Influence of temperature on embryonic development of Pontastacus leptodactylus freshwater crayfish, and characterization of growth and osmoregulation related genes

Narrow clawed crayfish, Pontastacus (Astacus) leptodactylus, represents an ecologically and economically valuable freshwater species. Despite the high importance of artificial breeding for conservation purpose and aquaculture potential, hatching protocols have not been developed so far in this species. Further, limited knowledge exists regarding the artificial egg incubation, the temperature effect on embryonic development, hatching synchronization and hatching rate. In the present study we investigated the temperature increase (from 17 oC to 22oC) effects in two different embryonic developmental stages of P. leptodactylus. Furthermore, two primer pairs for the Fibroblast Growth Factor Receptor 4 (FGFR4) gene cDNA amplification were successfully designed, characterising for the first time the FGFR4 gene in P. leptodactylus in relation to different developmental stages and temperatures. Apart from the FGFR4 gene, the Na+/K+-ATPase α-subunit expression was also explored. Both the FGFR4 and Na+/K+-ATPase α-subunit expression levels were higher in embryos closer to hatching. Egg incubation at 22oC for seven days led to significant increase of FGFR4 expression in embryos from earlier developmental stages. Nevertheless, temperature increase did not affect FGFR4 expression in eggs from latter developmental stages and Na+/K+-ATPase α-subunit expression in all developmental stages. Temperature increase represents therefore probably a promising strategy for accelerating hatching in freshwater crayfish particularly in early developmental stages. Specifically, our results indicate that FGFR4 expression increased in embryonic stages closer to hatching and that temperature influences significantly its expression in embryos from earlier developmental stages. Overall, these findings can provide a better understanding of artificial egg incubation of P. leptodactylus, and therefore can be employed for the effective management of this species, both for economic and biodiversity retention reasons.

tRNAGlu-derived fragments from embryonic extracellular vesicles modulate bovine embryo hatching

Transfer RNA-derived small RNAs (tsRNAs) have been shown to be involved in early embryo development and repression of endogenous retroelements in embryos and stem cells. However, it is unknown whether tsRNAs also regulate embryo hatching. In this study, we mined the sequencing data of a previous experiment in which we demonstrated that the microRNA (miRNA) cargo of preimplantation embryonic extracellular vesicles (EVs) influences embryo development. We thus profiled the tsRNA cargo of EVs secreted by blastocysts and non-blastocysts. The majority of tsRNAs was identified as tRNA halves originating from the 5´ ends of tRNAs. Among the 148 differentially expressed tsRNAs, the 19 nt tRNA fragment (tRF) tDR-14:32-Glu-CTC-1 was found to be significantly up-regulated in EVs derived from non-blastocysts. RT-qPCR assays confirmed its significant up-regulation in non-blastocyst embryos and their conditioned medium compared to the blastocyst group (P < 0.05). Inhibition of tDR-14:32-Glu-CTC-1 by supplementing antagomirs to the conditioned medium improved embryo hatching (P < 0.05). Transcriptomic analysis of embryos treated with tDR-14:32-Glu-CTC-1 antagomirs further showed differential expression of genes that are associated with embryo hatching and implantation. In summary, tDR-14:32-Glu-CTC-1 is up-regulated in non-blastocyst embryos and their secretions, and inhibition of tDR-14:32-Glu-CTC-1 promotes embryo hatching, while influencing embryo implantation-related genes and pathways. These results indicate that embryonic EVs containing specific tRFs may regulate preimplantation embryo development.

Three-dimensional morphology of bovine blastocysts hatched against lipopolysaccharide exposure in vitro

Embryo transfer in cattle is globally becoming more ubiquitous, but the pregnancy rate is lower than that of artificial insemination. The uterus contains its own bacteria, and concentrations of lipopolysaccharides (LPS) from gram-negative bacteria are higher in uteri affected by endometritis than in healthy uteri and they suppress embryogenesis. The purpose of this study was to investigate the morphological characteristics of bovine embryos with a higher viability and implantability, by analyzing the morphology of bovine blastocysts that successfully hatched under challenge of LPS, using an optical coherence tomography (OCT) system. Developing embryos produced by in vitro fertilization that had reached the blastocyst stage on Day 7 were three-dimensionally scanned using an OCT system, then were continued to culture with or without LPS until Day 9, when the presence or absence of hatching was determined. The OCT-captured three-dimensional images were used to quantify 20 different metrics, including inner cell mass (ICM), trophectoderm, blastocoel, and total embryo volume; each of the parameters was compared between the hatched and unhatched embryos. Under the LPS challenge, hatched embryos had higher ICM thickness and volume, and lower trophectoderm thickness than unhatched embryos. Furthermore, hatched embryos under LPS challenge had higher ICM thickness and ICM volume than hatched embryos without LPS challenge. The present results suggest the possibility that ICM thickness and ICM volume calculated by OCT system could be indices for good quality bovine embryos.

Functional importance of groups I and II chitinases, CHT5 and CHT10, in turnover of chitinous cuticle during embryo hatching and post-embryonic molting in the red flour beetle, Tribolium castaneum

Chitinases (CHT) comprise a large gene family in insects and have been classified into at least eleven subgroups. Many studies involving RNA interference (RNAi) have demonstrated that depletion of group I (CHT5s) and group II (CHT10s) CHT transcripts causes lethal molting arrest in several insect species including the red flour beetle, Tribolium castaneum, presumably due to failure of degradation of chitin in their old cuticle. In this study we investigated the functions of CHT5 and CHT10 in turnover of chitinous cuticle in T. castaneum during embryonic and post-embryonic molting stages. RNAi and transmission electron microscopic (TEM) analyses indicate that CHT10 is required for cuticular chitin degradation at each molting period analyzed, while CHT5 is essential for pupal-adult molting only. We further analyzed the functions of these genes during embryogenesis in T. castaneum. Real-time qPCR analysis revealed that peak expression of CHT10 occurred prior to that of CHT5 during embryonic development as has been observed at post-embryonic molting periods in several other insect species. With immunogold-labeling TEM analysis using a fluorescein isothiocyanate-conjugated chitin-binding domain protein (FITC-CBD) probe, chitin was detected in the serosal cuticle but not in any other regions of the eggshell including the chorion and vitelline membrane layers. Injection of double-stranded RNA (dsRNA) for CHT5 (dsCHT5), CHT10 (dsCHT10) or their co-injection (dsCHT5/10) into mature adult females had no effect on their fecundity and the resulting embryos developed normally inside the egg. There were no obvious differences in the morphology of the outer chorion, inner chorion and vitelline membrane among eggs from these dsRNA-treated females. However, unlike dsCHT5 eggs, dsCHT10 and dsCHT5/10 eggs exhibited failure of turnover of the serosal cuticle in which the horizontal chitinous laminae remained intact, resulting in lethal embryo hatching defects. These results indicate that group I CHT5 is essential for pupal-adult molting, whereas group II CHT10 plays an essential role in cuticular chitin degradation in T. castaneum during both embryonic hatching and all of the post-embryonic molts. CHT10 can serve in place of CHT5 in chitin degradation, except during the pupal-adult molt when both enzymes are indispensable to complete eclosion.

Developmental effects of zebrafish (Danio rerio) embryos after exposure to glyphosate and lead mixtures

Natural aquatic environments have a heterogeneous composition; therefore, simultaneous exposure to multiple contaminants is relevant and more realistic when assessing exposure and toxicity. This study examines the combinatorial effects of two compounds found ubiquitously in drinking water across the United States: glyphosate and lead acetate. Zebrafish (Danio rerio) embryos were used as a model for investigating developmental delays following controlled exposures. Six different environmentally relevant exposure concentrations of glyphosate, ranging from 0.001 to 10 ppm, and lead acetate, ranging from 0.5 to 4 ppm, were applied first as single exposures and then as co-exposures. The sublethal endpoints of hatching and coagulation were quantified to determine potencies. Results indicate that higher concentrations of the individual chemicals correlate with later hatching with correlation coefficients of 0.71 and 0.40 for glyphosate and lead acetate respectively, while the co-exposure at lower concentrations induced earlier hatching with a correlation coefficient 0.74. In addition, increased levels of coagulation and glutathione reductase activity were observed following co-exposure, as compared to the individual exposures, suggesting potential toxicological interactions. These results support the need for further work assessing the combined potencies of aquatic contaminants rather than individual exposures.

Tritiated thymidine induces developmental delay, oxidative stress and gene overexpression in developing zebrafish (Danio rerio)

Tritium is a betta emitter radionuclide. Being an isotope of hydrogen, it is easily transferred to different environmental compartments, and to human and non-human biota. Considering that tritium levels are expected to rise in the upcoming decades with the development of nuclear facilities producing tritium using fission processes, investigating the potential toxicity of tritium to human and non-human biota is necessary. Tritiated thymidine, an organic form of tritium, has been used in this study to assess its toxicity on fish embryo development. Zebrafish embryos (3.5 hpf; hours post fertilization) have been exposed to tritiated thymidine at three different activity concentrations (7.5; 40; 110 kBq/mL) for four days. These experiments highlighted that zebrafish development was affected by the exposure to organic tritium, with smaller larvae at 3 dpf after exposure to the two lowest dose rates (22 and 170 µGy/h), a delayed hatching after exposure to the two highest dose rates (170 and 470 µGy/h), an increase in the spontaneous tail movement (1 dpf) and a decrease in the heartbeat (3 dpf) after exposure to the highest dose rate. The results also highlighted an increase in ROS production in larvae exposed to the intermediate dose rate. A dysregulation of many genes, involved in apoptosis, DNA repair or oxidative stress, was also found after 1 day of exposure to the lowest tritium dose rate. Our results thus suggest that exposure to tritiated thymidine from a dose rate as low as 22 µGy/h can lead to sublethal effects, with an effect on the development, dysregulation of many genes and increase of the ROS production. This paper provides valuable information on toxic effects arising from the exposure of fish to an organic form of tritium, which was the main objective of this study.

