Course Of Embryogenesis Research Articles

Early Ontogeny of Cichlids Using Selected Species as Examples.

The purpose of this study was to characterize in detail the reproductive strategy, course of embryogenesis, and development of larvae in three species of fishes of the genus Cichlasoma: the green terror (Andinoacara rivulatus), the red discus (Symphysodon discus), and the jaguar cichlid (Parachromis managuensis). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. The developing eggs were observed under a microscope (Carl Zeiss Stereo Discovery. V12 and Nikon 2000SE software (NIS-Elements F 4.30.01 64-bit) from fertilization to larval hatching until complete yolk-sac resorption. The largest average number of eggs per female was found in the jaguar cichlid (x¯ = 2991 eggs), a smaller average number of eggs was shown in the green terror (x¯ = 922 eggs), and the red discus showed the smallest average number of eggs (x¯ = 300 eggs). There were significant differences in the sizes of the eggs of the studied species: jaguar cichlid eggs were the smallest (1.060 ± 0.05 mm3), red discus eggs were larger (1.070 ± 0.07 mm3), and green terror eggs were the largest (1.365 ± 0.16 mm3). The embryogenesis time in the red discus was 2132 °H (82 Hpf), in the green terror it was 2158 °H (83 Hpf), and the longest in the jaguar cichlid was 2470 °H (87 Hpf). At the end of embryogenesis, the average size of the larvae after hatching was measured (red discus x¯ = 4.346 mm, green terror x¯ = 5.203 mm, and jaguar cichlid x¯ = 5.301 mm) and the time of yolk-sac resorption from the moment of hatching to the transition from endogenous to exogenous feeding was determined (jaguar cichlid 5 days, green terror 6 days, and red discus 3 days). The results of this study may contribute to the development of reproductive biotechnology for the studied fishes that could be used in aquaculture and, thus, help protect them in their natural habitats.

О сроках сохранения фертильности икры и эмбриональном развитии минтая Gadus chalcogrammus (Gadidae) северной части Охотского моря

Experimental work was carried out to find out the timing of the fertility preservation for eggs remaining in the body cavity of the North Sea Alaska Pollock females after spawning, as well as the possibility of their normal course of embryogenesis. It was established that eggs remaining after spawning in the pollock female body cavity are not resorbed simultaneously. 2 months after mass spawning, 2.7 % of them still retain fertility, and, with artificial insemination, they are characterized by high survival, suffering no violations during embryogenesis. Data on the embryonic development of the species, the timing of the steps and main stages of embryogenesis, and the amount of heat required to achieve them are given. It is shown that pollock eggs and pre-larvae from residual fertility are significantly smaller in metric parameters than those from natural spawning, but morphologically are identical to them. Regional features of morphometric indicators for eggs and newly hatched pollock larvae in the northern part of the Sea of Okhotsk were revealed.

The influence of the water-salt extract of the medicinal leech Hirudo verbana Carena, 1820 on the general course of embryogenesis in rats after intraperitoneal administration

Background. The increase in infectious and non-infectious diseases occurrence during pregnancy prompts scientists to search for substances that can fight these ailments. This especially applies to natural substances that have virtually no side effects. These include substances obtained from medicinal leeches. These substances have a wide range of therapeutic effects; as to their practical use, all preclinical studies must be completed. This particularly refers to the presence of an embryotoxic effect. The aim of this work was to investigate the effect of the water-salt extract of the medicinal leech Hirudo verbana Carena, 1820 on the general course of embryogenesis in rats when administered intraperitoneally. Materials and Methods. The work was performed on female non-linear white rats. Two experimental groups of animals were injected intraperitoneally with a water-salt extract of the medicinal leech at a concentration of 5 μg/g of the animal, in a volume of 0.5 mL, three times before mating and three times during pregnancy every 3 days. Two control groups were injected intraperitoneally with physiological saline according to the same scheme as the experimental groups. Subsequently, one of the control and experimental groups underwent euthanasia, dissection of the abdominal cavity and uterine horns on the 20th day of pregnancy. We analyzed the total number of corpora lutea of pregnancy, the number of live and dead fetuses. Fetuses were weighed, examined for the presence of skin hematomas, mutilations, and external abnormalities in the develop­ment of internal organs. The other two groups of control and experimental animals were left until the offspring were born. Then the females of both groups were weighed, and their general condition was assessed. Newborn rats were examined, weight and body length were determined, mortality was recorded from the beginning of birth to 15 days, the presence of skin hematomas, mutilations, and external anomalies of the development of internal organs were checked. Results and discussion. The study established that the intraperitoneal injection of a water-salt extract of a medicinal leech before and during pregnancy in female rats does not cause any toxic effect during embryogenesis and at the early stages of post-embryonic ontogenesis. During the external examination of fetuses and offspring in both groups, no developmental anomalies were noted, all organs in both groups were of normal topography and size. The number of subcutaneous hematomas in the experimental group of fetuses compared to the control group decreased by an average of 50%, postnatal mortality decreased by an average of more than 3 times, as well as an increase in body weight in females, an increase in body weight and body length in the fetus and offspring in the early post-embryonic period ontogenesis (p <0.05). Conclusion. Intraperitoneal administration of a therapeutic dose of a water-salt extract of the medicinal leech to female rats before and during pregnancy, after every three days, does not have any toxic effect on the course of embryogenesis and later in early post-embryonic ontogenesis.

