Large Oocytes Research Articles

Decoding molecular features of bovine oocyte fate during antral follicle growth via single-cell multi-omics analysis†.

Antral follicle size is a useful predictive marker of the competency of enclosed oocytes for yielding an embryo following in vitro maturation and fertilization. However, the molecular mechanisms underpinning oocyte developmental potential during bovine antral follicle growth are still unclear. Here, we used a modified single-cell multi-omics approach to analyze the transcriptome, DNA methylome, and chromatin accessibility in parallel for oocytes and cumulus cells collected from bovine antral follicles of different sizes. Transcriptome profiling identified three types of oocytes (small, medium, and large) that underwent different developmental trajectories, with large oocytes exhibiting the largest average follicle size and characteristics resembling metaphase-II oocytes. Differential expression analysis and real-time polymerase chain reaction assay showed that most replication-dependent histone genes were highly expressed in large oocytes. The joint analysis of multi-omics data revealed that the transcription of 20 differentially expressed genes in large oocytes was associated with both DNA methylation and chromatin accessibility. In addition, oocyte-cumulus interaction analysis showed that inflammation, DNA damage, and p53 signaling pathways were active in small oocytes, which had the smallest average follicle sizes. We further confirmed that p53 pathway inhibition in the in vitro maturation experiments using oocytes obtained from small antral follicles could improve the quality of oocytes and increased the blastocyte rate after in vitro fertilization and culture. Our work provides new insights into the intricate orchestration of bovine oocyte fate determination during antral folliculogenesis, which is instrumental for optimizing in vitro maturation techniques to optimize oocyte quality.

Impact of seasonality on the reproductive physiology of diploid and tetraploid eastern oyster, Crassostrea virginica

Aquaculture production of triploid Eastern oyster, Crassostrea virginica, in the Gulf of Mexico (GoM) is reliant on naturally conditioned diploid females and tetraploid males. However, limited knowledge is available on their reproductive biology, including the gametogenic cycle. The aim was to quantify monthly changes in gametogenesis and gamete quality for triploid production in Eastern oyster in the GoM from June 2022 to July 2023. Monthly changes in temperature and salinity were recorded. Shell morphometrics and sex were determined. Sperm density, sperm activity, Spermatogenic Maturity Index (SMI), oocyte diameter, Oogenesis Maturity Index (OMI), and gonad coverage area were quantified. Mean monthly temperature ranged from 15.1 to 31.2 °C and salinity ranged from 12.5 to 27.6 PSU. Shell morphometrics increased over the annual cycle. When gametes were detectable, 48–80% of tetraploids and 45–70% of diploids were males. Hermaphrodites were identified in both ploidies in June; an additional tetraploid hermaphrodite was identified in March. Sperm density exhibited monthly fluctuations with high densities reported in June–July, September, and April–May. Sperm were motile when present, with high motility in June–July. High sperm velocity was also recorded in June–July and March–May. Tetraploids exhibited high SMI from June–September and April–May with increased variability in December–January. Mature sperm cells were predominant in tetraploids in June–July. Gonadal coverage was high from June–September and March–May. OMI was highest from June–September and March–May, while variability was high from August–March. Large oocyte diameters and gonad coverage areas were observed in June–July, September, and April–May. Together, these findings provide novel insights into reproductive dynamics for triploid production of Eastern oyster in GoM.