Hatchability evaluation of bovine IVF embryos using OCT-based 3D image analysis

Although embryo transfer is widely applied in cattle, many of the transferred embryos do not result in pregnancy. To determine a new parameter for bovine embryo evaluation, we investigated the relationships between in vitro hatchability and embryo morphological parameters using optical coherence tomography (OCT) that we established recently. Bovine embryos were obtained from Japanese Black cattle by in vitro fertilization (IVF). The quality of the blastocysts was examined under an inverted microscope and confirmed as Codes 1-3 according to the IETS standards for embryo evaluation. The OCT images of the embryos were captured on Day 7 after IVF, and the embryos were cultured until Day 9 to determine their hatchability. During OCT, the embryos were irradiated with near-infrared light for a few minutes to obtain three-dimensional images. In total, 22 parameters were assessed for each of the 42 embryos, of which 25 hatched (H embryos) and 17 did not (NH embryos). The thickness of the trophectoderm (TE) and TE+zona pellucida (ZP) was lesser, and the volumes of the TE, ZP, blastocoel, and whole embryo and blastocoel diameter were greater in the H embryos than in the NH embryos. PCA identified that the increase in the blastocoel-related value along with the decrease in the thickness-related value of the TE and/or ZP could be indicators for evaluating the hatchability of bovine IVF embryos. These results support the idea that OCT-captured structural data of blastocyst-stage embryos can be used as a potential model to predict the quality of bovine embryos.

Climate change effects on hatching success and embryonic development of fish: Assessing multiple stressor responses in a large-scale mesocosm study

Climate change threatens freshwater fish species due to predicted changes in thermal, sedimentary and hydrological properties of stream ecosystems. Gravel-spawning fish are particularly sensitive to such alterations as warming, higher inputs of fine sediment and low-flow all have potentially negative effects on the functionality of their reproductive habitat, the hyporheic zone. Multiple stressors can interact in synergistic and antagonistic manners, causing surprise-effects that cannot be predicted from the additive consideration of individual stressors. For obtaining reliable, yet realistic data on the climate change stressor effects warming (+3-4 °C), fine sediment (increase in <0.85 mm by 22 %) and low-flow (eightfold discharge-reduction), we constructed a unique large-scale outdoor-mesocosm facility consisting of 24 flumes to study individual and combined stressor responses in a fully-crossed, 3-way-replicated design. To acquire representative results reflecting individual susceptibilities of gravel-spawning fish species due to taxonomic affiliation or spawning seasonality, we studied hatching success and embryonic development in the three fish species brown trout (Salmo trutta L.), common nase (Chondrostoma nasus L.) and Danube salmon (Hucho hucho L.). Fine sediment had the most significant single negative effect on both hatching rates and embryonic development (-80 % in brown trout, -50 % in nase, -60 % in Danube salmon). When fine sediment was combined with one or both of the other stressors, we observed strongly synergistic stressor responses, being distinctly stronger in the two salmonid species than in the cyprinid nase. Danube salmon was most susceptible to synergistic effects due to warmer spring water temperatures exacerbating the fine sediment-induced hypoxia, hence leading to complete mortality of fish eggs. This study highlights that individual and multiple-stressor effects depend strongly on life-history traits of respective species and that climate change stressors have to be assessed in combination to obtain representative results due to the high level of synergisms and antagonisms detected in this study.

Embryonic encapsulated development of the gastropod Acanthina monodon is impacted by future environmental changes of temperature and pCO2

Egg capsules of the gastropod Acanthina monodon were maintained during the entire period of encapsulated development at three temperatures (10, 15, 20 °C) and two pCO₂ levels (400, 1200 μatm). Embryos per capsule, size at hatching, time to hatching, embryonic metabolic rates, and the resistance of juveniles to shell breakage were quantified. No embryos maintained at 20 °C developed to hatching. The combination of temperature and pCO₂ levels had synergistic effects on hatching time and developmental success, antagonistic effects on number of hatchlings per capsule, resistance to juvenile shell cracking and metabolism, and additive effect on hatching size. Juveniles hatched significantly sooner at 15 °C, independent of the pCO₂ level that they had been exposed to, while individuals hatched at significantly smaller sizes if they had been held under 15 °C/1200 μatm rather than at 10 °C/low pCO₂. Embryos held at the higher pCO₂ had a significantly greater percentage of abnormalities. For capsules maintained at low pCO₂ and 15 °C, emerging juveniles had less resistance to shell breakage. Embryonic metabolism was significantly higher at 15 °C than at 10 °C, independent of pCO₂ level. The lower metabolism occurred in embryos maintained at the higher pCO₂ level. Thus, in this study, temperature was the factor that had the greatest effect on the encapsulated development of A. monodon, increasing the metabolism of the embryos and consequently accelerating development, which was expressed in a shorter intracapsular development time, but with smaller individuals at hatching and a lower resistance of their shells to breakage. On the other hand, the high pCO₂ level suppressed metabolism, prolonged intracapsular development, and promoted more incomplete development of the embryos. However, the combination of the two factors can mitigate--to some extent--the adverse effects of both incomplete development and lower resistance to shell breakage.

FoxP2 protein decreases at a specific region in the chick midbrain after hatching

Forkhead-box subclass P member 2 (FOXP2/FoxP2) protein, a transcription factor, regulates the development of certain brain functions, including human speech and animal vocalization. Although rapid progress has been made in demonstrating a relationship between FoxP2 expression in the brain and vocalization of the zebra finch, a typical vocal learner, the relationship in avian vocal non-learners, including chickens remains elusive. Because the midbrain plays a key role in innate vocalization development, we analyzed the FoxP2 protein in the midbrain of chicks, which do not cheep before hatching but cheep and call after hatching. Western blot analyses showed a significant reduction in FoxP2 protein in the chick midbrain after hatching compared with the findings before hatching. Quantitative immunohistochemistry revealed that FoxP2-immunoreactive (ir) cells significantly decreased at the stratum gris fibrosum (SGFS) of the optic tectum in the chick midbrain after hatching compared with the findings before hatching. These findings support the notion that FoxP2-ir cell numbers decrease at a specific region in the midbrain after hatching may be involved in innate vocalization of avian vocal non-learners.

Hatching rhythm and clock gene expression in the egg of the pea aphid, Acyrthosiphon pisum

Many insects exhibit diel rhythms in physiology and behavior, driven by an endogenous circadian clock. Although aphids are paradigmatic insects whose photoperiodic time measurement is based on a heavily damped circadian clock, there is a lack of empirical data on such a damped circadian clock. The present study investigated the temporal distribution of hatching and the temporal expression patterns of circadian clock genes in the pea aphid, Acyrthosiphon pisum under light-dark (LD) cycles and constant darkness (DD). Hatching occurred intensively in the early photophase, and this rhythm persisted under LD cycles, but damped under DD for a few days. Of the six clock genes analyzed, cyc showed a temporal change in expression under LD cycles, whereas this temporal change was lost under DD. These results suggest that the circadian clock of A. pisum is easily damped during the embryonic stage, supporting the heavily damped oscillator model in photoperiodic time measurement of aphids.

Impact of mono(2-ethylhexyl) phthalate (MEHP) on the development of mouse embryo in vitro

Mono(2-ethylhexyl) phthalate (MEHP) is the most studied metabolite of di(2-ethylhexyl) phthalate (DEHP), a phthalate found in cosmetics, flooring, paints, and plastics products, including toys and medical tubing. Humans are frequently exposed to this compound due to its ubiquitous presence in our environment. DEHP and MEHP are known to be endocrine-disrupting chemicals and exposure levels have been associated to decreased reproductive success. However, few studies have focused on the direct effects of MEHP on embryos. The present study investigated effects of MEHP (0.1, 1, 10, 100 and 1000 µM) on mice preimplantation embryonic development, evaluating percentage of blastocyst formation, hatching from zona pellucida, methylation-related genes, cell lineage commitment, micronucleation, and adherens junction marker at different stages of development during in vitro culture for 6 days. We show MEHP negatively impacts embryo competence by reducing blastocyst formation and hatching at 100 and 1000 µM. In addition, 100 µM MEHP increases the expression of Tet3 gene in blastocysts, which is related to a reduction of DNA methylation, an important mechanism regulating gene expression. Exposed embryos that completed the hatching process in groups 0.1, 1 and 10 µM MEHP had similar number of inner cell mass and trophectoderm cells compared to the control, while micronucleation occurrence and E-cadherin expression was not affected in exposed morulae by MEHP at 10 or 100 µM. Our results showed that high concentrations of MEHP can negatively impact embryo development. New studies unveiling the mechanism of toxicity involved and encompassing further developmental stages are warranted for further understanding.

