Fertilization Of Eggs Research Articles

Outcomes of Social Egg Freezing: A Cohort Study and a Comprehensive Literature Review.

The purpose of this study is to evaluate the live birth outcome following oocyte thaw in women who underwent social egg freezing at Guy's Hospital, alongside a detailed published literature review to compare published results with the current study. A retrospective cohort study was conducted between January 2016 and March 2022 for all women who underwent egg freezing during this period. Overall, 167 women had 184 social egg freezing cycles. The mean age at freeze was 37.1 years and an average of 9.5 eggs were frozen per retrieval. In total, 16% of the women returned to use their frozen eggs. The mean egg thaw survival rate post egg thaw was 74%. The mean egg fertilisation rate was 67%. The pregnancy rate achieved per embryo transfer was 48% and the live birth rate per embryo transfer was 35%. We also noted that irrespective of age at freezing, a significantly high live birth rate was achieved when the number of eggs frozen per patient was 15 or more. Despite the rapid increase in social egg freezing cycles, the utilisation rate remains low. Pregnancy and live birth rate post thaw are encouraging if eggs are frozen at a younger age and if 15 eggs or more were frozen per patient.

Morphological changes in the adrenal glands of chickens under heat stress

Heat stress as a result of hyperthermia and dehydration of the body due to natural or artificial environmental factors negatively affects the well-being of birds. Heat stress factor can lead to significant economic losses in poultry farms due to a decrease in egg production, egg fertilization, hatching and viability of young animals, morphological indicators of eggs, an increase in bird mortality during maintenance and transportation, the occurrence of immunosuppression and metabolic disorders. Pathomorphological changes in the internal organs of birds under heat stress are classified as degenerative changes, necrosis, circulatory disorders, changes in tissue fluid, growth disorders, and inflammation. The adrenal gland affects the number of functional and metabolic processes in the body of birds, its hormones ensure its resistance to heat stress. In the current global warming climate, the study of the morphology of the adrenal gland of birds due to the action of a thermal stress factor is an urgent problem of poultry farming, since its solution contributes to the scientific justification of technologies for growing, using and treating birds. The aim of the study was to identify morphological changes in the adrenal gland of white leghorn chickens aged 3 months under heat stress. Anatomical, morphometric, microscopic and statistical research methods were used in the course of the study. It was found that the indicators of absolute mass and linear dimensions of the adrenal glands of chickens under heat stress increased relative to such indicators in clinically healthy chickens. Microscopically, circulatory disorders (edema, hyperemia, hemorrhages, congestion, thrombosis) were recorded in the adrenal glands of chickens, which on the 4th day of exposure to the heat stress factor were accompanied by activation of regenerative processes (an increase in the number of fibroblasts under the capsule) and secretory activity of endocrinocytes (an increase in the size of interrenal and suprarenal cells). Intense and prolonged stress of the adrenal glands of chickens caused by heat stress led to the withdrawal of their plastic and energy resources, and as a result caused the development of adrenal deficiency on Day 8, which was observed destructive and dystrophic changes in the interrenal and supraranal cells. The obtained data can be used to develop morphofunctional diagnostic and prognostic criteria for the state of both the adrenal glands and the avian organ as a whole under heat stress. In the future of further research-to study the features of the content and localization of nucleic acids, proteins, carbohydrates, lipids in the adrenal glands of chickens under heat stress.

Quality of fish eggs and production of androgenetic and gynogenetic doubled haploids (DHs).

