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Simple Summary: Few studies have been conducted on the signaling mechanism underlying chilling-induced embryonic diapause termination in insects. In the current study, we compared temporal changes in expression levels of insulin (bombyxin-A6, -Y1, and -Z1), ecdysone signaling (ecdysteroid-phosphate phosphatase (EPPase) and E75A), sorbitol dehydrogenase 2 (SDH2), and metabolic-related (trehalose transporter 1 (Tret1) and trehalase 1 (Treh1)) genes between chilled Bombyx mori eggs and eggs kept at 25 °C. Our results showed that expressions of all the above-mentioned genes remained at very low levels in eggs kept at 25 °C. However, in chilled eggs, differential temporal changes were detected according to different genes, with bombyxin-A6 and EPPase gene expressions being maintained at relatively constant, high levels. Expressions of the SDH2 and bombyxin-Z1 genes decreased during the first 15 days, and then SDH2 gene expression began to increase on day 30 after chilling, followed by increased expression of the bombyxin-Z1 gene. Relatively higher GSK-3β phosphorylation and ecdysteroid levels were also found in chilled eggs. From these results, we suggest that the upregulation of insulin/ecdysone signaling in chilled eggs is related to chilling-induced egg diapause termination in B. mori. In the present study, we investigated the possible correlation between insulin/ecdysone signaling and chilling-induced egg diapause termination in Bombyx mori. Changes in insulin (bombyxin-Z1) and ecdysteroid-phosphate phosphatase (EPPase) gene expression levels in chilled eggs (whose diapause had been terminated by chilling to 5 °C for 90 days) exhibited no significant increase after being transferred to 25 °C, which differed from both non-diapause eggs and HCl-treated eggs. We further compared the differential temporal expressions of insulin (bombyxin-A6, -Y1, and -Z1), ecdysone signaling (EPPase and E75A), and metabolic-related (trehalose transporter 1 (Tret1) and trehalase 1 (Treh1)) as well as sorbitol dehydrogenase 2 (SDH2) genes between chilled eggs and eggs kept at 25 °C. Our results showed that all gene expressions remained at very low levels in eggs kept at 25 °C. However, in chilled eggs, differential temporal changes were detected according to different genes, with bombyxin-A6 and EPPase gene expression levels being maintained at relatively constant, high levels. Higher expression levels of the E75A, Tret1, and Treh1 genes were also detected in chilled eggs. Expressions of the SDH2 and bombyxin-Z1 genes decreased during the first 15 days and then increased between days 30 and 90 of chilling. Ecdysteroid levels and phosphorylation of glycogen synthase kinase (GSK)-3β, a downstream target of insulin signaling, were maintained at relatively higher levels in chilled eggs. These results suggested that due to relatively higher insulin and ecdysone signaling levels in chilled eggs, relatively higher glucose metabolism was sustained, leading to the continued depletion of metabolic reserves. On day 30 of chilling, as a means to adjust nutrient requirements and maintain embryonic nutrient homeostasis, SDH2 gene expression began to increase, followed by increased expression of the bombyxin-Z1 gene. Along with high expressions of the bombyxin-Z1 and SDH2 genes, a decreased sorbitol level was suggested to eventually terminate diapause in B. mori eggs. To our knowledge, this is the first study to demonstrate the correlation between insulin/ecdysone signaling and chilling-induced embryonic diapause termination. [ABSTRACT FROM AUTHOR]

Embryonic diapause is a common evolutionary adaptation observed across a wide range of organisms. Artemia is one of the classic animal models for diapause research. The current studies of Artemia diapause mainly focus on the induction and maintenance of the embryonic diapause, with little research on the molecular regulatory mechanism of Artemia embryonic reactivation. The first 5 h after embryonic diapause breaking has been proved to be most important for embryonic reactivation in Artemia. In this work, two high-throughput sequencing methods, ATAC-seq and RNA-seq, were integrated to study the signal regulation process in embryonic reactivation of Artemia at 5 h after diapause breaking. Through the GO and KEGG enrichment analysis of the high-throughput datasets, it was showed that after 5 h of diapause breaking, the metabolism and regulation of Artemia cyst were quite active. Several signal transduction pathways were identified in the embryonic reactivation process, such as G-protein-coupled receptor (GPCR) signaling pathway, cell surface receptor signaling pathway, hormone-mediated signaling pathway, Wnt, Notch, mTOR signaling pathways, etc. It indicates that embryonic reactivation is a complex process regulated by multiple signaling pathways. With the further protein structure analysis and RT-qPCR verification, 11 GPCR genes were identified, in which 5 genes function in the embryonic reactivation stage and the other 6 genes contribute to the diapause stage. The results of this work reveal the signal transduction pathways and GPCRs involved in the embryonic reactivation process of Artemia cysts. These findings offer significant clues for in-depth research on the signal regulatory mechanisms of the embryonic reactivation process and valuable insights into the mechanism of animal embryonic diapause. [ABSTRACT FROM AUTHOR]

The domestic silkworm (Bombyx mori) is reared under controlled environments. Therefore, silkworms may be exposed at night to light used by humans working or living nearby. Artificial light at night (LAN) disturbs natural lighting cycles and negatively affects insect physiology, behavior, and ecology in the field. However, the effects of dim LAN on domestic silkworms have not been assessed in detail. The present study investigated the effects of night lighting on diapause regulation in Bombyx mori, with a focus on light sensitivity. The silkworm larvae were exposed to LAN at intensity varying from 0.1-100 lux under a short-day photoperiod that should induce diapauses, and then the incidence of diapause in eggs laid by resultant moths was evaluated. The incidence of diapause was 100 % in control (without night lighting) silkworms, but the incidence in those exposed to LAN = 0.1 lux was < 2 %. These results showed that exposing larvae to night lighting at 0.1 lux under a short-day photoperiod substantially inhibited diapause induction in the next generation. [ABSTRACT FROM AUTHOR]

Embryonic diapause is a special reproductive phenomenon in mammals that helps embryos to survive various harsh stresses. However, the mechanisms of embryonic diapause induced by the maternal environment is still unclear. Here, we uncovered that nutrient deficiency in uterine fluid was essential for the induction of mouse embryonic diapause, shown by a decreased concentration of arginine, leucine, isoleucine, lysine, glucose and lactate in the uterine fluid of mice suffering from maternal starvation or ovariectomy. Moreover, mouse blastocysts cultured in a medium with reduced levels of these six components could mimic diapaused blastocysts. Our mechanistic study indicated that amino acid starvation-dependent Gator1 activation and carbohydrate starvation-dependent Tsc2 activation inhibited mTORC1, leading to induction of embryonic diapause. Our study elucidates the essential environmental factors in diapause induction. [ABSTRACT FROM AUTHOR]

Embryonic and adult stem cells enable development and regeneration. Embryonic cells, like adult stem cells, can enter dormancy as part of their lifecycle. Recent evidence suggests that this cellular transition to dormancy requires active rewiring of metabolism. The dormancy-induced metabolic switches in embryonic and adult stem cells are explored here. [ABSTRACT FROM AUTHOR]

