Rate Of Embryonic Development Research Articles

A new method of estimating thermal performance of embryonic development rate yields accurate prediction of embryonic age in wild reptile nests

Temperature has a strong effect on ectotherm development rate. It is therefore possible to construct predictive models of development that rely solely on temperature, which have applications in a range of biological fields. Here, we leverage a reference series of development stages for embryos of the turtle Chelydra serpentina, which was described at a constant temperature of 20 °C. The reference series acts to map each distinct developmental stage onto embryonic age (in days) at 20 °C. By extension, an embryo taken from any given incubation environment, once staged, can be assigned an equivalent age at 20 °C. We call this concept “Equivalent Development”, as it maps the development stage of an embryo incubated at a given temperature to its equivalent age at a reference temperature. In the laboratory, we used the concept of Equivalent Development to estimate development rate of embryos of C. serpentina across a series of constant temperatures. Using these estimates of development rate, we created a thermal performance curve measured in units of Equivalent Development (TPCED). We then used the TPCED to predict developmental stage of embryos in several natural turtle nests across six years. We found that 85% of the variation of development stage in natural nests could be explained. Further, we compared the predictive accuracy of the model based on the TPCED to the predictive accuracy of a degree-day model, where development is assumed to be linearly related to temperature and the amount of accumulated heat is summed over time. Information theory suggested that the model based on the TPCED better describes variation in developmental stage in wild nests than the degree-day model. We suggest the concept of Equivalent Development has several strengths and can be broadly applied. In particular, studies on temperature-dependent sex determination may be facilitated by the concept of Equivalent Development, as development age maps directly onto the developmental series of the organism, allowing critical periods of sex determination to be delineated without invasive sampling, even under fluctuating temperature.

Effect of vitrification solutions on survival rate of cryopreserved Epinephelus moara embryos

Embryo cryopreservation is important for long-term preservation of germplasm and assisted reproduction. However, it is still very difficult to obtain viable embryos from cryopreserved fish embryos. In this study, embryos of Epinephelus moara were used to investigate the effects of various cryopreservation methods. Embryos in stages 10 pairs somite (10S), 18 pairs somite (18S), 22 pairs somite (22S), tail-bud (TB), embryo twitching (ET) and pre-hatch (PH) were treated with five-step equilibrium penetration in 40% PMG3T vitrification solution, which contained 15.75% 1,2-propylene glycol, 10.50% Methanol, 8.75% Glycerol and 5.00% Trehalose. We found that 18S, 22S, TB and ET stage embryos had higher survival rates and were more tolerant to the vitrification solution. Five-step equilibrium treatments on the embryos at the tail-bud stage were performed using two vitrification solutions: 40% PMG3T and 40% PMG3S, which consisted of 15.75% 1,2-propylene glycol, 10.50% Methanol, 8.75% Glycerol and 5.00% Sucrose. The embryonic survival rate under PMG3S treatment (63.36%) was significantly higher than PMG3T treatment (43.93%) (P < 0.05). PMG3S and PMG3T with concentrations of 35%, 40% and 45% were tested on tail-bud stage embryos. Higher concentration of the vitrification solution led to significantly lower embryonic survival rate (P < 0.05). The survival rate was 36.79–72.05% in PMG3S, and 37.11–55.18% in PMG3T, and there were non-significant differences in embryonic development and malformation rates among the groups treated with different concentrations. The embryonic normal development rates in PMG3S and PMG3T were 21.27% and 11.04%, and the malformation rates were 36.13% and 31.04%, respectively. The optimum treatment condition was 40 min using 40% PMG3S on embryos at the tail-bud stage. Both PMG3S and PMG3T were used for cryopreserving embryos at 16 pairs somite, tail-bud and ET stage in liquid nitrogen, where we obtained 190 surviving embryos, and 44 fishes underwent normal development and hatched. The survival rate of cryopreserved embryos was 5.15%, the normal development rate was 1.31%, and the malformation rate was 3.66%. We found that PMG3S and PMG3T were effective for cryopreservation of Epinephelus moara embryos. The results provide a foundation for further explorations of fish embryo cryopreservation techniques.