Induced development of haploid embryos (H) with only paternal (androgenesis) or maternal (gynogenesis) chromosomes requires irradiation of eggs before fertilization or activation of eggs with irradiated spermatozoa, respectively. To provide doubled haploids (DHs), androgenetic and gynogenetic haploid zygotes need to be subjected to the thermal or high hydrostatic pressure (HHP) shock to suppress the first mitotic cleavage and todouble paternal or maternal haploid set of chromosomes. Androgenesis and mitotic gynogenesis (mito-gynogenesis) result in the generation of fully homozygous individuals in a single generation. DHs have been utilized in selective breeding programs, in studies concerning the phenotypic consequences of recessive alleles and to evaluate the impact of sex chromosomes on the early ontogeny. Moreover, the use of DHs for the NGS approach radically improves de novo the assembly of the genomes. However, reduced survival of the doubled haploids limits the wide application of androgenotes and gynogenotes. The high mortality of DHs may be only partly explained by the expression of recessive traits. Observed inter-clutch variation in the survival of DHs developing in eggs originating from different females make it necessary to take a closer look at the quality of the eggs used during induced androgenesis and gynogenesis. Moreover, the developmental competence of eggs that are subjected to irradiation before fertilization in order to deactivate maternal chromosomes when undergoing induced androgenesis and exposed to the physical shock after fertilization that leads to the duplication of the zygotes in both mito-gynogenesis and androgenesis may be also altered as irradiation and sublethal values of temperatures and hydrostatic pressure are considered as harmful for the cell organelles and biomolecules. Here, recently provided results concerning the morphological, biochemical, genomic, and transcriptomic characteristics of fish eggs showing high and low competence for androgenesis and mito-gynogenesis are reviewed.

Kuluçkahane Kökenli F5 ve F6 Nesil Karadeniz Somonu Anaçlarının (Salmo labrax PALLAS, 1811) Üreme Performansları

In this study, reproductive performances of F5 and F6 generation hatchery-originated female Black Sea salmon (Salmo labrax) were evaluated to determine the effects of the ongoing selective breeding program. The study was conducted in freshwater pools and marine cage systems between 2018 and 2021. For the study, 53 specimens from F5 generation females with an average length of 52.71±7.08 cm and weight of 1561.29±639.76 gr, and also 56 broodstıcks specimens from F6 generation females with an average length of 51.92±5.35 cm and weight of 1506.12±417.28 gr were used. Gonad maturity controls and spawning studies were carried out in the 2018-2019, 2019-2020 and 2020-2021 breeding periods along the entire season, lasting from November to January. The number of ovulating females, their fecundity, egg diameters and fertilisation rates of eggs were recorded. In all seasons, 36.17% of F5 females ovulated in November, and the remaining females (63.83%) ovulated in December. Ovulation time in F6 females also showed a similar pattern of 1/3 of females (37.40%) ovulating in November and the remaining majority (62.60%) ovulating in December. According to the results, total egg yields as 4439.31±1675.69 and 4112.08±1041.16 egg/broodstock, relative egg yields as 2313.44±278.48 and 2345.76±516.30 egg/kg, egg diameters as 5.08±0.19 and 5.21±0.17 mm, and fertilisation rates as 96.78±3.24% and 96.63±3.73% were determined for F5 and F6 generations, respectively. In both generations, as the size of the broodstock increases, the total egg production increases (F5: r=0.9169, F6: r=0.74254), while the relative egg production (F5: r=-0.2526, F6: r=-0.3486) decreases. When the total egg yields and fertilisation rates were compared, the difference between the F5 and F6 groups was insignificant (p≤0.05). The condition factors of the two generations were found to be statistically similar (p≤0.05).

Ovarian stimulation methods at a single-assisted reproductive technology institution: a retrospective study of successful outcomes

Aim : to examine an efficacy of various stimulation methods in a group of successful pregnancies. Materials and Methods . In a single center retrospective study 47 pregnancy cases were examined after performing embryo transfers at our institution from the years 2017 to 2021. Patients were divided into four groups: i) clomiphene hyperstimulation (CH), ii) stimulation with gonadotropin-releasing hormone (GnRH) agonist, iii) with GnRH antagonist, and iv) progestin-primed ovarian stimulation (PPOS). Age, anti-Mullerian hormone, presence of chronic disease, number of in-vitro fertilizations prior to conception, dosage of follicle stimulating hormone (FSH), presence of premature luteinizing hormone surge, number of egg retrievals, fertilization rate, and live birth rate were assessed. Results. The number of pregnancies obtained by CH, agonist, antagonist, and PPOS methods comprised 25, 12, 2, and 8 cases, respectively. No significant difference in parameters between CH group and non-CH groups, excepting FSH was observed. The FSH was used in CH group and non-CH group at dose of 1108 ± 468 IU and 1756 ± 394 IU, respectively (p < 0.0001). Conclusion. CH is not commonly used due to potential luteal phase defects, but it is thought to be cost-effective, requiring lower FSH doses, requiring no ovulation suppression antagonists, and exerting no effect on frozen embryos or fetuses. Hence, CH could be a suitable protocol for egg retrieval in Japan.