Diapause characterization in the invasive alien mosquito species Aedes koreicus: a laboratory experiment

Abstract

Aedes koreicus is an invasive alien mosquito species native to Asia now introduced in several European countries, including northern Italy. In this temperate region, mosquito populations survive cold winter temperatures thanks to diapausing eggs or adults, depending on the species. In its native area, Ae. koreicus was reported to overwinter in the egg stage, but to the best of our knowledge, it is not confirmed whether overwintering eggs are actually diapausing or only in a quiescence stage, i.e., they might hatch as soon as external conditions are favorable. Based on previous laboratory studies, we established a diapausing Ae. koreicus colony, maintained at 21 °C with a photoperiod of 12L:12D. Females were allowed to lay eggs, which were consequently placed in water at different time intervals after oviposition, from 30 days to 5 months. We found that diapausing eggs younger than 3 months have a poor hatching rate, while after about 100 days we observed that almost all eggs hatched. Our findings highlight that water immersion alone did not lead to the hatching of eggs, as age was found to be a significantly important factor. We thus confirm effective diapause, occurring at the egg stage, for Ae. koreicus in a recently invaded area. Moreover, our quantification of diapause duration and hatching success might help in better designing future experiments and improving modeling efforts.

Graphical Abstract

Post-thaw dilution of Rhamdia quelen sperm improves the reproductive success

The aim was to evaluate the effect of a post-thaw dilution of Rhamdia quelen sperm in 1.1% NaCl (325 mOsm kg^-1; pH 7.6; 24 °C) solution on the quality and reproductive capacity. Sperm from eight males were cryopreservation in nitrogen vapor at - 170 °C for 18 h in 0.25 mL straws in a freezing medium containing 5% fructose, 5% Powdered milk, and 10% methanol. The samples were thawed and post-thaw diluted (1:20) in NaCl solution or not (control). The higher spermatozoa velocities were observed in the post-thaw diluted samples (curvilinear (VCL) - 69 ± 11 µm s^-1; average path (VAP) - 45 ± 8 µm s^-1; straight-line (VSL) - 43 ± 8 µm s^-1) compared to the control (VCL - 47 ± 10 µm s^-1; VAP - 31 ± 6 µm s^-1; VSL - 30 ± 6 µm s^-1). Greater straightness (STR), progression (PROG), and beat cross frequency (BCF) were observed in the post-thaw diluted samples (STR - 96 ± 7%; PROG - 666 ± 128 µm; BCF - 42 ± 2 Hz) than in control (STR - 95 ± 5%; PROG - 463 ± 92 µm; BCF - 40 ± 2 Hz). The strongly curled tail was the only morphology change that differ between the post-thaw diluted (5 ± 2%) and control (2 ± 1%). Membrane integrity, mitochondrial activity, and normal larvae rate were not different between treatments. Fertilization and hatching were higher in the post-thaw diluted sperm (93 ± 3%; 82 ± 9%) when compared to control samples (65 ± 13%; 55 ± 17%). Were used oocytes from one female, limiting these results. The post-thaw dilution improved the sperm kinetics and reproductive parameters. Thus, this methodology can be included in the sperm cryopreservation protocol for R. quelen.

The function of glucose metabolism in embryonic diapause of annual killifish

Annual killifish could survive as diapaused embryos buried in soil during dry seasons. When the embryos in diapause III were incubated in water, the larvae could be hatched quickly. However, the mechanism of diapause and hatching of annual killifish was ambiguous. In the present study, Nothobranchius guentheri were used as the model to clarify the physiological mechanism of diapause and hatching of annual killifish. The results indicated that incubation with water could significantly enhance the heart rate and blood circulation of embryos. To clarify the molecular mechanism, the transcriptomic analysis was used to compare the embryos in diapause I, diapause III, and hatching period. The results showed that DNA replication-related genes, cell division cycle 45 and proliferating cell nuclear antigen were more highly expressed in diapause I compared to diapause III. In addition, the transcript levels of glucagon, glucokinase and phosphofructokinase were more abundantly detected in hatching period compared to diapause III, but insulin receptor and insulin-like growth factor-binding protein were lower. These results indicated glucose metabolism might play an important role in diapause and hatching of killifish. To further confirm this result, several reagents involved in glucose metabolism were used to incubate embryos in diapause III. The results displayed that glucose and glucagon could both shorten the hatching time of embryos. In contrast, 2-deoxy-d-glucose, metformin, and insulin could prolong the hatching time and reduce the hatching rate. The results further confirmed that glucose metabolism played an important role in the diapause and hatching of annual killifish.

Evaluation of early feed access and algal extract on growth performance, organ development, gut microbiota and vaccine-induced antibody responses in broiler chickens

Hatching concepts such as on-farm hatching provide an opportunity to supply newly hatched chickens with optimal nutrition that support growth and development of a healthy gut. Brown algae contain bioactive compounds, especially laminarin and fucoidan that may improve intestinal health and immune responses. This study aimed to examine the effects of early access to feed and water posthatch and feed supplementation with algal extract rich in laminarin from Laminaria digitata, on growth performance, organ and microbiota development and antibody production. A total of 432 Ross 308 chicks were allotted to 36 rearing pens in a 2 × 3 factorial design with two hatching treatments and three dietary treatments. During chick placement, half of the pens were directly provided access to feed and water (Early) while half of the pens were deprived of feed and water for 38 h (Late). The chicks were fed three different starter diets until day 6; a wheat-soybean meal-based control diet, a diet with low inclusion of algal extract (0.057%) and a diet with high inclusion of algal extract (0.114%). Feed intake and BW were registered on pen basis at placement, days 1, 6, 12, 19, 26, 33 and 40. To induce antibody responses, all chicks were vaccinated against avian pneumovirus on day 10. Three chicks per pen were selected as focal animals and used for blood sampling on days 10 and 39. On days 6, 19, and 40, two birds per pen were killed and used for organ measurement and caecal digesta sampling for gut microbiota analysis using the Illumina Miseq PE 250 sequencing platform. Results showed that algal extract did not influence gut microbiota, gut development or vaccine-induced antibody responses. However, during the first 38 h, early-fed chicks consumed on average 19.6 g of feed and gained 27% in BW, while late-fed chicks lost 9.1% in BW which lowered BW and feed intake throughout the study (P < 0.05). Late chicks also had longer relative intestine, higher relative (g/kg BW) weight of gizzard and proventriculus but lower relative bursa weight on day 6 (P < 0.05). No effects of hatching treatment on microbiota or antibody response were detected. The microbiota was affected by age, where alpha diversity increased with age. In conclusion, this study showed that early access to feed but not algal extract improved the growth performance throughout the 40-day growing period, and stimulated early bursa development.

Effects of different types of primary microplastics on early life stages of rainbow trout (Oncorhynchus mykiss)

Plastic pollution is recognized as serious threat to aquatic organisms. The aim of this research was to determine the effect of environmentally realistic concentrations of various microplastics (MPs) on survival, growth, development and induction of endocrine, geno- and cytotoxic responses in the early life stages of rainbow trout Oncorhynchus mykiss. Fish were exposed for 69-days, from embryos at eyed-stage to mobile yolk-sac larvae, to pre-production pellets (3000 μm; polystyrene - PS and polyethylene terephthalate - PET). Additionally, since salmonid larvae are particularly exposed to light polymers after swimming up from the bottom, fish were also treated with PE microspheres (150-180 μm; polyethylene - PE) for both long (69-days, from embryos at eyed-stage) and short period (29 days, from larvae 3 weeks after hatching) to test the development stage-related effect on the growth parameters and fitness. Hatching success, rate and the survival of larvae did not differ among treatments. Although some alterations were found in the length gain after the long-term exposure and in the yolk-sac exhaustion rate in all PE treatments, the final size of larvae did not differ from the respective controls. PE-treated larvae have shown elevated corticosterone concentrations being significantly higher in fish exposed from the embryo stage. It was indicated for the first time that mobile yolk-sac larvae ingested MPs (up to 24% of larvae contained microspheres). No changes were recorded in cytotoxicity endpoints in any of the treatments, but exposure to PS pellets resulted in significantly higher frequencies of genotoxicity endpoints compared to the control treatment. This effect and aforementioned alterations in PE-treated larvae might result from the exposure to toxic MPs leaches. The fact that selected PAHs' levels reached the highest values in PS pellets and PE microspheres must be underlined.

Developmental exposure to MDMA (ecstasy) in zebrafish embryos reproduces the neurotoxicity adverse outcome 'lower motor activity' described in humans

The recreational use of MDMA (ecstasy) by pregnant women is associated with impaired neuromotor function in infants, but the Adverse Outcome Pathway behind this effect is not clear yet. We present for the first time the evaluation of developmental neurotoxic (DNT) effects of MDMA in zebrafish embryos. The aim of the study was to determine whether the zebrafish model reproduces the adverse outcome occurring in humans. We have studied the DNT effects of MDMA in zebrafish within a range of 5-250 μM performing different behavioural tests: spontaneous tail-coiling and light-dark locomotor response; after exposing the embryos to 4 different scenarios combining changes in pH, in starting exposure time and exposure duration. In these scenarios we evaluated the effects of MDMA in general embryonic development and compared the concentrations producing them with those inducing specific DNT effects. As a result, we have established the experimental conditions leading to the adverse outcome "lower motor activity" in zebrafish without producing general developmental delay or general toxicity. The experimental condition chosen opens the door to use this model in future mechanistic investigations to better characterize the Adverse Outcome Pathway associated with the adverse effects caused by MDMA prenatal exposure in humans.