Laying sequence interacts with incubation temperature to influence rate of embryonic development and hatching synchrony in a precocial bird.

Incubation starts during egg laying for many bird species and causes developmental asynchrony within clutches. Faster development of late-laid eggs can help reduce developmental differences and synchronize hatching, which is important for precocial species whose young must leave the nest soon after hatching. In this study, we examined the effect of egg laying sequence on length of the incubation period in Wood Ducks (Aix sponsa). Because incubation temperature strongly influences embryonic development rates, we tested the interactive effects of laying sequence and incubation temperature on the ability of late-laid eggs to accelerate development and synchronize hatching. We also examined the potential cost of faster development on duckling body condition. Fresh eggs were collected and incubated at three biologically relevant temperatures (Low: 34.9°C, Medium: 35.8°C, and High: 37.6°C), and egg laying sequences from 1 to 12 were used. Length of the incubation period declined linearly as laying sequence advanced, but the relationship was strongest at medium temperatures followed by low temperatures and high temperatures. There was little support for including fresh egg mass in models of incubation period. Estimated differences in length of the incubation period between eggs 1 and 12 were 2.7 d, 1.2 d, and 0.7 d at medium, low and high temperatures, respectively. Only at intermediate incubation temperatures did development rates of late-laid eggs increase sufficiently to completely compensate for natural levels of developmental asynchrony that have been reported in Wood Duck clutches at the start of full incubation. Body condition of ducklings was strongly affected by fresh egg mass and incubation temperature but declined only slightly as laying sequence progressed. Our findings show that laying sequence and incubation temperature play important roles in helping to shape embryo development and hatching synchrony in a precocial bird.

Latitudinal and Temperature-Dependent Variation in Embryonic Development Rate and Offspring Performance in a Freshwater Turtle.

The thermal environment of embryos differs significantly along a latitudinal cline, and the mechanism by which embryos respond to this geographic temperature variation has attracted increasing attention recently. Here, we carried out a common-garden experiment of egg incubation at two fluctuating temperature regimes to elucidate the latitudinal pattern and thermal dependence of the embryonic development rate and offspring performance in the Chinese soft-shelled turtle (Pelodiscus sinensis). Our results demonstrated significant temperature-by-population interactions on variations in the incubation period and hatchling righting response. The incubation period was shorter and the daily number of heart beats was higher in the medium- and high-latitude populations than in the low-latitude population at low incubation temperatures but not at high temperatures. Offspring from the medium- and high-latitude populations showed a faster righting response than those from the low-latitude population when incubated at low temperatures, whereas offspring from the high-latitude population showed a faster righting response than those from the medium-latitude population when incubated at high temperatures. This indicates that turtle embryos from different latitudinal locations may have evolved divergent thermal sensitivities of embryonic development in response to their respective nest environments.

Treatment with cyclic adenosine monophosphate modulators prior to in vitro maturation alters the lipid composition and transcript profile of bovine cumulus-oocyte complexes and blastocysts.

Mammalian oocytes resume meiosis spontaneously after removal from the ovarian follicle. We tested the effects of a 2-h prematuration treatment (Pre-IVM) with forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX) in bovine cumulus-oocyte complexes (COCs) on the lipid content of oocytes and blastocysts, on the membrane lipid composition of blastocysts and on the transcriptional profiling of cumulus cells and blastocysts in a high-throughput platform. Embryonic development rates to the morula (mean 56.1%) or blastocyst (mean 26.3%) stages were unaffected by treatment. Lipid content was not affected after Pre-IVM, but was increased after IVM in treated oocytes. Conversely, the lipid content was reduced in Pre-IVM blastocysts. Pre-IVM COCs generated blastocysts containing blastomeres with more unsaturated lipids in their membranes. Pre-IVM also altered the relative abundance of 31 gene transcripts after 2h and 16 transcripts after 24h in cumulus cells, while seven transcripts were altered in blastocysts. Our results suggest that the Pre-IVM treatment affected the lipid composition and transcriptional profiles of COCs and blastocysts. Therefore, Pre-IVM with FSK and IBMX could be used either to prevent spontaneous meiotic resumption during IVM or to modulate lipid composition in the membrane and cytoplasm of blastocysts, potentially improving bovine embryos.