Context: According to the established, older literature, the embryonic diapause (ED) in roe deer ends in late December. In many other species groups, phenological phases are shifting as a result of climatic changes. Whether this is the case in roe deer for the period of ED has not yet been explicitly investigated. Aim: The aim of this study was to obtain an up-to-date overview of the reproduction of roe deer in Bavaria, particularly with regard to climate change. Methods: For this purpose, uterus samples were taken from roe deer aged at least 1 year between September and January and examined macroscopically. The samples were collected during regular hunting activities in Bavaria in the years 2017–2020. Key results: A large proportion of the female roe deer examined was found to have been already engaged in reproduction. In 98% of the animals, Corpora lutea (CL) were present in the ovaries. Adult does had significantly more CL than did subadult does just reaching sexual maturity. In 75 roe deer does, 128 embryos, in total, were detected. On average, 1.67 embryos were found per doe with visible embryos. Of these does, 30% carried a single embryo, 67% were bearing twins and 3% were bearing triplets. The animals with visible embryos ranged in age from 1 to 12 years. In a few cases, ED was already completed in November or early December. By the end of the hunting season, a correspondingly wide variety of developmental stages of embryos was visible. Our study suggests potential indications that older animals or those with a higher body mass end ED earlier. Conclusions: Overall, the results indicated vigorous reproductive activity in the study area. The results showed that some individuals already end the ED in November or early December, so they may adapt to an earlier onset of the vegetation period. In contrast, we found a few individuals that ended the ED during January, which illustrates the temporal range of the ED. Implications: Whether the early end of diapause in these roe deer is a reaction to climatic changes or whether there are other underlying causes is something that requires further investigation. Roe deer are one of the most important game species in Europe. We have investigated whether embryonic development occurs earlier in roe deer. Indeed, we observed this in some of the does, but whether this is due to climate change needs further investigation. [ABSTRACT FROM AUTHOR]

Sugar transporters (Sts) play important roles in controlling carbohydrate transport and are responsible for mediating the movement of sugars into cells. Few studies have been conducted on expressions of Sts during insect embryonic development. In the present study, we investigated temporal expressions of St genes during the embryonic diapause process in Bombyx mori. We found that in HCl‐treated developing eggs, high gene expressions of trehalose transporter 1 (Tret1) were detected during middle and later embryonic development. St4 and St3 gene expressions gradually increased during the early stages, reached a small peak on Day 3, and large peaks were again detected on Day 7. However, in diapause eggs, expression levels of the Tret1, St4, and St3 genes all remained at low levels. Differential temporal changes in expressions of the Tret1, St4, and St3 genes found between diapause and HCl‐treated eggs were further confirmed using nondiapause eggs. Our results showed that nondiapause eggs exhibited similar changing patterns as those of HCl‐treated eggs, thus clearly indicating potential correlations between expressions of these genes and embryonic development. In addition, high gene expressions of Tret1 were also detected when dechorionated eggs were incubated in the medium. The addition of LY294002 (a specific phosphatidylinositol 3‐kinase [PI3K] inhibitor) and U0126 (a mitogen‐activated protein kinase/extracellular signal‐regulated kinase [ERK] kinase [MEK] inhibitor) partially inhibited Tret1 gene expression in dechorionated eggs, but did not affect either ecdysteroid‐phosphate phosphatase gene expression or ecdysteroid biosynthesis, clearly indicating that both PI3K and ERK are involved in increased gene expression of Tret1 that was independent of ecdysteroid levels. To our knowledge, this is the first comprehensive report to demonstrate the transcriptional regulation of St genes during embryonic development, thus providing useful information for a clearer understanding of insect egg diapause mechanisms. Highlights: Differential Sugar transporter (St) gene expressions were detected between diapause and developing eggs in Bombyx.High temporal expression levels in trehalose transporter 1 (Tret1), St3, and St4 genes were found in developing eggs.Increased Tret1 gene expression was also detected in dechorionated eggs.Phosphatidylinositol 3‐kinase and extracellular signal‐regulated kinase appear to be involved in dechorionated‐induced Tret1 gene expression.Temporal expressions of St genes appear to be regulated during embryonic development. [ABSTRACT FROM AUTHOR]

Mink embryos enter a period of diapause after the embryo develops into the blastocyst, and its reactivation is mainly caused by an increase in polyamine. The specific process of embryo diapause regulation and reactivation remains largely unexamined. This study aimed to identify changes in metabolites in the early pregnancy of mink by comparing and analyzing in serum metabolites up to twenty-nine days after mating. Blood samples were taken on the first day of mating, once a week until the fifth week. Metabolomic profiles of the serum samples taken during this period were analyzed by ultra-performance liquid chromatography/mass spectrometry. Multivariate statistical analyses identified differential metabolite expression at different time points in both positive and negative ion modes. The levels of dopamine, tyramine, L-phenylalanine, L-tyrosine, tyrosine, L-kynurenine, L-lysine, L-arginine, D-ornithine, and leucine changed significantly. These metabolites may be associated with the process of embryo diapause and subsequent reactivation. [ABSTRACT FROM AUTHOR]

Embryonic diapause is a unique stage of development that occurs in some mammalian species. Diapause serves as an evolutionary reproductive strategy to maximize the survivability of dam and offspring. Although individual mechanisms of control vary among species, the overarching physiology of diapause extends the length of pregnancy to delay parturition until either seasonal, environmental, nutritional, or internal physiologic constraints are optimal for parturition and rearing of young. This review discusses concepts and highlights control mechanisms unique to rodents, mink, and tammar wallabies. [ABSTRACT FROM AUTHOR]

Abstract Background Pacific walruses are found in Arctic regions of the Chukchi and Bering Sea where rapid changes in environmental conditions resulting in loss of sea ice are occurring. Therefore, accurate life history data are crucial for species management plans and longitudinal data collected over the lives of individual walruses housed in zoos and aquaria provide otherwise difficult to obtain biological information. Results While similar at birth, Gompertz regression curves indicated that males grew faster than females (p

Maternal silkworms (Bombyx mori) of bivoltine strains are destined to produce either diapause or non-diapause eggs depending on environmental factors, such as, temperature and photoperiod experienced during the egg and larval stages. However, the molecular mechanisms that program diapause, which depend on information about the environment, remain unclear. We aimed to identify genes that are involved in programming diapause in the next generation in bivoltine silkworms. We therefore screened differentially expressed genes (DEGs) in the larval brains of diapause- and non-diapause-egg producers kept under three different diapause-inducing conditions using cap analysis of gene expression. Under each condition, only temperature, illumination or photoperiod was changed during the egg or larval stage as a diapause-controlling stimulus to induce the production of diapause or non-diapause eggs. We then verified the expression of DEGs that were common to all the three conditions using real-time quantitative PCR. We investigated the functional involvement of candidate genes in programming diapause using double-stranded RNA interference (RNAi) for gene knockdown. The results showed more abundant juvenile hormone acid methyltransferase (Jhamt) and proton-coupled folate transporter (Pcft) gene expression in the brains of fifth instar larvae of producers of diapause eggs than those of non-diapause eggs under the three conditions. Furthermore, RNAi against either of these genes significantly decreased the incidence of diapause in the next generation. These findings indicate that both Jhamt and Pcft are involved in the programming of diapause in the silkworm brain. These genes could function in retaining information that leads to diapause in the next generation.