E-cigarette vaping liquids and the flavoring chemical cinnamaldehyde perturb bone, cartilage and vascular development in zebrafish embryos

As electronic cigarettes (e-cigarettes) become increasingly popular smoking devices, there is an increased risk for unintended exposure to e-cigarette liquids through improper disposal resulting in leaching into the environment, third hand vapor exposure through air, or embryonic exposure through maternal vaping. Thus, the safety of e-cigarettes for wildlife and developing embryos need to be thoroughly investigated. We examined perturbations in zebrafish embryonic development after exposures to two cinnamon flavored vaping liquids (with 12 mg/ml nicotine and without nicotine) for e-cigarettes from two different vendors, as well as the flavoring chemical cinnamaldehyde. We focused on the effects of the vaping liquids on hatching success and bone, cartilage and blood vessel development in 3-4 days old transgenic zebrafish larvae. We found that exposures to both of the vaping liquids perturbed the development of the cleithrum and craniofacial cartilage. Exposure to the liquids further caused non-overlapping and partially or completely missing intersegmental vessels. Hatching success was also reduced. Exposure to pure cinnamaldehyde replicated the effects of the vaping liquids with a 50% effect concentration (EC₅₀) of 34-41 µM. Quantification of the amount of cinnamaldehyde in the vaping liquids by mass spectrometry revealed EC₅₀s around 10-40 times lower than for pure cinnamaldehyde, suggesting that additional compounds or metabolites present in the vaping liquids mediate toxicity. Presence of nicotine in one of the vaping liquids decreased its EC₅₀s about two fold compared to the liquid without nicotine. Exposure to the humectants propylene glycol and vegetable glycerin did not affect the vascular, cartilage or bone development in zebrafish embryos. In conclusion, our study shows that exposure to cinnamaldehyde containing vaping liquids causes severe tissue-specific defects in developing embryos.

Effect of some fertilizers on hatching of cereal cysts nematode, Heterodera avenae

Experiments were conducted in laboratory and pot conditions to determine the effects of urea, di-ammonium phosphate (DAP), single super phosphate (SSP), muriate of potash (MOP) and zinc sulphate (ZnSO₄) on hatching of Heterodera avenae. Two concentrations of each fertilizer were tested in lab for which 10 cysts and 5 ml of each concentration were taken in 5 cm diameter Petri plates. Observations were recorded at weekly intervals up to six weeks. Urea, DAP, SSP and MOP inhibited hatching and ZnSO₄ increased it. After six weeks, hatching was least (5.45%) in higher dose of urea and greatest (46.9%) in higher dose of ZnSO₄. In pot experiment, two doses of urea and single dose of SSP, MOP, and ZnSO₄ were applied in H. avenae-infested soil and WH-1105 wheat was sown. Observations on nematodes in roots, soil and remaining cyst contents were recorded 40 days after sowing. Among all the fertilizers, least nematodes in soil and roots were found at higher dose of urea and greatest number in ZnSO₄.

Slight induction and strong inhibition of Heterodera glycines hatching by short-chain molecules released by different plant species

New management tools are necessary to reduce the damage caused by the soybean cyst nematode (SCN), Heterodera glycines. Identification of molecules that can stimulate second-stage juveniles (J2) hatching in an environment without food may contribute to that. In in vitro experiments, we evaluate the effect of volatile organic compounds (VOCs) released by soybean (Glycine max), bean (Phaseolus vulgaris), ryegrass (Lolium multiflorum), and alfalfa (Medicago sativa) on H. glycines egg hatching. VOCs released by all plant species significantly (p < 0.05) increased egg hatching. Short-chain molecules released by leaves and roots of soybean and bean increased the hatching up to 71.4%. The analysis of the volatilome done by gas chromatography coupled with mass spectrometry revealed 44 compounds in the plant emissions. Four of them, namely 3-octanol, 1-hexanol, hexanal and linalool were tested individually as hatching inductors. Under concentrations of 200, 600, and 1,000 µg/ml there was no hatching induction of H. glycines J2 by these compounds. On the other hand, in these concentrations, the compounds 3-octanol and 1-hexanol caused hatching reduction with values similar to the commercial nematicide carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methyl carbamate). In subsequent tests, the compounds 1-hexanol and 3-octanol showed lethal concentration values required to kill 50% of thenematode population (LC50) of 210 and 228 µg/ml, respectively, in the first experiment and, 230 and 124 µg/mlin the second one. Although we have not identified any molecules acting as hatching factor (HF), here we present a list (44 candidate molecules) that can be explored in future studies to find an efficient HF.

Constitutive and differential expression of transport protein genes in Parascaris univalens larvae and adult tissues after in vitro exposure to anthelmintic drugs

The equine roundworm Parascaris univalens has developed resistance to the three anthelmintic substances most commonly used in horses. The mechanisms responsible for resistance are believed to be multi-genic, and transport proteins such as the P-glycoprotein (Pgp) family have been suggested to be involved in resistance in several parasites including P. univlaens. To facilitate further research into the mechanisms behind drug metabolism and resistance development in P. univalens we aimed to develop an in vitro model based on larvae. We developed a fast and easy protocol for hatching P. univalens larvae for in vitro studies, resulting in a hatching rate of 92 %. The expression of transport protein genes pgp-2, pgp-9, pgp-11.1, pgp-16.1 and major facilitator superfamily (MFS) genes PgR006_g137 and PgR015_g078 were studied in hatched larvae exposed to the anthelmintic drugs ivermecin (IVM) 10^-9 M, pyrantel citrate (PYR) 10^-6 M and thiabendazole (TBZ) 10^-5 M for 24 h. In comparison, the expression of these transport protein genes was studied in the anterior end and intestinal tissues of adult worms in vitro exposed to IVM, TBZ and PYR, at the same concentrations as larvae, for 3 h, 10 h and 24 h. Larval exposure to sub-lethal doses of IVM for 24 h did not affect the expression levels of any of the investigated genes, however larvae exposed to PYR and TBZ for 24 h showed significantly increased expression of pgp-9. In vitro drug exposure of adult worms did not result in any significant increases in expression of transport protein genes. Comparisons of constitutive expression between larvae and adult worm tissues showed that pgp-9, pgp-11.1, pgp-16.1 and MFS gene PgR015_g078 were expressed at lower levels in larvae than in adult tissues, while pgp-2 and MFS gene PgR006_g137 had similar expression levels in larvae and adult worms. All investigated transport protein genes were expressed at higher rates in the intestine than in the anterior end of adult worms, except pgp-11.1 where the expression was similar between the two tissues. This high constitutive expression in the intestine suggests that this is an important site for xenobiotic efflux in P. univalens. Despite the fact that the results of this study show differences in expression of transport protein genes between larvae and adult tissues, we believe that the larval assay system described here will be an important tool for further research into the molecular mechanisms behind anthelmintic resistance development and for other in vitro studies.

Meloidogyne enterolobii egg extraction in NaOCl versus infectivity of inoculum on cucumber

Extraction of eggs of Meloidogyne spp. in sodium hypochlorite (NaOCl) is a helpful procedure to assess the population levels and to obtain inoculum. In this sense, laboratory and greenhouse experiments were done to evaluate the effect of the NaOCl concentration on the viability of M. enterolobii eggs. Additionally, the objective of this investigation was to corroborate the preferable treatments to count populations in cucumber galled roots or to obtain inoculum of M. enterolobii. It was shown that the effect of the NaOCl concentration on the viability of M. enterolobii eggs is potentially detrimental. The NaOCl concentration caused a higher hatching, which in turn, resulted in non-infective larvae. Therefore, the best treatments to obtain inoculum of eggs of M. enterolobii included the 0.75% NaOCl (with 8-min stirring), 0.5% NaOCl (with stirring for 8, 12, and 16 min), and 0.3% NaOCl concentration (with stirring for 8, 12, 16, and 20 min). For a correct estimate of the egg population in roots, we show by several treatments that a concentration of 0.5% NaOCl (with stirring for 8, 12, and 16 min) and 0.75% NaOCl (with 8-min stirring) give the highest results.

Hatching pattern and coexistence of Aedes aegypti and Aedes albopictus (Culicidae) in a subtropical city, Argentina, after three decades of coexistence

Aedes aegypti and Aedes albopictus are mosquito vectors of numerous arboviruses of sanitary importance. Presently in Argentina, neither Ae. aegypti nor Ae. albopictus, have displaced the other species in the places where they coexist, since the introduction of the latter in 1998. In this study, we evaluated whether these species coexist at different scales (ovitrap, microhabitat and habitat) in the city of Eldorado, Misiones province, northeast Argentina. We also analyzed the seasonal variation and climate variables related to the delay in egg hatching of both species. Mosquitoes were collected weekly, from June 2017 to May 2018, using ovitraps placed in urban areas. We conclude that Ae. aegypti and Ae. albopictus coexist in the study area, at the ovitrap, microhabitat and habitat scales. Furthermore, no pronounced pattern of delayed hatching has been observed for either species; however, eggs of Ae. albopictus laid during colder weeks and less rainfall needed a greater number of immersions to hatch, while for Ae. aegypti those laid during weeks with low rainfall and high temperatures showed the longest delay in hatching response.