Oocyte retrieval in social fertility preservation: challenging traditional beliefs on gonadotropin dosing and follicular size

ObjectivesTo investigate treatment approaches for fertility preservation patients, with a focus on timing of oocyte retrieval, and to determine whether their characteristics differ from those of other IVF patients. Additionally, to evaluate the significance of follicle size on triggering day in the context of fertility preservation.MethodsThis retrospective cohort study was conducted in a tertiary, university-affiliated medical center. It compared 140 matched patients undergoing social fertility preservation to 140 patients undergoing IVF treatment due to male factor infertility.ResultsPatients undergoing fertility preservation received a higher initial gonadotropin dose and had more oocytes retrieved than the control group. Within the fertility preservation cohort, a negative correlation was observed between the rate of large follicles and the number of retrieved oocytes. While there was no significant association between rate of large follicles and oocyte maturation rate in the entire group, age-stratified analysis revealed a negative relationship. Analysis revealed that although traditional treatment determinants such as follicular size and gonadotropin dosing were considered, peak estradiol levels were consistently identified as significant predictors of treatment outcomes.ConclusionsPhysicians may modify treatments for fertility preservation, emphasizing a higher gonadotropin dosage to maximize oocyte retrieval. Elevated estradiol levels can serve as a real-time predictive marker for the number of mature oocytes. While treatment strategies can influence outcomes, intrinsic patient factors, particularly baseline ovarian function, remain crucial. These results challenge beliefs regarding the importance of larger follicles and suggest the need for a tailored approach, considering patient age and specific fertility preservation objectives.

A new insight on evaluation of the fertility and pregnancy outcome in patients with primary Sjögren syndrome: a propensity score matched study in multi-IVF centers

BackgroundPrimary Sjögren syndrome (pSS) is often related to adverse neonatal outcomes. But it’s currently controversial whether pSS has an adverse effect on female fertility and clinical pregnancy condition. More importantly, it’s unclear regarding the role of pSS in oocyte and embryonic development. There is a lack of comprehensive understanding and evaluation of fertility in pSS patients.ObjectiveThis study aimed to investigate oocyte and embryonic development, ovarian reserve, and clinical pregnancy outcomes in Primary Sjögren syndrome (pSS) patients during in vitro fertilization (IVF) treatment from multi-IVF centers.MethodsWe performed a muti-central retrospective cohort study overall evaluating the baseline characteristics, ovarian reserve, IVF laboratory outcomes, and clinical pregnancy outcomes between the pSS patients and control patients who were matched by Propensity Score Matching.ResultsFollowing PSM matching, baseline characteristics generally coincided between the two groups. Ovarian reserve including anti-müllerian hormone (AMH) and antral follicle counting (AFC) were significantly lower in the pSS group vs comparison (0.8 vs. 2.9 ng/mL, P < 0.001; 6.0 vs. 10.0, P < 0.001, respectively). The pSS group performed significant reductions in numbers of large follicles, oocytes retrieved and MII oocytes. Additionally, pSS patients exhibited obviously deteriorate rates of oocyte maturation, 2PN cleavage, D3 good-quality embryo, and blastocyst formation compared to comparison. As for clinical pregnancy, notable decrease was found in implantation rate (37.9% vs. 54.9%, P = 0.022). The cumulative live birth rate (CLBR) following every embryo-transfer procedure was distinctly lower in the pSS group, and the conservative and optimal CLBRs following every complete cycle procedure were also significantly reduced in the pSS group. Lastly, the gestational weeks of the newborns in pSS group were distinctly early vs comparison.ConclusionPatients with pSS exhibit worse conditions in terms of female fertility and clinical pregnancy, notably accompanied with deteriorate oocyte and embryo development. Individualized fertility evaluation and early fertility guidance are essential for these special patients.

#297 : The Impact of Large Perivitelline Space and Fragmented Polar Body Oocytes on the Quality of Embryos and Pregnancy Loss in IVF Program