Functional and Proteomic Alterations of F1 Capacitated Spermatozoa of Adult Mice Following Gestational Exposure to Bisphenol A.

Studies regarding bisphenol A (BPA) exposure and male (in)fertility have conventionally focused on modifications in ejaculated spermatozoa function from exposed individuals. However, mammalian spermatozoa are incapable of fertilization prior to achieving capacitation, the penultimate step in maturation. Therefore, it is necessary to investigate BPA-induced changes in capacitated spermatozoa and assess the consequences on subsequent fertilization. Here, we demonstrate the effect of gestational BPA exposure (50 μg/kg bw/day, 5 mg/kg bw/day, and 50 mg/kg bw/day) on the functions, biochemical properties, and proteomic profiles of F1 capacitated spermatozoa from adult mice. The data showed that high concentrations of BPA inhibited motility, motion kinematics, and capacitation of spermatozoa, perhaps because of increased lipid peroxidation and protein tyrosine nitration, and decreased intracellular ATP levels and protein kinase-A activity in spermatozoa. We also found that BPA compromised the rates of fertilization and early embryonic development. Differentially expressed proteins identified between BPA-exposed and control groups play a critical role in energy metabolism, stress responses, and fertility. Protein function abnormalities were responsible for the development of several diseases according to bioinformatics analysis. On the basis of these results, gestational exposure to BPA may alter capacitated spermatozoa function and the proteomic profile, ultimately affecting their fertility potential.

Effect of cryopreservation on the pre-hatching behavior in the Mexican fruit fly Anastrepha ludens Loew (Diptera, Tephritidae)

In a sampling of untreated embryos of the economically important fruit pest species, Anastrepha ludens, the cumulative hatch percentage in the lab was noted to be ∼85%. Approximately 70% of the larvae had eclosed through the posterior pole of the egg. This process is effected by the act of Pole Reversal (PR) of the fully developed pre-hatch larva from the wider anterior to the narrower posterior pole of the egg. Investigation of the effects of cryopreservation and various pretreatments prior to cryostorage on the PR behavior was prompted by the observation of significantly lower proportion of cryopreserved embryos exhibiting the PR behavior. Pretreatments (dechorionation and permeabilization) followed by vitrification resulted in delayed hatching, reflecting a slower embryonic development rate of ∼10 h. A smaller proportion of the treated embryos either eclosed from the anterior end of the egg or did not eclose at all despite complete development and prehatch gnawing activity. In the untreated controls, 24.0% of the embryos eclosed from the anterior pole. After permeabilization and cryopreservation, 83% and 55% (adjusted hatch) of the embryos were noted to hatch this way, respectively. An analysis of the hatch count after the treatments shows that factors contributing to the embryos' inability to properly invert polarity is not solely due to cryopreservation but also due to the pretreatment procedures including dechorionation and permeabilization. In fact, the permeabilization pre-treatment contributed the highest to this phenomenon lending support to the view that chemical toxicity rather than physical effects of cryopreservation play a major role in post-cryopreservation effects.

Larval Behavior and Longevity in the Cold-Water Coral Lophelia pertusa Indicate Potential for Long Distance Dispersal