Evaluation of the effect of different concentrations of organic amendments and botanical extracts on the mortality and hatching of Meloidogyne javanica

Organic amendments and botanical extracts are considered as some of the eco-friendly alternatives to chemical pesticide in suppressing plant pathogenic nematodes (PPN). Root-knot nematode (RKN) is the most important group of PPN distributed globally causing both qualitative and quantitative damage to many crops. Vermicompost and biogas digestate (BD) are two forms of organic amendments reported to have potential to limit RKN infestation. Likewise, marigold (Tagates spp.) and cabbage (Brassica oleracea) are two widely studied botanicals having shown their potential to control RKN. However, there was not much in vitro research related to organic amendments and botanicals targeting a particular species of RKN to observe their nematicidal effect. An in vitro experiment was undertaken to evaluate the effect of these organic amendments and botanical extracts at different concentrations (10.0%, 25.0%, 50.0% and 100.0%) on the hatching and mortality of Meloidogyne javanica at different time spans. Mortality of J₂ and inhibition of hatching of egg mass of M. javanica differed significantly (p < 0.0001) among the interaction effect of treatments and incubation time for both organic amendments and botanical extracts. Findings of this experiment indicated that potentiality for increasing mortality and inhibition of hatching was higher and steadier in botanical extracts than those of organic amendments.

Functional evaluation of culture filtrates of Bacillus subtilis and Pseudomonas fluorescens on the mortality and hatching of Meloidogyne javanica

Rhizospheric bacteria Bacillus subtilis and Pseudomonas fluorescens are two widely tested biological control agents against root-knot nematodes (RKN) of different crops. However, their performance as bio-control agents varies with their place of origin. Culture filtrates of rhizospheric bacteria contain some intermediary metabolites that have nematicidal activity. An in vitro experiment was undertaken to evaluate the functionality of culture filtrates of B. subtilis (MN252542.1) and P. fluorescens (MN256394.1) at different concentrations (1.0%, 2.5%, 5.0%, 7.0%, 10.0% and 25.0%) on the hatching and mortality of Meloidogyne javanica at different time span. Bacterial strains were isolated from rhizospheric soils of Bangladesh. At three days after incubation (DAI), 25.0% concentration of culture filtrates of both B. subtilis and P. fluorescens showed 100.0% mortality of second stage juveniles (J2) of M. javanica. Additionally, 25.0% concentration of culture filtrates of both bacteria showed 100.0% inhibition of hatching at one week after incubation (WAI). A decreasing trend in hatching of M. javanica was observed with the increment of the concentration of culture filtrates and progression of incubation time. The findings of this experiment reveal that culture filtrates of these accessions of B. subtilis and P. fluorescens are effective for controlling M. javanica and would be potential candidates for developing bio-nematicides.

Low temperature tolerance of three Aedes albopictus strains (Diptera: Culicidae) under constant and fluctuating temperature scenarios

Background

Aedes albopictus, a vector of numerous viruses and filarial worms, has already established in 20 countries in Europe, mainly colonising subtropical regions. Continuing adaptation to climatic conditions in temperate areas would probably result in a spread to more northern European countries, producing an increasing risk of mosquito-borne pathogen transmission over a much greater area. Based on previous studies showing that Ae. albopictus is able to overwinter in Germany, this study aims to determine more exactly its ecological limits of enduring low temperatures.

Methods

Non-diapausing and experimentally induced diapausing eggs of three different Ae. albopictus strains (tropical, subtropical and temperate origins) were exposed to four different regimes with constant temperatures and three different regimes with fluctuating temperatures in a course of a day for a minimum of 2 and a maximum of 30 days. The hatching rate of larvae after cold exposure of the eggs was taken as a measure of cold tolerance.

Results

The experiments showed that the tropical Ae. albopictus strain had a lower cold tolerance than the subtropical and the temperate strains. The eggs of all used strains were able to survive constant temperatures as low as −5 °C for an exposure period of 30 days, while constant temperatures as low as −10 °C were endured for 2 days by the tropical strain and for 10 and 20 days by the subtropical and temperate strains, respectively. At fluctuating temperatures, both the subtropical and the temperate strains exhibited hatching under all temperature regimes, even with a minimum temperature of −10 °C, whereas the tropical strain ceased hatching after an exposure period of 30 days under the temperature regime with a minimum temperature of −10 °C. The analyses showed that the temperature played the major role in interpreting the hatching rates of the eggs. The condition, whether the eggs were diapausing or not, had no significant influence, although results indicated a slightly higher cold tolerance of diapausing eggs at −10 °C.

Conclusions

It must be expected that subtropical and temperate strains of Ae. albopictus are able to withstand common central European winters and are able to establish in considerable parts of the continent.

Variation in hatching responses of Nematodirus battus eggs to temperature experiences

BACKGROUND

Nematodirus battus, unlike most other gastrointestinal nematodes, undergoes maturation to an infective larva within the egg. Historically, eggs were considered to require a period of chilling over winter followed by a period of temperature above 10 °C for synchronous hatching to occur (generally in spring). Anecdotal reports of Nematodirus infection out-with spring in veterinary journals and the farming press suggest that the concentrated pasture abundance of N. battus infective larvae may be changing. In order for control practices to be adapted, and unexpected disease outbreaks to be avoided, it is important to quantify how parasite epidemiology is changing and research the drivers behind it.

METHOD

The present study investigated the in vitro hatching response to temperature experiences (with and without a period of chilling) for egg samples of 90 N. battus populations obtained from 73 commercial sheep farms. Six aliquots of larvated eggs were prepared per population, three aliquots were placed at 4 °C for 6  weeks to provide a chill stimulus then incubated at the optimal hatching temperature for the species. The remaining three aliquots of eggs were incubated at the hatching temperature without a prior chill stimulus and the number of hatched larvae was compared between treatments.

RESULTS

Median hatch rate across all populations with chilling was 45% (95% CI: 42-48%) and without chilling was 4% (95% CI: 2-6%). Inter-population variation in hatching ranged from 0 to 87% of eggs able to hatch in the absence of a chill stimulus, mean non-chill hatching was 13 ± 2% of eggs (mean ± SE). Non-chill hatching rates were greater than chilled hatching rates in seven of the 90 populations tested.

CONCLUSIONS

Clearly, the variation in hatching responses to temperature experience is very large and therefore the seasonality of the parasite may vary not only between regions but also at farm level. In contrast to what previous work has suggested, there was a geographical trend towards higher non-chill hatching in the Northern parts of the UK.

Novel understanding of toxicity in a life cycle perspective - The mechanisms that lead to population effect - The case of Ag (nano)materials

Silver (Ag) is amongst the most well studied nanomaterials (NMs), although most studies have only dealt with a single AgNM at a time and one biological endpoint. We here integrate the results of various testing-tools (endpoints) using a terrestrial worm, the standard ecotoxicological model organism Enchytraeus crypticus. Exposure spanned both water and soil exposure, it covered all life stages (cocoons, juveniles and adults), varying exposure durations (1-2-3-4-5-21 days), and covered 5 biological endpoints: hatching success, survival, reproduction, avoidance and gene expression (qPCR target genes GABA and Acetyl cholinesterase). We tested 4 Ag materials: PVP coated (PVP-AgNM), non-coated (NC-AgNM), the JRC reference Ag NM300K and AgNO₃. Results showed that short-term exposure via water to assess impact on cocoons' hatching predicted longer term effects such as survival and reproduction. Moreover, if we extended the exposure from 11 to 17 day this allowed discrimination between hatch delay and impairment. Exposure of juveniles and adults via water showed that juveniles were most sensitive with survival affected. Across materials the following toxic ranking was observed: AgNO₃ ≥ Ag NM300K ≫ NC-AgNM ≥ PVP-AgNM. E. crypticus avoided AgNO₃ in a dose-response manner, avoiding most during the first 24 h. Avoidance of Ag NM300K and NC-AgNM only occurred during the first 24 h and the PVP coated AgNM were not avoided at all. The up-regulation of the GABA triggering anesthetic effects, indicated the high ecological impact of Ag materials in soil: Ag affects the GABAergic system hence organisms were not able to efficiently avoid and became intoxicated, this caused impacts in terms of survival and reproduction.

Eggshell and environmental bacteria contribute to the intestinal microbiota of growing chickens

Background

The initial intestinal microbiota acquired from different sources has profound impacts on animal health and productivity. In modern poultry production practices, the source(s) of the establishing microbes and their overall contribution during development of gastrointestinal tract communities are still unclear. Using fertilized eggs from two independent sources, we assessed the impact of eggshell- and environmental-associated microbial communities on the successional processes and bacterial community structure throughout the intestinal tract of chickens for up to 6 weeks post-hatch.

Results

Culturing and sequencing techniques identified a viable, highly diverse population of anaerobic bacteria on the eggshell. The jejunal, ileal, and cecal microbial communities for the egg-only, environment-only, and conventionally raised birds generally displayed similar successional patterns characterized by increasing community richness and evenness over time, with strains of Enterococcus, Romboutsia, and unclassified Lachnospiraceae abundant for all three input groups in both trials. Bacterial community structures differed significantly based on trial and microbiota input with the exception of the egg-exposed and conventional birds in the jejunum at week 1 and the ileum at week 6. Cecal community structures were different based on trial and microbiota input source, and cecal short-chain fatty acid profiles at week 6 highlighted functional differences as well.

Conclusion

We identified distinct intestinal microbial communities and differing cecal short-chain fatty acid profiles between birds exposed to the microbiota associated with either the eggshell or environment, and those of conventionally hatched birds. Our data suggest the eggshell plays an appreciable role in the development of the chicken intestinal microbiota, especially in the jejunum and ileum where the community structure of the eggshell-only birds was similar to the structure of conventionally hatched birds. Our data identify a complex interplay between the eggshell and environmental microbiota during establishment and succession within the chicken gut. Further studies should explore the ability of eggshell- and environment-derived microbes to shape the dynamics of succession and how these communities can be targeted through interventions to promote gut health and mitigate food-borne pathogen colonization in poultry.

