Quantitative staging of embryonic development of the tobacco hawkmoth,Manduca sexta

Summary A complete timetable of embryonic development of the tobacco hawkmoth,Manduca sexta (Lepidoptera: Sphingidae), is presented. Using living embryos, 20 developmental stages from oviposition to hatching are described with respect to their morphological and physiological maturation. This staging series provides a simple method to identify the stage ofManduca development during all phases of embryogenesis.     

Embryonic development and hatching of chirocephalus diaphanus prévost (Crustacea: Anostraca) in nature

The embryonic development and hatching of C. diaphanus under natural conditions were investigated. Most of the embryonic development takes place during the dry period of the pond. Thus eggs are ready to hatch as soon as the pond is filled with rainwater.The pattern of the distribution of eggs on the bottom of the pond has a great value for the survival of the species. Adult females tend to lay their eggs mainly in the central parts of the pond.Department of Biology, University of Southampton     

Whole-embryo culture of Drosophila : development of embryonic tissues in vitro

Summary We have devised techniques to culture whole, dissected embryos of Drosophila melanogaster. We examine multiple aspects of the morphological and physiological development of the epidermis, musculature, nervous system, and internal organs in this cultured preparation, and show that in vitro development closely parallels normal embryogenesis. These techniques permit a wide range of experimental manipulations during embryogenesis and allow us to extend observations through late embryonic stages, after cuticle deposition. Applications of this technique are presented.     

Effects of seasonal variation in host quality and availability on parasitism by the egg parasitoid Telenomus coloradensis

Hemlock looper, Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), is one of the most important defoliator in North American forests. The common egg parasitoid Telenomus coloradensis Crawford (Hymenoptera: Platygastridae) plays a significant role as a natural control agent, with parasitism levels in spring typically higher than in fall. The objectives of this study were to quantify changes in host acceptance and reproductive performance of the parasitoid in relation to (1) host egg fertilization in fall, (2) host diapause status, (3) host embryonic development in spring, and (4) host deprivation during summer. Our results indicate that T. coloradensis do not have the capacity to develop in unfertilized host eggs, whereas early‐diapausing eggs are more suitable for the parasitoid than post‐diapausing eggs. Furthermore, the host physiological suitability decreases with embryonic development in spring. Finally, a host deprivation period during the summer tends to negatively affect the parasitic activity of T. coloradensis. These laboratory results confirm previous hypotheses concerning T. coloradensis seasonal ecology and contribute to a better understanding of the effect of hemlock looper egg physiology and availability on the reproductive potential of T. coloradensis.     

Post‐embryonic development of canal and superficial neuromasts and the generation of two cranial lateral line phenotypes

The relatively simple structural organization of the cranial lateral line system of bony fishes provides a valuable context in which to explore the ways in which variation in post‐embryonic development results in functionally distinct phenotypes, thus providing a link between development, evolution, and behavior. Vital fluorescent staining, histology, and scanning electron microscopy were used to describe the distribution, morphology, and ontogeny of the canal and superficial neuromasts on the head of two Lake Malawi cichlids with contrasting lateral line canal phenotypes (Tramitichromis sp. [narrow‐simple, well‐ossified canals with small pores] and Aulonocara stuartgranti [widened, more weakly ossified canals with large pores]). This work showed that: 1) the patterning (number, distribution) of canal neuromasts, and the process of canal morphogenesis typical of bony fishes was the same in the two species, 2) two sub‐populations of neuromasts (presumptive canal neuromasts and superficial neuromasts) are already distinguishable in small larvae and demonstrate distinctive ontogenetic trajectories in both species, 3) canal neuromasts differ with respect to ontogenetic trends in size and proportions between canals and between species, 4) the size, shape, configuration, physiological orientation, and overall rate of proliferation varies among the nine series of superficial neuromasts, which are found in both species, and 5) in Aulonocara, in particular, a consistent number of canal neuromasts accompanied by variability in the formation of canal pores during canal morphogenesis demonstrates independence of early and late phases of lateral line development. This work provides a new perspective on the contributions of post‐embryonic phases of lateral line development and to the generation of distinct phenotypes in the lateral line system of bony fishes. J. Morphol. 277:1273–1291, 2016. © 2016 Wiley Periodicals, Inc.     

