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Publications (127)
Background
Early embryogenesis is characterized by dramatic cell proliferation and movement. In most insects, early embryogenesis includes a phase called the uniform blastoderm, during which cells evenly cover the entirety of the egg. However, the embryo of the German cockroach, Blattella germanica, like those of many insects within the super order...
Exoskeletons are a defining character of all arthropods that provide physical support for their segmented bodies and appendages as well as protection from the environment and predation. This ubiquitous yet evolutionarily variable feature has been instrumental in facilitating the adoption of a variety of lifestyles and the exploitation of ecological...
Background: Early embryogenesis is characterized by dramatic cell proliferation and movement. In most insects, early embryogenesis includes a phase called the uniform blastoderm, during which cells evenly cover the entirety of the egg. However, the embryo of the German cockroach, Blattella germanica, like those of many insects within the super orde...
Exoskeletons are a defining character of all arthropods that provide physical support for their segmented bodies and appendages as well as protection from the environment and predation. This ubiquitous yet evolutionarily variable feature has been instrumental in facilitating the adoption of a variety of lifestyles and the exploitation of ecological...
The conquest of land by arthropods is commonly believed to be a surface phenomenon associated with the arrival of photosynthetic plants, atmospheric oxygenation, and an ozone shield in the mid-Paleozoic Era. However, recent molecular and fossil evidence suggests terrestrial fauna may have first appeared in the Cambrian, before the proliferation of...
Signaling networks are redeployed across different developmental times and places to generate phenotypic diversity from a limited genetic toolkit. Hormone signaling networks in particular have well-studied roles in multiple developmental processes. In insects, the ecdysone pathway controls critical events in late embryogenesis and throughout post-e...
The stable isotopes composition of chemolithoautotrophic cave ecosystems is known to differ from epigenic caves. Here we show that in addition, dead carbon (devoid of ¹⁴C), is utilized and transferred throughout this ecosystem, rendering it unsuitable for radiocarbon dating. The connectivity of the Ayyalon Cave ecosystem with the surface is studied...
Lycosa (Araneae, Lycosidae) is a wolf spider genus typical of subtropical latitudes in the western Palearctic. Despite being erected over 200 years ago, the taxonomy of Lycosa is still unclear. Many species formerly ascribed to it are currently being moved to other genera, while new species are still being described. The species of Lycosa of the we...
Synopsis
The anterior-most unit of the crown-group arthropod body plan includes three segments, the pre-gnathal segments, that contain three neuromeres that together comprise the brain. Recent work on the development of this anterior region has shown that its three units exhibit many developmental differences to the more posterior segments, to the...
The three anterior-most segments in arthropods contain the ganglia that make up the arthropod brain. These segments, the pre-gnathal segments (PGS), are known to exhibit many developmental differences to other segments, believed to reflect their divergent morphology. We have analyzed the expression and function of the genes involved in the conserve...
Segmentation is both a morphological phenomenon and a developmental process occurring in bilaterally symmetrical animals. A segmented body plan is one in which repeated body units are arranged along the anterior–posterior axis, each unit containing elements from a number of organ systems. Segmentation is found in three phyla: the arthropods, anneli...
Evippinae (Araneae, Lycosidae) is a subfamily of old-world lycosids, comprising six genera and 67 species, most of them typically found in xeric habitats. Although Israel is located between the two distribution-centers of the subfamily, Africa and central Asia, only two species of the genus Evippa Simon, 1882, namely E. arenaria (Audouin, 1826) and...
The three anterior-most segments in arthropods contain the ganglia that make up the arthropod brain. These segments, the pre-gnathal segments, are known to exhibit many developmental differences to other segments, believed to reflect their divergent morphology. We have analyzed the expression and function of the genes involved in the segment-polari...
The homeobox transcription factor Caudal has conserved roles in all Bilateria in defining the posterior pole and in controlling posterior elongation. These roles are seemingly similar and are difficult to disentangle. We have carried out a detailed analysis of the expression, function and interactions of the caudal ortholog of the milkweed bug, Onc...
The Drosophila blastoderm gene regulatory network is one of the best studied networks in biology. It is composed of a series of tiered sub-networks that act sequentially to generate a primary segmental pattern. Many of these sub-networks have been studied in other arthropods, allowing us to reconstruct how each of them evolved over the transition f...