Under ovarian hormone control, dormant blastocysts obtain implantation capacity (known as blastocyst activation) through their global gene expression. After the activated blastocysts communicate with the receptive uterus, the implantation-competent blastocysts start the implantation. Although dormant and activated blastocysts have different gene expression levels, the regulatory mechanisms underlying these transcriptions remain unclear. Hence, this study aimed to analyze epigenetic marks in dormant and activated blastocysts. In mice, blastocyst dormancy is artificially induced by daily progesterone injection without estrogen supplementation after peri-implantation ovariectomy; when estrogen is administered concomitantly, blastocyst activation and implantation occur. These phenomena demonstrate a mouse model of delayed implantation. We collected dormant and activated blastocysts from a delayed implantation mouse model. RNA-seq, methylated DNA immunoprecipitation (MeDIP)-seq, and chromatin immunoprecipitation (ChIP)-seq for H3K4 me3 and H3K27 me3 were performed using dormant and activated blastocysts. Cell cycle–related transcripts were affected during blastocyst activation. DNA methylations were accumulated in downregulated genes in the activated blastocysts. Histone H3 trimethylations were globally altered between the dormant and activated blastocysts. Dormant and activated blastocysts have unique methylation patterns on DNA and histone H3, with high correlation to gene expression. DNA methylation and histone modification can regulate preimplantation blastocyst activation. [ABSTRACT FROM AUTHOR]

The embryonic diapause of the giant panda (Ailuropoda melanoleuca) has caused great difficulties in monitoring pregnancy in this vulnerable species. The secretion of prolactin (PRL) from anterior pituitary glandular lactotropic cells is an important signal for the termination of embryonic dormancy. Currently, the mechanism by which PRL affects embryonic diapause in giant pandas and methods for detecting PRL in this species is poorly understood. In this study, the first sandwich enzyme immunoassay for detecting PRL in giant panda urine was established by using two antigiant panda PRL antibodies prepared as coating and labeling antibodies, and PRL recombinant proteins prepared via the prokaryotic system as standards. The established method was used to detect the levels of PRL in the urine of giant pandas during pregnancy. At the same time, the changes in PRL levels in giant pandas and the relationship between PRL and progestagen levels were analyzed during the luteal phase. The results showed that in female giant pandas, PRL levels significantly increased before the progestagen peak, and during the luteal phase, the PRL level was significantly greater in giant pandas that gave birth than in those that did not give birth and those in the nonestrus group. To the best of our knowledge, this is the first study to preliminarily explore the mode of action of PRL in the gestation period of giant pandas and lays a foundation for further study of the regulatory mechanisms of endocrine hormones in the giant panda., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The blastocyst of the European roe deer (Capreolus capreolus) undergoes a period of decelerated growth and limited metabolism. During this period known as embryonic diapause, it floats freely in the uterus encircled by the histotroph. Prior to implantation, reactivation is marked by rapid embryonic growth and conceptus elongation. We hypothesized that the uterine fluid, which is known to undergo changes in its composition to support early embryonic development, contributes to controlling embryonic growth during diapause and elongation. We therefore characterized the pre-implantation uterine fluid metabolome during diapause and at elongation by mass spectrometry and particularly assessed nonpolar lipids, polar metabolites, acylcarnitines, and polyamines. Our results show that triglycerides and diglycerides levels decreased at elongation, likely serving as a source for membrane synthesis rather than for energy production. A functional analysis identified glycolysis as a key pathway during elongation, which may compensate for the energy requirements during this phase. We also observed an increase of sphingomyelin; prostaglandin precursors; and the amino acids asparagine, glutamine, and methionine upon elongation. The sphingolipid and glycerophospholipid metabolism pathways were implicated during elongation. Particularly, spermidine, and to some extent spermine but not putrescine-levels significantly increased in the uterine fluid during elongation, indicating their significance for reactivation and/or proliferation at embryo elongation. We conclude that the roe deer uterine fluid sustained dynamic compositional changes necessary to support the energy- and resource-intensive conceptus elongation. However, it remains to be determined whether these changes are the cause or a consequence of embryo elongation. Studying the metabolic changes and molecular interactions in the roe deer during diapause and elongation not only reveals insights into aspects of its reproductive strategy, but also deepens our knowledge of embryo metabolic demands and developmental velocities across species., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

In response to short days in autumn, most temperate multivoltine insects enter diapause, a state in which development or reproduction is suppressed or arrested, which serves to coordinate their development and physiology (or that of offspring) with annual changes in the environment (i.e. photoperiodism). This response is mediated by a measurement of time based on photoperiod (photoperiodic time measurement), which is thought to be regulated by a circadian clock. However, some studies also demonstrate the involvement of the circadian clock in an output process that generates phenotypes associated with diapause. To gain further insight into this, we silenced the Clock (Clk) gene, the main regulator of the circadian clock, in the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae). Silencing the Clk gene using RNA interference (Clk RNAi) in female crickets resulted in abnormal circadian rhythms under constant darkness and light-dark conditions, thereby indicating the central role of this gene in the circadian clock mechanism. Clk RNAi females exhibited long-day oviposition behaviour, even when reared under short-day conditions, thereby indicating the involvement of Clk in photoperiodic time measurement. In addition, Clk RNAi females immediately laid non-diapause-type eggs, which was not recorded in control females under either short-day or long-day conditions and cannot be explained in terms of dysfunction of photoperiodic time measurement. Accordingly, we speculate that Clk could also be involved in a downstream process that results in the laying of diapause-type eggs.

Background: Pacific walruses are found in Arctic regions of the Chukchi and Bering Sea where rapid changes in environmental conditions resulting in loss of sea ice are occurring. Therefore, accurate life history data are crucial for species management plans and longitudinal data collected over the lives of individual walruses housed in zoos and aquaria provide otherwise difficult to obtain biological information. Results: While similar at birth, Gompertz regression curves indicated that males grew faster than females (p < 0.0001) in weight (99 kg vs 57.6 kg/y) and length (26.9 cm vs 26.3 cm/y) with physical differences being detected by age 3 for weight and age 7 for length. Males reached adult weight at 13.5 ± 3.3 y and females by age 12.3 ± 2.3 y. The mean age at first ovulation and at first conception occurred at 8.8 y and 9.6 y. Greater than 75% of all conceptions and calving occurred between February and March and from May to June, respectively. Mean gestation lasted 423 d and false pregnancies lasted at least 169 d with a decrease (p < 0.05) in serum progesterone concentration between false pregnancy and pregnancy occurring within 6 months after ovulation. Based on these results, we estimated embryonic diapause to last from 120 to 139 days, and fetal growth last ~ 284 days. All males older than 8 y had an increase in serum testosterone and body weight that was highest in February and lowest in July. Overall, no differences were observed between male and female survival, with a mean (± SEM) life expectancy of 19.5 ± 1.5 y, respectively. Currently, the oldest male and female captive walruses are 40 and 43 y, respectively. Conclusions: Data provided herein include details of life history characteristics of zoo and aquaria housed walruses that are useful for wild population recovery models. In particular, results on survivorship and the identification of the most vulnerable period for calf survival can help with model development and suggests that for recovery to occur birthing locations for this species must be protected. [ABSTRACT FROM AUTHOR]