Notch signaling in mouse blastocyst development and hatching

Background

Mammalian early embryo development requires a well-orchestrated interplay of cell signaling pathways. Notch is a major regulatory pathway involved in cell-fate determination in embryonic and adult scenarios. However, the role of Notch in embryonic pre-implantation development is controversial. In particular, Notch role on blastocyst development and hatching remains elusive, and a complete picture of the transcription and expression patterns of Notch components during this time-period is not available.

Results

This study provided a comprehensive view on the dynamics of individual embryo gene transcription and protein expression patterns of Notch components (receptors Notch1–4; ligands Dll1 and Dll4, Jagged1–2; and effectors Hes1–2), and their relationship with transcription of gene markers of pluripotency and differentiation (Sox2, Oct4, Klf4, Cdx2) during mouse blastocyst development and hatching. Transcription of Notch1–2, Jagged1–2 and Hes1 was highly prevalent and dynamic along stages of development, whereas transcription of Notch3–4, Dll4 and Hes2 had a low prevalence among embryos. Transcription levels of Notch1, Notch2, Jagged2 and Hes1 correlated with each other and with those of pluripotency and differentiation genes. Gene transcription was associated to protein expression, except for Jagged2, where high transcription levels in all embryos were not translated into protein. Presence of Notch signaling activity was confirmed through nuclear NICD and Hes1 detection, and downregulation of Hes1 transcription following canonical signaling blockade with DAPT. In vitro embryo culture supplementation with Jagged1 had no effect on embryo developmental kinetics. In contrast, supplementation with Jagged2 abolished Jagged1 transcription, downregulated Cdx2 transcription and inhibited blastocyst hatching. Notch signaling blockade by DAPT downregulated transcription of Sox2, and retarded embryo hatching.

Conclusion

Transcription of Notch genes showed a dynamic pattern along blastocyst development and hatching. Data confirmed Notch signaling activity, and lead to the suggestion that Notch canonical signaling may be operating through Notch1, Notch3, Jagged1 and Hes1. Embryo culture supplementation with Jagged1 and Jagged2 unveiled a possible regulatory effect between Jagged1, Cdx2 and blastocyst hatching. Overall, results indicate that a deregulation in Notch signaling, either by its over or under-activation, affects blastocyst development and hatching.

Effect of heat treatment on pre-stocking of Turkey eggs and its impact on incubation and hatching

Egg stocking is used to meet housing demands in the hatchery industry. Stocking periods longer than 10 days of occur commonly, despite the fact that this practice causes productive losses during the incubation process. To minimize these losses, eggs are heated before incubation to stimulate the embryo, thereby reducing the range of birth intervals. The objective of this study was to determine whether heat treatment (37.5 °C) prior to incubation would improve hatching rates. We also determined the heat-exposure time necessary to improve productivity. We stored 5376 Nicholas pedigree eggs, aged between 40 and 51 weeks, for seven days. These eggs were distributed in three groups: groups 1 and 2 received 4 and 6 h of heat treatment, respectively; group 3 was used as control (no heat treatment, remaining at 17 °C). After heat treatment, the eggs were stored for 7 days at 17 °C, together with eggs from the control group. We found significant variation in the cumulative dispersion of birds born during the hatch window; greater numbers of birds were born in group 1 that underwent the 4-h heat treatment with a 24-h hatch window and in group 3 that underwent the 6-h heat treatment with a 12-h hatch window. Hatch rate, yolk retention and the relationship between average chick weight/average egg weight did not differ between treatments. These data suggest that heat treatment modulates the hatch window; nevertheless, the treatment did not influence the average weight the chicks, the number of chicks born, the percentage of hatching or yolk retention.

Optimization of sterlet (Acipenser ruthenus) egg incubation

Sterlet Acipenser ruthenus was used to assess egg and embryo development when incubated at 17 °C in Petri dishes placed in a hatchery tank (300 L recirculating dechlorinated water) with incubation occurring in a static tabletop system in an air-conditioned laboratory, or in a 700 L Q-cell incubator. Eggs in each dish were placed in a plastic box with 300 mL dechlorinated water. Separated eggs from three individual females were fertilized using pooled sperm from four males with there being four replicates. There were no differences (P > 0.05) in mean percentages of neurulation and embryos undergoing cleavage for eggs incubated in the hatchery tank and with use of the static tabletop system. Furthermore, there were no differences (P >  0.05) in percentage of embryos undergoing cleavage, neurulation and hatching for each female when eggs were incubated using the two systems. Results indicate a Petri dish placed in a small plastic box with 300 mL of dechlorinated water was adequate for incubation of sterlet eggs. Results of the study also indicate that with the static system: 1) eggs should be fertilized from each female to retain individual identity; 2) eggs should be dispersed in Petri dishes to avoid clumping; 3) water should be changed at 24 h, but not at 48 h (neurulation) post-fertilization; and 4) embryos that do not optimally develop should be removed the day after neurulation (72 h of post-fertilization period) and water should be exchanged every day subsequent to the 48 h time-point post-fertilization.

Effect of supplementation with organic and inorganic minerals on the performance, egg and sperm quality and, hatching characteristics of laying breeder hens

This experiment was conducted to evaluate the effects of dietary supplementation with organic micro-minerals on egg production, egg quality, sperm quality and hatching of eggs of laying breeder hens. A total of 144 White Plymouth Rock hens and 36 Red Rhode Island roosters were used. For each treatment, birds were assigned to eight replicates with six hens and 12 replicates with one rooster. Birds were fed a basal diet (BD) containing only inorganic micro-minerals (10 mg Cu, 60 mg Fe, 70 mg Mn, 75 mg Zn and 0.3 mg Se per kg of diet) or a BD +500 g/ton of organic micro-mineral (OMM) product (2.5 mg Cu, 17.5 mg Fe, 20 mg Mn, 27.5 mg Zn and 0.080 mg Se per kg of diet) and BD +800 g/ton of OMM (4 mg Cu, 28 mg Fe, 32 mg Mn, 44 mg Zn and 0.128 mg Se per kg of ration). At 43, 44, 45 and 49 wks, egg production was greater with the BD +800 g OMM treatment than with the BD. Egg quality was not affected as a result of diet. Sperm viability was greater in roosters fed BD +800 g of OMM than those fed the BD. Fertility was greater for eggs from hens fed the BD +500 g OMM compared with BD. In conclusion, addition of organic minerals to the diet resulted in l an increased egg production and viability of rooster spermatozoa and egg fertility were greater with feeding of OMM.

Post-release breeding success of oil-rehabilitated and non-rehabilitated little blue penguins, Eudyptula minor, following the M/V Rena oil spill, New Zealand

During the 2011 M/V Rena oil spill in Tauranga, New Zealand, 383 little blue penguins (LBP, Eudyptula minor) were oiled, rescued and rehabilitated, with 90.6% surviving to be released back to the wild. We monitored the post-release breeding success of rehabilitated LBPs to assess the effectiveness of the rehabilitation process. Breeding success was monitored during the first breeding season post-release (2012-13) to assess productivity for both rehabilitated and control penguins (breeding pairs of rehabilitated or non-oiled (control) birds). Egg laying, hatching and fledging success rates for pairs of rehabilitated and control penguins were both within ranges reported for other LBP colonies in Australia and New Zealand. The only significant difference between rehabilitated and control pairs was that hatching success was reduced in the first season after release for rehabilitated pairs. Overall, rehabilitation appeared to reverse most potential negative effects of oiling on the post-release breeding success of rehabilitated LBP.

Dynamic transcriptome sequencing and analysis during early development in the bighead carp (Hypophthalmichthys nobilis)

BACKGROUND

Early development is a key process of the life history of fish. However, the relationship between the transcriptome and the dynamic regulation of early development is still uncharacterized in the bighead carp (Hypophthalmichthys nobilis). In the present study, we performed transcriptome analysis of six development stages in H. nobilis, aiming to understand the dynamic molecular regulation of early development in this fish.

RESULTS

A total of 76,573 unigenes were assembled from clean sequence reads, with an average length of 1768 base. Among which, 41,742 (54.54%) unigenes were annotated to public protein databases, and an additional 59,014 simple sequence repeat (SSR) loci were identified among the unigenes. Furthermore, 30,199 differentially expressed transcripts (DETs) (fold change > 4 or < 0.25, and the false discovery rate FDR < 0.01) were observed in comparisons between the adjacent developmental stages, and nine expression patterns (profiles) were simulated using series-cluster analysis across six developmental stages. The unigenes expression level markedly increased after the DS1 stage (early blastula), and the numbers of DETs gradually decreased during subsequent development. The largest transcriptomic change (up- or down-regulated) was detected during the period from DS1 to DS2 (6-somite stage), which was enriched for many biological processes and metabolic pathways related to maternal to zygotic transition (MZT). Distinctly protein-protein interaction (PPI) networks were plotted for DETs during the period from DS1 to DS2. The genes (or proteins) from the same pathways were integrated together, and showed with obvious co-regulation patterns. In the series-cluster analysis, a remarkable profile of gene expression (profile_48) was identified that is probably related to the hatching during H. nobilis development, and the strict co-expression of a hatching enzyme gene (hce1) with 33 other annotated genes was identified from this profile.

CONCLUSIONS

The results indicated that strict dynamic regulation occurs during the early development in H. nobilis, especially in embryogenesis before hatching. This study provides valuable new information and transcriptomic resources related to H. nobilis early development, and for certain events such as MZT and hatching.