Background:
Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding gen...
Background:
Segmentation in arthropods typically occurs by sequential addition of segments from a posterior growth zone. However, the amount of tissue required for growth and the cell behaviors producing posterior elongation are sparsely documented.
Results:
Using precisely staged larvae of the crustacean, Thamnocephalus platyurus, we systematic...
Segmentation is fundamental to the arthropod body plan. Understanding the evolutionary steps by which arthropods became segmented is being transformed by the integration of data from evolutionary developmental biology (evo-devo), Cambrian fossils that allow the stepwise acquisition of segmental characters to be traced in the arthropod stem-group, a...
Background
The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyse...
Fully segmented body plans are found in three phyla. These phyla are among the most successful on earth. The segmented body plan is not a single character, but a complex phenomenon, which evolved through a series of evolutionary steps. I suggest a hypothetical reconstruction of the steps involved in the appearance of segmented body plans, starting...
Background: One of the best studied developmental processes is the Drosophila segmentation cascade. However, this cascade is generally considered to be highly derived and unusual, with segments being patterned simultaneously, rather than the ancestral sequential segmentation mode. We present a detailed analysis of the segmentation cascade of the mi...
Background
Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genom...
One of the best studied developmental processes is the Drosophila segmentation cascade. However, this cascade is generally considered to be highly derived and unusual. We present a detailed analysis of the sequential segmentation cascade of the milkweed bug Oncopletus fasciatus, as a comparison to Drosophila, with the aim of reconstructing the evol...
Segmentation is both a morphological phenomenon and a developmental process occurring in bilaterally symmetrical animals. A segmented body plan is one in which repeated body units are arranged along the anterior–posterior axis, each unit containing elements from a number of organ systems. Segmentation is found in three phyla: the arthropods, anneli...
Background
The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyse...
The last few years have seen a significant increase in the amount of data we have about the evolution of the arthropod body plan. This has come mainly from three separate sources: a new consensus and improved resolution of arthropod phylogeny, based largely on new phylogenomic analyses; a wealth of new early arthropod fossils from a number of Cambr...
Our understanding of the genetics of arthropod body plan development originally stems from work on Drosophila melanogaster from the late 1970s and onward. In Drosophila, there is a relatively detailed model for the network of gene interactions that proceeds in a sequential–hierarchical fashion to define the main features of the body plan. Over the...
We describe the dynamic process of abdominal segment generation in the milkweed bug Oncopeltus fasciatus We present detailed morphological measurements of the growing germband throughout segmentation. Our data are complemented by cell division profiles and expression patterns of key genes, including invected and even-skipped as markers for differen...
The axes of insect embryos are defined early in the blastoderm stage. Genes involved in this polarization are well known in Drosophila, but less so in other insects, such as the milkweed bug Oncopeltus fasciatus. Using quantitative PCR, we looked at differential expression of several candidate genes for early anterior-posterior patterning and found...
The large milkweed bug Oncopeltus fasciatus was one of the main study insects for a range of biological questions throughout much of the 20(th) century. Its importance waned with the introduction of Drosophila melanogaster as a genetic model organism. The evo-devo revolution of the turn of the century re-introduced Oncopeltus into the scientific co...
Segments are formed simultaneously in the blastoderm of the fly Drosophila melanogaster through a hierarchical cascade of interacting transcription factors. Conversely, in many insects and in all non-insect arthropods most segments are formed sequentially from the posterior. We have looked at segmentation in the milkweed bug Oncopeltus fasciatus. P...
Embryos knocked down for Dl through maternal RNAi, fixed 36-38 hours after egg laying and stained for the expression of eve, inv and wg. In all three cases expression is similar to wildtype.
A germband stage embryo knocked down for Dl through maternal RNAi, fixed 40 hours after egg laying and stained for the expression of wg. The embryo is shown dissected but unmounted. Expression in anterior segments (those formed in the blastoderm) is normal, but the growth zone is misshapen and shows no expression of wg.
Embryos knocked down for Dl through maternal RNAi, fixed 36-38 hours after egg laying and stained for the expression of eve, inv and wg. In all three cases expression is similar to wildtype.
