Embryo Size Research Articles

Microinjection of Xenopus tropicalis Embryos.

Microinjection is an important technique used to study development in the oocyte and early embryo. In Xenopus, substances such as DNA, mRNA, and morpholino oligonucleotides have traditionally been injected into Xenopus laevis, because of their large embryo size and the relatively long time from their fertilization to first division. In the past few decades, Xenopus tropicalis has become an important model in developmental biology; it is particularly useful in genetic studies. The advent and rapid development of CRISPR-Cas9 technology has provided an array of targeted gene manipulations for which X. tropicalis is particularly suited. The equipment and protocol for X. tropicalis microinjection is broadly transferable from X. laevis There are important differences between the species to consider, however, including the smaller embryo size and faster embryo development time in X. tropicalis There are a number of solutions and reagents that differ in concentration and composition as well. Here we describe a microinjection protocol specifically for studies in X. tropicalis.

The upper Aptian–middle Albian Simplorbitolina lineage: an example of nepionic acceleration in Lower Cretaceous Orbitolinidae (Foraminifera)

ABSTRACT Evolutionary lineages within the conical agglutinated family Orbitolinidae are mainly evidenced by the increased complexity of their inner structure. In this respect, gradual changes in the exoskeleton resulting in the evolution of beams and rafters in the marginal zone refer above all to lineages within the subfamily Dictyoconinae. In contrast hereto, the increasing size and complexity of the simple megalospheric embryo as well as the reduction of the initial spiral stage defines lineages within the subfamily Orbitolininae (e.g., Praeorbitolina-Mesorbitolina). The case of the upper Aptian–middle Albian Simplorbitolina lineage, the ancestor-descendant relationship of the three species S. aquitanica, S. manasi, and S. conulus represents a rare example of the Dictyoconinae displaying a successive reduction of the initial spiral stage along with an increase of both embryo size and complexity of the marginal zone. This process, which is known as spiral reduction or nepionic acceleration, is well recorded from other groups of Larger Benthic Foraminifera (fossil and extant) such as the calcareous Rotaliida. The occurrences and palaeogeographic distributional pattern of Simplorbitolinas are reviewed. The present study is preliminary based on a well-preserved assemblage of megalospheric specimens of Simplorbitolina aquitanica (Schroeder) from the upper Aptian Reocín Formation of northern Spain (Cantabria).

Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio

Knowing a tree crop’s seasonal growth and development as a function of heat accumulation can facilitate scheduling of irrigation, pesticide applications, and harvest. Our objective was to compare the goodness of fit of applied models and determine which provides the best description of pistachio nut growth as a function of thermal unit accumulation. Three fruit growth traits of pistachio—pericarp (hull) + endocarp (shell) size, endocarp thickening and hardening, and embryo (kernel) size—exhibited clear nonlinear dependence on heat accumulation. We tested three nonlinear models—Michaelis–Menten, three-parameter logistic, and Gompertz—fitted to fruit development data to create a tool to forecast pest susceptibility and harvest timing. Observation of development began at full bloom and ended at harvest. Data were collected from six pistachio cultivars in one experimental and eight commercial orchards over 3 years. Analyses of residual distribution, parameter standard errors, coefficient of determination (R2) and the Akaike information criterion (AIC) all demonstrated the Gompertz function was the best model. Cultivars differed significantly in all the three parameters (Asym, b, and c) for all three traits with the Gompertz model, demonstrating the Gompertz model can adjust to incorporate cultivar differences. The growth curve of the three traits together provided integrated information on nut biomass accumulation that facilitates predicting the critical timing for multiple orchard management practices.

Evaluation of embryotoxicity and fetotoxicity of Clindamycin phosphate under normal and elevated levels of serum Hydrogen sulfide in rats