Comparative analysis of the composition of sterols in embryogenic and nonembryogenic cell lines of <i>Larix sibirica</i> Ledeb.

The cell lines of Siberian larch (Larix sibirica Ledeb.), possessing different embryogenic potential, were studied. Qualitative and quantitative content of sterol components was comparatively analyzed in their tissues with the help of gas chromatography-mass spectrometry. Significant differences in these parameters were found between both groups of the lines in fractions of free sterols and their esters. In addition to sterol compounds, squalen, which is a triterpenic intermediate in sterol biosynthesis, was revealed. Of free sterols, -sitosterol, campesterol, isofucosterol, and stigmasterol dominated in the embryogenic lines, while -sitosterol, campesterol, and stigmasterol in nonembryogenic ones. The campesterol concentration was 1.31.9 times higher in the embryogenic than nonembryogenic lines. Since campesterol is a precursor of brassinosteroids, it is likely that its level is high due to an embryogenic state of these cell lines. Only the embryogenic lines contained appreciable amounts of isofucosterol. The fraction of sterol esters exhibited wider component diversity in the nonembryogenic than the embryogenic lines. In all the cell lines, among the identified sterol esters, the substances without double bonds, bearing, as a structural fragment, a sterane coreperhydrocyclopenta[a]phenanthrenewere the most abundant. Their content ranged from 52 to 71% of the total amount of sterol esters. The revealed differences in the compositions of sterols and their esters, between the L. sibirica cell lines with different embryogenic potential, witness to the considerable rearrangements in sterol metabolism in the course of embryogenesis. The line-specific differences may indicate the involvement of these metabolites in formation of embryos.