Examination of the effects of inbreeding on reproductive capacity in the Pacific oyster, Crassostrea gigas

The Pacific oyster (Crassostrea gigas) has been widely cultured as a commercially important bivalve. Intercrossing of inbred strains is regarded as an efficient method to increase yield (heterosis), so the development of inbred lines is common in the breeding strategies of C. gigas. However, inbreeding usually reduces physiological efficiency or reproductive capacity. The effects of inbreeding on gonadal development and reproductive capacity remain to be explored in oysters. In the present study, the monthly gonadal development of an inbred and a control population was observed. Compared with the control population, the delayed gonadal development in the inbred population may require more time and cost for breeders in the artificial breeding process. We investigated how inbreeding influenced female and male gametic traits, including reproductive effort, egg diameter, fertilization rate, hatching rate, sperm motility, sperm longevity, and sperm curvilinear velocity, as well as sperm competitiveness based on a male's share of paternity. We found no inbreeding depression for egg diameter, fertilization rate, or sperm motility. However, maternal inbreeding decreased reproductive effort and hatching rate, and paternal inbreeding decreased sperm longevity, curvilinear velocity, and competitiveness. Our results show evidence of inbreeding depression in the gonadal development and reproductive capacity of C. gigas, which could help us in a better understanding and management of inbreeding in oyster aquaculture.

Effect of dietary lutein on the egg production, fertility, and oxidative injury indexes of aged hens.

The present study aimed to investigate the effect of dietary lutein on egg production, follicles, reproductive hormones, fertility, hatchability, and oxidative injury indexes of hens. Treatments consisted of a control diet (CON) and three lutein-supplementing diets at 25 (L1), 50 (L2), or 75 (L3) mg/kg of diet. Egg production was measured using 576 Arbor Acres breeder hens at 61 to 65 wk and follicles grades, reproductive hormones, fertility, hatchability, tissue lutein contents, and oxidative injury indexes were determined at 65 wk. The results showed that at 65 wk, lutein- supplementing diets increased (p<0.05) egg production, follicular grades, fertility, hatchability, estradiol (E2), luteinizing hormone, progesterone (PROG), lutein content in the serum and yolk, compared to CON. L2 and L3 showed more pronounced (p<0.05) effects on egg production, PROG, and yolk lutein content than L1. With the increase of lutein doses from 25 to 75 mg/kg, there were linear increases (p<0.05) in egg production, lutein content, and PROG, and a quadratic trend (p<0.05) in E2. For the oxidative injury products, lutein-supplementing diets decreased (p<0.05) malondialdehyde (MDA) and protein carbonyl (PCO) in the serum, MDA and 8-hydroxy 2 deoxyguanosine (8-OHdG) in the yolk. There were linear decreases (p<0.05) in 8-OHdG in the serum, MDA, PCO, and 8-OHdG in the yolk, a quadratic trend (p<0.05) on serum 8-OHdG. It is concluded that lutein supplementation can improve egg production and fertility by beneficially regulating reproductive hormones and oxidative status in aged hens.

