity of FP-speract is only 7.6-fold smaller than speract, even when the FP is twenty times larger than the decapeptide. We also tested the ability of eCFP-speract to induce sperm physiological responses by measuring membrane potential, intracellular Ca2+ concentration and intracellular pH and neither showed significant differences between 10 nM speract and 10 nM eCFP-speract. Another important feature of our analogue is that it maintains its fluorescence when is bound to its receptor. Finally and most importantly, we used eCFP-speract and mVenus-speract as a pair for Fluorescence Resonance Energy Transfer (FRET) assays and obtained positive signal upon receptor binding. This result, strongly suggests that the speract receptor exists as an oligomer (at least as a dimer) or that a single receptor has multiple binding sites. This property may explain positive and/or negative cooperatively of SAP-receptor interactions as previously reported.

Alcalase treatment for elimination of stickiness in pikeperch (Sander luciopercaL.) eggs under controlled conditions

Elimination of egg stickiness is an important factor in artificial reproduction of pikeperch (Sander lucioperca L.). This study was conducted to evaluate the effectiveness of Alcalase enzyme to remove the adhesive layer of pikeperch eggs. The eggs were treated with Alcalase at 0.5, 1.0, 1.5, 2.0 and 5.0 mL L−1 or a milk/talc solution 2 min post insemination. Duration of exposure was 2 min in Alcalase and 60 min in milk/talc. The highest, albeit not significant, hatching rate (85.4%) was found with 1.5 mL L−1 of Alcalase, but hatching rates were similar in 0.5, 1.0 and 2.0 mL L−1. Hatching rates were significantly lower groups treated with 5.0 mL L−1 Alcalase enzyme (56.4%) compared to groups treated with milk powder and talc (61.3%). Nominally complete removal of adhesiveness was observed in 1.5 and 2 mL L−1. All Alcalase treatments led to significantly lower incubation duration compared with the traditional milk/talc treatment. The application of Alcalase successfully eliminated pikeperch egg stickiness in less time than with traditional milk/clay/talc methods.

Successful Induction of Intra-specific Androgenesis in Widow Tetra, Gymnocorymbus ternetzi (Boulenger 1895) Using UV Irradiation

A protocol for elimination of the maternal egg genome in widow tetra (WT), Gymnocorymbus ternetzi (Boulenger 1895) using contrasting black and albino strains was successfully optimised. Maternal genome elimination is a pre-requisite for inducing androgenesis. In the present study, UV-irradiation for 3 min inactivated the maternal nuclear genome in eggs of the black WT. A single layer of black WT eggs exposed to a UV-G bulb (254 nm, 40 W) at a height of 25 cm and at a final intensity of 4.2 W. m -2 successfully eliminated the WT egg genome. Androgenotes were generated by fusing genome-inactivated eggs with fresh sperm. Fertilisation was achieved by mixing fresh albino tetra sperm with irradiated eggs and adding water to initiate sperm motility. Following fertilisation by fresh albino WT sperm, 22- min-old embryos were shocked at 41 °C for 2 min to restore diploidy. Survival of androgenotes was 11% and 8% at hatching and maturity while that of the controls were 94% and 67%, respectively. Maternal genome inactivation was confirmed by (i) albino body colour in the diploid fry and adult, (ii) haploid karyotype and (iii) embryonic development. Hatched haploid androgenotes showed normal embryonic development but exhibited severe haploid syndrome while diploid androgenotes resembled albino WT and displayed a diploid karyotype.

Chlorinated, brominated, and fluorinated organic pollutants in Nile crocodile eggs from the Kruger National Park, South Africa

Repeated annual episodes of Nile crocodile deaths in two isolated areas of the Kruger National Park prompted the investigation of possible organohalogen pollutant involvement. Crocodile eggs were collected close to one of the mortality sites (Gorge) as well as from a crocodile farm (CF) as reference. ∑DDT was significantly higher in Gorge (450ng/g wm) than in CF eggs (85ng/g wet mass). Percentage DDT of ∑DDT was significantly higher in CF (14 per cent) than in Gorge eggs (5 per cent). Mean ∑DDT was almost 70 times higher than mean ∑PCB in Gorge eggs. HCB, β-HCH, mirex, brominated flame retardants (BFRs), and perfluorinated compounds (PFCs) occurred at lower concentrations. We believe that the BFR and PFCs data represent the first published results for any crocodile egg. Thickening of the outer eggshell layer of Gorge eggs was significantly associated with higher concentrations of ∑DDT. Concentrations of ∑DDT and other pollutants were in the same range as eggs from elsewhere, where there were no mortalities. Concentrations of ∑DDT in eggs from healthy Australian crocodiles were of the same orders of magnitude as the current study, making it highly unlikely that the concentrations of pollutants measured in the present study would have caused or substantially contributed towards the mortalities observed. Concerns about reproduction and behaviour remain. As large predators, crocodilians are at the apex of the freshwater aquatic food web. More research is needed to guide measures to manage African freshwater systems so that it will also sustainably accommodate these large, long-lived animals.

