# Ultrastructure and Transcriptome Analysis Reveal Sexual Dimorphism in the Antennal Chemosensory System of Blaptica dubia

## TL;DR

This study shows that male and female Blaptica dubia have different antennal structures and gene activity related to sensing chemicals, suggesting evolved differences in how they interact with their environment.

## Contribution

The study reveals novel insights into sexual dimorphism in chemosensory systems through combined ultrastructural and transcriptomic analysis in Blaptica dubia.

## Key findings

- Males and females of Blaptica dubia show distinct antennal sensilla morphology and gene expression profiles.
- Transcriptomic analysis identified 5664 differentially expressed genes, including chemosensory-related genes like CSPs, OBPs, GRs, Ors, and IRs.
- Sex-specific differences in chemosensory gene expression suggest divergent chemical communication strategies between the sexes.

## Abstract

Blaptica dubia relies on its chemosensory system to perform essential behaviors such as mate localization and environmental interactions. This study employed integrated morphological and transcriptomic analyses to investigate sexual dimorphism in this system. The results revealed significant differences between males and females in both sensilla morphology and gene expression profiles. These disparities suggest that the two sexes may have evolved distinct chemosensory strategies, providing new perspectives for understanding adaptive evolution in Blattodea insects.

This study distinguished male and female individuals by wing morphology (males with long wings, females with short wings) and investigated sexual dimorphism in the chemosensory system of Blaptica dubia through integrated ultrastructural and transcriptomic analyses. Scanning electron microscopy (SEM) was used to characterize the type, number, and distribution of antennal sensilla, while Illumina HiSeq sequencing, Gene Ontology/Kyoto Encyclopedia of Genes and Genomes (GO/KEGG) annotation, and Quantitative Real-time Reverse Transcription Polymerase Chain Reaction (qRT-PCR) validation were employed to analyze sex-specific gene expression profiles. Both sexes exhibited Böhm’s bristles, chaetic, trichoid, and basiconic sensilla. Males showed significantly more chaetic sensilla on the pedicel and longer type I/II chaetic sensilla on the flagellum, whereas females had longer ST2 sensilla. Basiconic sensilla were predominantly flagellar-distributed and more abundant/longer in males. No sexual differences were observed in Böhm’s bristles. Transcriptomics revealed 5664 differentially expressed genes (DEGs) (2541 upregulated; 3123 downregulated), enriched in oxidation-reduction, extracellular space, lysosome, and glutathione metabolism. KEGG analysis identified five key pathways: lysosome, glutathione metabolism, cytochrome P450-mediated xenobiotic/drug metabolism, and ascorbate/aldarate metabolism. Among 11 chemosensory-related DEGs, chemosensory proteins (CSPs) and odorant binding proteins (OBPs) were downregulated in males, while gustatory receptors (GRs), olfactory receptors (Ors), and ionotropic receptors (IRs) were upregulated. These results demonstrate profound sexual dimorphism in both antennal sensilla morphology and chemosensory gene expression, suggesting divergent sex-specific chemical communication strategies in Blaptica dubia, with implications for understanding adaptive evolution in Blattodea.