The life cycle of many marine benthic species includes a pelagic larval stage that governs the connectivity between populations. Larval transport is a function of hydrodynamic and biological processes. Knowledge of how larval traits affect dispersal will increase the accuracy of biophysical models used to predict connectivity, and is of paramount importance for management and conservation. This study examines the larval traits of the cold-water coral Lophelia pertusa that forms widespread and highly diverse ecosystems in the deep ocean. We monitored development, swimming behaviour, and survival under different environmental conditions. We found that the embryonic development rate doubled when the rearing temperature was increased from normal conditions of 7–8°C to 11–12°C. Pre-competent planulae migrated vertically upwards at a speed of 0.5–0.7 mm s-1 and crossed salinity gradients with a maximum tested difference of 5 psu with no hesitation. At three weeks, planulae had a fully developed mouth and started feeding on animal derivatives, picoplankton, and possibly smaller size microalgae. Presence of food significantly altered the swimming pattern, and feeding was corroborated by direct observation. Planulae survived for up to ten months in a salinity of 25 psu, which together with the vertical migration pattern and feeding indicates that larvae may spend a period of their pelagic phase in the photic zone. After 50 days, larvae were still in a very good condition as deduced by maintained high swimming speed. Survival rate of developed planulae was on average 60% over a 3-month period, and maximum longevity was a full year, in laboratory cultures.

Signatures of selection in embryonic transcriptomes of lizards adapting in parallel to cool climate.

Populations adapting independently to the same environment provide important insights into the repeatability of evolution at different levels of biological organization. In the 20th century, common wall lizards (Podarcis muralis) from southern and western Europe were introduced to England, north of their native range. Nonnative populations of both lineages have adapted to the shorter season and lower egg incubation temperature by increasing the absolute rate of embryonic development. Here, we tested if this adaptation is accompanied by signatures of directional selection in the transcriptomes of early embryos and, if so, if nonnative populations show adaptive convergence. Embryos from nonnative populations exhibited gene expression profiles consistent with directional selection following introduction, but different genes were affected in the two lineages. Despite this, the functional enrichment of genes that changed their expression following introduction showed substantial similarity between lineages, and was consistent with mechanisms that should promote developmental rate. Moreover, the divergence between nonnative and native populations was enriched for genes that were temperature-responsive in native populations. These results indicate that small populations are able to adapt to new climatic regimes, but the means by which they do so may largely be determined by founder effects and other sources of genetic drift.

Developmental competence of goat oocytes vitrified at immature and mature stage in comparsion to fresh oocytes after in vitro fertilization using cauda epididymal spermatozoa

The oocytes were cryopreserved at 2 developmental check points, viz. immature and metaphase II stage, and the outcome of in vitro fertilization (IVF) was assessed as compared to fresh oocytes. The oocytes were cryopreserved by solid surface vitrification technique using equilibration media (4% ethylene glycol) followed by vitrification media (0.5 M sucrose + 35% ethylene glycol + 0.5% polyvinyl pyrollidone). The mature oocytes were pre-treatedwith cytochalasin B for 30 min before vitrification. The vitrified-thawed oocytes of both groups as well fresh oocytes were fertilized with buck epididymal sperm. The results revealed a significantly higher rate of embryonic development in vitrified-thawed immature oocytes as compared to that in vitrified-thawed mature oocytes at all the embryonic stages. The embryonic developmental rate under fresh oocyte group was significantly higher than both vitrified groups. Results indicated that the immature goat oocytes could be a better candidate for long term storage of female germplasm as well as dissemination into distant places.

Embryogenesis of vitrified mature bovine oocytes is improved in the presence of multi-layered cumulus cells.

This study was aimed at evaluating the effects of multi-layered cumulus cells (MCCs) during vitrification and in vitro fertilization (IVF) of mature bovine oocytes and embryogenesis after IVF. The rates of cleavage and blastocyst formation were higher in vitrified and fertilized oocytes with MCCs than in denuded oocytes (P < 0.05), but were comparable to the rates in fresh oocytes with MCCs or without (denuded). When the MCC-enclosed oocytes were denuded before IVF, blastocyst formation rate reduced compared with that in vitrified oocytes with MCCs (P < 0.05). This suggested that the MCCs surrounding the mature bovine oocytes play important roles during cryopreservation: protecting them against freezing and promoting their survival and development post IVF, thereby increasing the success rates of IVF and embryonic development. Herein, we showed for the first time that calves could be produced using only 14–19 vitrified mature oocytes with MCCs from the ovaries of individual cows post slaughter.