mTOR kinase is needed for the development and stabilization of dendritic arbors in newly born olfactory bulb neurons

Neurogenesis is the process of neuron generation, which occurs not only during embryonic development but also in restricted niches postnatally. One such region is called the subventricular zone (SVZ), which gives rise to new neurons in the olfactory bulb (OB). Neurons that are born postnatally migrate through more complex territories and integrate into fully functional circuits. Therefore, differences in the differentiation of embryonic and postnatally born neurons may exist. Dendritogenesis is an important process for the proper formation of future neuronal circuits. Dendritogenesis in embryonic neurons cultured in vitro was shown to depend on the mammalian target of rapamycin (mTOR). Still unknown, however, is whether mTOR could regulate the dendritic arbor morphology of SVZ‐derived postnatal OB neurons under physiological conditions in vivo. The present study used in vitro cultured and differentiated SVZ‐derived neural progenitors and found that both mTOR complex 1 and mTOR complex 2 were required for the dendritogenesis of SVZ‐derived neurons. Furthermore, using a combination of in vivo electroporation of neural stem cells in the SVZ and genetic and pharmacological inhibition of mTOR, it was found that mTOR was crucial for the growth of basal and apical dendrites in postnatally born OB neurons under physiological conditions and contributed to the stabilization of their basal dendrites. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1308–1327, 2016     

The plurennial life cycles of the European Tettigoniidae (Insecta: Orthoptera)

Summary The effect of drought on embryonic development and on hatching was studied in 13 European Tettigoniidae species. Drought can affect development in three different ways: (1) Embryonic development proceeds slower than if the eggs are in contact with water; (2) it stops (for final diapause) in an earlier embryonic stage; (3) it affects maintenance and termination of the initial embryonic diapause.In many Tettigoniidae species, the initial diapause is prolonged, and may last several years. Without draught stress, between 1 and 7 cold treatments in the laboratory, and with eggs of the Tettigonia-species between 1 and 6 winters in the field were necessary to enable all eggs to complete initial diapause. In Central European species, the number of eggs maintaining initial diapause significantly increased when the eggs had no contact with water at the time when they should recover from diapause. In contrast, termination of initial diapause in Tettigonia caudata from Greece, when the environment became favorable for growth again, was highest in that group of eggs that had lost most water in a preceding period of drought. The importance of the prolonged initial diapause for the survival of unpredictable adverse conditions is discussed.     

Reproduction and development of common species of peanut worms (Sipuncula) from the Sea of Japan

This study deals with the reproduction and development of the most common species of peanut worms from the Sea of Japan: Thysanocardia nigra, Themiste pyroides, and Phascolosoma agassizii. Data on the time of reproduction and larval settlement and the distribution of these species in Peter the Great Bay are provided. The peculiarities of gametogenesis, spawning, and embryonic, larval, and postlarval development are described. The reproductive biology of representatives of these species from the western and eastern Pacific is examined in a comparative aspect.     

Tissue-specific and embryonic expression of the retinoid X receptors in Sebastiscus marmoratus

Retinoid X receptors (RXRs) are highly conserved members of the nuclear receptor family and mediate various physiological processes in vertebrates. Most studies on RXRs have concentrated on their structure and function in mammals and their characterization and developmental expression in Danio rerio. However, there is little information concerning the distribution of RXRs in teleost tissues. In the present study, we cloned partial sequences of three RXR subtypes (RXRa, -b, -g) from Sebastiscus marmoratus by RACE PCR and analyzed the phylogeny of the teleost and the tetrapod RXR genes, and identified some inconsistencies with previous studies. The tissue-specific and embryonic expression profiles of each RXR gene were explored using real time quantitative PCR. This analysis demonstrated that these RXRs were expressed in all test tissues indicating their participation in many physiological processes. However, we found a great difference in the distribution of RXRg between teleosts and mammals. Furthermore, we followed expression of the three subtypes through various embryo developmental stages and found that the RXRa orthologues of teleosts might be involved in the development of the anterior hindbrain, tailbud and neural crest and in the formation of the pharynx and fin, that RXRb played ubiquitous roles in fish early development, and that RXRg probably played a role in brain and nervous system development and function.     

