# Identification of ecdysteroids and ecdysteroidogenic genes in dragonflies and damselflies

## TL;DR

This study identifies ecdysteroids and related genes in dragonflies and damselflies, revealing their roles in metamorphosis and ecdysis.

## Contribution

The study reveals conserved ecdysteroidogenic genes and their expression patterns in Odonata, a key insect group.

## Key findings

- Ecdysone and 20-hydroxyecdysone levels correlate with ecdysis and metamorphosis in Odonata.
- 7-dehydrocholesterol is consistently present in hemolymph across species and stages.
- Most ecdysteroidogenic genes are conserved and expressed in diverse tissues in Odonata.

## Abstract

Ecdysteroids are critical in regulating biological processes such as ecdysis, metamorphosis, embryogenesis, and reproduction in insects. Nevertheless, the ecdysteroid repertoire and expression patterns of their synthesis genes in Odonata (dragonflies and damselflies), which belong to the most-ancestral winged insect group, have remained elusive. In this study, we examined the ecdysteroid profile of eight Odonata species and the ecdysteroid fluctuation during metamorphosis in the damselfly Ischnura senegalensis (Zygoptera, Coenagionidae) and the dragonfly Pseudothemis zonata (Anisoptera, Libellulidae). We found that ecdysone and 20-hydroxyecdysone (20E) titers corresponded to the progression of ecdysis in the penultimate nymphal instar and metamorphosis in the final nymphal instar, whereas 7-dehydrocholesterol was consistently present in the hemolymph of all the examined species and developmental stages. Considering that a higher amount of 20E was detected than ecdysone, 20E is important for inducing ecdysis and metamorphosis in Odonata, like other insects. We also confirmed that the majority of ecdysteroidogenic genes were conserved in Odonata, and their stage- and region-specific expression patterns were examined in I. senegalensis and P. zonata. Unexpectedly, most ecdysteroidogenic genes were expressed in a variety of tissues. Our study provides insights into the evolution and diversification of the ecdysteroidogenic pathway among insects.

The online version contains supplementary material available at 10.1038/s41598-025-08387-3.