Development of the Pre-gnathal Segments in the Milkweed Bug Oncopeltus fasciatus Suggests They Are Not Serial Homologs of Trunk Segments
Lev O, Chipman AD. Frontiers in cell and developmental biology, August 2021.
Read the paper Free to read · doi:10.3389/fcell.2021.695135
What this paper is about
The three front segments of an insect carry the brain and develop differently from the rest of the body. The question is whether they are modified versions of ordinary body segments or something else.
The authors knocked down segment-polarity genes in the large milkweed bug and found the front segments do not behave like trunk segments, which argues against them being simple repeats.
Summarised here from the abstract below. Not the authors’ words.
Abstract
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 conserved segment-polarity network, including genes from the Wnt and Hedgehog pathways, in the PGS, compared with the trunk segments, in the hemimetabolous insect Oncopeltus fasciatus. Gene function was tested by manipulating expression through RNA interference against components of the two pathways. We show that there are fundamental differences in the expression patterns of the segment polarity genes, in the timing of their expression and in the interactions among them in the process of pre-gnathal segment generation, relative to all other segments. We argue that given these differences, the PGS should not be considered serially homologous to trunk segments. This realization raises important questions about the differing evolutionary ancestry of different regions of the arthropod head.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
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title = {Development of the Pre-gnathal Segments in the Milkweed Bug Oncopeltus fasciatus Suggests They Are Not Serial Homologs of Trunk Segments (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/development-of-the-pre-gnathal-segments-in-the-milkweed-2021/},
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