P-797 Benefit of Replicating Mammalian Gametes

Abstract Study question Can haploid parthenogenetic and androgenetic embryos generate haploid embryonic stem cells (haESCs) and function as respective oocytes and spermatozoa? Summary answer Haploid embryos generated blastocysts capable of yielding haESCs. Haploid blastomeres of both sexes served as multiple copies of gamete substitutes. What is known already Although creating diploid digyneic or dispermic embryos through nuclear transfer is possible, the conceptuses rarely achieve normal preimplantation development due to unbalanced epigenomes, demonstrating the requirement of both parental epigenomes in the course of embryogenesis. Haploid parthenogenetic embryos can be achieved by inducing calcium oscillations of a metaphase II oocyte, while the paternal counterpart can be generated through the insemination of enucleated oocytes. These embryos may serve to generate haESCs for heterozygosity identification and can be used for reproductive purposes in animal models. Study design, size, duration To generate parthenogenetic embryos, metaphase II oocytes from B6D2F1 mice were artificially activated. Androgenetic embryos were generated from the insemination of enucleated oocytes. Haploid embryos were cultured to blastocysts and seeded on feeder cells (MEF) to derive haESCs. Haploid blastomeres from 8-cell embryos of either sex were isolated and used as artificial gametes; artificial oocytes were generated by grafting a parthenogenetic blastomere to an enucleated recipient oocyte. Androgenetic blastomeres were used as male gametes. Participants/materials, setting, methods Parthenogenetic embryos were generated by exposing metaphase II oocytes to calcium ionophore. Another cohort of B6D2F1 oocytes were enucleated and underwent piezo-ICSI to generate androgenetic embryos. Sendai-virus–mediated nuclear transfer was performed using parthenogenetic blastomeres as donor nucleuses to generate artificial oocytes and subsequently fertilized. Androgenetic blastomeres were used as sperm substitutes by fusion with an intact oocyte to generate zygotes. Control embryos were generated by piezo-actuated ICSI. Developmental characteristics were recorded by time-lapse microscopy. Main results and the role of chance A total of 129 oocytes were parthenogenetically activated by calcium ionophore, and 119 developed a female pronucleus. Androgenetic embryos were generated from the insemination of 375 ooplasts; 317 developed a male pronucleus. The monopronuclear appearance of haploid embryos of both sexes was comparable to the fertilization of control at 90.7%. Haploid embryo development for both sexes up to the 4-cell stage matched the control. However, from the 8-cell stage onward, parthenogenetic and androgenetic embryos cleaved at a lower rate compared to the control at 76.4%, 59.3% and 92.7% (P < 0.0001), respectively. The haploid genome affected the rate of compaction at 73.6%, 55.3%, and 89.2% (P<0.0001), respectively, and the rate of blastulation at 27.8%, 11.2%, and 80.8% (P<0.00001) respectively. Androgenetic embryos showed delayed cleavage from the 4-cell stage onward, while the parthenogenetic counterparts had similar morphokinetics to the control. A total of 20 parthenogenetic and 18 androgenetic blastocysts were plated on MEF, yielding 5 parthenogenetic and 3 androgenetic haESC lines. Both haESCs yielded beating cardiomyocytes on day 10 of differentiation while maintaining haploidy. The utilization of haploid pseudo blastomeres as gametes yielded 93 reconstructed biparental embryos that resulted in 71 blastocysts (76.3%). Time-lapse morphokinetics were comparable to the control. Limitations, reasons for caution Haploid embryos developed to blastocysts at a remarkably lower rate than the control, particularly the androgenotes; however, they can yield pluripotent haESCs capable of differentiation in the mesoderm and subsequent cardiogenesis prone to self-diploidization. Once this system is replicated in humans, the role of the centrosome needs to be investigated. Wider implications of the findings Our study has demonstrated the feasibility of propagating both male and female genomes from single gametes for reproductive applications. Indeed, once a stable culture of haESCs is achieved, genotyped pluripotent haESCs can be used to help identify heterozygosity for inherited disorders. Trial registration number N/A

Хронічний вплив хлориду кадмію на ембріогенез щурів при ізольованому та комбінованому з сукцинатами цинку та міді внутрішньошлунковому введенні в експерименті

The purpose of the study was to determine the degree of embryotoxicity of cadmium chloride at a dose of 2.0 mg/kg in isolated intragastric administration and to search for possible bioantagonists among zinc and copper succinates in combination with cadmium chloride in a chronic experiment in pregnant female rats. Materials and methods. The study was conducted on 64 pregnant female Wistar rats, which were distributed as follows: the first group – control; the second group – the isolated introduction of a solution of cadmium chloride at a dose of 2.0 mg/kg; the third group – the combined introduction of a solution of cadmium chloride at a dose of 2.0 mg/kg and zinc succinate at a dose of 5 mg/kg; the fourth group – the combined introduction of a solution of cadmium chloride at a dose of 2.0 mg/kg and copper succinate at a dose of 0.1 mg/kg. The possible negative effect of the studied substances on embryonic development was determined by the ability to increase the level of all types of embryonic mortality. Results and discussion. The calculation of the obtained results showed that the isolated chronic administration of cadmium chloride at a dose of 2.0 mg/kg has a pronounced embryotoxic effect on the number of embryos, total embryonic mortality, preimplantation and postimplantation embryonic mortality on the 13th and 19th day of embryogenesis in the experiment on rats. Cadmium and its compounds are one of the first eco-pollutants. The problem of embryotoxicity and fetotoxicity of microelements is of great practical importance, because a significant number of women work in industry and in hazardous production conditions and are often exposed to heavy metals, which is very dangerous for the fetus and offspring. Aspects of chronic influence on the course of embryogenesis of cadmium salts with microelements, which have bioanatagonistic properties in relation to the toxicity of heavy metals, have been little studied. Thus, an important area of morphological experimental research is the search for new possible bioantagonists of cadmium toxicity among trace elements that can affect dyslementosis, maintaining homeostasis, including during pregnancy. Conclusion. According to all criteria of embryotoxicity, isolated administration of cadmium has a pronounced embryotoxic effect, which is expressed in reducing the number of embryos in the manure and increasing all types of embryonic mortality. Combined administration of zinc or copper succinates with cadmium chloride has a modifying effect on the embryotoxicity of cadmium chloride in terms of basic embryotoxicity, and succinates themselves can be considered as potential bioantagonists of cadmium in chronic exposure in the experiment on rats