Background and Aims: Extracytoplasmic oocyte abnormalities such as Large Perivitelline Space (LPVS) and Fragmented Polar Body (FrPB) are frequently detected in human oocytes during IVF procedures. The purpose of this research is to determine the relationship of LPVS, FrPB, and their combination on embryo quality and pregnancy loss. Method: The 36 positive pregnancy cases from under 40 years old patients that underwent ICSI using normospermia at RS Pondok Indah IVF Centre were observed. Patients were stimulated with r-FSH utilizing an antagonist protocol for 10-11 days, then r-HCG was administered as a trigger 36 hours before retrieval. Oocytes were classified as follows: (a) normal, (b) large perivitelline space (LPVS), (c) polar body fragmentation (FrPB), and (d) a combination of LPVS and FrPB. The Shapiro-Wilk and Kruskal-Wallis tests were used to determine the effect between each of the categories of oocyte with D3 and D5 embryo quality, along with pregnancy loss. Results: The results indicate that there was no significant distinction among the groups in terms of embryo quality on D3 and D5, as well as pregnancy loss (p=0.187, 0.881, and 0.561, respectively). Conclusion: It could have been concluded that LPVS, FrPB, and their combination have no impact on embryo quality and pregnancy loss.

The consequences of tetraploidy on Caenorhabditis elegans physiology and sensitivity to chemotherapeutics

Polyploid cells contain more than two copies of each chromosome. Polyploidy has important roles in development, evolution, and tissue regeneration/repair, and can arise as a programmed polyploidization event or be triggered by stress. Cancer cells are often polyploid. C. elegans nematodes are typically diploid, but stressors such as heat shock and starvation can trigger the production of tetraploid offspring. In this study, we utilized a recently published protocol to generate stable tetraploid strains of C. elegans and compared their physiological traits and sensitivity to two DNA-damaging chemotherapeutic drugs, cisplatin and doxorubicin. As prior studies have shown, tetraploid worms are approximately 30% longer, shorter-lived, and have a smaller brood size than diploids. We investigated the reproductive defect further, determining that tetraploid worms have a shorter overall germline length, a higher rate of germ cell apoptosis, more aneuploidy in oocytes and offspring, and larger oocytes and embryos. We also found that tetraploid worms are modestly protected from growth delay from the chemotherapeutics but are similarly or more sensitive to reproductive toxicity. Transcriptomic analysis revealed differentially expressed pathways that may contribute to sensitivity to stress. This study reveals phenotypic consequences of whole-animal tetraploidy that make C. elegans an excellent model for ploidy differences.

Rescue of follicle development after oocyte-induced ovary dysfunction and infertility in a model of POI.

The mechanisms and aetiology underlying the development of premature ovarian insufficiency (POI) are poorly understood. However, the oocyte clearly has a role as demonstrated by the Double Mutant (DM) mouse model where ovarian dysfunction (6weeks) is followed by POI (3months) due to oocyte-specific deletion of complex and hybrid N- and O-glycans. The ovaries of DM mice contain more primary follicles (3a stage) accompanied by fewer developing follicles, indicating a block in follicle development. To investigate this block, we first analysed early follicle development in postnatal (8-day), pre-pubertal (3-week) and post-pubertal (6-week and 3-month) DM (C1galt1 F/F Mgat1 F/F:ZP3Cre) and Control (C1galt1 F/F Mgat1 F/F) mice. Second, we investigated if transplantation of DM ovaries into a "normal" endocrine environment would restore follicle development. Third, we determined if replacing DM ovarian somatic cells would rescue development of DM oocytes. At 3-week, DM primary 3a follicles contain large oocytes accompanied by early development of a secondGC layer and increased GC proliferation. At 6-week, DM primary 3a follicles contain abnormally large oocytes, accompanied with decreased GC proliferation. Transplantation of DM ovaries into a 'normal' endocrine environment did not restore normal follicle development. However, replacing somatic cells by generating reaggregated ovaries (ROs) did enable follicle development to progress and thus highlighted intra-ovarian factors were responsible for the onset of POI in DM females. Thus, these studies demonstrate oocyte-initiated altered communication between GCs and oocytes results in abnormal primary follicles which fail to progress and leads to POI.

Improved estimates of abortion rates in tsetse (Glossina spp.).