Proteomic Analysis of Eggs from Mytilus edulis Females Differing in Mitochondrial DNA Transmission Mode

Many bivalves have an unusual mechanism of mitochondrial DNA (mtDNA) inheritance called doubly uniparental inheritance (DUI) in which distinctly different genomes are inherited through the female (F genome) and male (M genome) lineages. In fertilized eggs that will develop into male embryos, the sperm mitochondria remain in an aggregation, which is believed to be delivered to the primordial germ cells and passed to the next generation through the sperm. In fertilized eggs that will develop into female embryos, the sperm mitochondria are dispersed throughout the developing embryo and make little if any contribution to the next generation. The frequency of embryos with the aggregated or dispersed mitochondrial type varies among females. Previous models of DUI have predicted that maternal nuclear factors cause molecular differences among unfertilized eggs from females producing embryos with predominantly dispersed or aggregated mitochondria. We test this hypothesis using females of each of the two types from a natural population. We have found small, yet detectable, differences of the predicted type at the proteome level. We also provide evidence that eggs of females giving the dispersed pattern have consistently lower expression for different proteasome subunits than eggs of females giving the aggregated pattern. These results, combined with those of an earlier study in which we used hatchery lines of Mytilus, and with a transcriptomic study in a clam that has the DUI system of mtDNA transmission, reinforce the hypothesis that the ubiquitin-proteasome system plays a key role in the mechanism of DUI and sex determination in bivalves. We also report that eggs of females giving the dispersed pattern have higher expression for arginine kinase and enolase, enzymes involved in energy production, whereas ferritin, which is involved in iron homeostasis, has lower expression. We discuss these results in the context of genetic models for DUI and suggest experimental methods for further understanding the role of these proteins in DUI.

The effects of a short-term molt method using cassava meal, broken rice, or corn on ovarian regression, bone integrity, and postmolt egg production and quality in older (95 week) laying hens

This study was conducted to determine the ability of different molt diets to induce molt in 95-wk-old hens. The hens were randomly assigned to 4 treatments of 60 birds each: 1) molted by full feeding with broken rice (BROK), 2) corn (CRN), 3) cassava (CASS), or 4) nonmolted control (CONT) for 14 d. At 15 d, all hens were fed a layer diet (17% CP), and production performance was measured for 20 wk. Feed intake was depressed (P < 0.05) in the CASS treatment compared with BROK and CRN treatments during the 14 d. The most significant BW loss occurred in the CASS treatment (21.9%), whereas BROK and CRN treatments were 7.6 and 9.3%, respectively. The CASS treatment resulted in total cessation of egg production within 7 d, whereas those of BROK and CRN treatments decreased to 3.7 and 8.7%, respectively. Ovary weights, oviduct weights, and oviduct lengths of the CASS treatment were not significantly different from those of BROK and CRN treatments (P > 0.05). The weight of spleen and thymus glands, blood heterophil:lymphocyte ratios, bone parameters, and mortality during the 14-d treatment were not affected by treatments. No significant differences were found among treatments for postmolt cumulative egg production, egg weight, feed intake, and mortality. Significant (P < 0.05) improvements in albumen quality were observed in the CASS treatment, although shell thickness of this treatment was reduced (P < 0.05) compared with the CONT treatment in wk 2 after the 14-d treatment. With respect to shell ultrastructural traits, the palisade layer of CASS eggs was shorter (P < 0.05) than that of CONT eggs determined in wk 2 after the 14-d treatment. In addition, evidence of abnormal mammillae was detected in an egg produced by the CASS hens. This research indicates that cassava diets can induce molt in hens. Nonetheless, the technique needs to be adjusted to improve postmolt egg production and shell quality.

Sperm-egg interaction and fertility of Japanese breeder quails from 10 to 61 weeks

The influence of the age of Japanese breeder quails was studied by the analysis of fertility and sperm-egg interactions on the perivitelline layer of fertile eggs along the reproductive lifetime. Thus, 10 quail couples were observed every 30 d from 70 to 430 d. In each analyzed period, the males remained with the females for 24 h, and the oviposited eggs were analyzed up to the laying of 3 consecutive infertile eggs. The eggs were examined, and their fertility and the number of sperm (sptz)adhering to the outer perivitelline layer over the germinal disc were determined and expressed as sptz/mm(2). The age of the males had no effect (P > 0.05) on the maintenance of fertility after mating and on the number of sperm in the fertile eggs. The age of the females influenced (P < 0.05) the sptz/mm(2), which decreased 8 d after copulation. The probability of the eggs being fertile diminished with the age of the females combined with the time after copulation, and this probability became lower than 20% after 9 d. The number of sperm trapped in the perivitelline layer overlaying the germinal disc was reduced as a function of the age of the females and the time after copulation. From 3 sptz/mm(2) and on, the quails presented a 95% probability of having their eggs fertilized in females up to 55 wk of age. For breeder Japanese quails, the age of the females represents an important factor for fertility maintenance.