Embryonic diapause is an enigmatic state of dormancy that interrupts the normally tight connection between developmental stages and time. This reproductive strategy and state of suspended development occurs in mice, bears, roe deer, and over 130 other mammals and favors the survival of newborns. Diapause arrests the embryo at the blastocyst stage, delaying the post-implantation development of the embryo. This months-long quiescence is reversible, in contrast to senescence that occurs in aging stem cells. Recent studies have revealed critical regulators of diapause. These findings are important since defects in the diapause state can cause a lack of regeneration and control of normal growth. Controlling this state may also have therapeutic applications since recent findings suggest that radiation and chemotherapy may lead some cancer cells to a protective diapause-like, reversible state. Interestingly, recent studies have shown the metabolic regulation of epigenetic modifications and the role of microRNAs in embryonic diapause. In this review, we discuss the molecular mechanism of diapause induction. [ABSTRACT FROM AUTHOR]

Previous reports indicate that red pandas (Ailurus fulgens styani) may experience fetal loss during gestation; however, neither the rate nor timing of pregnancy failure has been described in this species. The objective of this study was to utilize ultrasound video and images collected between 2010 and 2020 at the Cincinnati Zoo and Botanical Garden to better characterize pregnancy loss and fetal development. Trans-abdominal ultrasound examinations were performed on six female red pandas over a 10-year period, resulting in 12 profiles. Pregnancy was diagnosed via ultrasound in 10 of 12 profiles, and 40.0% of pregnancies showed evidence of fetal loss prior to parturition. Pregnancy loss was classified into lost (2 of 10; 20.0%), in which no cubs were produced, or partial loss (2 of 10; 20.0%), in which two concepti were visualized via ultrasound, but only one cub was born. Fetal loss occurred between days 51 and 23 pre-partum. Fetal growth characteristics were documented, including skeletal ossification (occurring between days 32 and 27 pre-partum), crown-rump length, head length, cranial length, and fetal heart rate (173–206 b.p.m.). These findings provide novel insights into pregnancy loss, may serve as a reference for milestones of fetal development, and may be useful in diagnosing pregnancy and assessing pregnancy loss in red pandas.

IntroductionClimate change is altering the reproductive phenology of many organisms, but the factors that influence the timing of gestation in ursids are still poorly understood. Higher temperatures in spring are already causing an earlier den exit in some brown bear populations, and a temporal mismatch between hibernation and reproduction could have dramatic consequences for reproductive success. Therefore, understanding the factors that control the timing of these events is important to forecast the consequences of climate change on population growth rates.MethodsIn this study, we used abdominal temperature loggers and GPS collars with acceleration sensors on 23 free-ranging pregnant female brown bears living in two areas in Sweden (61°N and 67°N latitude) to pinpoint hibernation and reproductive events. We investigated how intrinsic and extrinsic factors influence the termination of embryonic diapause and parturition, as well as their impact on reproductive success.ResultsThe termination of embryonic diapause was later in the northern area compared to the southern area and occurred earlier when ambient temperature at den entry was higher in both areas. In the southern area, young adults (i.e., females = 7 years old) had a delayed parturition when bilberry abundance was low the year of mating. Additionally, young adults had a lower reproductive success than adults and their probability to reproduce successfully was dependent on bilberry abundance, whereas adult females were not affected by this parameter.DiscussionAs den exit occurs later in the northern study area, we suggest that a later parturition might ensure that females lactate their cubs in the den for a reasonable amount of time while fasting. Similarly, a later parturition combined with an earlier emergence could allow young adults to spend less time in the den lactating if they could not reach an optimal body condition prior to hibernation. But as a result, their cubs are younger and more vulnerable when they leave the den leading to lower survival rates. Our results suggest that a decreased berry abundance in the fall could impact the reproductive and hibernation phenology of Scandinavian brown bear females and lead to a lower cub survival with potential consequences on the population dynamics.

Under laboratory conditions, the effect of temperature on the reversible arrest in embryo development, which occurs as a result of winter spawning, was studied in the hermit crab Pagurus proximus, Komai, 2000 from Amurskiy Bay (Peter the Great Bay, Sea of Japan). In clutches of females that spawned under natural conditions at a water temperature of 5°C and below, an increase in water temperature to 14–16°C led to the termination of embryonic diapause and the synchronous resumption of egg development, regardless of whether the temperature conditions changed at the beginning or at the end of the winter breeding season. No embryonic diapause was observed in clutches of females of P. proximus that were captured in December–April and spawned in the laboratory at a water temperature of 14–16°С. From this it follows that the primary signal for diapause initiation and termination in P. proximus is temperature, which directly affects the embryo. The data we obtained confirm that embryonic diapause of the hermit crab P. proximus is not obligate but is induced by habitat conditions, primarily by ambient temperature. The possibility of using P. proximus as a model object for studying the mechanisms of embryonic diapause in decapods is considered. [ABSTRACT FROM AUTHOR]

Abstract Insect eggshells must meet various demands of developing embryos. These demands sometimes conflict with each other; therefore, there are tradeoffs between eggshell properties, such as robustness and permeability. To meet these conflicting demands, particular eggshell structures have evolved in diverse insect species. Here, we report a rare eggshell structure found in the eggshell of a cicada, Cryptotympana facialis. This species has a prolonged egg period with embryonic diapause and a trait of humidity-inducible hatching, which would impose severe demands on the eggshell. We found that in eggs of this species, unlike many other insect eggs, a dedicated cleavage site, known as a hatching line, was formed not in the chorion but in the serosal cuticle. The hatching line was composed of a fine furrow accompanied by ridges on both sides. This furrow-ridge structure formed in the terminal phase of embryogenesis through the partial degradation of an initially thick and nearly flat cuticle layer. We showed that the permeability of the eggshell was low in the diapause stage, when the cuticle was thick, and increased with degradation of the serosal cuticle. We also demonstrated that the force required to cleave the eggshell was reduced after the formation of the hatching line. These results suggest that the establishment of the hatching line on the serosal cuticle enables flexible modification of eggshell properties during embryogenesis, and we predict that it is an adaptation to maximize the protective role of the shell during the long egg period while reducing the barrier to emerging nymphs at the time of hatching.