Abortion rates were assessed among 170, 846 tsetse (154,228 Glossina pallidipes and 19,618 Glossina morsitans morsitans) sampled in Zimbabwe in 1988-1999. The study produced improved estimates of abortion rates and how these varied with fly age and size and temperatures experienced during pregnancy. An abortion was diagnosed if the uterus was empty and the largest oocyte <0.82 of the expected mature length. Abortion rates for G. pallidipes and G. m. morsitans were 0.64% (95% ci: 0.59-0.69) and 0.83% (0.62-1.10) for trapped flies and 2.03% (1.77-2.31) and 1.55% (1.20-1.98) for flies from artificial refuges. Abortion rates increased with increasing temperature and decreased with increasing wing length and wing fray. Contrary to laboratory findings, abortion rates did not increase in the oldest flies. Percentages of tsetse with empty uteri, regardless of abortion status, were significantly higher than estimated abortion percentages. For tsetse from traps, 4.01% (95% ci: 3.90-4.13) of G. pallidipes and 2.52% (2.14-2.95) of G. m. morsitans had empty uteri; for flies from artificial refuges, the percentages were 12.69% (12.07-13.34) and 14.90% (13.82-16.02), respectively. Abortion losses are small relative to losses at all other stages of life.

Preantral follicle numbers and size in heifers carrying Trio, a bovine high fecundity allele.

The bovine high fecundity allele, Trio, results in the occurrence of multiple ovulations and is characterized by antral follicles that develop slower and acquire ovulatory capacity at smaller sizes. This study provides novel information on the effect of the Trio allele on early folliculogenesis. The bovine high fecundity allele, Trio, causes overexpression in granulosa cells (GCs) of SMAD6, an inhibitor of BMP15-activated SMAD signalling. Furthermore, the Trio allele results in antral follicles that develop slower, acquire ovulatory capacity at smaller sizes, and have three-fold greater ovulation rate compared to half-sib non-carriers. The present study was designed to determine preantral follicle numbers and size in Trio carrier and non-carrier cattle testing the hypothesis that inhibition of SMAD signalling would alter preantral follicle activation and/or growth. Ovarian tissues from Trio carrier (n = 12) and non-carrier (n = 12) heifers were obtained by laparotomy after follicle wave synchronization. Follicle numbers and dimensions were determined for each stage of development (primordial, transitional, primary, and secondary) from paraffin-embedded sections. There were no differences in the number of primordial, transitional, or secondary follicles or in antral follicle count, circulating AMH, or ovarian volume between carriers and non-carriers. Trio carriers had ~2.5-fold greater (P < 0.01) number of primary follicles than non-carriers, and transitional and primary follicles were larger (~1.2-fold; P < 0.1) in Trio carriers. Oocyte volume of primordial and transitional follicles was not different between genotypes; however, oocytes were larger (P < 0.05) in primary (~1.3-fold) and secondary (~1.8-fold) follicles for Trio carriers. Granulosa cell numbers were not different (P > 0.3) between carriers and non-carriers, irrespective of the stage of development. These results suggest that, after primordial follicle activation, follicles in Trio carrier cattle have slower progression through the primary stage, hence the larger oocyte and greater number of primary follicles.

Life-history of the Caucasian dwarf goby Knipowitschia caucasica in an Iranian coastal wetland of the southern Caspian Sea

The Caucasian dwarf goby Knipowitschia caucasica is a small fish in the coastal wetlands of the southern Caspian Sea. The objective of this work was to describe its life-history aspects from individuals collected in the Gomishan wetland of Iran, a highly degraded ecosystem. We collected 707 fish along 18 months and calculated a short life span, TL∞=47.25mm for males, and TL∞=43.05mm for females, high mortality rate (1.84 and 5.83 year-1 for males and females, respectively), female dominance (M: F as 1: 1.22), low fecundity (average absolute fecundity: 672 oocytes.female-1 and mean relative fecundity 1209 oocyte.g-1 ), comparatively large oocytes (0.593 mm, ranging from 0.220 to 0.924 mm) and dependence on the wetland for spawning. Given adverse environmental changes in wetlands, we support the hypothesis that life-history traits confer this fish a high probability of extinction.