Cleavage of Early Mouse Embryo with Damaged DNA.

The preimplantation period of embryogenesis is crucial during mammalian ontogenesis. During this period, the mitotic cycles are initiated, the embryonic genome is activated, and the primary differentiation of embryonic cells occurs. All cellular abnormalities occurring in this period are the primary cause of fetal developmental disorders. DNA damage is a serious cause of developmental failure. In the context of DNA damage response on the cellular level, we analyzed the course of embryogenesis and phenotypic changes during the cleavage of a preimplantation embryo. Our results document that DNA damage induced before the resumption of DNA synthesis in a zygote can significantly affect the preimplantation development of the embryo. This developmental ability is related to the level of the DNA damage. We showed that one-cell embryos can correct the first cleavage cycle despite low DNA damage and incomplete replication. It seems that the phenomenon creates a predisposition to a segregation disorder of condensed chromatin that results in the formation of micronuclei in the developmental stages following the first cleavage. We conclude that zygote tolerates a certain degree of DNA damage and considers its priority to complete the first cleavage stage and continue embryogenesis as far as possible.

The Effect of an Anthropogenic Magnetic Field on the Early Developmental Stages of Fishes—A Review

The number of sources of anthropogenic magnetic and electromagnetic fields generated by various underwater facilities, industrial equipment, and transferring devices in aquatic environment is increasing. These have an effect on an array of fish life processes, but especially the early developmental stages. The magnitude of these effects depends on field strength and time of exposure and is species-specific. We review studies on the effect of magnetic fields on the course of embryogenesis, with special reference to survival, the size of the embryos, embryonic motor function, changes in pigment cells, respiration hatching, and directional reactions. We also describe the effect of magnetic fields on sperm motility and egg activation. Magnetic fields can exert positive effects, as in the case of the considerable extension of sperm capability of activation, or have a negative influence in the form of a disturbance in heart rate or developmental instability in inner ear organs.

Effects of broiler breeder strain, age, and eggs preheating profile in single-stage systems on the hatchability of eggs and quality of chicks

Preheating can increase the efficiency of commercial broiler breeding. A slow increase in temperature can counteract the negative effects of water condensation on the surface of the shell and reduces the thermal shock to the embryos. It is essential to design different preheating profiles because of the variances between breeds in terms of egg construction and the course of embryogenesis, along with the influence of the parental flocks' age on hatching rates. This study aimed to analyze six preheating profiles with different time and temperature patterns (A–F), which were immediately applied before the egg incubation began. These profiles were used for two broiler breeder strains – Hubbard Flex and Ross 308 – for the entire laying cycle divided into six age ranges: 25–30, 31–36, 37–42, 43–48, 49–54, and 55–60wk of life. A total of 7839250 Hubbard Flex and 57167060 Ross 308 eggs were used in the study. The eggs were stored for 4–7d before the preheating profile was applied. Mortality during incubation, hatchability, and the quality of chicks were analyzed. The most favorable results were obtained with profile B – 02 h (25.0 °C):02 h (29.4 °C):02 h (32.2 °C):02 h (35.0 °C):02 h (37.8 °C), while the worst results were obtained with profile C – 03 h (23.9 °C):03 h (25.0 °C):04 h (32.2 °C). These findings indicated that compared to a rapid temperature increase during incubation, multistage slow heating of eggs is more advantageous as it enables achieving better hatchability from apparent fertile eggs and obtaining more first-grade chicks. An analysis of the interaction of different preheating profiles with flock age and breed of parental flock revealed that profile C is not suitable for eggs from older flocks, in particular Ross 308. Deterioration of hatchability of chicks from apparent fertile eggs was also confirmed for flocks over 49wk of life after the application of profile E – 03 h (77 °C):02 h (29.4 °C):02 h (32.2 °C):01 h (35.0 °C):02 h (37.8 °C). Increased early and late mortality of embryos was observed in the case of Hubbard Flex after the use of profile D – 03 h (25.0 °C):02 h (29.4 °C):01 h (32.2 °C):02 h (35.05 °C):02 h (37.8 °C). Based on the obtained results, it can be recommended that profile B can be applied for the entire duration of Ross 308 and Hubbard Flex flock utilization to achieve high egg hatchability and obtain high-quality chicks.