Detection of phosphorylated mitogen-activated protein kinase in the developing spinal cord of the mouse embryo

Global understanding of the proteome is a major research topic. The comprehensive visualization of the distribution of proteins in vivo or the construction of in situ protein atlases may be a valuable strategy for proteomic researchers. Information about the distribution of various proteins under physiological and pathological conditions should be extremely valuable for the basic and clinical sciences.The mitogen-activated protein kinase (MAPK) cascade plays an essential role in intracellular signaling in organisms. This cascade also regulates biological processes involving development, differentiation, and proliferation. Phosphorylation and dephosphorylation are integral reactions in regulating the activity of MAPKs. Changes in the phosphorylation state of MAPKs are rapid and reversible; therefore, the localizations of physiologically phosphorylated MAPKs in vivo are difficult to accurately detect. Furthermore, phosphorylated MAPKs are likely to change phosphorylated states through commonly used experimental manipulations.In the present study, as a step toward the construction of in situ phosphoprotein atlases, we attempted to detect physiologically phosphorylated MAPKs in vivo in developing spinal cords of mice. We previously reported an improved immunohistochemical method for detecting unstable phosphorylated MAPKs. The distribution patterns of phosphorylated MAPKs in the spinal cords of embryonic mice from embryonic day 13 (E13) to E17 were observed with an improved immunohistochemical method. Phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) and phosphorylated c-Jun N-terminal kinase 1/2 (p-JNK1/2) were strongly observed in the marginal layer and the dorsal horn from E13 to E17. Our results suggest that p-ERK1/2 and p-JNK1/2 play critical roles in the developing spinal cord. Constructing phosphoprotein atlases will be possible in the future if this work is systematically developed on a larger scale than we presented here.     

Embryonic development and maternal regulation of murine circadian clock function

The importance of circadian clocks in the regulation of adult physiology in mammals is well established. In contrast, the ontogenesis of the circadian system and its role in embryonic development are still poorly understood. Although there is experimental evidence that the clock machinery is present prior to birth, data on gestational clock functionality are inconsistent. Moreover, little is known about the dependence of embryonic rhythms on maternal and environmental time cues and the role of circadian oscillations for embryonic development. The aim of this study was to test if fetal mouse tissues from early embryonic stages are capable of expressing endogenous, self-sustained circadian rhythms and their contribution to embryogenesis. Starting on embryonic day 13, we collected precursor tissues for suprachiasmatic nucleus (SCN), liver and kidney from embryos carrying the circadian reporter gene Per2::Luc and investigated rhythmicity and circadian traits of these tissues ex vivo. We found that even before the respective organs were fully developed, embryonic tissues were capable of expressing circadian rhythms. Period and amplitude of which were determined very early during development and phases of liver and kidney explants are not influenced by tissue preparation, whereas SCN explants phasing is strongly dependent on preparation time. Embryonic circadian rhythms also developed in the absence of maternal and environmental time signals. Morphological and histological comparison of offspring from matings of Clock-Δ19 mutant and wild-type mice revealed that both fetal and maternal clocks have distinct roles in embryogenesis. While genetic disruptions of maternal and embryonic clock function leads to increased fetal fat depots, abnormal ossification and organ development, Clock gene mutant newborns from mothers with a functional clock showed a larger body size compared to wild-type littermates. These data may contribute to the understanding of the ontogenesis of circadian clocks and the risk of disturbed maternal or embryonic circadian rhythms for embryonic development.     