Reproductive Characteristics of Pseudecheneis sulcatus (Siluriforms: Sisoridae) in the Lower Yarlung Zangbo River, Tibet

The present research offers novel understandings of the reproductive biology of Pseudecheneis sulcatus (McClelland, 1842) found in the Yarlung Zangbo Grand Canyon, a biodiversity hotspot. Reproductive characteristics of Pseudecheneis sulcatus, including their maturation age, fertility, spawning season, and maximum body size, constitute important aspects of its life-history traits. We collected a total of 310 specimens from the Yarlung Zangbo River’s Motuo reach between March and November 2016 and found the male-to-female ratio to be 0.73:1, markedly different from the anticipated 1:1. The total length of individuals ranged from 72 to 207 mm, while overall weight ranged from 2.5 to 65.0 g. Their length at first maturity was estimated as 131 mm in males and 132 mm in females. Based on the adult proportion and fluctuation in the monthly gonadosomatic index (GSI) and size distribution of oocytes, spawning was determined to occur from March to June. The absolute fecundity ranged between 247 and 2886 eggs, while the fluctuation in average relative fertility ranged between 16.8 and 77.1 eggs/g of fish. The fecundity of P. sulcatus was linearly correlated to the overall weight and length of the fish along with the ovarian weight. In conclusion, P. sulcatus spawned synchronously in spring and early summer, exhibiting low fecundity and large oocytes. Our results provided basic information in understanding how this species adapted well to the unique canyon environment, which may be useful for developing a sustainable conservation plan for P. sulcatus at the lower reach of the Yarlung Zangbo River.

Analysis of reproductive traits reveals complex population dynamics on a small geographical scale in Atlantic herring

Atlantic herring (Clupea harengus) has a complex population structure and displays a variety of reproductive strategies. Differences in reproductive strategies among herring populations are linked to their time of spawning, as well as to their reproductive investment which can be an indicator for migratory vs. stationary behavior. These differences are reflected in the number of oocytes (fecundity) and the size of the oocytes prior spawning. We studied potential mixing of herring with different reproductive strategies during the spring spawning season on a coastal spawning ground. It has been hypothesized that both spring and autumn spawning herring co-occur on this specific spawning ground. Therefore, we investigated the reproductive traits oocyte size, fecundity, fertilization success as well as length of the hatching larvae during the spring spawning season from February to April. We used a set of 11 single nucleotide polymorphism markers (SNPs), which are associated with spawning season, to genetically identify autumn and spring spawning herring. Reproductive traits were investigated separately within these genetically distinct spawning types. Furthermore, we used multivariate analyses to identify groups with potentially different reproductive strategies within the genetic spring spawners. Our results indicate that mixing between ripe spring and autumn spawners occurs on the spawning ground during spring, with ripe autumn spawners being generally smaller but having larger oocytes than spring spawners. Within spring spawners, we found large variability in reproductive traits. A following multivariate cluster analysis indicated two groups with different reproductive investment. Comparisons with other herring populations along the Norwegian coastline suggest that the high variability can be explained by the co-occurrence of groups with different reproductive investments potentially resulting from stationary or migratory behavior. Fertilization success and the length of the hatching larvae decreased with progression of the spawning season, with strong inter-individual variation, supporting our findings. Incorporating such complex population dynamics into management strategies of this species will be essential to build its future population resilience.