Lineage-Resolved Enhancer and Promoter Usage during a Time Course of Embryogenesis.

Enhancers are essential drivers of cell states, yet the relationship between accessibility, regulatory activity, and invivo lineage commitment during embryogenesis remains poorly understood. Here, we measure chromatin accessibility in isolated neural and mesodermal lineages across a time course of Drosophila embryogenesis. Promoters, including tissue-specific genes, are often constitutively open, even in contexts where the gene is not expressed. In contrast, the majority of distal elements have dynamic, tissue-specific accessibility. Enhancer priming appears rarely within a lineage, perhaps reflecting the speed of Drosophila embryogenesis. However, many tissue-specific enhancers are accessible in other lineages early on and become progressively closed as embryogenesis proceeds. We demonstrate the usefulness of this tissue- and time-resolved resource to definitively identify single-cell clusters, to uncover predictive motifs, and to identify many regulators of tissue development. For one such predicted neural regulator, l(3)neo38, we generate a loss-of-function mutant and uncover an essential role for neuromuscular junction and brain development.

Biological Features of the Northwest Pre-Caspian Saiga Population at Different Sizes

The abundance of the saiga antelope (Saiga tatarica tatarica L., 1766) in the Northwest Pre-Caspian region has remained at an extremely low level over the past 20 years. Comparison of some biological parameters of the population for periods with different numbers of animals made it possible to reveal a number of low-population features. Thus, along with a decrease in the number of saigas (from 800 000 heads in 1958 to 4500 in 2016), its habitat area also decreased (from 60 000–70 000 to 2000–3000 km2, respectively), and a significant part of the population transitioned to a sedentary lifestyle in the protected areas of the Chernye Zemli ecoregion. A long-time deficiency of sexually mature males in the population (less than 10%) led to a decrease in its growth and, consequently, to a decrease in its number. At the same time, the total fecundity of females decreased (from 1.27 ± 0.25 calves in years of high abundance to 0.92 ± 0.39 recently) due to an increase in barrenness in different age groups caused by the lack of males in the population. Males prevail over females in newborns (51.9 and 48.1%, respectively). The increased weight of newborn saiga calves (100 g on average for both males and females) and their decreased mortality in the first days after birth (under favorable weather conditions) indirectly indicate the normal course of embryogenesis and a sufficient quantity and quality of feed. An increase in the proportion of sexually mature stags will lead to an increase in the population number, as the reproductive functions of the population practically did not change during the period of its depression.

Selected factors that affect the results of artificial hatching of the golden pheasant (Chrysolophus pictus) in aviary breeding – a preliminary study

Abstract The aim of the study was to investigate selected factors that affect the course of embryogenesis and the quality of golden pheasant chicks during artificial incubation.

Cardiogenesis with a focus on vasculogenesis and angiogenesis.

The initial intraembryonic vasculogenesis occurs in the cardiogenic mesoderm. Here, a cell population of proendocardial cells detaches from the mesoderm that subsequently generates the single endocardial tube by forming vascular plexuses. In the course of embryogenesis, the endocardium retains vasculogenic, angiogenic and haematopoietic potential. The coronary blood vessels that sustain the rapidly expanding myocardium develop in the course of the formation of the cardiac loop by vasculogenesis and angiogenesis from progenitor cells of the proepicardial serosa at the venous pole of the heart as well as from the endocardium and endothelial cells of the sinus venosus. Prospective coronary endothelial cells and progenitor cells of the coronary blood vessel walls (smooth muscle cells, perivascular cells) originate from different cell populations that are in close spatial as well as regulatory connection with each other. Vasculo- and angiogenesis of the coronary blood vessels are for a large part regulated by the epicardium and epicardium-derived cells. Vasculogenic and angiogenic signalling pathways include the vascular endothelial growth factors, the angiopoietins and the fibroblast growth factors and their receptors.

