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Background <p>Lineage-specific adult structures form through modifications of pre-existing juvenile body parts during postembryonic development in insects. It remains unclear how these novel traits originate from ancestral structures within the constrained body plan. In the coffin-headed cricket <i>Loxoblemmus equestris</i>, an ancestral rounded head shape directly transforms into a flattened derived form in a sex-specific manner. To understand the origin of novel traits, we investigated the development of the adult head in <i>L</i>. <i>equestris</i> as a model of lineage-specific novelty. </p> Results <p>We found that head morphologies remained sexually monomorphic until the final molt, and the male-specific head shape emerged in the frons region during the transition to adulthood in <i>L. equestris</i>. Two- and three-dimensional morphological analyses revealed that the sexual dimorphism in the frons epithelial folding patterns appeared in the late final nymphal instar. These results suggest that the male-specific novel head development is linked to the final molt in <i>L</i>. <i>equestris</i>. We tested this hypothesis by knocking down the metamorphic gene network (MGN) comprised of <i>Krüppel-homolog 1</i> (<i>Kr-h1</i>), <i>broad</i> (<i>br</i>), and <i>Ecdysone induced protein 93F</i> (<i>E93</i>). Despite the timing shifts of the nymph-to-adult transition caused by knockdown of the MGN, male-specific head structures are formed only after the final molt.</p> Conclusions <p>These results demonstrate that the novel male head structures are formed during the final molt through the formation of sex-specific epithelial patterns in <i>L. equestris</i>. This highlights the unique metamorphic lifecycle with the final molt as a driver that has created lineage- and sex-specific adult forms in insects.</p>

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Lineage-specific head development in the coffin-headed cricket Loxoblemmus equestris links the final molt with novel trait evolution

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月16日

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  • Mizuho Yoneda,
  • Shinichi Morita,
  • Teruyuki Niimi,
  • Takaaki Daimon,
  • Takahiro Ohde

摘要

Background

Lineage-specific adult structures form through modifications of pre-existing juvenile body parts during postembryonic development in insects. It remains unclear how these novel traits originate from ancestral structures within the constrained body plan. In the coffin-headed cricket Loxoblemmus equestris, an ancestral rounded head shape directly transforms into a flattened derived form in a sex-specific manner. To understand the origin of novel traits, we investigated the development of the adult head in L. equestris as a model of lineage-specific novelty.

Results

We found that head morphologies remained sexually monomorphic until the final molt, and the male-specific head shape emerged in the frons region during the transition to adulthood in L. equestris. Two- and three-dimensional morphological analyses revealed that the sexual dimorphism in the frons epithelial folding patterns appeared in the late final nymphal instar. These results suggest that the male-specific novel head development is linked to the final molt in L. equestris. We tested this hypothesis by knocking down the metamorphic gene network (MGN) comprised of Krüppel-homolog 1 (Kr-h1), broad (br), and Ecdysone induced protein 93F (E93). Despite the timing shifts of the nymph-to-adult transition caused by knockdown of the MGN, male-specific head structures are formed only after the final molt.

Conclusions

These results demonstrate that the novel male head structures are formed during the final molt through the formation of sex-specific epithelial patterns in L. equestris. This highlights the unique metamorphic lifecycle with the final molt as a driver that has created lineage- and sex-specific adult forms in insects.