A germband stage embryo knocked down for Dl through maternal RNAi, fixed 40 hours after egg laying and stained for the expression of wg. The embryo is shown dissected but unmounted. Expression in anterior segments (those formed in the blastoderm) is normal, but the growth zone is misshapen and shows no expression of wg.
Background: Our understanding of the early evolution of the arthropod body plan has recently improved significantly through advances in phylogeny and developmental biology and through new interpretations of the fossil record. However, there has been limited effort to synthesize data from these different sources. Bringing an embryological perspectiv...
Abstract
Background
The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population...
The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some spe...
The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some spe...
Hexapoda not only constitutes the largest taxon in the biological world; its representatives are also the best-studied invertebrates. This chapter will give an overview of general principles of hexapod development, mostly in reference to the detailed description of Drosophila melanogaster (see Chap. 1). The description will be divided along key dev...
By any criterion, Insecta (as a subtaxon of Hexapoda) is the most successful taxon on the planet (see Chaps. 2 and 3 for the inclusion of the various subtaxa in Hexapoda versus Insecta). The number of described insect species nears one million, and they are found in almost every ecosystem, forming the major component of animal biomass in most. With...
Author Summary
Arthropods are the most abundant animals on earth. Among them, insects clearly dominate on land, whereas crustaceans hold the title for the most diverse invertebrates in the oceans. Much is known about the biology of these groups, not least because of genomic studies of the fruit fly Drosophila , the water flea Daphnia , and other s...
Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Striga...
The fauna of Chilopoda Geophilomorpha of Israel has been analyzed after examining 128 new specimens from 35 localities, reinterpreting all published data including 103 records, and relating occurrence of species with major climatic parameters. A key to identification has been compiled. A total of 17 species are distinguished, of which three are rep...
The anterior and posterior ends of the insect embryo are patterned through the terminal patterning system, which is best known from the fruitfly Drosophila melanogaster. In Drosophila, the RTK receptor Torso, and its presumed co-activator Torso-like, initiate a signaling cascade, which activates two terminal gap genes, tailless and huckebein. These...
The orphan nuclear receptor gene knirps and its relatives encode a small family of highly conserved proteins. We take advantage of the conservation of the family, using the recent prevalence of genomic data, to reconstruct its evolutionary history, identifying duplication events and tracing the intron-exon structure of the genes over evolution. Man...
The process of head development in insects utilizes a set of widely conserved genes, but this process and its evolution are not well understood. Recent data from Tribolium castaneum have provided a baseline for an understanding of insect head development. However, work on a wider range of insect species, including members of the hemimetabolous orde...
The early embryo of the milkweed bug, Oncopeltus fasciatus, appears as a single cell layer - the embryonic blastoderm - covering the entire egg. It is at this blastoderm stage that morphological domains are first determined, long before the appearance of overt segmentation. Central to the process of patterning the blastoderm into distinct domains a...
Different sources of data on the evolution of segmentation lead to very different conclusions. Molecular similarities in the developmental pathways generating a segmented body plan tend to suggest a segmented common ancestor for all bilaterally symmetrical animals. Data from paleontology and comparative morphology suggest that this is unlikely. A p...
The centipede Strigamia maritima forms all of its segments during embryogenesis. Trunk segments form sequentially from an apparently undifferentiated disk of cells at the posterior of the germ band. We have previously described periodic patterns of gene expression in this posterior disc that precede overt differentiation of segments, and suggested...
The evolution of arthropod segment number provides us with a paradox, because, whereas there is more than 20-fold variation in this character overall, most classes and orders of arthropods are composed of species that lack any variation in the number of segments. So, what is the origin of the higher-level variation? The centipede order Geophilomorp...
In the past decade or so, there has been a significant increase in the available data on the developmental mechanisms underlying the process of segmentation in a wide range of arthropod taxa. This large body of data makes it possible to attempt, albeit cautiously, a comparative analysis of the various aspects of the segmentation process, and to try...
Accurate and efficient identification to the species level of early larval stages has long been a problematic step in the study of marine invertebrates, due to the extremely small size of the larvae and their lack of diagnostic morphological characters. It is nonetheless, a prerequisite for any ecological study. As a consequence, a number of molecu...