Reliable pregnancy diagnostics would be beneficial for monitoring polar bear (Ursus maritimus) populations both in situ and ex situ, but currently there is no method of non-invasive pregnancy detection in this species. Recent reports in several carnivore species described the identification of fecal proteins that may serve as pregnancy biomarkers; however, repeatability has been limited. The objective of the current analysis was to utilize an unbiased, antibody-free, label-free method for the identification and quantification of fecal proteins to determine if differences associated with pregnancy are detectable in polar bears. Protein was extracted from fecal samples (n = 48) obtained from parturient (n = 6) and non-parturient (n = 6) profiles each at four timepoints: pre-breeding season, embryonic diapause, early placental pregnancy, and mid-placental pregnancy. Protein was prepared and analyzed on the Thermo Orbitrap Eclipse nanoLC-MS/MS system. A total of 312 proteins was identified and quantified; however, coefficients of variation (CV) were high for both abundance ratio variability (384.8 ± 61.0% SEM) and within group variability (86.8 ± 1.5%). Results of this study suggest that the inconsistencies in specific protein concentrations revealed previously by antibody-based assays may not be due to that methodology's limitations, but rather, are reflective of true variation that exists among samples. [ABSTRACT FROM AUTHOR]

Recent data suggest that most genotoxic agents in cancer therapy can lead to shock of genome and increase in cell size, which leads whole genome duplication or multiplication, formation of polyploid giant cancer cells, activation of an early embryonic program, and dedifferentiation of somatic cells. This process is achieved via the giant cell life cycle, a recently proposed mechanism for malignant transformation of somatic cells. Increase in both cell size and ploidy allows cells to completely or partially restructures the genome and develop into a blastocyst-like structure, similar to that observed in blastomere-stage embryogenesis. Although blastocyst-like structures with reprogrammed genome can generate resistant or metastatic daughter cells or benign cells of different lineages, they also acquired ability to undergo embryonic diapause, a reversible state of suspended embryonic development in which cells enter dormancy for survival in response to environmental stress. Therapeutic agents can activate this evolutionarily conserved developmental program, and when cells awaken from embryonic diapause, this leads to recurrence or metastasis. Understanding of the key mechanisms that regulate the different stages of the giant cell life cycle offers new opportunities for therapeutic intervention. [ABSTRACT FROM AUTHOR]

ABSTRACT: At the time of oviposition, the chicken embryo is in its blastodermal stage. The blastoderm displays the unique ability to undergo developmental arrest at low temperatures in a process called “embryonic diapause.” In the wild, diapause occurs in freshly laid eggs until the last egg of the clutch has been laid, providing an evolutionary advantage to hens that can synchronously hatch their eggs. The poultry industry utilizes the diapause phenomenon to store eggs before incubation, thereby mitigating their logistic problems. The embryos can only be stored at particular embryonic stages—termed “diapause developmental window” (DW)—if they are to continue to develop normally thereafter. Both cellular and molecular mechanisms define the limits of this DW which broadly comply with onset of blastulation to early gastrulation. Storage conditions affect the cellular and molecular characteristics of the embryo during this window and their ability to successfully resume development (SRD). At storage temperatures of ~12°C to 18°C, embryos can undergo diapause for a short period (up to 7 days (d)) without affecting SRD. However, following longer period of diapause (up to 28 d), embryo stored at ~12°C, but not at ~18°C, can resume development normally. Moreover, eggs can be heated before or during the storage period which will lead to their commencing in development; however, unlike the non-heated embryos, the storage temperature for heated embryos, which are more advance in developing, is not clear. Thus, based on SRD, this review brings evidence supporting the notion that a lower storage temperature is beneficial for early-stage blastoderms whereas a higher storage temperature is favorable for later-stage/gastrulating embryos. Our understanding of the molecular mechanisms underlying the relationship between storage temperature and development stage within the DW is rather limited. However, it is expected to become relevant in light of the effect of selective breeding of modern avian birds on the advancement of embryonic development stage. Thus, this review discusses parameters that are regulated during the DW and affect SRD, and presents the need to adopt new storage techniques. The pre-managerial decision of required duration of storage with manipulation of storage temperature in the currently used storage techniques may improve SRD characteristics.

The energetically costly mammalian investment in gestation and lactation requires plentiful nutritional sources and thus links the environmental conditions to reproductive success. Flexibility in adjusting developmental timing enhances chances of survival in adverse conditions. Over 130 mammalian species can reversibly pause early embryonic development by switching to a near dormant state that can be sustained for months, a phenomenon called embryonic diapause. Lineage-specific cells are retained during diapause, and they proliferate and differentiate upon activation. Studying diapause thus reveals principles of pluripotency and dormancy and is not only relevant for development, but also for regeneration and cancer. In this review, we focus on the molecular regulation of diapause in early mammalian embryos and relate it to maintenance of potency in stem cells in vitro. Diapause is established and maintained by active rewiring of the embryonic metabolome, epigenome, and gene expression in communication with maternal tissues. Herein, we particularly discuss factors required at distinct stages of diapause to induce, maintain, and terminate dormancy.

Embryonic diapause in mammals leads to a reversible developmental arrest. While completely halted in many species, European roe deer (Capreolus capreolus) embryos display a continuous deceleration of proliferation. During a 4-mo period, the cell doubling time is 2 to 3wk. During this period, the preimplantation blastocyst reaches a diameter of 4 mm, after which it resumes a fast developmental pace to subsequently implant. The mechanisms regulating this notable deceleration and reacceleration upon developmental resumption are unclear. We propose that amino acids of maternal origin drive the embryonic developmental pace. A pronounced change in the abundance of uterine fluid mTORC1-activating amino acids coincided with an increase in embryonic mTORC1 activity prior to the resumption of development. Concurrently, genes related to the glycolytic and phosphate pentose pathway, the TCA cycle, and one carbon metabolism were up-regulated. Furthermore, the uterine luminal epithelial transcriptome indicated increased estradiol-17ß signaling, which likely regulates the endometrial secretions adapting to the embryonic needs. While mTORC1 was predicted to be inactive during diapause, the residual embryonic mTORC2 activity may indicate its involvement in maintaining the low yet continuous proliferation rate during diapause. Collectively, we emphasize the role of nutrient signaling in preimplantation embryo development. We propose selective mTORC1 inhibition via uterine catecholestrogens and let-7 as a mechanism regulating slow stem cell cycle progression. [ABSTRACT FROM AUTHOR]

The problem of the coexistence of closely related species of Paguroidea (Decapoda: Anomura) and the main mechanisms of structuring the communities of these species in sympatry are discussed: differential use of habitats, competition for resources, and physiological resistance to abiotic factors. It is thought that the competition for gastropod shells among hermit crabs may be particularly high at the larval settlement stage. This review discusses the peculiarities of larval settlement, reproductive phenology, and differences in reproductive characteristics of hermit crabs, which allow sympatric species in temperate waters to reduce the competition for shell resource in the early life stages. [ABSTRACT FROM AUTHOR]