Expression analysis of glutathione S-transferases and ferritins during the embryogenesis of the tick Haemaphysalis longicornis

In the tick life cycle, embryogenesis is the only stage of development wherein no blood meal is required. Nevertheless, even in the absence of a blood meal, which is the source of nutrients as well as the ferrous iron and heme that could cause oxidative stress in ticks, malondialdehyde (MDA) has been reported to increase during this period. Additionally, the knockdown of some oxidative stress–related molecules such as ferritin has resulted in abnormal eggs and embryonic death.Here, we investigate the gene and protein expression profiles of the identified glutathione S-transferases (GSTs) and ferritins (Fers) of the tick H. longicornis during embryogenesis through quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blotting, respectively. We also confirm the lipid peroxidation and ferrous iron concentration level using a thiobarbituric acid reactive substances (TBARS) assay. Finally, we attempt to correlate these findings with the events occurring by establishing a staging process in H. longicornis embryos.Lipid peroxidation increased during the course of embryogenesis, as does the amount of GST proteins. On the other hand, the GST genes have high expression at the 1st day post-oviposition, during the early stage of embryogenesis and at day 10 during the period wherein the germ band is observable. Fer gene expression also starts to increase at day 10 and peaks at day 15. In the ferritin proteins, only the secretory ferritin (Fer2) is detected and constitutively expressed during embryogenesis.Events occurring during embryogenesis, such as energy production and iron metabolism for cellular proliferation and differentiation cause oxidative stress in the embryo. To counteract oxidative stress, it is possible that the embryo may utilize oxidative stress–related molecules such as GSTs and Fer2, which could be either maternally or embryo-derived.

Toxicological potential of penconazole on early embryogenesis of white mice Mus musculus in either pre- or post-implantation exposure.

The present investigation was conducted to evaluate the effect of penconazole (PEN) fungicide on early embryogenesis of white mice. In the first experiment, 48 pregnant females were divided into different groups; the first group is control (G1). The second group (G2) was treated daily with PEN (30-, 20-, 10-, 5-mg/kg BW). The third group (G3) was treated with PEN (5-mg/kg BW; day after the other day). The fourth group (G4) was treated with PEN (2.5-mg/kg BW daily) during pre-implantation stage (from the 1st to the 4th day of gestation). The fifth group (G5) was treated with PEN (2.5-mg/kg BW daily) during post-implantation (from the 5th to the 8th day of gestation). The pregnant females were sacrificed at the 14th day of gestation. In the second experiment, 63 pregnant females were classified into control, PEN-treated during pre-implantation period (2.5-mg/kg BW), and PEN-administered during post-implantation period (2.5-mg/kg BW). Each group was sacrificed at stages E6.5, E7.5, E8.5, E9.5, E11.5, E14.5, and E18.5. The high doses of PEN in the first experiment showed failed pregnancy, foetoresorption, and embryo disorganization. High doses of PEN induce alterations in the uterus tissue at the level of histology and immunohistochemistry for the expression of TGFβ2, TNFR2, Caspase 10, and HSP70. The low doses of PEN in the second experiment showed upregulated expression of TGFβ2, TNFR2, Caspase 10, and HSP70 at stages E6.5 and E7.5. In conclusion, PEN was found to alter the suitable uterine environment for proper implantation and development at the levels of histological and immunohistochemical that could create a risk during the full course of embryogenesis.

Abnormal Development of Hyalomma Marginatum Ticks (Acari: Ixodidae) Induced by Plant Cytotoxic Substances.