Factors Influencing Fertility and Hatchability of Poultry

Poultry production at all scales of operation is wholly dependent on the supply of day-old chicks. Two important factors that have a significant impact on the supply of day-old chicks are fertility and hatchability. Hatchability is the proportion of fertile eggs that actually hatch, whereas fertility refers to the proportion of fertile eggs that are incubated. Understanding the elements that affect the fertility and hatchability of eggs is important. Breeds, diet, age of the hens, environmental stress, egg weight, shell thickness, porosity, and form index are the most important variables that affect fertility and hatchability. The internal and exterior egg characteristics are diminished by heat stress. Heat illness has an impact on all stages of the breeder's semen production. The fertility and hatchability of eggs are impacted by various facilities, including storage crates, hatcheries, and incubators. As a result, offering the best management and developing intervention strategies for improvement can increase poultry fertility and hatchability. Keywords: Poultry, eggs, fertility, hatchability DOI: 10.7176/JBAH/13-8-01 Publication date: May 31 st 2023

Ecological Features and Opportunities for Economic Use of the Solovetsky Archipelago Freshwater Ichthyofauna

The species composition and taxonomic diversity of the Solovetsky Archipelago freshwater ichthyofauna were revealed, and a description of the current state of the fish was given. The belonging of fish to freshwater faunistic complexes and ecological groups (nature of feeding and mode of natural reproduction) was examined. Currently, 14 species of fish were found in the inland waters of the Solovetsky Islands, including local and alien species with varying degrees of acclimatization effect. A possible annual catch of freshwater fish has been established, which could be considered optimal. If it is necessary to organize freshwater aquaculture, pasture cultivation in the lakes of the Solovetsky Archipelago of the whitefish complex seems promising. It is based on the collection and fertilization of eggs at temporary fish breeding stations, its subsequent incubation at fish farms and the release of reared juveniles into feeding lakes.

Variations in the concentration of free amino acids during the early development of the Pacific red snapper Lutjanus peru

The free amino acids (FAAs) profile and its variations during the embryonic development and yolk-sac larvae of Pacific red snapper Lutjanus peru are described. The concentration of 15 FAAs (nine essentials and six non-essentials) was evaluated by reverse-phase high-performance liquid chromatography. The fertilized eggs of L. peru contain a small concentration of FAAs (4.77 ± 0.89 nmol ind-1). However, the variations in the FAAs pool during the early development are similar to the changes reported in other species with small pelagic eggs. The essential free amino acids are more abundant than the non-essential free amino acids throughout the studied period. During the egg stage, an increase in the FAAs was observed, and after hatching, isoleucine, leucine, lysine, and alanine were the FAAs that decreased the most during the yolk-sac larvae stage. The hatching rate was correlated with the total FAAs, the fraction of essential free amino acids, and the concentrations of glutamic acid, threonine, and valine in the egg stage, suggesting a possible role as a determinant in egg quality. Further studies are required to assess the role of FAAs in other aspects of egg development, like fertilization rate and egg buoyancy.

Effects of chilled storage and cryopreservation of sperm, and sperm to egg ratio on fertilization success in lumpfish (Cyclopterus lumpus)

Lumpfish males usually release small amounts of milt and are therefore often sacrificed for surgical harvesting of gonads. To optimize the utilization of sperm obtained by dissection of the gonads, a series of small-scale fertilization experiments was carried out in petri dishes. Sperm extracted from homogenized gonads were diluted 1:1 with a commercial extender solution before use (AquaBoost®SpermCoat). Fertilization success was evaluated as percentage eyed eggs ∼120 day-degrees post fertilization. Firstly, the effect of chilled storage (3 °C) of diluted milt were evaluated by fertilizing eggs (2.27 × 105 sperm/egg) from two freshly stripped females every 2nd or 3rd day over a 14-day period. Storage time did not affect the fertilization rates which were high throughout the 14-days trial period (89.1–99.8%). Secondly, the effect of sperm to egg ratio of cryopreserved and chilled stored sperm (3 °C for 3 days) on fertilization rate was investigated and compared by fertilizing eggs from three separate females with six different sperm to egg ratios (1.25 × 105 to 2 × 109). For both storage methods, only the lowest sperm to egg ratio (1.25 × 105) resulted in a significant lower but still high fertilization rate (80.7%). Using freshly extracted sperm at lower sperm to egg ratios (1.25 × 105 to 3.1 × 104) to fertilize eggs from three females revealed, however, no relationship between sperm to egg ratio and fertilization rates as they were high for all ratios (91.2–93.4%). Two additional experiments were undertaken at a real scale to validate the petri dish results at higher egg numbers and volumes. A fixed volume of 40 ml eggs (∼4800 eggs) was fertilized with four sperm to egg ratios ranging from 3.1 × 104 to 5 × 105. All sperm to egg ratios resulted in high fertilization rates ranging from 93.7 to 99%. In the second real scale experiment increasing volumes of eggs (1 up to 160 ml) were fertilized with a fixed sperm to egg ratio (2.5 × 105). The fertilization success (95.9–97.5%) was not affected by egg volume. In conclusion, the current study showed that lumpfish sperm can be chilled stored at 3–4 °C for 14 days and can be cryopreserved and thawed without any significant reduction in fertilization success under the conditions used in this study. Compared to other marine teleosts, lumpfish require a low sperm to egg ratio for successful fertilization, but the critical low ratio to obtain high fertilization was not revealed in this study.