Although the role of ecdysteroids in regulating egg diapause process in Bombyx mori is well documented, temporal changes in expression levels of genes involved in ecdysteroid biosynthesis and its downstream signaling are less well understood. In the present study, we studied changes in expression levels of genes involved in ecdysteroid biosynthesis and its downstream signaling during embryonic development of B. mori. Results showed that in diapause eggs, the expression of ecdysteroid‐phosphate phosphatase (EPPase) gene and Halloween genes (Spook [Spo] and Shade [Shd]) remained at very low levels. However, in eggs whose diapause initiation was prevented by HCl, significant increases in the messenger RNA (mRNA) levels of EPPase, Spo, and Shd were detected during embryonic development. Other Halloween genes (Neverland [Nvd] and Phantom [Phm]) also showed different changes between diapause and HCl‐treated eggs. However, genes of Disembodied (Dib) and Shadow (Sad) showed similar changes in both diapause and HCl‐treated eggs. We further investigated changes in expression levels of ecdysone receptor genes (EcRA, EcRB1, and USP) and downstream signaling genes (E75A, E75B, E74A, E74B, Br‐C, HR3, HR4, KR‐H1, and FTZ‐F1). Results showed that genes of EcRA and the other nuclear receptors (E75A, E75B, E74A, HR3, HR4, KR‐H1, and FTZ‐F1) exhibited significant differential patterns between diapause and HCl‐treated eggs, with increased levels being detected during later stages of embryonic development in HCl‐treated eggs. Differential temporal changes in expressions of genes involved ecdysteroid biosynthesis and its downstream signaling found between diapause and HCl‐treated eggs were further confirmed using nondiapause eggs. Our results showed that nondiapause eggs exhibited the same changing patterns as those in HCl‐treated eggs, thus clearly indicating potential correlations between expressions of these genes and embryonic development in B. mori. To our knowledge, this is the first comprehensive report to study the transcriptional regulation of ecdysteroidogenic and ecdysteroid signaling genes, thus providing useful information for a clearer understanding of insect egg diapause mechanisms. Research highlights: Higher expression levels of EPPase, Spo, Shd, ​and ecdysteroid signaling genes were detected in developing eggs than in diapause eggs.Expressions of ecdysteroidogenic and ecdysteroid signaling genes are related to Bombyx egg development. [ABSTRACT FROM AUTHOR]

Insect eggshells must meet various demands of developing embryos. These demands sometimes conflict with each other; therefore, there are tradeoffs between eggshell properties, such as robustness and permeability. To meet these conflicting demands, particular eggshell structures have evolved in diverse insect species. Here, we report a rare eggshell structure found in the eggshell of a cicada, Cryptotympana facialis. This species has a prolonged egg period with embryonic diapause and a trait of humidity-inducible hatching, which would impose severe demands on the eggshell. We found that in eggs of this species, unlike many other insect eggs, a dedicated cleavage site, known as a hatching line, was formed not in the chorion but in the serosal cuticle. The hatching line was composed of a fine furrow accompanied by ridges on both sides. This furrow-ridge structure formed in the terminal phase of embryogenesis through the partial degradation of an initially thick and nearly flat cuticle layer. We showed that the permeability of the eggshell was low in the diapause stage, when the cuticle was thick, and increased with degradation of the serosal cuticle. We also demonstrated that the force required to cleave the eggshell was reduced after the formation of the hatching line. These results suggest that the establishment of the hatching line on the serosal cuticle enables flexible modification of eggshell properties during embryogenesis, and we predict that it is an adaptation to maximize the protective role of the shell during the long egg period while reducing the barrier to emerging nymphs at the time of hatching. [ABSTRACT FROM AUTHOR]

Embryonic diapause is an enigmatic phenomenon that appears in diverse species. Although regulatory mechanisms have been established, there is much to be discovered. Herein, we have made the first comprehensive attempt to elucidate diapause regulatory mechanisms using a computational approach. We found transcription factors unique to promoters of genes in diapause species. From pathway analysis and STRING PPI networks, the signaling pathways regulated by these unique transcription factors were identified. The pathways were then consolidated into a model to combine various known mechanisms of diapause regulation. This work also highlighted certain transcription factors that may act as 'master transcription factors' to regulate the phenomenon. Promoter analysis further suggested evidence for independent evolution for some of regulatory elements involved in diapause. [ABSTRACT FROM AUTHOR]

Embryonic diapause is a reproductive adaptation that enables some mammalian species to halt the otherwise continuous pace of embryonic development. In this dormant state, the embryo exploits poorly understood regulatory mechanisms to preserve its developmental potential for prolonged periods of time. Here, using mouse embryos and single-cell RNA sequencing, we molecularly defined embryonic diapause at single-cell resolution, revealing transcriptional dynamics while the embryo seemingly resides in a state of suspended animation. Additionally, we found that the dormant pluripotent cells rely on integrin receptors to sense their microenvironment and preserve their viability via Yap/Taz-mediated prosurvival signaling., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

In this report, a rare case of pregnancy in a mouse without mating and during breastfeeding is presented. Out-bred NMRI mice were prepared for mating. Two female mice without superovulation were caged with one male. The next morning, vaginal plaque was not detected; therefore, females were kept in the cage with the same male for 4 more days. One of the females delivered 4 offspring: one female and three males. This female conceived again without mating, 21 days after the first delivery and during the breastfeeding period and this time delivered 16 offspring: 13 males and 3 females. The more likely explanation for this rare, second parturition is embryonic diapause.

Embryonic diapause (ED) is a temporary arrest of an embryo at the blastocyst stage when it waits for the uterine receptivity signal to implant. ED used by over 100 species may also occur in normally "nondiapausing" mammals when the uterine receptivity signal is blocked or delayed. A large number of lipid droplets (LDs) are stored throughout the preimplantation embryo development, but the amount of lipids varies greatly across different mammalian species. Yet, the role of LDs in the mammalian egg and embryo remains unknown. Here, using a mouse model, we provide evidence that LDs play a crucial role in maintaining ED. By mechanical removal of LDs from zygotes, we demonstrated that delipidated embryos are unable to survive during ED. LDs are not essential for normal prompt implantation, without ED. We further demonstrated that with the progression of ED, the amount of intracellular lipid reduces, and composition changes. This decrease in lipid is caused by a switch from carbohydrate metabolism to lipid catabolism in diapausing blastocysts, which also exhibit increased release of exosomes reflecting elevated embryonic signaling to the mother. We have also shown that presence of LDs in the oocytes of various mammals positively corelates with their species-specific length of diapause. Our results reveal the functional role of LDs in embryonic development. These results can help to develop diagnostic techniques and treatment of recurrent implantation failure and will likely ignite further studies in developmental biology and reproductive medicine fields. [ABSTRACT FROM AUTHOR]

In species displaying embryonic diapause, the developmental pace of the embryo is either temporarily and reversibly halted or largely reduced. Only limited knowledge on its regulation and the inhibition of cell proliferation extending pluripotency is available. In contrast with embryos from other diapausing species that reversibly halt during diapause, embryos of the roe deer Capreolus capreolus slowly proliferate over a period of 4--5 months to reach a diameter of approximately 4 mm before elongation. The diapausing roe deer embryos present an interesting model species for research on preimplantation developmental progression. Based on our and other research, we summarise the available knowledge and indicate that the use of embryonic stem cells (ESCs) would help to increase our understanding of embryonic diapause. We report on known molecular mechanisms regulating embryonic diapause, as well as cellular dormancy of pluripotent cells. Further, we address the promising application of ESCs to study embryonic diapause, and highlight the current knowledge on the cellular microenvironment regulating embryonic diapause and cellular dormancy. [ABSTRACT FROM AUTHOR]

