The reproductive biology of lampreys is of special interest given the group has retained many developmental features reminiscent of the earliest vertebrates. Herein I report spawning behavior in the Least Brook Lamprey (Lampetra aepyptera) from southern Indiana and provide descriptions of its embryonic development. Nesting activities began in mid-March when water temperatures ranged from 10 to 12 C, as two or more individuals dug out shallow depressions in loose gravel immediately above riffles. Communal spawning groups (>10 individuals) subsequently formed at the nest sites when the water temperature rose above 12 C. Embryos generated from the gametes of spawning adults underwent gastrulation 72 h after fertilization, neurulation after 6 d, and hatched after 14 d. Prolarvae developed melanophores 19 d after fertilization, eyespots were visible by 20 d, and the velum began to beat 25 d after fertilization. Expulsion of yolk from the intestine and filter feeding occurred 26 d after fertilization. Embryonic development in L. aepyptera largely matches the embryonic stages established for the Sea Lamprey (Petromyzon marinus), with subtle differences in the sequence of specific developmental features. These descriptions clarify conflicting accounts of spawning activities for L. aepyptera and provide staging criteria for future investigations into its embryonic development.

We investigated the development of allotriploid embryos derived from a cross between female starry flounder Platich thys stellatus and male stone flounder Kareius bicoloratus. The second cleavage, mid-blastula, gastrula, and Kupffer’s vesicle appearance stages, and hatching of embryos began 3.7, 25.6, 45.7, 87.7, and 213.2 h after cold shock at 6°C, respectively. The hatching and development time of triploid interspecific hybrid eggs was approximately the same as those of diploid starry flounder eggs at the same incubation temperature.

Three tissues to gastrulation.

Multicellular organisms develop from fertilized eggs or asexual propagules. In the case of animals the developmental processes by which their bodies take form originated in several phases beginning between 600 and 700 million years ago, in the Ediacaran period. Genes and signaling pathways, many of which were present in unicellular ancestors, came to mediate morphogenesis and cell pattern formation by virtue of bringing into play physical effects that were newly relevant on the scale of cell aggregates. Focusing on “liquid-like” properties of cell clusters and their capacity to act as “excitable media,” this review explores how the products of ancient and some novel genes of what became the “developmental toolkit” were variously employed to mobilize well-characterized physical effects and processes (cohesivity, phase separation and disaggregation, surface and shape polarization of cells, chemical oscillation, reaction–diffusion coupling) in the cell aggregates that eventually evolved into animal bodies and organs. This interplay of physics and genetics led to the generation of morphological motifs such as the tissue layering of gastrulation, lumen formation, body elongation, triploblasty, segmentation, and patterning of endoskeletal elements. Since not all founding lineages had identical sets of toolkit genes, not all morphogenetic and patterning processes were equally present in their descendents. These “physico-genetic” factors collectively account for the conservation and diversity of body plans seen in the present-day animal phyla. Keywords: “basal” metazoans; basal lamina; convergent extension; diploblasts; liquid tissue; lumen formation; multilayering; saltational evolution; segmentation; triploblasts; tetrapod limbs

