Abstract
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.
Posterior segments are formed sequentially, through what is probably the ancestral arthropod mechanism. Formation of anterior segments bears many similarities to the
Drosophila
segmentation mode. These segments appear nearly simultaneously in the blastoderm, via a segmentation cascade that involves orthologues of
Drosophila
gap genes working through a functionally similar mechanism. We suggest that simultaneous blastoderm segmentation evolved at or close to the origin of holometabolous insects, and formed the basis for the evolution of the segmentation mode seen in
Drosophila
. We discuss the changes in segmentation mechanisms throughout insect evolution, and suggest that the appearance of simultaneous segmentation as a novel feature of holometabolous insects may have contributed to the phenomenal success of this group.
Funder
Israel Science Foundation
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
30 articles.
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