An alarming number of large mammalian species with low reproduction rates is threatened with extinction. As basic knowledge of reproductive physiology is currently lacking in many species, increasing the understanding of reproductive physiology is imperative and includes the development of novel artificial reproduction technologies. Despite the relatively comprehensive knowledge on molecular mechanisms underlying reproduction in livestock species such as cattle, pregnancy failures are likewise far from understood. Contrary to other wildlife species, the European roe deer (Capreolus capreolus) displays a remarkably high pregnancy rate. In parts, cattle and roe deer exhibit comparable features of preimplantation embryo development. Therefore, understanding the high fertility rate in the roe deer holds a great potential for cross-species knowledge gain. As the only known species among the artiodactylae, the roe deer displays a long period of embryonic diapause. The preimplantation blastocyst reaches a diameter of 1 mm only at around 4 months compared to around 13 days post estrus in cattle. The expanded blastocyst survives in a uterine microenvironment that contains a unique set of yet unidentified factors that allow embryonic stem cells to proliferate at low pace without impairing their developmental potential. Upon reactivation, intimate embryo-maternal communication comparable to those reported in cattle is thought to occur. In this review, current knowledge, parallels and differences of reproductive physiology in cattle and roe deer are reviewed. The roe deer is proposed as a unique model species to (1) enhance our knowledge of fertility processes, (2) define factors that support embryo survival for an extended period, (3) advance knowledge on embryonic stem cells, and (4) unravel potential implications for the development of novel strategies for artificial reproductive technologies. [ABSTRACT FROM AUTHOR]

Superfoetation is when ovulation and fertilisation occur during pregnancy. Coupled with embryonic diapause, superfoetation presents an intriguing female reproductive advantage in terms of cryptic choice of males. Unfortunately, few studies have identified species possessing both superfoetation and embryonic diapause. We aim to reinterpret existing data on reproductive physiology in the stoat Mustela erminea and suggest it may be a previously overlooked species that possesses this combination. By increasing our knowledge of such reproductive systems, we can further our understanding of a cryptic sexually selected function and better explain the evolutionary gain and loss of embryonic diapause in mammals. [ABSTRACT FROM AUTHOR]

This review examines the main characteristics of the reproductive strategy in hermit crabs: the sex ratio, the age (size) of onset of maturity, fecundity, and duration of the incubation period, as well as their dependence on the availability and quality of accessible gastropod shells. The latitudinal variation in reproductive characteristics and the peculiarities of reproduction of coastal hermit crabs in temperate waters are discussed. [ABSTRACT FROM AUTHOR]

The majority of pregnancy loss in ruminants occurs during the preimplantation stage, which is thus the most critical period determining reproductive success. Here, we performed a comparative transcriptome study by sequencing total mRNA from corpus luteum (CL) collected during the preimplantation stage of pregnancy in Finnsheep, Texel and F1 crosses. A total of 21,287 genes were expressed in our data. Highly expressed autosomal genes in the CL were associated with biological processes such as progesterone formation (STAR, CYP11A1, and HSD3B1) and embryo implantation (e.g., TIMP1, TIMP2 and TCTP). Among the list of differentially expressed genes, sialic acid-binding immunoglobulin (Ig)-like lectins (SIGLEC3, SIGLEC14, SIGLEC8), ribosomal proteins (RPL17, RPL34, RPS3A, MRPS33) and chemokines (CCL5, CCL24, CXCL13, CXCL9) were upregulated in Finnsheep, while four multidrug resistance-associated proteins (MRPs) were upregulated in Texel ewes. A total of 17 known genes and two uncharacterized non-coding RNAs (ncRNAs) were differentially expressed in breed-wise comparisons owing to the flushing diet effect. The significantly upregulated TXNL1 gene indicated potential for embryonic diapause in Finnsheep and F1. Moreover, we report, for the first time in any species, several genes that are active in the CL during early pregnancy (including TXNL1, SIGLEC14, SIGLEC8, MRP4, and CA5A). [ABSTRACT FROM AUTHOR]

Currently, the success of targeted anticancer therapies largely depends on the correct understanding of the dormant state of cancer cells, since it is increasingly regarded to fuel tumor recurrence. The concept of cancer cell dormancy is often considered as an adaptive response of cancer cells to stress, and, therefore, is limited. It is possible that the cancer dormant state is not a privilege of cancer cells but the same reproductive survival strategy as diapause used by embryonic stem cells (ESCs). Recent advances reveal that high autophagy and mTOR pathway reduction are key mechanisms contributing to dormancy and diapause. ESCs, sharing their main features with cancer stem cells, have a delicate balance between the mTOR pathway and autophagy activity permissive for diapause induction. In this review, we discuss the functioning of the mTOR signaling and autophagy in ESCs in detail that allows us to deepen our understanding of the biology of cancer cell dormancy.

Diapause is an alternative developmental trajectory allowing insects to enter dormancy and persist through predictable periods of seasonally unfavorable conditions. This crucial ecological adaptation defines the geographic and seasonal abundance of many insect pollinators, pests, and vectors. Understanding the hormonal changes by which insects coordinate the perception of external, diapause-inducing cues with the physiological mechanisms that lead to developmental arrest is a long-standing goal in biology. The hormonal regulation of diapause tends to vary by the life stage at which development arrest occurs; for example, diapause is typically regulated by ecdysteroids in larvae and pupae, and by juvenile hormones in adults. However, little is known about the hormonal control of embryonic diapause, particularly in Diptera. To address this fundamental gap, we directly measured 20-hydroxyecdysone (20HE) (via LC-MS/MS) and juvenile hormone III (JH3) (via GC-MS) in diapause and non-diapause eggs of the Asian tiger mosquito, Aedes albopictus. While 20HE abundance did not differ, diapause eggs had lower JH3 abundance than non-diapause eggs. These results are corroborated by transcriptional and manipulative evidence suggesting that reduced JH3 regulates diapause in this medically important mosquito.

The silkworm Bombyx mori exhibits a photoperiodic response (PR) for embryonic diapause induction. This article provides a comprehensive review of literature on the silkworm PR, starting from early works on population to recent studies uncovering the molecular mechanism. Makita Kogure (1933) conducted extensive research on the PR, presenting a pioneering paper on insect photoperiodism. In the 1970s and 80s, artificial diets were developed, and the influence of nutrition on PR was well documented. The photoperiodic photoreceptor has been investigated from organ to molecular level in the silkworm. Culture experiments demonstrated that the photoperiodic induction can be programmed in an isolated brain (Br)-subesophageal ganglion (SG) complex with corpora cardiaca (CC)-corpora allata (CA). The requirement of dietary vitamin A for PR suggests the involvement of opsin pigment in the photoperiodic reception, and a cDNA encoding an opsin (Boceropsin) was cloned from the brain. The effector system concerning the production and secretion of diapause hormone (DH) has also been extensively investigated in the silkworm. DH is produced in a pair of posterior cells of SG, transported to CC by nervi corporis cardiaci, and ultimately released into the hemolymph. Possible involvement of GABAergic and corazonin (Crz) signal pathways was suggested in the control of DH secretion. Knockout (KO) experiments of GABA transporter ( GAT ) and circadian clock genes demonstrated that GAT plays a crucial role in PR through circadian control. A model outlining the PR mechanism, from maternal photoperiodic light reception to DH secretion, has been proposed.