Widespread use of antibiotics in clinical practice leads to the development of antibiotic resistance and encourages the search for new ways of modulation of their therapeutic effect. One of the potentially successful modulators may be Hydrogen sulfide, but the mechanisms of its action require careful studies, including toxicological. The aim of the study was to study the effect of Hydrogen sulfide levels on the embryotoxicity and fetotoxicity of oral and intravaginal Clindamycin phosphate administration. The experimental study was performed on 60 pregnant female rats, which were divided into 6 experimental groups: group 1 – control group; group 2 – high level of serum Hydrogen sulfide; group 3 – Clindamycin phosphate intravaginally; group 4 – Clindamycin phosphate intravaginally with high level of serum Hydrogen sulfide; group 5 – Clindamycin phosphate orally; group 6 – Clindamycin phosphate orally with high level of serum Hydrogen sulfide. We studied the dynamics of weight gain in pregnant rats, the number of corpora lutea, the number of implantation sites in the uterus, the number of live and dead fetuses, preimplantation and postimplantation mortality, as well as the dynamics of body weight gain and mental development of offspring. Artificially increasing the serum level of Hydrogen sulfide in pregnant rats led to an increase in maternal weight gain, an increase in the weight and cranio-caudal size of embryos, as well as a decrease in the number of resorbed fetuses and postimplantation mortality. The insignificant toxic effect of high doses of oral Clindamycin phosphate was leveled in the group with elevated indices of serum Hydrogen sulfide. Rats born to females with elevated levels of serum Hydrogen sulfide showed faster rates of weight gain and normal mental development according to the “open field” test.

Zebrafish: An Attractive Model to Study Staphylococcus aureus Infection and Its Use as a Drug Discovery Tool.

Non-mammalian in vivo disease models are particularly popular in early drug discovery. Zebrafish (Danio rerio) is an attractive vertebrate model, the success of which is driven by several advantages, such as the optical transparency of larvae, the small and completely sequenced genome, the small size of embryos and larvae enabling high-throughput screening, and low costs. In this review, we highlight zebrafish models of Staphyloccoccus aureus infection, which are used in drug discovery and for studying disease pathogenesis and virulence. Further, these infection models are discussed in the context of other relevant zebrafish models for pharmacological and toxicological studies as part of early drug profiling. In addition, we examine key differences to commonly applied models of S. aureus infection based on invertebrate organisms, and we compare their frequency of use in academic research covering the period of January 2011 to January 2021.

Scaling of internal organs during Drosophila embryonic development

Many species show a diverse range of sizes; for example, domestic dogs have large variation in body mass. Yet, the internal structure of the organism remains similar, i.e., the system scales to organism size. Drosophila melanogaster has been a powerful model system for exploring scaling mechanisms. In the early embryo, gene expression boundaries scale very precisely to embryo length. Later in development, the adult wings grow with remarkable symmetry and scale well with animal size. Yet, our knowledge of whether internal organs initially scale to embryo size remains largely unknown. Here, we utilize artificially small Drosophila embryos to explore how three critical internal organs—the heart, hindgut, and ventral nerve cord (VNC)—adapt to changes in embryo morphology. We find that the heart scales precisely with embryo length. Intriguingly, reduction in cardiac cell length, rather than number, appears to be important in controlling heart length. The hindgut, which is the first chiral organ to form, displays scaling with embryo size under large-scale changes in the artificially smaller embryos but shows few hallmarks of scaling within wild-type size variation. Finally, the VNC only displays weak scaling behavior; even large changes in embryo geometry result in only small shifts in VNC length. This suggests that the VNC may have an intrinsic minimal length that is largely independent of embryo length. Overall, our work shows that internal organs can adapt to embryo size changes in Drosophila, but the extent to which they scale varies significantly between organs.

Hypertrophy of Adipose Tissues in Quail Embryos by in ovo Injection of All-Trans Retinoic Acid.

Excessive adipose accretion causes health issues in humans and decreases feed efficiency in poultry. Although vitamin A has been known to be involved in adipogenesis, effects of all-trans retinoic acid (atRA), as a metabolite of vitamin A, on embryonic adipose development have not been studied yet. Avian embryos are developing in confined egg environments, which can be directly modified to study effects of nutrients on embryonic adipogenesis. With the use of quail embryos, different concentrations of atRA (0 M to 10 μM) were injected in ovo at embryonic day (E) 9, and adipose tissues were sampled at E14. Percentages of fat pad weights in embryo weights were significantly increased in the group injected with 300 nM of atRA. Also, among three injection time points, E5, E7, or E9, E7 showed the most significant increase in weight and percentage of inguinal fat at E14. Injection of atRA at E7 increased fat cell size in E14 embryos with up-regulation of pro-adipogenic marker genes (Pparγ and Fabp4) and down-regulation of a preadipocyte marker gene (Dlk1) in adipose tissues. These data demonstrate that atRA promotes hypertrophic fat accretion in quail embryos, implying important roles of atRA in embryonic development of adipose tissues.