Effect of Differences in Betta Fish (Betta Splendes) Strains on Fecundity, Fertility, Egg Diameter and Hatchability

Betta fish (Betta splendens) has export and import potential. Several popular betta fish strains include halfmoon, crown tail, double tail, and placard. We used the observation method to observe four betta fish strains with five replications. The four fish strains were spawned and will be dissected to obtain the female betta fish's gonads. The parameters observed in this study were fecundity, egg diameter, fertility, and hatchability. This study's data analysis method was analysis of variance (ANOVA) with Duncan's multiple range test. Based on the findings of the observations, it is known that the results of betta fish spawning and gonadal dissection on these various betta fish strains show a significant difference in fish fecundity (P 0.05). However, no significant difference in egg diameter, fertility, or hatchability was observed (P &gt; 0.05). Betta splendes strains differ in terms of fecundity, fertility, hatching rate, and egg size.

Эффективность использования солевого раствора при искусственном осеменении икры радужной форели Oncorhynchus mykiss (Waibaum, 1972) и ладожской палии Salvelinus alpinus lepechini (Gmelin, 1788)

In order to increase the level of fertilization of eggs, the effect of buffer solution on sperm activity and the effectiveness of its use as a medium for insemination eggs of rainbow trout which was grown in conditions of flowing water and in recirculation aquaculture system (RAS), as well as Ladoga palia, were tested. In male trout and palia, the number of motile spermatozoa and their activity were higher in solution than in water. In trout which was grown in running water, the percentage of eggs fertilization increased significantly when use solution only in cases when the eggs were contaminated with the contents of burst eggs. In fish grown in the RAS, the replacement of water with a buffer solution increased the level of fertilization in all test variants, regardless of the presence or absence of contamination of the eggs. In Ladoga palia, the result of insemination was the same in water and in solution.

Dengue Exposure and Wolbachia wMel Strain Affects the Fertility of Quiescent Eggs of Aedes aegypti.

(1) Background: The deployment of the bacterium Wolbachia to reduce arbovirus transmission is ongoing in several countries worldwide. When Wolbachia-carrying Aedes aegypti are released and established in the field, females may feed on dengue-infected hosts. The effects of simultaneous exposure on life-history traits of Ae. aegypti to Wolbachia wMel strain and dengue-1 virus DENV-1 remain unclear. (2) Methods: We monitored 4 groups (mosquitoes with either DENV-1 or Wolbachia, coinfected with DENV-1 and Wolbachia, as well as negative controls) to estimate Ae. aegypti survival, oviposition success, fecundity, collapsing and fertility of quiescent eggs for 12 weeks. (3) Results: Neither DENV-1 nor Wolbachia had a significant impact on mosquito survival nor on mosquito fecundity, although the last parameter showed a tendency to decrease with ageing. There was a significant decrease in oviposition success in individuals carrying Wolbachia. Wolbachia infection and storage time significantly increased egg collapse parameter on the egg viability assay, while DENV-1 had a slight protective effect on the first four weeks of storage. (4) Conclusions: Despite limitations, our results contribute to better understanding of the tripartite interaction of virus, bacteria and mosquito that may take place in field conditions and aid in guaranteeing the Wolbachia strategy success.