Risk factors associated with preterm birth in singletons born after IVF: a national cohort study

Research questionWhat are the risk factors for prematurity other than intrauterine growth restriction in singletons after IVF? DesignData were collected from a national registry, based on an observational prospective cohort of 30,737 live births after assisted reproductive technology (fresh embryo transfers: n = 20,932 and frozen embryo transfer [FET] n = 9805) between 2014 and 2015. A population of not-small for gestational age singletons conceived after fresh embryo transfers and FET, and their parents, was selected. Data on a number of variables were collected, including type of infertility, number of oocytes retrieved and vanishing twins. ResultsPreterm birth occurred in 7.7% (n = 1607) of fresh embryo transfers and 6.2% (n = 611) of frozen–thawed embryo transfers (P < 0.0001; adjusted odds ratio [aOR] = 1.34 [1.21–1.49]). Endometriosis and vanishing twin increased the risk of preterm birth after fresh embryo transfer (P < 0.001; aOR 1.32 and 1.78, respectively). Polycystic ovaries or more than 20 oocytes retrieved also increased preterm birth risk (aOR 1.31 and 1.30; P = 0.003 and P = 0.02, respectively); large oocyte cohort (>20) was no longer associated with the risk of prematurity in FET. ConclusionEndometriosis remains a risk for prematurity even in the absence of intrauterine growth retardation, which suggests a dysimmune effect. Large oocyte cohorts obtained by stimulation, without clinical polycystic ovary syndrome diagnosed before attempts, do not affect FET outcomes, reinforcing the idea of a phenotypic difference in the clinical presentation of polycystic ovary syndrome.

Some Observations on the Reproductive Biology of the Mediterranean Pennatulacean Pteroeides Spinosum (Ellis and Solander, 1786) (Cnidaria: Octocorallia: Pennatulacea)

Sea pens are some of the most important structural species in soft bottom benthic communities. Pteroeides spinosum is a shallow-water pennatulacean (Cnidaria: Octocorallia: Pennatulacea) habiting NE Atlantic-Mediterranean bottoms. In this study, sixteen colonies of Pteroeides spinosum collected from NW Mediterranean Sea (Cap de Creus, Spain) at 99–106 m depth in July (2012), were used to acquire information of their reproductive biology, and to enable a comparison with other pennatulaceans. Our colonies of Pteroeides spinosum are gonochoric showing a bimodal oocyte frequency distribution and an unimodal spermatocyst diameter distribution. All polyp leaves contained oocytes and spermatocysts in different size classes, with those small and translucent spermatocysts/ oocytes (size-class I) often found near the base or lower end of the gastrovascular cavities of polyps. The largest observed diameter was 668 μm for spermatocysts and 687 μm for oocytes. Mean potential relative fecundity (PRF) ranged between 7–17 oocytes per polyp. The effective reproductive effort (ERE) reached a value of ca. 30,000 large oocytes per colony. As was observed for all pennatulaceans previously studied, no sign of hermaphroditism or internal fertilization was detected in our colonies of Pteroeides spinosum.

Lagging X chromatids specify the orientation of asymmetric organelle partitioning in XX spermatocytes of Auanema rhodensis.

The unequal partitioning of molecules and organelles during cell division results in daughter cells with different fates. An extreme example is female meiosis, in which consecutive asymmetric cell divisions give rise to 1 large oocyte and 2 small polar bodies with DNA and minimal cytoplasm. Here, we test the hypothesis that during an asymmetric cell division during spermatogenesis of the nematode Auanema rhodensis, the late segregating X chromatids orient the asymmetric partitioning of cytoplasmic components. In previous studies, the secondary spermatocytes of wild-type XO males were found to divide asymmetrically to generate functional spermatids that inherit components necessary for sperm viability and DNA-containing residual bodies that inherit components to be discarded. Here we extend that analysis to 2 novel contexts. First, the isolation and analysis of a strain of mutant XX pseudomales revealed that such animals have highly variable patterns of X-chromatid segregation. The pattern of late segregating X chromatids nevertheless predicted the orientation of organelle partitioning. Second, while wild-type XX hermaphrodites were known to produce both 1X and 2X sperm, here, we show that spermatocytes within specific spermatogonial clusters exhibit 2 different patterns of X-chromatid segregation that correlate with distinct patterns of organelle partitioning. Together this analysis suggests that A. rhodensis has coopted lagging X chromosomes during anaphase II as a mechanism for determining the orientation of organelle partitioning.