Features of growth and development of egg cross chicken embryos «Lomann Brown»

Purpose:to study morphometric parameters of absolute values of linear and weight body sizes, specific growth rate and relative (allometric) growth of chicken embryos of the «Lohmann Brown» egg cross at different stages of embryogenesis.Materials and methods.The absolute values of linear and weight body sizes of chicken embryos were estimated using morphometric methods. The formula of I. I. Schmalhausen and S. Brody was calculated the specific growth rate of length and body weight of chicken embryos by the formula simple allometry — relative (allometric) growth of body length from body mass.Results.This is manifested in the increase in the specific growth rate of body length of the embryo at 5 days of the late-fetal stage, 8th, 10th, 12th day of the early-fetal stage and specific growth rate of body mass for 6 days of the late-fetal stage of the late-fetal stage, 10-th and 12-th day of the early-fetal stage. At all stages of embryo development, there is a negative allometry of the relative growth rate of the embryo body length, except for 14 days of the mid-fetal stage, where negative isometry was observed (b=-1,000). Higher values of the power coefficient reflecting the slower growth of the embryo in length relative to their body weight, observed in late-fetal stage at 5-6 days (b=0,913-0,995), in early-fetal stage — 10-e (b=0,960) and 12 days (b=0,928), in mid-fetal stage — 13-th (b=0,821) and 15 days (b=0,981) and late-fetal stage — 20 days (b=0,836).Conclusion.New knowledge derived from this study can be applied not only in research, but in the poultry industry to assess the impact of preincubation processing of eggs on the development of embryos and embryonic mortality at different stages of embryogenesis, the definition of normal and abnormal development of embryos, as well as to assess the impact of other factors, artificial incubation on embryo development, hatchability of eggs and safety of poultry.

Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures.

Simple SummaryIn embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, concerning morphological development, expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation, apoptosis and gene-specific and global DNA methylation. Temperature during storage did not affect embryo size. There were no changes in pH and lipid peroxidation of the medium irrespective of group. mRNA expression and gene-specific DNA methylation of genes related to growth and development, maternal recognition of pregnancy, DNA methylation and apoptosis in stored embryos (5 °C and 20 °C) were altered when compared to fresh embryos. Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Short-term storage, regardless of temperature, may compromise embryo development after transfer.In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and the establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, on: (i) morphological development; (ii) expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation and apoptosis, and (iii) gene-specific and global DNA methylation. Embryos (n = 80) were collected on day seven or day eight after ovulation and assigned to four groups: day seven control (E7F, fresh); day seven, stored for 24 h at 5 °C (E5C); day seven, stored for 24 h at 20 °C (E20C) and day eight control (E8F, fresh 24h time control). The embryos and the storage medium (EquiHold, holding medium, Minitube, Tiefenbach, Germany) from all treatment groups were analyzed for (i) medium temperature, pH, and lipid peroxidation (malondialdehyde; MDA) and (ii) embryo morphology, mRNA expression and DNA methylation (immunohistochemistry and gene-specific DNA methylation). The size of embryos stored at 5 °C was larger (p < 0.01), whereas embryos stored at 20 °C were smaller (p < 0.05) after 24 h. There were no changes in pH and MDA accumulation irrespective of the group. The mRNA expression of specific genes related to growth and development (POU5F1, SOX2, NANOG), maternal recognition of pregnancy (CYP19A1, PTGES2), DNA methylation (DNMT1, DNMT3A, DNMT3B) and apoptosis (BAX) in the E5C and E20C were either up or downregulated (p < 0.05) when compared to controls (E7F and E8F). The immune expression of 5mC and 5hmC was similar among treatment groups. Percentage of methylation in the CpG islands was lower in the specific genes ESR1, NANOG and DNMT1 (p < 0.001) in E20C embryos when compared to E8F (advanced embryo stage). Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Although our results suggest some beneficial effects of storage at 20 °C in comparison to 5 °C, the short-term storage, regardless of temperature, modified gene expression and methylation of genes involved in embryo development and may compromise embryo viability and development after transfer.

