Search results for "Head segmentation"
showing 4 items of 4 documents
Segmental Organization of Cephalic Ganglia in Arthropods
2007
Cephalic ganglia in arthropods encompass neuromeres of the supraesophageal ganglion (i.e., the brain) and the subesophageal ganglion. Whereas neuromeres of the subesophageal ganglion are clearly distinguishable, the segmental pattern of the brain is derived and less well understood. In this article, we give an overview of the current state of a long-lasting debate on the segmental organization of the arthropod head and brain, discussing embryonic morphological and molecular data, with a main focus on insects. Embryonic expression data on key developmental genes such as engrailed, orthodenticle, and Hox genes will be summarized to compare the metameric organization of the head (sub- and supr…
Expression of en and wg in the embryonic head and brain of Drosophila indicates a refolded band of seven segment remnants
1992
ABSTRACT Based on the expression pattern of the segment polarity genes engrailed and wingless during the embryonic development of the larval head, we found evidence that the head of Drosophila consists of remnants of seven segments (4 pregnathal and 3 gnathal) all of which contribute cells to neuromeres in the central nervous system. Until completion of germ band retraction, the four pregnathal segment remnants and their corresponding neuromeres become arranged in an S-shape. We discuss published evidence for seven head segments and morphogenetic movements during head formation in various insects (and crustaceans).
Fate-mapping in the procephalic region of the embryonic Drosopbila head
1994
Using intracellular horseradish peroxidase injection we traced the developmental fate of early gastrula cells of the procephalic region in the stage 16/17 embryo. Morphogenetic movements in the developing brain are described in three dimensions. The results are related to head segmentation, and an early gastrula fate map of pregnathal head segments is proposed.
Spatial and temporal pattern of neuroblasts, proliferation, and Engrailed expression during early brain development in Tenebrio molitor L. (Coleopter…
2003
Abstract In insects, the knowledge of embryonic brain development is still fragmentary, and comparative data are scarce. In this study, we explored aspects of embryonic brain development in the coleopteran Tenebrio molitor . A detailed description is provided of the spatial and temporal pattern of the embryonic brain neuroblasts during 18–60% of embryonic development. Approximately 125 brain NBs have been identified in each hemisphere of the brain at about 40% of embryonic development. A subset of five neuroblasts, among them the two progenitors of the mushroom bodies and two progenitors of the larval antennal lobe, are morphologically identifiable by their larger size. As revealed by incor…