Bird embryogenesis takes place in a relatively protected environment that can be manipulated especially well in domestic fowl (chickens) where incubation has long been a commercial process. The embryonic developmental process has been shown to begin in the oviduct such that the embryo has attained either the blastodermal and/or gastrulation stage of development at oviposition. Bird embryos can be affected by "maternal effects," and by environmental conditions during the pre-incubation and incubation periods. "Maternal effects" has been described as an evolutionary mechanism that has provided the mother, by hormonal deposition into the yolk, with the potential to proactively influence the development of her progeny by exposing them to her particular hormonal pattern in such a manner as to influence their ability to cope with the expected wide range of environmental conditions that may occur post-hatching. Another important aspect of "maternal effects" is the effect of the maternal nutrient intake on progeny traits. From a commercial broiler chicken production perspective, it has been established that greater cumulative nutrient intake by the hen during her pullet rearing phase prior to photostimulation resulted in faster growing broiler progeny. Generally, maternal effects on progeny, which have both a genetic and an environmental component represented by yolk hormones deposition and embryo nutrient utilization, have an important effect on the development of a wide range of progeny traits. Furthermore, commercial embryo development during pre-incubation storage and incubation, as well as during incubation per se has been shown to largely depend upon temperature, while other environmental factors that include egg position during storage, and the amount of H2O and CO2 lost by the egg and the subsequent effect on albumen pH and height during storage have become important environmental factors to be considered for successful embryogenesis under commercial conditions. Manipulating environmental temperature during the period of egg storage, during the intermediate pre-incubation period, and incubation period per se has been found to significantly affect embryo development, hatching progress, chick quality at hatching, and chick development post-hatching. These temperature manipulations have also been shown to affect the acquisition of thermotolerance to subsequent post-hatching thermal challenge. This chapter will focus on: a. "maternal effects" on embryo and post-hatching development; b. environmental effects during the post-ovipositional period of egg storage, the intermediate pre-incubation period, and incubation period per se on chick embryogenesis and subsequent post-hatching growth and development; and c. effects of temperature manipulations during the pre-incubation and incubation periods on acquisition of thermotolerance and development of secondary sexual characteristics in broiler chickens.

SUMMARY The fine structure of Artemia salina Leach (Crustacea Anostraca) egg-shell at the gastrula stage has been studied with the scanning electron microscope (SEM) and its amino-acids have been analyzed. SEM studies of the morphology of the egg-shell—the first reported for Crustacea—show it to consist of three well-defined layers: a compact inner fibrous layer or embryonic cuticle, a thick alveolar layer and an outer cortical layer. No specialized micropylar area, typical of the eggs of many invertebrate species, has ever been found. The amino-acid composition data reveal a rather uniform amino-acid content. There is no one predominant amino-acid residue: alanine, aspartic acid, serine and proline are the most abundant with similar relative values while sulphur-containing amino-acids (cystine and methionine) have been found only in small quantities. The amino acid composition of A. salina egg-shell has been compared with that of cirripede eggs and the relationships discussed.

Getting to Grips with Gastrulation

The concentrations of anti-oxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (SeGPx), and low molecular weight free-radical scavengers such as reduced glutathione (GSH) and ascorbic acid (vitamin C) were evaluated during the period from gastrulation (GS) to 25 days post-hatch (dph) in the larvae of Asian Seabass, Lates calcarifer. Oxidative damage due to lipid peroxidation (LPO) was also assessed, by evaluation of the formation of malondialdehyde (MDA). All the three anti-oxidant enzymes, SOD, CAT and GPx, showed high activities during gastrulation, suggesting an increased metabolic rate during the period of embryonic development. Though the SOD activity apparently decreased progressively during 3-20 dph of larval development, the difference was not significant. CAT showed high activity during gastrulation and remained constant up to 3 dph, suggesting an increased need to metabolise hydrogen peroxide (H2O2) and organic peroxides. In contrast, SeGPx activity increased progressively from 5 dph to 25 dph during larval development, indicating an increased need to detoxify lipid peroxides. This is evident from the observation of increased lipid peroxidation from 10 dph to 25 dph during larval development. GSH levels were low at gastrulation, indicating increased metabolic rate and formation of lipid radicals during this period, corresponding to the decrease in the level of ascorbic acid, which is consumed for regeneration of GSH.

Gastrulation: From Cells to Embryo, Stern, C.D., Ed.