Diapause is an alternative developmental trajectory allowing insects to enter dormancy and persist through predictable periods of seasonally unfavorable conditions. This crucial ecological adaptation defines the geographic and seasonal abundance of many insect pollinators, pests, and vectors. Understanding the hormonal changes by which insects coordinate the perception of external, diapause-inducing cues with the physiological mechanisms that lead to developmental arrest is a long-standing goal in biology. The hormonal regulation of diapause tends to vary by the life stage at which development arrest occurs; for example, diapause is typically regulated by ecdysteroids in larvae and pupae, and by juvenile hormones in adults. However, little is known about the hormonal control of embryonic diapause, particularly in Diptera. To address this fundamental gap, we directly measured 20-hydroxyecdysone (20HE) (via LC-MS/MS) and juvenile hormone III (JH3) (via GC-MS) in diapause and non-diapause eggs of the Asian tiger mosquito, Aedes albopictus. While 20HE abundance did not differ, diapause eggs had lower JH3 abundance than non-diapause eggs. These results are corroborated by transcriptional and manipulative evidence suggesting that reduced JH3 regulates diapause in this medically important mosquito. [ABSTRACT FROM AUTHOR]

Blue-breasted quail has been recognized as a potential model animal. The aim of this study is to investigate the low-temperature-induced embryonic diapause in blue-breasted quail. To this end, the early embryonic staging in blue-breasted quail was briefly described and various incubation temperatures were tested. While the embryonic diapause in early blue-breasted quail embryos can be induced when the eggs were stored at 21°C, a lower temperature such as 16°C yielded a significantly better hatchability (P = 0.0231). Additionally, prolonged storage duration from 3, 7 to 14 d significantly reduced the hatchability (P < 0.0001). Visual examination on the unhatched eggs revealed that reduced hatchability in prolonged storage was significantly correlated with embryonic mortality during the first half of incubation period (R2 = 0.9999, P = 0.0055). High-throughput RNA sequencing with de novo assembly showed that a gene network cluster consisted of ND4, ND5, ND6 , and COX3 , which are components of mitochondrial respiratory complexes, was down-regulated in the cold-stored embryos, while a stress-responsive gene network cluster consisted of JUN, ATF3 , and DUSP1 was up-regulated. Accordingly, cell death in the blastoderm was significantly increased as the storage duration prolonged from 3 to 10 d. Taken together, our study provided basic information on the temperature-induced embryonic diapause in blue-breasted quail. Furthermore, transcriptomic analysis sheds light for the molecular basis on how blastoderm cells respond to the prolonged cold-stress and stay diapause. [ABSTRACT FROM AUTHOR]

• LY294002 inhibited phosphorylation of GSK-3β and Akt in Bombyx eggs. • Changes in Akt phosphorylation were different between diapause and developing eggs. • Changes in bombyxin-Z1 gene expression coincided with Akt phosphorylation. • Bombyxin/Akt signaling is related to Bombyx embryonic diapause process. Our previous study showed that phosphorylation of glycogen synthase kinase (GSK)-3β is related to the embryonic diapause process in Bombyx. However, the upstream signaling pathway was not clearly understood. In the present study, we examined bombyxin/Akt signaling in relation to the embryonic diapause process of B. mori. Results showed that GSK-3β phosphorylation stimulated by dechorionation was blocked by LY294002, a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, indicating involvement of PI3K in GSK-3β phosphorylation in dechorionated eggs. Direct determination of Akt phosphorylation showed that dechorionation stimulated Akt phosphorylation. The Akt phosphorylation was blocked by LY294002. Temporal changes in Akt phosphorylation showed that different changing patterns exist between diapause and developing eggs. Relatively higher phosphorylation levels of Akt were detected between days 3 and 5 after oviposition in non-diapause eggs compared to those at the same stages in diapause eggs. Upon treatment with HCl, which prevents diapause initiation, Akt phosphorylation levels exhibited a later and much broader peak compared to diapause eggs. Examination of expression levels of the bombyxin-Z1 gene showed that in diapause eggs, a major peak occurred 1 day after oviposition, and its level then sharply decreased on day 2. However, in both non-diapause and HCl-treated eggs, a major broad peak was detected between days 1 and 4 after oviposition. These temporal changes in bombyxin-Z1 gene expression levels during embryonic stages coincided with changes in Akt phosphorylation, indicating that bombyxin-Z1 is likely an upstream signaling component for Akt phosphorylation. Taken together, our results indicated that PI3K/Akt is an upstream signaling pathway for GSK-3β phosphorylation and is associated with the diapause process of B. mori eggs. To our knowledge, this is the first study to demonstrate the potential correlation between bombyxin/Akt signaling and the embryonic diapause process. [ABSTRACT FROM AUTHOR]

The population and reproductive characteristics of the hermit crab Pagurus brachiomastus (Thallwitz, 1892) have been examined in Vostok Bay (Peter the Great Bay, Sea of Japan). The average population density of P. brachiomastus was lowest in the spring (2.4 ± 0.6 ind./m2) and highest (3.1 ± 0.4 ind./m2) in the summer; the biomass was 18.24 ± 3.75 and 22.83 ± 2.80 g/m2, respectively. Hermit crabs were found throughout the depth range from 0 to 12 m, but were most numerous at a depth of approximately 5–6 m, with an average population density of 8.3 ± 3.7 ind./m2 and a biomass of 39.09 ± 8.51 g/m2 in the summer. The shield length of males varied from 1.3 to 10.3 mm (on average, 5.3 ± 2.2 mm), that of females varied from 1.3 to 10.6 mm (on average, 4.3 ± 1.5 mm), and that of ovigerous females varied from 1.5 to 8.4 mm (on average, 4.4 ± 1.5 mm). The male to female ratio varied from 0.8 to 3.3 during the observation period, with an average of 1.7. Spawning continued from March through August. The proportion of ovigerous females increased from 8.5% in March to 82.8% in May; embryos in clutches remained in the early stage of development until the second 10-day period of May. Egg development was resumed when the water temperature reached 10°C. Breeding was asynchronous: in June–August, females with late-stage embryos and females with recently laid eggs were observed, indicating the possibility of repeated spawning. The data we obtained showed that the favorable coexistence of P. brachiomastus with other sympatric species in the study area is provided by the spatial dissociation of their clusters and differences in size characteristics, as well as the presence of an embryonic diapause in egg development in part of the females and the possibility of repeated spawning. [ABSTRACT FROM AUTHOR]