Selected steps of swine ICSI method to overcome seasonal effect and achieve acceptable early embryonic development, a preliminary study.

Porcine intra cytoplasmic sperm injection's (ICSI) efficacy by selected protocol steps was investigated. Three trials per year's period (hot, medium, cold) were carried out. Only large size follicles (6-8mm) were aspirated, brilliant cresyl blue (BCB) test was performed and only the BCB+ oocytes were in vitro maturated (40h) and involved to ICSI process. The presumptive embryos were in vitro cultured (15h). Raw boar semen and SpermCatch® as slowing medium were used. No differences were observed between periods regarding early embryonic development and maturation competence. ICSI achieves acceptable porcine early embryonic development rates under the investigated conditions.

Altered embryonic development in northern bobwhite quail (Colinus virginianus) induced by pre-incubation oscillatory thermal stresses mimicking global warming predictions.

Global warming is likely to alter reproductive success of ground-nesting birds that lay eggs normally left unattended for days or even weeks before actual parental incubation, especially in already warm climates. The native North American bobwhite quail (Colinus virginianus) is such a species, and pre-incubation quail eggs may experience temperatures ≥45°C. Yet, almost nothing is known about embryonic survival after such high pre-incubation temperatures. Freshly laid bobwhite quail eggs were exposed during a 12 day pre-incubation period to one of five thermal regimes: low oscillating temperatures (25–40°C, mean = 28.9°C), high oscillating temperatures (30–45°C, mean = 33.9°C), low constant temperatures (28.85°C), high constant temperatures (mean = 33.9°C), or commercially employed pre-incubation temperatures (20°C). After treatment, eggs were then incubated at a standard 37.5°C to determine subsequent effects on embryonic development rate, survival, water loss, hatching, and embryonic oxygen consumption. Both quantity of heating degree hours during pre-incubation and specific thermal regime (oscillating vs. non-oscillating) profoundly affected important aspects of embryo survival and indices of development and growth Pre-incubation quail eggs showed a remarkable tolerance to constant high temperatures (up to 45°C), surviving for 4.5±0.3 days of subsequent incubation, but high oscillating pre-incubation temperature increased embryo survival (mean survival 12.2±1.8 days) and led to more rapid development than high constant temperature (maximum 38.5°C), even though both groups experienced the same total heating degree-hours. Oxygen consumption was ~200–300 μl O2.egg.min-1 at hatching in all groups, and was not affected by pre-incubation conditions. Oscillating temperatures, which are the norm for pre-incubation quail eggs in their natural habitat, thus enhanced survival at higher temperatures. However, a 5°C increase in pre-incubation temperature, which equates to the predicted long-term increases of 5°C or more, nonetheless reduced hatching rate by approximately 50%. Thus, while pre-incubation bobwhite eggs may be resiliant to moderate oscillating temperature increases, global warming will likely severely impact wild bobwhite quail populations, especially in their strongholds in southern latitudes.

Ocean acidification impacts the embryonic development and hatching success of the Florida stone crab, Menippe mercenaria

The deterioration of coastal habitats due to anthropogenic activities is being caused by nutrient rich runoff which will likely result in more frequent and severe extremes in seawater pH. The embryonic and larval stages of many coastal species may not have the physiological ability to tolerate these extreme shifts in pH forecasted for future oceans. The stone crab, Menippe mercenaria, was used to determine the impact of low seawater pH on embryonic development and hatching success. Ovigerous females were maintained in environments characteristic of both present-day and reduced seawater pH. Lower pH significantly reduced the rate of embryonic development (i.e., time to hatching) by ~24%, but had no effect on the size of developing embryos (i.e., embryonic volume). Larvae that successfully hatched were not morphologically different between treatments, although hatching success was reduced by 28% in lower pH seawater. Hatching success was also more variable in the reduced pH treatment indicating that some broods may be more tolerant to changes in seawater acidity. Variable hatching success under acidified conditions suggests that stone crab embryos may have the capacity to acclimatize to future seawater pH conditions.