105 Sexual dimorphism in equine D8 blastocysts

In mammals, male embryos grow faster. Equine embryo size is highly variable for same developmental stage, with no reported relation to embryo sex nor gene expression. Our objective was to evaluate gene expression sexual dimorphism on equine D8 blastocysts. Non-nursing, Saddlebred mares located on 2 experimental farms were inseminated with the semen of one unique stallion per farm. At 8 d post ovulation, 17 and 11 embryos from each farm, each from a different dam, were recovered by uterine flushing and bissected to obtain samples of pure (TE) or inner cell mass enriched (TE-ICM) trophoblast. RNA expression was analyzed separately in the TE-ICM and the TE of 16 female and 12 male embryos using paired end, non-oriented RNA sequencing (Illumina, NextSeq500). To discriminate gene expression in the ICM from that in the TE, deconvolution (DeMixT R package) was used on the TE-ICM data. Differential expression was analyzed (DESeq2) with farm and embryo size as cofactors using a false discovery rate (FDR) < 0.05 cutoff. Gene Set Enrichment Analysis was performed using the KEGG and GO BP databases. Out of the 13,786 and 13,210 genes expressed in ICM and TE, respectively, only 184 (51.1% on X chromosome) in ICM and 415 (39.0% on X chromosome) in TE were differentially expressed, with 111 genes in common. Overall, 145 in ICM and 312 in TE genes were significantly upregulated in female. As reported in bovine embryos, glucose-6-phosphate dehydrogenase (G6PD) was upregulated in female (log2 Fold Change = 0.96 in ICM and 0.83 in TE; both FDR <0.001). G6PD is required for detoxification of oxygen radicals that have both cellular damage and growth-stimulant effects. Reduced levels of oxygen radicals have been hypothesized to be responsible for the growth delay in female bovine embryos. In ICM cells, 16 and 1 gene sets were enriched in male embryos in GO BP and KEGG, respectively while 3 KEGG pathways were enriched in female ICM. In the TE part, 27 and 6 gene sets were enriched in male embryos in GO BP and KEGG, respectively, while no pathway was enriched in female embryos. Biological processes enriched in male embryos are mostly common between ICM and TE and are related to translation and spliceosome, ribosome biogenesis, mitochondrial function, cytoskeleton organization and amino acid metabolism. Pathways that were only enriched in male ICM relate to potassium ion homeostasis while in TE, they relate to protein export. In females, enriched pathways in ICM were related to Krebs cycle, glycosaminoglycan degradation and lysosome. Thus, although no growth retardation has been observed in equine female embryo, sexual dimorphism in gene expression of genes unrelated to the sex chromosomes is observed.

Seed morphometry and ultrastructure studies on some Turkish orchids (Orchidaceae).

Orchid seeds have great morphological variations that imply the phylogenetic relationship of the species depending on the biodiversity of the family or act as an adaptation to seed dispersal mechanisms depending on the life form. This study aims to both describe and analyse the qualitative and quantitative traits of 12 Turkish orchids representing epidendroids and orchidoids in detail to investigate which properties are diagnostic among these taxa and also reveal if seed properties are differentiated in relationship to the ecological preferences of the studied species. Both qualitative and quantitative features were determined, and measurements were obtained using light and scanning electron microscopy. We applied the unweighted pair group method with arithmetic mean (UPGMA) cluster analysis and canonical discriminant analysis to the qualitative and quantitative traits. Furthermore, we analyzed the same orchid seed in correlation with ecological traits such as habitats and the elevation preferences of species. This study confirmed the usefulness of both data sets for effectively assessing the variation of orchid seeds. Although the seed characters such as the cell shape differences in the chalazal or medial region, seed sizes, cell numbers on the longitudinal axis, and periclinal wall ornamentation are taxonomically conserved, some other characteristics such as seed shape, the absence of periclinal wall ornamentation, and larger embryo size imply ecological adaptation or developmental achievement for germination. This study confirms the diagnostic value of both qualitative and quantitative seed features, which are effective in explaining the orchid seed variety.