The increasing application of toxic plant substances to deter and fight ticks proves the need for investigations focused on the elucidation of their impact on the developmental stages and populations of these arthropods. We examined the course of embryogenesis and egg hatch in Hyalomma marginatum ticks under the effect of cytotoxic plant substances. The investigations demonstrated that the length of embryonic development of egg batches treated with 20 μL of a 0.1875% colchicine solution did not differ significantly from that in the control group. Colchicine caused the high mortality of eggs (16.3%) and embryos (9.7%), disturbances in larval hatch (8.1%), and lower numbers of normal larval hatches (65.6%). In 0.2% of the larvae, colchicine induced anomalies in the idiosoma (67.6%) and gnathosoma (22.5%) as well as composite anomalies (8.5%). The study demonstrates that cytotoxic compounds with an effect similar to that of colchicine can reduce tick populations and cause teratological changes, which were observed in the specimens found during field studies. Since there are no data on the toxic effects of active plant substances on other organisms and the risk of development of tick resistance, a strategy for the use of such compounds in tick control and the management of plant products should be developed.

The effect of sublethal concentrations of deltamethrin and alphacypermethrin on the fecundity and development of Ixodes ricinus (Acari: Ixodidae) eggs and larvae

Two pyrethroids, deltamethrin (D) and alphacypermethrin (AC), have been used as commercial products for tick control worldwide. However, the effects of sublethal doses of these compounds on various tick species and their developmental stages have not been fully explored yet, although such knowledge could contribute to a more effective application of both pyrethroids and simultaneous reduction of their costs and undesirable side effects, including the harmful impact on other organisms and environmental contamination. This study investigates the effect of sublethal concentrations of D and AC applied to engorged females on the fecundity, development of eggs and larvae, and the number of offspring in the Ixodes ricinus (L.) tick, which is the most important vector of tick-borne diseases of humans in Europe. After detachment from rabbit’s skin, fully engorged I. ricinus females were treated with 20 μl of pyrethroid solutions at five concentrations from 0.01562 to 0.25% and kept at 28 °C and 75% relative humidity. The impact of the pyrethroids on maturation and development of eggs as well as development of larvae was assessed based on parameters of the preoviposition and oviposition periods and the course of embryogenesis and egg hatch. The investigations have shown that both tested acaricides reduce the reproductive rate in I. ricinus females by inhibition of egg development and disturb embryonic development and larval hatch. Females did not lay eggs at concentrations higher than 0.0625% AC and 0.125% D. The lower concentrations of both pyrethroids disturbed or inhibited the embryogenesis and egg hatch in I. ricinus.

The endosperm development and the variations of structures of embryo sacs: unravelling the low fecundity of Zephyranthes candida (Amaryllidaceae)

To unravel a low fecundity in Zephyranthes candida (Lindl.) Herb., the development of the endosperm was studied using conventional paraplast section technique. The results show that the endosperm develops normally and comprises four major stages viz. syncytial, cellularization, differentiation and maturation. Both proliferation of antipodal cells and their close contact with the primary endosperm nucleus were observed, which should favor transportation of nutrients and accelerate development of embryo and endosperm. In Z. candida, at least four events of nuclear migration occurred during the course of embryogenesis and endosperm development. The 12.7% structurally and functionally abnormal ovules, along with the 22.3% collapsed and aborted ovules observed accounts for the low fecundity to some extent.

Development of Methods and Techniques to Visualize Mechanical Tension in Embryos Using Genetically Encoded Fluorescent Mechanosensors

Lately, the growing body of quantitative data has provided evidence of the importance of mechanical forces in embryogenesis. The study of spatial and temporal distribution of mechanical tension in the course of embryogenesis is one of the most important problems of modern developmental biology. Development of genetically encoded fluorescent mechanosensors allowed their application in an intravital study of mechanical tension in developing embryos via noninvasive techniques. The possibility of applying fluorescent mechanosensors based on vinculin and C-cadherin to visualize mechanical tension in tissues of Gallus and Xenopus embryos was studied. The methods to express and detect these proteins, as well as process the resulting images, were elaborated. The best results were obtained using Xenopus embryos and the vinculin-based mechanosensor.

How to Make a Worm Twitch

Understanding how the nervous system generates behavior is a long-standing goal of neuroscience. The early nervous system develops alongside other tissues and organs in the course of embryogenesis and is crucial for establishing the organism’s early behavioral repertoire, including its ability to perform coordinated movements. The roundworm Caenorhabditis elegans has long been an important model system for studying developmental processes and offers several powerful features that aid such investigations, including its rapid embryonic development and its known and invariant cell lineage (1).