Temperature Dependence of Membrane Lipid Composition in Early Blastula Embryos of Lytechinus pictus: Selective Sorting of Phospholipids into Nascent Plasma Membranes

Lytechinus pictus eggs were fertilized and incubated at 10, 16, and 23°C until the early blastula stage of embryonic development. The phospholipid composition of the embryos and control unfertilized eggs remain identical and unchanged as incubating temperatures are varied; thus, neither incubating temperature, fertilization nor membrane assembly affect their total phospholipid composition. This result agrees with metabolic studies by others, using only a single incubation temperature, and indicates that embryonic development to the early blastula stage occurs with little, if any, de novo phospholipid biosynthesis. However, as in all poikilotherms, the phospholipid composition of the nascent plasma membranes varies with the incubation temperature. Thus, until the blastula stage of embryonic development, the lipids of these newly formed plasma membranes are derived from lipid pools within the embryo whose phospholipid composition is static. The variation of plasma membrane composition is primarily reflected in an increase in the phosphatidylethanolamine (PE): phosphatidylcholine (PC) ratio as incubating temperatures decrease; this is achieved by an exchange of PE for PC. Several mechanisms are considered for the specificity of the selective sorting and assembly of these phospholipids into the nascent plasma membranes. Received: 16 March 1999/Revised: 15 May 1999     

Host regulation and the embryonic development of the endoparasitoid Toxoneuron nigriceps (Hymenoptera: Braconidae)

Insect endoparasitoids modulate the host physiology through the injection of maternal-derived substances into the host, inducing physiological and hormonal changes in the host's internal environment to benefit parasitoid development. These changes are direct to control host development and regulate nutrient availability to the developing parasitoid, and they are synchronized with parasitoid development. Eggs of some of these parasitoids have low yolk content and require nutrients from the host hemolymph to initiate and complete embryogenesis. We report changes in the amino acid composition and protein profile of the host hemolymph of the endoparasitoid Toxoneuron nigriceps, and improved the in vitro culture of pre-germ band stage eggs. The protein profile of parasitized larvae was similar to controls throughout the embryonic development, but total amino acid concentration decreased in the first 2 h after parasitization, significantly increasing in the following hours up to 8 h. Amino acid levels were higher in parasitized larvae from 16 to 28 h after parasitization. Comparison of single amino acids indicated amino acids involved in energy metabolism (Krebs cycle) followed a trend during parasitoid embryogenesis, and their changes were correlated with embryonic development. Improvement in the in vitro development of 6 h-old eggs of T. nigriceps was obtained by adding factors released by the host fat body to the artificial medium, while a cell lysate stimulated embryogenesis and allowed the full development of newly laid eggs in vitro.     

The Embryonic and Larval Development of Polypterus senegalusCuvier, 1829: its Staging with Reference to External and Skeletal Features, Behaviour and Locomotory Habits

The embryonic and larval development of the Polypteriformes, the presumed sister group of all other living actinopterygians, is poorly known. The main reason is the scarcity of successful breedings in captivity and therefore the lack of developmental series of any one polypterid species. A series of five successful breedings of P. senegalusnow makes it possible to define developmental stages of this species based on numerous closely timed specimens. The staging given here focuses on external embryonic and larval features: epidermal surface structures documented by SEM, colour pattern, development of fins and squamation, larval feeding and locomotory behaviour. The development of P. senegalusis characterized by a long free embryonic phase. Suction feeding is performed from the beginning of larval life (apterolarval phase). The pectoral fins start to become employed for slow locomotion and as supportive structures at around the same time. Olfactorily guided prey capture, however, is observed later in the pterolarval phase. Quantitative kinematic data also demonstrate a change in the mode of undulatory locomotion during this phase. Sustained axial undulation becomes confined to the posterior abdominal and caudal region of the body. At about the same time the paraxial high frequency undulation of the pectoral fin fold is replaced by the characteristic propeller-like movement of much greater amplitude and wavelength. Surfacing for aerial breathing is not seen before a marked change in colouration has taken place at the beginning of the juvenile period. The external gills slowly become reduced during this period. The definitions of larval and juvenile stages given here may advance understanding of developmental processes in the ontogeny of these primitive actinopterygians, and may serve as a tool for comparison with the ontogeny of Tetrapoda and Dipnoi, as well as to that of some “primitive” groups of Actinopterygii. Judging from its distribution among extant taxa, embryonic and larval ciliation is a character that most probably belongs to the grundplan? of Osteognathostomata. Phylogenetic evaluation is not so clear for the two other prominent embryonic and larval specializations found in Polypterus: upper labial attachment glands and opercular external gills. © 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.     