Genetic architecture of embryo size and related traits in maize

The embryo in maize has a critical role in controlling kernel nutrition components and grain yield. We measured five embryo weight and size traits, six kernel weight and size traits, and five embryo-to-kernel ratio traits in a nested association mapping (NAM) population of 611 recombinant inbred lines (RILs) derived from four inbred lines including the high-oil, giant-embryo line BY815 as the common parent. Using three statistical methods, we identified 5–22 quantitative trait loci (QTL) for each trait, explaining 4.7%–46.7% of the phenotypic variation. The genetic architecture of maize embryo size and its related traits appeared to be dominated by multiple small-effect loci with little epistasis, and the genetic control underlying embryo size appeared to be distinct from that underlying kernel size. A trait–QTL association network included 205 nodes and 439 edges and revealed 28 key loci associated with at least three traits. Cloned maize genes including ZmUrb2, Emp12 and ZmBAM1d, maize orthologs of known rice genes that control seed size including BG1, XIAO and GS9, and 11 maize orthologs of Arabidopsis EMBRYO-DEFECTIVE (EMB) genes were identified as underlying these key loci. Further, the phenotypic and genetic relationships between embryo size and kernel size were evaluated, and genetic patterns for identified loci that control embryo size and its related traits were proposed. Our findings reveal distinct genetic architectures for embryo size, kernel size, and embryo-to-kernel ratio traits and establish a foundation for the improvement of embryo-size-mediated kernel nutrition and grain yield.

DETEKSI VARIASI SOMAKLONAL PLANLET Jatropha curcas Linn. HASIL REGENERASI EMBRIO SOMATIK DENGAN MARKA MOLEKULAR ISSR

Physic nut (Jatropha curcas Linn.) has the potential as a source of sustainable biofuels. Somatic embryo proliferation of J. curcas may cause somaclonal variations. This research aimed to investigate somaclonal variations of J. curcas somatic embryo derived-plantlet using ISSR markers. Somatic embryos of J. curcas at the globular phase were cultured on liquid MS medium supplemented with 0, 0.5, 1.0, 1.5, and 2.0 mg L-1 of 2,4-D. Parameter observed were embryos weight, embryos volume, colour, and size of embryos. After proliferation, the embryos were cultured on a germination medium until the cotyledonary phase. The results showed that proliferation of J. curcas somatic embryos was optimal, with the highest weight and volume, at MS medium added with 1 mg L-1 2,4-D.

Production and Molecular Identification of Interspecific Hybrids between Phaius mishmensis (Lindl. and Paxton) Rchb. f. and Phaius tankervilliae (Banks) Blume

This study aimed at assessing the hybridization feasibility and evaluating genetic fidelity of the hybrid seedlings originated from Phaius mishmensis (Lindl. and Paxton) Rchb. f. and P. tankervilliae (Banks) Blume. Intra- and interspecific hybridization between Phaiusmishmensis (Lindl. and Paxton) Rchb. f. and P. tankervilliae (Banks) Blume were examined to establish the primary hybrid, observe their cross ability and identify the F1 hybrids using sequence-characterized amplified region (SCAR) markers. Self-incompatibility and cross ability of P. mishmensis and P. tankervilliae were tested before starting the breeding program. Results showed that they were self-compatible orchids. The interspecific hybridization between P. mishmensis and P. tankervilliae was achieved with the highest pod setting (80%), seed germination percentage (94.8%) and the rate of protocorm development into mature seedlings (stage 6) (10.6%), but the smallest size of embryo with width 46.5 μm, length 67.3 μm was also observed when P. mishmensis was taken as the female parent. A comparative study on leaf morphology and anatomy of plantlets regenerated from intra- and interspecific hybrids of P.mishmensis and P. tankervilliae showed a transitional character to the parental species. Herein, the presence of interspecific hybrids between P.mishmensis and P. tankervilliae, as well as their reciprocal cross, was verified using Pmis524 SCAR markers developed by the decamer primer.