1. Fictive swimming is an experimental model to study early motor development. As vestibular activity also affects the development of spinal motor projections, the present study focused on the question whether in Xenopus laevis tadpoles, the rhythmic activity of spinal ventral roots (VR) during fictive swimming revealed age-dependent modifications after hypergravity exposure. In addition, developmental characteristics for various features of fictive swimming between stages 37/38 and 47 were determined. Parameters of interest were duration of fictive swimming episodes, burst duration, burst frequency (i.e., cycle length), and rostrocaudal delay. 2. Ventral root recordings were performed between developmental stage 37/38, which is directly after hatching and stage 47 when the hind limb buds appear. The location of recording electrodes extended from myotome 4 to 17. 3. Hypergravity exposure by 3 g-centrifugation lasted 9 to 11 days. It started when embryos had just terminated gastrulation (stage 11/19-group), when first rhythmical activity in the ventral roots appeared (stage 24/27-group), and immediately after hatching (stage 37/41-group). Ventral root recordings were taken for 8 days after termination of 3 g-exposure. 4. Between stage 37/38 (hatching) and stage 47 (hind limb bud stage) burst duration, cycle length and rostrocaudal delay recorded between the 10th and 14th postotic myotome increased while episode duration decreased significantly. In tadpoles between stage 37 and 43, the rostrocaudal delay in the proximal tail part was as long as in older tadpoles while in caudal tail parts, it was shorter. During this period of development, there was also an age-dependent progression of burst extension in the proximal tail area that could not be observed between the 10th and 14th myotome. 6. After termination of the 3 g-exposure, the mean burst duration of VR activity increased significantly (p < 0.01) when 3 g-exposure started shortly after gastrulation but not when it started thereafter. Other parameters for VR activity such as cycle length, rostrocaudal delay and episode duration were not affected by this level of hypergravity. 7. It is postulated that (i) functional separation of subunits responsible for intersegmental motor coordination starts shortly after hatching of young tadpoles; and that (ii) gravity exerts a trophic influence on the development of the vestibulospinal system during different periods of embryonic development leading to the formation of more rigid neuronal networks earlier in the spinal than in the ocular projections.

Fog shapes up myosin for gastrulation

Gastrulation: from cells to embryo

A stern view of gastrulation

I. INTRODUCTION The body plan of the Caenorhabditis elegans embryo is established during the first few cleavages. The reproducible orientations of these cleavages coupled with asymmetric localization of cytoplasmic components initiate processes that establish the three principal axes of the body and set the fates of the six founder cells. In this chapter, we review the current understanding of mechanisms controlling the early cleavages, and we address the following issues: (1) when and how embryonic polarity is established, (2) how cytoplasmic factors are differentially partitioned along an axis, and (3) how spindle positioning is controlled to generate cells of the correct sizes, in the correct positions, and with the correct contents. A. Overview of Embryogenesis For detailed descriptions of C. elegans embryogenesis, see Sulston et al. (1983), which describes the entire embryonic lineage, and Wood (1988) and Strome (1989). It takes 14 hours at 20°C for a newly fertilized embryo to complete embryogenesis and hatch from its eggshell into a juvenile worm. During the first few hours, the embryo undergoes a series of four unequal divisions, to produce five somatic founder cells (AB, E, MS, C, and D) and the primordial germ cell (P 4 ) by the 28-cell stage (Figs. 1 and 2a–i). Gastrulation begins at the 28-cell stage when the two daughters of E move to the interior of the embryo (Fig. 2i), followed later by P 4 and some of the descendants of MS, C, D, and AB. These cell movements, coupled with continued proliferation, result in a generally...