Developmental differences between two marine turtle species and potential consequences for their survival at hatching

Anatomical variation is a major source for natural selection. Marine turtles are endangered and survival predictions are of important biological, ecological, social, and political value. Here, we perform a preliminary study illustrating how comparative embryology permits understanding of ontogenetic variation as a contributor for evolutionary fitness. To that end, we studied samples of Chelonia mydas and Caretta caretta embryos relative to a standardized staging system from the literature. We examined external anatomy using discrete characters in order to document interspecific variation during development of these species. We employed the 'Standard Event System to Study Vertebrate Embryos' to examine fitness-relevant structures. These include the limb paddles and elbows of Ch. mydas, which differentiate relatively late in ontogeny. We detected interspecific variation in the timing of trait differentiation - such as the egg tooth, closure of skull vault, carapace formation, and scale covering - and propose that these differences might be functionally and ecologically relevant for marine turtles.

Adaptation to temperate climates: Evidence of photoperiod-induced embryonic dormancy in Aedes aegypti in South America

Dormancy is a developmental arrest in arthropods, in response to unfavorable conditions in temporally varying environments. In Aedes aegypti, the supposed inability of eggs to inhibit hatching has been used to explain the restriction of this species to tropical and subtropical regions. However, the geographic range of Ae. aegypti is constantly expanding towards temperate regions. Thus, the aim of the present study was to assess the ability of Ae. aegypti individuals from a temperate region (Buenos Aires City, Argentina) to enter photoperiod induced dormancy. To this end, we exposed both the parental generation and the eggs to short-day (SD: 10L:14D) and long-day (LD: 14L:10D) photoperiods, and studied the temporal variation in egg hatching. The experiment consisted of 28 treatment combinations of three factors: parental photoperiod (SD or LD), egg storage photoperiod (SD or LD), and age of eggs (14, 28, 42, 56, 70, 91, and 112 days). The results showed a lower hatching response with the SD parental photoperiod, and a trend to higher hatching with longer egg storage time in all photoperiod treatment combinations. The egg storage photoperiod showed no effect on egg hatching. In both parental photoperiod treatments, egg replicates of most ages from different females showed a large variability, with some replicates with lowest hatching response and others with highest hatching response. Our results show the ability of Ae. aegypti to inhibit egg hatching in response to a short-day photoperiod, which could allow the further expansion of this species to regions with colder winters.

Failure of complete hatching of ICSI-derived human blastocyst by cell herniation via small slit and insufficient expansion despite ongoing cell proliferation

PURPOSE

To assess the effect of intracytoplasmic sperm injection (ICSI) on embryo hatching and visualise the effects of zona thinning (ZT) on the embryo using time-lapse monitoring.

METHODS

In vitro fertilisation (IVF) (n = 178) and ICSI (n = 110)-derived cryopreserved blastocysts were donated by patients who previously had a baby. This study investigated the impacts of IVF, ICSI, laser-assisted hatching by ZT and formation of ICSI penetration trace on zona pellucida of IVF-derived blastocyst on blastcyst diameter, the estimated number of trophectoderm (TE) cells and completed hatching rate.

RESULTS

The completed hatching rate and diameters of the completely hatched blastocysts at hatching commencement and at the maximum expansion were significantly greater in the IVF than in ICSI groups. The completed hatching rate significantly increased with ZT in both groups. The maximum diameters of the completely hatched blastocysts were significantly smaller in the ZT than in non-ZT groups. The estimated TE cell numbers increased from hatching commencement to their maximum expansion points. The incompletely hatched ICSI-derived blastocysts intermittently herniated cells via small slits until degeneration. The completed hatching rate significantly decreased by the formation of ICSI penetration trace on zona pellucida of IVF-derived blastocyst.

CONCLUSION

ICSI-derived blastocysts intermittently release proliferating cells and extracted TE cells and/or inner cell masses via a small slit; thus, blastocyst expansion is not sufficiently increased, leading to a reduced complete hatching rate. Therefore, the ICSI penetration trace potentially has negative effects on blastocyst expansion process in vitro and is a risk factor for the failure of completed hatching.

Chemically induced plasticity in early life history of Palaemon argentinus: are chemical alarm cues conserved within palaemonid shrimps?

Most aquatic animals use infochemicals from both conspecifics and heterospecifics to assess local predation risks and enhance predator detection. Released substances from injured conspecifics and other species (chemical alarm cues) are reliable cues to indicate an imminent danger in a specific habitat and often mediate the development of inducible defenses. Amphibian and fish embryos have been shown to acquire this information while at the embryonic stage of development, in relation to the developing nervous system and sensory development. With the exception of Daphnia, there is no information on chemically mediated responses to alarm cues in embryos of any crustacean groups. Therefore, we tested whether embryo exposure to chemical cues simulating predation on conspecifics or heterospecifics (closely related, non-coexisting species), or a mixture of both, alters embryonic developmental time, size and morphology of the first larval instar in Palaemon argentinus (Crustacea: Decapoda). Embryonic exposure to chemical alarm cues from conspecifics shortened the embryonic developmental time and elicited larger larvae with a longer rostrum. Rostrum length of the first larval instar changed independently of their size, thus elongated rostra can be considered a defensive feature. Embryonic developmental time was not altered by chemical alarm cues from either heterospecifics or the mixed cues treatment; however, exposure to these cues resulted in larger larvae compared with the control group. Chemically induced morphological plasticity in larvae in response to alarm cues from con- and heterospecifics suggests that such cues are conserved in palaemonids shrimps, providing embryos with an innate recognition of heterospecific alarm cues as predicted by the phylogenetic relatedness hypothesis.

Enabling Hamster Embryo Culture System: Development of Preimplantation Embryos

Development of preimplantation embryos, from fertilization to hatched-blastocyst stage, has been a challenging task, regardless of the mammalian species being studied. While the mouse model has been versatile for studying in vitro development of early embryos, other rodent species are important to gain insights into comparative early embryogenesis. The golden hamster (Mesocricetus auratus) offers unique advantages to study cellular and molecular regulation of gamete maturation, fertilization and preimplantation development, including the phenomenon of blastocyst hatching. Achieving in vitro fertilization and first cleavage division is relatively easy; however, subsequent development past the two-/four-cell stage had been difficult in hamsters. Pioneering research, carried out over three decades has markedly enabled successful in vitro development of one-cell embryos to blastocysts. This article provides a comprehensive perspective (historical and current) on the embryo culture systems and details an optimized culture protocols to achieve normal and viable development of preimplantation embryos in the golden hamster.

Effects of aluminium and cadmium on hatching and swimming ability in developing zebrafish

Aluminium and cadmium are biologically non-essential metals with a role in neurodegenerative and neuromuscular diseases. As an attractive model for neurobehavioural studies, zebrafish at 6 h post fertilization were exposed to 9, 18, 36 and 72 μM CdCl₂ and 50, 100 and 200 μM AlCl₃, respectively, for 72 h, and motility such as distance moved, mean velocity, cumulative movement, meander and heading were measured by DanioVision equipment. The hatching time was also analysed. A delay in the exit from the chorion was observed in all treated larvae with respect to the controls. CdCl₂ acted on the exit from the chorion of larvae with a dose-dependent delay. By contrast, the delay caused by AlCl₃ was greater at low concentrations. A dose-dependent reduction in swimming performance was observed in the larvae exposed to CdCl₂. Instead, for those exposed to AlCl₃, swimming performance improved at higher concentrations although values were in general lower than those of control. All the parameters had a similar trend except the meander parameter which showed a dose-dependent reduction. These data show that cadmium and aluminium can delay hatching and alter swimming ability in the early developmental stages of zebrafish, albeit with different effects, suggesting that exposure to sublethal concentrations of both metals can change behavioural parameters.

Growth potential of bovine embryos presenting abnormal cleavage observed through time lapse cinematography

Time-lapse monitoring (TLM) has emerged as a novel technology for the continuous and noninvasive evaluation of embryos. TLM has revealed the prevalence of specific dysmorphisms such as abnormal development during the early-cleavage stage of embryos. However, little information is available on the prevalence and consequences of abnormal cleavage in bovine embryos. Hence, this study aimed to investigate growth potential of bovine embryos presenting abnormal cleavage, such as reverse cleavage (RC), direct cleavage (DC), and irregular and unsmooth ruffling of the oolema membrane (ruffling). Bovine embryos derived through in vitro fertilization (IVF) were cultured in the microwell culture dishes, and the kinetics of in vitro development were observed through TLM at 20-min intervals for 10 d. Approximately 36% of embryos that developed into a blastocyst presented abnormal cleavage. Morphokinetic evaluations revealed that RC, DC, and ruffling embryos showed slower development compared to embryos with normal cleavage (P < 0.01). Embryos with RC and DC, but not ruffling, revealed impaired hatchability (P < 0.05) with increased collapses of the blastocyst cavity until hatching (P < 0.0001). Moreover, the RC and DC embryos presented increased chromosomal aneuploidy (P < 0.05). These results suggest a compromised viability of embryos with RC and DC. This is the first report that clarified the effect of abnormal cleavage on the morphokinetics and growth potential of bovine IVF embryos. Results indicate that the kinetic evaluation of bovine embryos using the time-lapse imaging system will be beneficial for selecting embryos with a high viability.