Advances of Silver Iodide Seeding Agents for Weather Modification

Silver iodide (AgI) is the most widely-used seeding agent in field experiment and operations of weather modification. There are several nucleation modes for AgI seeding agents, and the nucleation process is affected by many factors including atmospheric temperature, humidity, particle size, composition of seeding agent and its particle generation method. The nucleation efficiency, nucleation modes affect the number of nucleated crystals, and thus affect the seeding effect.Through laboratory research of cloud chamber and theoretical calculation, the critical embryo sizes required for different nucleation mechanisms, nucleation threshold temperature, nucleation mechanisms, factors effecting nucleation for AgI and with some other added materials are analyzed. It is currently accepted that there are four nucleation mechanisms, including deposition, condensation freezing, contact freezing and immersion freezing nucleation. And it is recognized that nucleation processes depend on the varied temperature, humidity, and cloud conditions that can be encountered in the atmosphere. Immersion nucleation refers to nucleation of freezing by a particle immersed in water, and deposition nucleation refers to nucleation of the ice phase from the vapor, contact nucleation refers to the nucleation of the freezing induced by a particle during first contact with supercooled water, and condensation freezing is the nucleation of the freezing from the condensation of vapor to liquid droplet.The ice-nucleating properties and nucleation effectiveness of cloud seeding materials produced by burning acetone solutions or pyrotechnics of AgI and other materials are tested in a wind-tunnel cloud chamber test facility along with isothermal cloud chamber and dynamic cloud chamber. Through laboratory test, different formulations are compared, and high nucleation efficiency of seeding materials are selected, and nucleation features for four nucleation modes separately are obtained.Silver iodide seeding cloud model are based on a combination of theory and laboratory results. The ice nucleation schemes employed in cloud models vary widely. Hsie's seeding scheme simulated both contact-freezing and deposition nucleation on the laboratory measured effectiveness spectra of nucleus. Meyers seeding scheme considers all the four processes on cloud chamber results of ice-forming processes by AgI. In China, AgI seeding models are developed since the 1990s, either similar with Hsie's seeding scheme on three nucleation mechanisms, or similar with Meyers seeding scheme on four nucleation mechanisms.

Relationship of size and shape rice seed to early seedling vigor traits

Rice crop improvement program for direct-seeded has been directed at identifying the quality of seeds with rapid uniform germination and biomass accumulation during the initial phase of seedling establishment. Seed and embryo size are thought as two critical factors in the emergence of faster and vigorous seedlings. For the reason, this study was purposed to evaluate the relationship between the size and shape of rice seed with embryo size and its effects on germination. This study was designed using rice seeds from 55 genotypes, which were grouped in three sizes (medium, long, and extra-long) and two shapes (medium and slender). Germination was conducted with the top of paper method in a controlled germinator (24h lighting, 25 ± 2°C, 95%). We have found that the size and shape of seed significantly affected (α < 0.05) to embryo length, the time of radicles and plumules emergence, and seedling dry weight. Longer seeds tended to have longer embryos and emerged of radicles and plumules faster. Meanwhile, longer seeds with slender shape tend to have greater seedling dry weight. The results informed that the size and shape of rice seeds could be considered important characters for early seedling vigor traits in direct-seeded systems.

Temperature induced changes in the development of embryos and paralarvae of the merobenthic octopus, Octopus tetricus

Incubation temperatures can extend or decrease the time required for the embryos of marine invertebrates to hatch, while also greatly influencing the morphology and survival of hatchlings, characteristics which are of critical importance in hatchery production. This study examines the effect of incubation temperatures (16, 19, 22, 25 °C and ambient seawater temperature) on the development time to hatch, egg morphometric ontogeny and the hatching success in the common Sydney octopus, Octopus tetricus. These parameters were assessed at regular intervals for eggs from three broods placed in artificial incubation tanks at four temperatures between 16 and 25 °C, while the remainder of the eggs for each of the broods were incubated in ambient seawater under female care. The time to hatch had an inverse relationship to incubation temperature with the egg development time to hatch being halved at 25 °C (26–32 days) compared to 16 °C (67–69 days). Despite the markedly different development times there were no differences in the survival or quality of the resulting hatched paralarvae, although there was an overall tendency for inner yolk sac volume to decrease with increasing rearing temperature but not consistently among broods. There were differences in the number, size and quality of embryos in the three broods which tended to persist throughout their development, but these did not appear to be related to the size of the female octopus or water temperature prior to egg laying. The overall hatching success of eggs in artificial incubation tanks was above 90% for the brood of one female (F1) while for the other two it was 71% (F3) and 57% (F2) mostly likely as a direct result of being compromised by infection of the egg strings. Improvements in hatchery practice is required to prevent such infections for future paralarval production. The results demonstrate a wide thermal tolerance for the early developmental stages of O. tetricus with the potential to manipulate egg incubation temperatures to better meet the timing of hatchery production requirements.