Predicting population's oocyte maturation competence and evaluating individual's latency time using in vitro oocyte maturation in pikeperch (Sander lucioperca)

Artificial reproduction of pikeperch (Sander lucioperca) is characterized by the unpredictability of latency time (LT) as well as the variability of egg quality depending on the time of hormonal stimulation. To predict latency time and thus enhance fertilization outcomes, the present study evaluated whether in vitro maturation techniques could be utilized to assess the status of oocyte maturation competence (OMC). Oocyte samples from nine pond-reared females originating from the Czech Republic (CZECH) and 12 intensively cultured females originating from river Körös (HAKI) were catheterized at the time of hormonal stimulation and cultured in L15 medium supplied with 100 ng/mL of DHP. The stage of final oocyte maturation (FOM) was monitored both in vivo and in vitro and egg quality features were evaluated. HAKI group was characterized by larger oocytes at the time of stimulation (934.4 ± 32.9 μm vs. 860.0 ± 22.7 μm), as well as higher embryo survival (77.7 ± 10.4% vs 53.5 ± 28.8%), suggesting that artificial reproduction was performed prematurely for CZECH group. Oocytes from HAKI fish displayed a higher share of maturing oocytes (41.4 ± 9.1% vs. 13.8 ± 17.6%) and in all samples germinal vesicle breakdown was noticed, while in the CZECH group it was so only in oocytes of one fish. With respect that all fish ovulated after the gonadoliberin stimulation, gonadotropin-regulated OMC is assumed. A correlation was found between the in vivo and in vitro LTs in the HAKI group only (r = 0.791, P = 0.002), indicating a certain autonomy of ovarian follicle of other parts of the physiological axis after completed OMC. The in vitro techniques show great promise for practical application in hatcheries to evaluate the aptness for hormonal stimulation on both individual and population levels.

The Reproductive Characteristics of Garra tibetana, an Endemic Labeonine Fish in the Lower Yarlung Tsangpo River, Tibet, China

The reproductive characteristics of an endemic labeonine fish, Garra tibetana, were investigated by examining 778 individuals collected monthly, from December 2015 to November 2016, in the lower Yarlung Tsangpo River, Tibet, China. Results showed that females predominated in the overall population with a sex ratio of 1:0.73, while the sex ratio for the mature individuals was 1:1. Standard length at first maturity was estimated as 82.4 mm for females and 55.4 mm for males based on logistic regression. Analyses based on the monthly variation of the gonad-somatic index, monthly proportion of gonad development, and frequency distribution of oocyte diameter demonstrated the spawning period of G. tibetana to be from February to April, with a peak in March. Absolute fecundity ranged from 113 to 440 oocytes, with a mean of 201.8 ± 58.7 oocytes. The relative fecundity ranged from 6 to 18 oocytes per gram, with a mean of 11.7 ± 2.6 oocytes per gram. Absolute fecundity showed positive correlations with standard length, body weight, and gonad weight, revealing that larger females produced more offspring. In conclusion, G. tibetana matures early and spawns synchronously from February to April, with low fecundity and large oocytes. These reproductive characteristics could explain why this species is dominant in its habitat and also provide valuable information for developing applicable management and conservation strategies.

The prophase oocyte nucleus is a homeostatic G-actin buffer.