Sperm retrieval rates (SRR) and clinical outcomes after testicular sperm extraction (TESE) in the etiology of azoospermia

In assisted reproductive techniques, it is necessary to collect clinical outcomes in a separate group of patient background and provide it for patients. Sperm retrieval rates (SRR) and clinical outcomes after intracytoplasmic sperm injection (ICSI) with testicular sperm in the etiology azoospermia have hardly been investigated. We report that ICSI outcomes in men undergoing TESE have performed in our clinic latest three years. A retrospective study in the etiology of azoospermia. The studies applied conventional TESE (n=165) for OA patients, ED patients, and oligozoospermic patients and microdissection TESE (micro TESE) (n=843) for NOA patients performed in our clinic between September 2013 and March 2017 were used to analyze for SRR. Azoospermia in a patient with normal-size testes (>16mL) and normal FSH suggested obstructive etiology. The diagnosis of OA also required confirmation of normal spermatogenesis by testicular biopsy. The etiology of NOA included unexplained NOA, Klinefelter syndrome, azoospermia factor (AZF) c microdeletion of the Y chromosome, and post chemotherapy NOA. In addition, a total of 396 couples had 727 TESE-ICSI cycles (94 couples and 170 TESE-ICSI cycles for OA and 302 couples and 557 cycles for NOA) were evaluated in embryonic development rates and clinical pregnancy rates (CPR). Spermatozoa were retrieved 100% (118/118) of obstructive azoospermia (OA), 40.6% (43/106) of Klinefelter syndrome (KS), 20.5% (98/479) of unexplained NOA (NOA), 81.8% (27/33) of AZFc microdelection, and 40.9% (18/44) of post chemotherapy NOA. SRR of OA was significantly higher and unexplained NOA were lower than any other groups. SRR with the primary TESE (49.7%) is significantly higher than with the TESE after who had previously undergone with no sperm found (31.0%) (P<0.001). Especially, the significant difference was observed in KS (48.8% and 15.4%, p<0.01) and unexplained NOA (23.9% and 12.5%, p<0.01), respectively. Two pronuclei (2PN) rates in OA (64.0%) and post chemotherapy NOA (69.3%) were significantly higher, but in AZFc microdelection (47.0%) was significantly lower than any other groups. Blastocyst development rate in AZFc microdelection (33.9%) was significantly lower than any other groups and the rates in KS (41.9%) was lower than in OA (50.8%). Good-quality blastocyst rates in OA (42.6%) and post chemotherapy NOA (45.2%) were significantly higher, but the rate in AZFc microdelection (33.9%) was lower than any other groups. CPR per embryo transfer cycle was lower in unexplained NOA (30.0%), KS (28.6%) and AZFc microdelection (26.6%) than in OA (42.4%). Micro TESE is particularly helpful for successful sperm retrieval in KS and AZFc microdeletion cases, however, the motile and better sperm retrieval from testicular tissue seems to be a critical key to succeed and rationale for good embryonic development and clinical pregnancy.

Evaluation of a new sperm density gradient and sperm wash for assisted reproductive technology