Characterization of pregnancy-associated glycoproteins and progesterone as a predictor of twins and conceptus loss in high-risk-pregnancy Holstein cows

The objective of this study was to characterize plasma concentrations of pregnancy-associated glycoprotein (PAG) and progesterone (P4) as predictors of twins and pregnancy loss in Holstein cows with high-risk pregnancies. High-risk pregnancy was characterized using transrectal ultrasonography 37 d after artificial insemination (AI) based on the following criteria: small embryo size <15 mm, n = 10), slow heartbeat (<60 beats per minute, n = 11), and extra-amniotic membrane (additional amniotic membrane, n = 3). A cohort of twins (n = 41) diagnosed at d 37 post-AI was also enrolled. Each high-risk and twin pregnancy cow was paired with a cow of the same parity carrying a normal singleton at d 37 post-AI (control, n = 65). Blood samples were collected to measure PAG and P4 at d 37, 44, and 51 post-AI. Statistical analysis was performed using ANOVA, logistic regression, and receiver operator characteristic (ROC) curve with JMP software (SAS Institute Inc., Cary, NC). Pregnancy loss at d 51 post-AI was greater in high-risk pregnancies than in controls and twins (control = 1.5%; high-risk = 87.5%; twins = 12.2%). Concentration of PAG at d 37 post-AI did not differ among groups (control = 5.3 ± 0.7; high-risk = 4.8 ± 1.2; twins = 4.0 ± 0.9 ng/mL). Concentration of P4 at d 37 post-AI was greater in twins than in high-risk pregnancies and control, and lesser in high-risk pregnancies than in controls (control = 7.0 ± 0.3; high-risk = 5.9 ± 0.4; twins = 8.4 ± 0.3 ng/mL). Regression and ROC analysis for PAG at d 37 post-AI did not find a threshold to predict pregnancy loss or twins. Regression and ROC analysis for P4 at d 37 post-AI found that a threshold of 6.5 ng/mL predicted pregnancy loss with an area under the curve (AUC) of 0.64, and a threshold of 7.2 ng/mL predicted twins with AUC of 0.71. In summary, pregnancy loss and twins were predicted with only moderate accuracy by P4 concentration at d 37 post-AI, and the variability in PAG concentrations at d 37 post-AI was not sufficient to generate a threshold to predict pregnancy loss and twins in Holstein lactating cows.

What Drives Life-History Variation in the Livebearing Fish Poeciliopsis prolifica? An Assessment of Multiple Putative Selective Agents

Life-history traits are directly linked to fitness, and therefore, can be highly adaptive. Livebearers have been used as models for understanding the evolution of life histories due to their wide diversity in these traits. Several different selective pressures, including population density, predation, and resource levels, can shape life-history traits. However, these selective pressures are usually considered independently in livebearers and we lack a clear understanding of how they interact in shaping life-history evolution. Furthermore, selective pressures such as interspecific competition are rarely considered as drivers of life-history evolution in poeciliids. Here we test the simultaneous effects of several potential selective pressures on life-history traits in the livebearing fishPoeciliopsis prolifica.We employ a multi-model inference approach. We focus on four known agents of selection: resource availability, stream velocity, population density, and interspecific competition, and their effect on four life-history traits: reproductive allocation, superfetation, number of embryos, and individual embryo size. We found that models with population density and interspecific competition alone were strongly supported in our data and, hence, indicated that these two factors are the most important selective agents for most life-history traits, except for embryo size. When population density and interspecific competition increase there is an increase in each of the three life-history traits (reproductive allocation, superfetation, and number of embryos). For individual embryo size, we found that all single-agent models were equivalent and it was unclear which selective agent best explained variation. We also found that models that included population density and interspecific competition as direct effects were better supported than those that included them as indirect effects through their influence on resource availability. Our study underscores the importance of interspecific competitive interactions on shaping life-history traits and suggests that these interactions should be considered in future life-history studies.

A staging table of embryonic development for a viviparous (live-bearing) lizard Eremias multiocellata (Squamata: Lacertidae).

As the only viviparous reptile in China that has both temperature-dependent sex determination (TSD) and genetic-dependent sex determination (GSD) mechanisms, Eremias multiocellata is considered as an ideal species for studying the sex determination mechanism in viviparous lizards. However, studies on embryonic stage of viviparous lizards and morphological characteristics of each stage are limited. In the present study, the embryonic development process of E. multiocellata is divided into 15 stages (stages 28-42) according to the morphology of embryos. Embryos sizes are measured and continuous dynamic variation of some key features, including limbs, genitals, eyes, pigments, and brain scales are color imaged by a stereoscopic microscope. Furthermore, based on these morphological characteristics, we compare the similarities and differences in the embryonic development of E. multiocellata with other squamate species. Our results not only identified the staging table of E. multiocellata with continuous changes of external morphological characteristics but also developed a staging scheme for an important model species that provides a necessary foundation for study of sex determination in a viviparous lizard.