Differential toxicity of functionalized polystyrene microplastics to clams (Meretrix meretrix) at three key development stages of life history

Little knowledge is available on impact of microplastics (MPs) on the bivalve larvae at different developmental stages throughout their life history, especially for metamorphic stage. Therefore, this study aims to evaluate the toxic responses of carboxylated (PS-COOH) and amino (PS-NH₂) polystyrene MPs on the developing clam larvae at three key life stages, i.e., fertilized eggs, D-veliger larvae, and umbo larvae. PS-COOH and PS-NH₂ significantly decreased the hatching rates by 5.79-39.5% and developmental rates by 4.78-7.86% of the clam larvae relative to the unexposed clam larvae. The toxicity of MPs followed the order: hatching stage > metamorphosis > D-veliger larvae stage, showing stage-dependent toxic effects. Moreover, PS-NH₂ with a smaller hydrodynamic diameter showed a greater toxicity to the developing larvae compared to PS-COOH. Our study highlighted the stage-dependent toxic effects of MPs on the developing clam larvae, thus posing ecological risks to population succession of marine bivalves and aquatic ecosystems.

First report of the occurrence and different types of conjoined twins in common whitefish Coregonus maraena larvae originating from the Baltic Sea

This paper describes for the first time various forms of conjoined twins in the common whitefish Coregonus maraena originating from the brackish waters of the Baltic Sea. The occurrence of conjoined twins was observed during the hatching of whitefish under controlled conditions. Two types of twins were identified: symmetric (parapagus) and asymmetric (parasitic form). The percentage of conjoined twins among the whitefish did not exceed 0.01% of the hatched larvae. The forms of twins observed in this study were similar to conjoined twins occurring among humans. One main type, parapagus, was identified in the group of symmetric twins with 3 subtypes: diprosopus parapagus, dicephalic parapagus and dithoracic parapagus. In its parasitic form, the parasitic twin occurred as a 'cyclops' or just as an eye growing out of the other twin's head. We conclude that fish, as well as their fertilised eggs, can be used as a model system to observe how such twins are joined in humans because of the similarity with conjoined twins occurring in humans. Because of internal fertilisation in fish, as well as the size and transparency of egg cells in these animals, it is possible to observe the process of fertilisation, cell division and formation of an embryo and subsequently of twins, as a model for humans.

Effects on fertility of motile sperm to egg ratio with use of cryopreserved Rhamdia quelen semen at different post-activation times

The aim in the present study was to evaluate the effects of motile sperm:oocyte ratio and the use of thawed spermatozoa at different post-activation times in artificial reproduction of gray catfish (Rhamdia quelen). Cryopreserved sperm samples were evaluated for sperm motility and velocity using Computer Assisted Sperm Analysis (CASA). The sperm activation curves were generated using a non-linear statistical model and were used to assess the spermatozoa velocity after thawing. Thus, the oocytes were mixed with thawed sperm at a motile sperm:oocyte ratio of 70,000, 90,000, 110,000, 130,000, 150,000 and 170,000. The thawed sperm were used at 11, 16 and 30 s after spermatozoa activation. At these times, the sperm velocities corresponded to 52, 37 and 21 μm/s. The effects of experimental factors (spermatozoa:oocyte ratio and time after sperm activation) on oocyte fertilization, egg hatching, and percentage of normal larvae were evaluated. The response surface analysis indicated there was no interaction (P >  0.05) between the motile spermatozoa:oocyte ratio and time after sperm activation on fertilization, hatching or percentage of normal larvae. The time after sperm activation, however, affected (P <  0.05) in a directly proportional waythe oocyte fertilization and egg hatching rates. The time after sperm activation affected the sperm velocity and oocyte fertilization and egg hatching rates. Thus, the use of thawed sperm immediately after sperm activation or with the greatest sperm velocities (11s; 52 μm/s; 62.59% motility) at a relatively lesser motile sperm:oocyte ratio (70,000:1) allows for acceptable fertilization (48.68% for fertilization; 29.61% for hatching) in Rhamdia quelen.

Toxicity of TiO2, SiO2, ZnO, CuO, Au and Ag engineered nanoparticles on hatching and early nauplii of Artemia sp

The potential of environmental release enhances with increased commercial applications of the nanomaterials. In this work, a simple and efficient test to estimate the acute toxicity of nanoparticles is carried out on Artemia species and their hatching rates. We have tested six different engineered nanoparticles (silver, gold, copper oxide, zinc oxide, TiO₂ and SiO₂ nanoparticles) and three soluble salts (CuSO₄, ZnSO₄ and AgNO₃) on Artemia sp. The physicochemical properties of the nanoparticles involved in this study were analyzed in normal water and marine water. Hydrated and bleached Artemia cysts were allowed to hatch in continuously aerated, filtered sterile salt water containing nanoparticles; hatching of viable nauplii and total hatchlings have been recorded. In parallel, standard Artemia toxicity test was conducted on the nauplii monitoring the viability. In hatching experiments, a reduction in hatching rate was observed along with mortality of newly hatched nauplii. The results of the hatching experiment and of the standard Artemia test showed a good correlation. The toxicity of the nanoparticles was compared and the order of toxicity was estimated as Ag>CuO>ZnO>Au>TiO₂>SiO₂. The study thus suggests that the hatching test itself is a reliable assay for determining the toxicity of nanomaterials.

Effects of the fungicide ortho-phenylphenol (OPP) on the early development of sea urchin eggs

In this study, we assessed the impact of imidazole fungicide ortho-phenylphenol (OPP) on the early development of a marine invertebrate, the sea urchin, a marine bioindicator. Fungicides are widely used and have been reported to accumulate not only in farm soil but also in freshwater and seawater sediments. Therefore, it is essential to clarify the effects of OPP on marine environments. Toxicity was estimated as the inhibition ratio of the 120 min-embryo and/or the 24 h-embryo development. The addition of OPP to embryos of the two sea urchin species, Scaphechinus mirabilis (S. mirabilis) and Strongylocentrotus nudus (S. nudus), at 0.1 mM or higher, resulted in acute toxicity (cell death). The IC₅₀ value of the 120 min-embryos or the 24 h-embryos for S. mirabilis and S. nudus with OPP was around 0.06 mM, indicating that fertilized eggs and embryos of the sea urchin are more sensitive to OPP than higher vertebrates. In addition, in the presence of OPP (0.005-0.05 mM), the proportion (%) of the gastrula keeping the fertilization membrane increased, suggesting that OPP (0.005-0.05 mM) inhibited the hatching process, possibly by affecting the hatching enzyme activity.

When and where to hatch? Red-eyed treefrog embryos use light cues in two contexts

Hatching timing is under strong selection and environmentally cued in many species. Embryos use multiple sensory modalities to inform hatching timing and many have spontaneous hatching patterns adaptively synchronized to natural cycles. Embryos can also adaptively shift their hatching timing in response to environmental cues indicating immediate threats or opportunities. Such cued shifts in hatching are widespread among amphibians; however, we know little about what, if anything, regulates their spontaneous hatching. Moreover, in addition to selection on hatching timing, embryos may experience benefits or suffer costs due to the spatial orientation of hatching. Amphibian eggs generally lack internal constraints on hatching direction but embryos might, nonetheless, use external cues to inform hatching orientation. The terrestrial embryos of red-eyed treefrogs, Agalychnis callidryas, hatch rapidly and prematurely in response to vibrational cues in egg-predator attacks and hypoxia if flooded. Here we examined A. callidryas’ use of light cues in hatching timing and orientation. To assess patterns of spontaneous hatching and the role of light cues in their diel timing, we recorded hatching times for siblings distributed across three light environments: continuous light, continuous dark, and a 12L:12D photoperiod. Under a natural photoperiod, embryos showed a clear diel pattern of synchronous hatching shortly after nightfall. Hatching was desynchronized in both continuous light and continuous darkness. It was also delayed by continuous light, but not accelerated by continuous dark, suggesting the onset of dark serves as a hatching cue. We examined hatching orientation and light as a potential directional cue for flooded embryos. Embryos flooded in their clutches almost always hatched toward open water, whereas individual eggs flooded in glass cups often failed to do so, suggesting the natural context provides a directional cue. To test if flooded embryos orient hatching toward light, we placed individual eggs in tubes with one end illuminated and the other dark, then flooded them and recorded hatching direction. Most embryos hatched toward the light, suggesting they use light as a directional cue. Our results support that A. callidryas embryos use light cues to inform both when and where to hatch. Both the spatial orientation of hatching and the timing of spontaneous hatching may affect fitness and be informed by cues in a broader range of species than is currently appreciated.

Copper inhibits hatching of fish embryos via inducing reactive oxygen species and down-regulating Wnt signaling

The copper ion (Cu²⁺) has been reported to suppress the hatching of fish. However, little is known about the underlying mechanism. In this study, copper nanoparticles (CuNPs) and Cu²⁺ were shown to significantly suppress hatching of zebrafish in a dosage-dependent manner, and reactive oxygen species (ROS) scavengers NAC (N-acetylcysteine) & GSH (reduced glutathione) and Wnt signaling agonist BIO (6-bromoindirubin-3'-oxime) significantly alleviated the suppressing effects of Cu²⁺ and CuNPs on egg hatching. Mechanistically, NAC, GSH, and BIO recovered the egg hatching in copper-treated group via increasing the embryonic motility rather than stimulating the expression and secretion of hatching enzymes before hatching. Additionally, no significant difference in egg hatching was observed between the control and Cu²⁺-treated group at 72 hpf (hours post fertilization) in cox17 mutant embryos, in which little ROS was producd after copper stimulation. This may be the first report that Cu²⁺ and CuNPs suppress embryonic motility and the subsequent hatching via inducing ROS and at the same time down-regulating Wnt signaling in fish embryos.