Sperm preparation is an important factor that affects the results of conventional IVF and ICSI. Typically, separation methods that yield a higher number of motile spermatozoa combine density-gradient centrifugation with a subsequent swim-up procedure. However, fertilization in vivo is not only based on absolute sperm numbers, but also on their functional capability. A sperm preparation solution that mimics the physiology of the sperm environment in vivo was developed as the ORIGIO® GradientTM (OG) system. The effect of this new sperm preparation system in ART is still unknown. The aim of this study was to evaluate and compare sperm quality and IVF/ICSI outcomes following density gradient sperm preparation with two different media: Percoll and the OG. A prospective quasi-randomized controlled study was performed in a single IVF center between January 2016 and October 2016. We examined 87 conventional IVF cycles and 167 ICSI cycles. Patients were allocated to two groups randomly: for the control group, sperm preparation was performed using 80% Percoll solution (Sigma) with Sperm Washing Medium (Irvine Scientific); for the test group, sperm preparation was performed using 80% OG with ORIGIO® Sperm Wash (Origio). Only cycles using fresh autologous gametes were included. We excluded testicular sperm extraction-ICSI cycles and cycles combining IVF/ICSI. Sperm preparation was performed using density gradient centrifugation in the control or test solutions (25 min at 500 g) with a subsequent swim-up (30 min). We analyzed 668 inseminated (IVF) and 966 microinjected (ICSI) oocytes. All embryos were cultured using the same protocol. Sperm quality and IVF/ICSI outcomes were compared between the two groups. In both the IVF and ICSI cycles, there were no significant differences in patient characteristics, semen parameters before preparation (ejaculate volume, total and motile sperm concentrations, and percentage motility) or sperm quality after preparation (motile sperm concentration, and percentage motility), when comparing the two groups. Among the 87 conventional IVF cycles, 44 were in the control group and 43 were in the test group. The fertilization rate in the test group was significantly higher (P < 0.05) than in the control group (77.6% vs. 68.2%, respectively). The high-quality embryo formation rate on day 2 in the test group was significantly higher (P < 0.05) than in the control group (48.5% vs. 37.3%, respectively). The cleavage and blastocyst formation rates were similar between the test and control group (97.4% vs. 99.5%, and 58.3% vs. 57.6%, respectively). Among the 167 ICSI cycles, 87 were in the control group and 80 were in the test group. The fertilization, cleavage, high quality embryo rate on day 2 and blastocyst formation rates were similar between the test and control groups (83.8% vs. 82.3%, 98.1% vs. 99.3%, 47.6% vs. 50.9%, and 56.1% vs. 54.6%, respectively). This new sperm preparation system improved the fertilization and early embryonic development rates in conventional IVF cycles.

Intraspecific Variation in and Environment-Dependent Resource Allocation to Embryonic Development Time in Common Terns.

Embryonic development time is thought to impact life histories through trade-offs against life-history traits later in life, yet the inference is based on interspecific comparative analyses only. It is largely unclear whether intraspecific variation in embryonic development time that is not caused by environmental differences occurs, which would be required to detect life-history trade-offs. Here we performed a classical common-garden experiment by incubating fresh eggs of free-living common terns (Sterna hirundo) in a controlled incubation environment at two different temperatures. Hatching success was high but was slightly lower at the lower temperature. While correcting for effects of year, incubation temperature, and laying order, we found significant variation in the incubation time embryos required until hatching and in their heart rate. Embryonic heart rate was significantly positively correlated within clutches, and a similar tendency was found for incubation time, suggesting that intrinsic differences in embryonic development rate between offspring of different parents exist. Incubation time and embryonic heart rate were strongly correlated: embryos with faster heart rates required shorter incubation time. However, after correction for heart rate, embryos still required more time for development at the lower incubation temperature. This suggests that processes other than development require a greater share of resources in a suboptimal environment and that relative resource allocation to development is, therefore, environment dependent. We conclude that there is opportunity to detect intraspecific life-history trade-offs with embryonic development time and that the resolution of trade-offs may differ between embryonic environments.

Effects of synthetic polymers on in vitro maturation of sheep oocytes and subsequent developmental capacity after parthenogenetic activation or fertilization