Cardiac development in crayfish: ontogeny of cardiac physiology and aerobic metabolism in the red swamp crayfish Procambarus Clarkii

The cardiovascular system performs key physiological functions even as it develops and grows. The ontogeny of cardiac physiology was studied throughout embryonic and larval development in the red swamp crayfish Procambarus clarkii using videomicroscopic dimensional analysis. The heart begins to contract by day 13 of development (at 25°C, 20 kPa O₂). Prior to eclosion, heart rate (ƒH) decreases significantly. Previous data suggests that the decrease in cardiac parameters prior to hatching may be due to an oxygen limitation of the embryo. Throughout development, metabolizing mass and embryonic oxygen consumption primarily increased while egg surface area remains constant. The limited area for gas exchange of the egg membrane, in combination with the increasing oxygen demand of the embryo could result in an inadequate diffusive supply of oxygen to developing tissues. To determine if the decrease in cardiac function was the result of an internal hypoxia experienced during late embryonic development, early and late stage embryos were exposed to hyperoxic water (PO₂ =40 kPa O₂). The ƒH in late stage embryos increased significantly over control values when exposed to hyperoxic water suggesting that the suppression in cardiac function observed in late stage embryos is likely due to a limited oxygen supply.     

Development of polyembryonic insects: a major departure from typical insect embryogenesis

 The parasitic wasp Copidosoma floridanum represents the most extreme form of polyembryonic development known, forming up to 2000 embryos from a single egg. To understand the mechanisms of embryonic patterning in polyembryonic wasps and the evolutionary changes that led to this form of development we have analyzed embryonic development at the cellular level using confocal and scanning electron microscopy. C. floridanum embryogenesis can be divided into three phases: (1) early cleavage that leads to formation of a primary morula, (2) a proliferative phase that involves partitioning of embryonic cells into thousands of morulae, and (3) morphogenesis whereby individual embryos develop into larvae. This developmental program represents a major departure from typical insect embryogenesis, and we describe several features of morphogenesis unusual for insects. The early development of polyembryonic wasps, which likely evolved in association with a shift in life history to endoparasitism, shows several analogies with mammalian embryogenesis, including early separation of extraembryonic and embryonic cell lineages, formation of a morula and embryonic compaction. However, the late morphogenesis of polyembryonic wasps proceeds in a fashion conserved in all insects. Collectively, this suggests a lack of developmental constraints in early development, but a strong conservation of the phylotypic stage. Received: 27 June 1997 / Accepted: 11 January 1998     

MIRO1 influences the morphology and intracellular distribution of mitochondria during embryonic cell division in Arabidopsis

Regulating the morphology and intracellular distribution of mitochondria is essential for embryo development in animals. However, the importance of such regulation is not clearly defined in plants. The evolutionarily conserved Miro proteins are known to be involved in the regulation of mitochondrial morphology and motility. We previously demonstrated that MIRO1, an Arabidopsis thaliana orthologue of the Miro protein, is required for embryogenesis. An insertional mutation in the MIRO1 gene causes arrest of embryonic cell division, leading to abortion of the embryo at an early stage. Here we investigated the role of MIRO1 in the regulation of mitochondrial behaviour in egg cells and early-stage embryos using GFP-labeled mitochondria. Two-photon laser scanning microscopy revealed that, in miro1 mutant egg cells, mitochondria are abnormally enlarged, although egg cell formation is nearly unaffected. After fertilization and subsequent zygotic cell division, the homozygous miro1 mutant two-celled embryo contained a significantly reduced number of mitochondria in its apical cell compared with the wild type, suggesting that the miro1 mutation inhibits proper intracellular distribution of mitochondria, leading to an arrest of embryonic cell division. Our findings suggest that proper mitochondrial morphology and intracellular distribution are maintained by MIRO1 and are vital for embryonic cell division.