Mammalian DNA contains relatively large amounts of a modified base, 5-methyl-cytosine (m5C). Methylation of cytosine is catalyzed by DNA(cytosine-5)methyltransferase (DNA MTase). DNA methylation seems to play an important role in the regulation of gene expression during development. Thus, m5C may inhibit transcription by preventing the binding of transcription factors and/or by altering chromatin structure. The DNA methylation patterns of the male and female pronuclei are erased in the morula and early blastula, and when the blastocyst forms, most of the DNA has become demethylated. Following implantation, however, there is a surge of de novo methylation affecting the entire genome, and already by gastrulation DNA is methylated to an extent characteristic of that of the adult animal. During subsequent development, tissue-specific genes undergo programmed demethylation, which may cause their activation. Site-directed mutagenesis of the DNA MTase gene, has recently shown that DNA methylation is absolutely required for normal development of the early mouse embryo. DNA methylation and polyamine synthesis depend on a common substrate, S-adenosylmethionine (AdoMet). As a consequence, changes in cellular polyamine levels may affect the degree of DNA methylation. When the first step in the polyamine biosynthetic pathway is blocked, F9 teratocarcinoma stem cells accumulate large amounts of decarboxylated AdoMet, the aminopropyl group donor in polyamine synthesis, and go through terminal differentiation into parietal endoderm cells. The accumulation of decarboxylated AdoMet is a direct consequence of the polyamine-depleted state of the cell. Although the decarboxylated AdoMet molecule contains a methyl group, it does not act as a methyl group donor in DNA methylation. Instead it acts as a competitive inhibitor of DNA MTase. A consequence of polyamine depletion is therefore genome-wide loss of DNA methylation due to insufficient maintenance methylation during successive rounds of DNA replication. Our recent finding that prevention of the accumulation of decarboxylated AdoMet counteracts the differentiative effect lends further support to the hypothesis proposed.

An extensive gelatinous material occupies the primary body cavity of larval echinoderms (auricu laria, bipinnaria, ophiopluteus, and echinopluteus) and hemichordates (tornaria). Its presence and its recovery of shape following application and release of force were demonstrated by dissection of larvae in a suspension of sumi ink. A gel in the primary body cavity explains struc tures that occur in all ofthese five larval forms: (1) con cave body surfaces bounded by thin epithelia and (2) muscles unopposed by other muscles. A gel filled pri mary body cavity invalidates deductions of morphoge netic mechanisms that assume a fluid filled cavity, an as sumption implicit in many models of blastulation, gas trulation, and movement of mesenchyme cells. A gelatinous primary body cavity permits body plans and morphogenetic processes not possible with a fluid filled cavity and permits development oflarge larvae with little cellular material. The taxonomic distribution ofgebfilled body cavities is not known, but gel filled cavities are pos sible wherever fluid motion has not been demonstrated or is not a functional necessity.

GASTRTULATION has often been observed and described in the Lepidoptera, but it remains a controversial topic. Differences of opinion concern chiefly two points: (a) how does gastrulation take place; and (b) does the process take place in the same way along the whole embryo or differently in different parts of the embryo ?

Journal of Experimental ZoologyVolume 135, Issue 3 p. 483-501 Article Experimental modification of gastrulation in the frog Ralph Holt Cheney, Ralph Holt Cheney Brooklyn College, Brooklyn, New York and the Marine Biological Laboratory, Woods Hole, MassSearch for more papers by this authorMorris Edward Kaighn, Morris Edward Kaighn Brooklyn College, Brooklyn, New York and the Marine Biological Laboratory, Woods Hole, Mass The authors wish gratefully to acknowledge the assistance of Robert Rothman in sectioning some of the embryos.Search for more papers by this author Ralph Holt Cheney, Ralph Holt Cheney Brooklyn College, Brooklyn, New York and the Marine Biological Laboratory, Woods Hole, MassSearch for more papers by this authorMorris Edward Kaighn, Morris Edward Kaighn Brooklyn College, Brooklyn, New York and the Marine Biological Laboratory, Woods Hole, Mass The authors wish gratefully to acknowledge the assistance of Robert Rothman in sectioning some of the embryos.Search for more papers by this author First published: August 1957 https://doi.org/10.1002/jez.1401350306 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume135, Issue3August 1957Pages 483-501 RelatedInformation

E stata determinata l'attivita proteasica nelle differenti regioni della blastula e della gastrula diDiscoglossus pictus. Nella blastula non esiste una differenza di attivita fra meta animale e vegetativa, quando si prenda come riferimento l'azoto citoplasmatico. Nella giovane gastrula il territorio presuntivo della corda e del sistema nervoso mostra una attivita piu elevata della epidermide presuntiva.