There are few studies considering functional roles of synthetic polymers on small ruminant oocytes matured in vitro. In this study, the effects of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) on in vitro maturation of sheep oocytes were evaluated and compared in order to determine whether synthetic polymers can replace serum and be used for in vitro maturation of sheep oocytes. Simultaneously, the effects of synthetic polymers presented in the maturation medium on subsequent embryonic development were also assessed. Sheep cumulus−oocyte complexes were cultured in the maturation medium supplemented with 10% fetal bovine serum (FBS), 3mg/ml PVP, or 1mg/ml PVA, respectively. The rates of oocyte maturation and embryonic development after parthenogenetic activation (PA) or in vitro fertilization (IVF) were recorded. The data indicated that the presence of PVP in the maturation medium does not have any negative effects on sheep oocytes matured in vitro when compared to FBS, as concern oocyte maturation and subsequent embryonic developmental capacity. Additionally, after PA, the embryonic developmental capability of in vitro matured sheep oocytes in the presence of PVA was not significantly different from that of oocytes matured in the presence of FBS or PVP. By contrast, when PVA was added to the maturation medium, the blastocyst formation rate after IVF (28.05%±5.42%) was significantly lower than that of oocytes matured in the presence of FBS (36.33±4.37%, P<0.05) or PVP (38.94±5.19%, P<0.05). However, there were no significant differences in the oocyte cleavage rate among the three groups. Additionally, the embryonic developmental capacity in the PVP group were similar to those in the FBS group (P>0.05). In conclusion, synthetic polymer as a serum replacement can efficiently maintain the procedure of oocyte maturation and subsequent embryonic developmental capacity in sheep. The PVP is more beneficial to in vitro maturation of sheep oocytes compared to PVA.

Parental care mitigates carry-over effects of poor early conditions on offspring growth

Poor developmental conditions can have long-lasting negative effects on offspring phenotypes, but impacts often differ among species. Contrasting responses may reflect disparities in experimental protocols among single-species studies or inherent differences among species in their sensitivity to early conditions and/or ability to mitigate negative impacts. We used a common experimental protocol to assess and compare the role of parental care in mitigating effects of poor early conditions on offspring among 4 sympatric bird species in the wild. We experimentally induced low incubation temperatures and examined effects on embryonic developmental rates, hatching success, nestling growth rates, and parental responses. We examined the generality of these effects across 4 species that differ in their phylogenetic history, breeding ecology, and life histories. We found that cooling led to delayed hatching in all species, but carry-over effects on offspring differed among species. Parents of some but not all species increased their offspring provisioning rates in response to experimental cooling with critical benefits for offspring growth rates. Our study shows for the first time that species exhibit clear differences in the degree to which they are affected by poor early conditions. Observed differences among species demonstrate that parental care is a critical mechanism for mitigating potential negative effects on offspring and suggest that parental responses may be constrained to varying degrees by ecology and life histories.

Beneficial effects of glutathione supplementation during vitrification of mouse oocytes at the germinal vesicle stage on their preimplantation development following maturation and fertilization in vitro

Oocyte cryopreservation is imperative for assisted reproductive technologies (ART). Although cryopreservation of oocytes at the Metaphase II has been widely used, immature oocytes at the germinal vesicle stage (GV-oocytes) need to be cryopreserved in certain situations such as cancer patients; however, the success rate of embryonic development from the GV-oocytes remains low largely due to the requirement for in vitro maturation (IVM). Our aim was to investigate the effects of glutathione (GSH) supplementation during vitrification and warming of mouse GV-oocytes on the preservation of developmental competence. GV-oocytes within cumulus oocyte complexes (COCs) were collected from C57BL/6J (B6) and (B6.DBA)F1 mouse strains and subjected to vitrification and warming, followed by IVM. The vitrification, warming or IVM medium was supplemented with GSH at 0–4.0 mM. In vitro matured oocytes were then fertilized in vitro and cultured in KSOMaa up to 4 days. The first cleavage and blastocyst development were evaluated morphologically, and their rates were statistically analysed by one-way ANOVA followed by Tukey's multiple comparisons test. The difference was considered significant at P < 0.05. The results showed that GSH supplementation in the IVM medium exhibited no or rather inhibitory effects on the first cleavage or blastocyst development in both mouse strains except that 1.0 mM GSH increased the blastocyst development rate in B6. By contrast, 1 mM GSH supplementation during vitrification and warming increased the blastocyst development rate in both mouse strains, more efficiently in B6 than (B6.DBA)F1. In conclusion, GSH supplementation during vitrification and warming of GV-oocytes protects the oocytes from freezing-inflicted loss of developmental competence.