Evaluation of reproductive and productive qualities of roosters of different lines of the IZA-F-15 cross

Artificial insemination of poultry allows for an increase in reproductive qualities, reduces feed costs for products, and improves breeding work. The authors evaluated the reproductive and productive attributes of roosters of two different lines on adult birds of the IZA-F-15 cross by phases and during the effective period. All hens in both groups belonged to the maternal form of this cross. It was found that the males of the M-22 line were superior to their peers of the M-99 line in terms of ejaculate volume and the number of sperm per 1 ml in the productive period phases and for the entire cycle of their use. The sperm parameters (number of standard forms of spermatozoa and their motility) were similar in both groups of roosters and amounted to 71.35 - 73.79% and 7.07 - 7.5 points, respectively. Roosters of the M-22 line were superior to those of the M-99 line in terms of a set of indicators of reproductive qualities (ejaculate volume, sperm count per 1 ml, fertility and hatching egg yield). Differences in hands were statistically significant. However, the egg production of laying hens and the average weight of their eggs were high. Using males of different lines in artificial insemination did not reveal significant differences in these indicators. The fertility of eggs and the yield of hatching eggs significantly increased in hens inseminated with the sperm of M-22 roosters (group 2), compared with the control, respectively, from 95.94 to 97.33 and from 89.14 to 91.14%. At the same time, the output of broiler chickens in both groups was at a high level and almost the same (80.21 and 82.25%).

Alternative signal pathways underly fertilization and egg activation in a fish with contrasting modes of spawning

BackgroundThe processes of fertilization and egg activation are vital for early embryogenesis. However, while the mechanisms associated with key events during these processes differ among species and modes of spawning, the signal pathways underlying these processes are opaque for many fishes, including economically important species.ResultsWe investigated phenotypic traits, ultrastructure and protein expression levels in the eggs of the topmouth culter (Culter alburnus), a protected and economically important freshwater fish that exhibits two spawning modes, producing semi-buoyant eggs and adhesive eggs. Unfertilized eggs of C. alburnus were examined, as well as eggs at fertilization and 30 min post fertilization. Our results showed that in semi-buoyant eggs, energy metabolism was activated at fertilization, followed by elevated protein expression of cytoskeleton and extracellular matrix (ECM)-receptor interactions that resulted in rapid egg swelling; a recognized adaptation for lotic habitats. In contrast, in adhesive eggs fertilization initiated the process of sperm-egg fusion and blocking of polyspermy, followed by enhanced protein expression of lipid metabolism and the formation of egg envelope adhesion and hardening, which are adaptive in lentic habitats.ConclusionOur findings indicate that alternative signal pathways differ between modes of spawning and timing during the key processes of fertilization and egg activation, providing new insights into the molecular mechanisms involved in adaptive early embryonic development in teleost fishes.

Evaluation of Duck Egg Hatching Characteristics with a Lightweight Multi-Target Detection Method

Since it is difficult to accurately identify the fertilization and infertility status of multiple duck eggs on an incubation tray, and due to the lack of easy-to-deploy detection models, a novel lightweight detection architecture (LDA) based on the YOLOX-Tiny framework is proposed in this paper to identify sterile duck eggs with the aim of reducing model deployment requirements and improving detection accuracy. Specifically, the method acquires duck egg images through an acquisition device and augments the dataset using rotation, symmetry, and contrast enhancement methods. Then, the traditional convolution is replaced by a depth-wise separable convolution with a smaller number of parameters, while a new CSP structure and backbone network structure are used to reduce the number of parameters of the model. Finally, to improve the accuracy of the network, the method includes an attention mechanism after the backbone network and uses the cosine annealing algorithm in training. An experiment was conducted on 2111 duck eggs, and 6488 duck egg images were obtained after data augmentation. In the test set of 326 duck egg images, the mean average precision (mAP) of the method in this paper was 99.74%, which was better than the 94.92% of the YOLOX-Tiny network before improvement, and better than the reported prediction accuracy of 92.06%. The number of model parameters was only 1.93 M, which was better than the 5.03 M of the YOLOX-Tiny network. Further, by analyzing the concurrent detection of single 3 × 5, 5 × 7 and 7 × 9 grids, the algorithm achieved a single detection number of 7 × 9 = 63 eggs. The method proposed in this paper significantly improves the efficiency and detection accuracy of single-step detection of breeder duck eggs, reduces the network size, and provides a suitable method for identifying sterile duck eggs on hatching egg trays. Therefore, the method has good application prospects.