ABSTRACTFormation of healthy mammalian eggs from oocytes requires specialised F-actin structures. F-actin disruption produces aneuploid eggs, which are a leading cause of human embryo deaths, genetic disorders and infertility. We found that oocytes contain prominent nuclear F-actin structures that are correlated with meiotic developmental capacity. We demonstrate that nuclear F-actin is a conserved feature of healthy mammalian oocytes and declines significantly with female reproductive ageing. Actin monomers used for nuclear F-actin assembly are sourced from an excess pool in the oocyte cytoplasm. Increasing monomeric G-actin transfer from the cytoplasm to the nucleus or directly enriching the nucleus with monomers led to assembly of stable nuclear F-actin bundles that significantly restrict chromatin mobility. By contrast, reducing G-actin monomer transfer by blocking nuclear import triggered assembly of a dense cytoplasmic F-actin network that is incompatible with healthy oocyte development. Overall, our data suggest that the large oocyte nucleus helps to maintain cytoplasmic F-actin organisation and that defects in this function are linked with reproductive age-related female infertility.This article has an associated First Person interview with Federica Giannini, joint first author of the paper.

Effects of soya lecithin addition on the growth, antioxidant capacity, gonad development and nutritional quality of adult sea urchin (Strongylocentrotus intermedius)

This study was conducted to investigate the effects of soya lecithin (SL) addition on the growth, antioxidant capacity, gonad development and nutritional quality of adult sea urchin (Strongylocentrotus intermedius). Five palm oil (PO)-based feeds were formulated with graded addition of SL (0%, 1.5%, 3%, 4.5%, and 6%). Fish oil (FO)- based feed (6% fish oil + 0% SL) and fresh kelp (Saccharina japonica) were used as the control diets. Each diet was randomly assigned to ten cages of sea urchins. The feeding experiment was performed in autumn season and lasting for 30 days. The results showed that the weight gain rate and gonadosomatic index were decreased due to moderate or higher addition level (3–6%) of SL. A low dosage (1.5%) of SL resulted in the most ideal attractive color and antioxidant capacity. The promoting effects of SL on the gonad development were observed at a low dosage, and were reflected by more sperm, larger oocytes and a thicker oocyte layer. However, the promoting effects of SL on gonad development were eliminated as the addition level increased to 4.5%. Male S. intermedius fed 1.5% SL showed comparable gametogenesis (stage III) to that of males fed FO and kelp. However, female S. intermedius fed formulated feeds showed markedly slower gonad development than those fed kelp, with all individuals staying in stage I and II. The deposition of arachidonic acid (ARA, 20:4n-6) increased while eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and n-3/n-6 polyunsaturated fatty acid (PUFA) decreased as the SL addition increased. Although FO resulted in the highest growth rate and LC-PUFA deposition, it negatively affected the antioxidant capacity. In conclusion, the optimal SL requirement was recommended to be no more than 1.5% in the PO-based diets for adult S. intermedius from the perspective of growth, antioxidant capacity, gonad development and nutritional quality. PO based diets showed comparable effects to FO based diets on the growth performance and gonad development. These results can contribute to optimization of the feed formulation for producing S. intermedius gonads that are high in quantity and quality.

Genetic polymorphisms of reproductive hormones and their receptors in assisted reproduction technology for patients with polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies in women of childbearing, which is defined by the accumulation of multiple, small fluid-filled ovarian cysts without the selection of a single dominant follicle. Most PCOS phenotypes are characterized by the absence of spontaneous ovulation, resistance toward ovulation inductors, the production of a large immature oocytes number, and the high prevalence of ovarian hyperstimulation syndrome, resulting in reduced assisted reproductive technologies (ART) programs effectiveness. The review analyses current data about the relationship between polymorphism genotypes of KISS genes, follicle stimulating hormone (FSH), luteinizing hormone (LH), anti-Müllerian hormone (AMH) and their receptors genes, gonadotropin-releasing hormone (GnRH), estrogen, and progesterone receptors genes, the PCOS risk and the features of ovarian response to stimulation during ART cycles. The use of single nucleotide polymorphisms (SNPs) as prognostic markers of ART programs outcomes would provide a personalized approach to the drugs and doses choice for ovarian stimulation and significantly increase the chance of pregnancy.