Topographie der Anlagenkomplexe der Cephalregion vonTachycines (Saltatoria) beim Keimstreif

Wada, Shoji

doi:10.1007/bf00625790

Cited by 11 publications

(2 citation statements)

References 2 publications

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“…DISCUSSION Comparative morphological studies on a variety of insect species led to numerous theories concerning the segmental organization of the insect head, placing the number of segments as low as three and as high as seven (1-4). In the head of a Saltatoria, the camel cricket, seven "morphogenetic units" have been defined by ablation experiments (30 (7). Our analysis of the neural elements and their deletion in various head mutants are consistent with seven morphological units, which can be assigned to the three prominent gnathal and four pregnathal segments, placing the optic region to the second metamer (7) rather than to the nonsegmental acron (5).…”

supporting

confidence: 63%

Number, identity, and sequence of the Drosophila head segments as revealed by neural elements and their deletion patterns in mutants.

Schmidt‐Ott

González‐Gaitán

Jäckle

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

103

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The development of the insect head tagma involves massive rearrangements and secondary fusions of segment anlagen during embryogenesis. Due to the lack of reliable morphological markers, the number, identity, and sequence of the head segments, particularly in the pregnathal region, are still a matter of ongoing debates. We examined the complex array of internal structures of the embryonic Drosophila melanogaster head such as the sensory structures and nerves of the peripheral and stomatogastric nervous systems, and we used embryonic head mutations causing a lack of overlapping segment anlagen to unravel the segmental identity and the sequence of the neural elements. Our results provide evidence for seven distinct segments in the Drosophila head, each characterized by a specific set of sensory neurons, consistent with the proposal that insects, myriapods, and crustaceans share a monophyletic evolutionary tree from a common annelid-like ancestor.The insect body is composed of metamerically repeated units. While segmentation is obvious in the "trunk" region, the segmental organization of the head is still obscure (1-7). By distinct cuticular features, three gnathal segments (mandibula, maxilla, and labium) can be distinguished in the posterior head region. The anterior pregnathal region, however, is poor in diagnostic morphological structures (8). Morphological and evolutionary studies based on epidermal head structures (5, 8), coelomic cavities, or brain regions (1-4) have so far failed to unambiguously determine the number and identity of pregnathal segments in the insect head. Due to the evolutionary changes that resulted in the "acephalic" appearance of higher dipteran larvae, the segmental composition of the Drosophila head was analyzed only recently. The detailed fate map analysis of a few cuticular specializations of the larval Drosophila head by laser ablation studies suggested six segments-i.e., three pregnathal and three gnathal segments (5). This interpretation was questioned through a detailed analysis of the expression patterns of the segment polarity genes engrailed (en) and wingless (wg), which serve as molecular markers for metamers in the prospective trunk and gnathal regions of the Drosophila embryo. This analysis suggested the possibility of seven instead of only six head segments (7). Here we present additional and more substantial evidence for seven head segments which is based on detailed analysis of internal head structures such as sensory organs. Their axons fasciculate to give rise to seven distinct sensory projections to the brain. The analysis of the patterns of sense organs deleted in various head segmentation mutants allows us to make an assignment of the sense organs to their segments of origin.MATERIALS AND METHODS Drosophila melanogaster strains were kept under standard conditions; wild-type and mutant embryos were obtained as described (9). The en expression patterns of embryos lacking tor activity (collected from homozygous torPM females) (10, 11) and of embryos homozygous ...

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supporting

confidence: 63%

Number, identity, and sequence of the Drosophila head segments as revealed by neural elements and their deletion patterns in mutants.

Schmidt‐Ott

González‐Gaitán

Jäckle

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

103

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“…Ablation studies of early insect embryos have contributed to the notion of four prognathal "proliferation centers," each providing segmental components (Wada, 1966a): anteriorly the c1ypeolabrum, followed by the eyes, optic lobes, mushroom bodies, and the central body. The third and fourth centers relate to the antennal segments (and its associated neural structures, the antennallobes), and the intercalary segment, or tritocerebrum.…”

Section: Evidence For Head Segmentation In Insect Preoral Neuropilmentioning

confidence: 99%

The arthropod mushroom body: Its functional roles, evolutionary enigmas and mistaken identities

Strausfeld

Buschbeck

Gomez

1995

Experientia Supplementum

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Insects share the same physical environment as terrestrial vertebrates. However, insects are vastly more successful in terms of their adaptive radiation and colonization. The biomass of insects alone is said to outweigh all other organisms and it can be speculated that their evolutionary success is a consequence, not only of their environmental colonization, but also of their behavioral versatility which sets them apart from other terrestrial arthopods. If this hypothesis is correct, it might be expected that there exist neural organizations that are peculiar to, or greatly elaborated in, the Insecta alone. This chapter describes the occurrence among selected arthropods of a brain region that, in eusocial insects, reaches great complexity and is implicated in learning and memory. Its identification in various taxa is assessed against the background of current theories of arthropod evolution and brain segmentation.

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Die Embryogenese des Gehirns paurometaboler Insekten

Malzacher

1968

Die Embryogenese Des Gehirns Paurometaboler Insekten

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Topographie der Anlagenkomplexe der Cephalregion vonTachycines (Saltatoria) beim Keimstreif

Cited by 11 publications

References 2 publications

Number, identity, and sequence of the Drosophila head segments as revealed by neural elements and their deletion patterns in mutants.

Number, identity, and sequence of the Drosophila head segments as revealed by neural elements and their deletion patterns in mutants.

The arthropod mushroom body: Its functional roles, evolutionary enigmas and mistaken identities

Die Embryogenese des Gehirns paurometaboler Insekten

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