Ranking parameters driving siring success during sperm competition in the North African houbara bustard

Sperm competition is a powerful force driving the evolution of ejaculate and sperm traits. However, the outcome of sperm competition depends on many traits that extend beyond ejaculate quality. Here, we study male North African houbara bustards (Chlamydotis undulata undulata) competing for egg fertilization, after artificial insemination, with the aim to rank the importance of 14 parameters as drivers of siring success. Using a machine learning approach, we show that traits independent of male quality (i.e., insemination order, delay between insemination and egg laying) are the most important predictors of siring success. Traits describing intrinsic male quality (i.e., number of sperm in the ejaculate, mass motility index) are also positively associated with siring success, but their contribution to explaining the outcome of sperm competition is much lower than for insemination order. Overall, this analysis shows that males mating at the last position in the mating sequence have the best chance to win the competition for egg fertilization. This raises the question of the importance of female behavior as determinant of mating order.

Nondestructive prediction of fertilization status and growth indicators of hatching eggs based on respiration

Respiration continues throughout the incubation of eggs and is closely related to fertilization status and changes in chick embryo growth. Here, we explored the relationship between egg respiration, fertilization status, and growth indicators during incubation. First, we studied the changes in respiration of eggs during incubation and found that O2 consumption and CO2 emission were increased gradually during incubation and reached a maximum value when the shells were broken by the chick (21 days). Next, we established models to classify eggs according to the difference in respiration between fertilized and unfertilized eggs early during incubation using random forest (RF), logical regression, and support vector machine (SVM). The accuracy rates of RF and SVM on the third day of incubation were 99.32% and 98.63%, respectively, and reached 100% on the fifth day. Finally, a linear model was used to establish the relationship between chicken embryo respiration and yolk free body mass (YFBM) (R2 values of 0.99 and 0.98 for the early and late incubation periods, respectively), heart mass (R2 = 0.94), liver mass (R2 = 0.97), and the digestive system (DS) mass (R2 = 0.98). The R2 values for the relationships between the real and the predicted YFBM values and heart, liver, and DS masses were 0.98, 0.89, 0.87 and 0.88, respectively, indicating the good fit of the model. This study provides a theoretical basis for the detection of sterile eggs and dead-embryo eggs during incubation.

Benzo(a)pyrene exposure in early life suppresses spermatogenesis in adult male zebrafish and association with the methylation of germ cell-specific genes

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that are widely present in aquatic ecosystems. To assess the impact of early-life exposure to benzo[a]pyrene (BaP), a representative PAH, on reproductive ability in adult male zebrafish (Danio rerio), fertilized embryos were exposed to 0.05, 0.5, 5 and 50 nM of BaP for 96 h, and then the hatched larvae were raised to adulthood in clean water. In one-year-old male fish, the percentage of spermatozoa in testis was significantly reduced in the 0.5, 5 and 50 nM treatments. When the treated fish were mated with untreated fish, significantly decreased rate of egg fertilization and hatching success and significantly elevated malformation rate the F1 larvae were observed in the 0.5, 5 and 50 nM treatments. The transcriptional levels of genes along the brain-pituitary-gonadal axis, involving gnrh3, gnrhr3, fshβ, lhβ, lhγ, lhrγ and ar, were downregulated. In addition, embryonic BaP exposure upregulated the promotor methylation of germ cell-specific genes in the testis of adult fish. The upregulated methylation of ddx4, dnd1, nanos2 in the testis might be associated with the downregulated mRNA levels of these genes, which could be another reason for the inhibition of spermatogenesis. These results indicate that early-life exposure to BaP suppress the reproductive capability of adult male fish, which would cause a decrease in fish population.