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Updated: Mar 16, 2026
Resurrection of Dormant Daphnia magna: Protocol and Applications
Published on: January 19, 2018
Comparative ovarian microarray analysis of juvenile hormone-responsive genes in water flea Daphnia magna: potential
Kenji Toyota1,2, Timothy D Williams1, Tomomi Sato3
1School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK.
Abstract:
The freshwater zooplankton Daphnia magna has been extensively employed in chemical toxicity tests such as OECD Test Guidelines 202 and 211. Previously, it has been demonstrated that the treatment of juvenile hormones (JHs) or their analogues to female daphnids can induce male offspring production. Based on this finding, a rapid screening method for detection of chemicals with JH-activity was recently developed using adult D. magna. This screening system determines whether a chemical has JH-activity by investigating the male offspring inducibility. Although this is an efficient high-throughput short-term screening system, much remains to be discovered about JH-responsive pathways in the ovary, and whether different JH-activators act via the same mechanism. JH-responsive genes in the ovary including developing oocytes are still largely undescribed. Here, we conducted comparative microarray analyses using ovaries from Daphnia magna treated with fenoxycarb (Fx; artificial JH agonist) or methyl farnesoate (MF; a putative innate JH in daphnids) to elucidate responses to JH agonists in the ovary, including developing oocytes, at a JH-sensitive period for male sex determination. We demonstrate that induction of hemoglobin genes is a well-conserved response to JH even in the ovary, and a potential adverse effect of JH agonist is suppression of vitellogenin gene expression, that might cause reduction of offspring number. This is the first report demonstrating different transcriptomics profiles from MF and an artificial JH agonist in D. magna ovary, improving understanding the tissue-specific mode-of-action of JH. Copyright © 2016 John Wiley & Sons, Ltd.
Insights
Juvenile hormones (JHs) can induce male offspring in Daphnia magna. This study reveals conserved hemoglobin gene induction and potential vitellogenin suppression by JH agonists in the ovary, impacting offspring.
Area of Science:
- Environmental Toxicology
- Developmental Biology
- Molecular Endocrinology
Background:
- Daphnia magna is a key model organism for chemical toxicity testing (e.g., OECD Guidelines 202, 211).
- Juvenile hormones (JHs) or their analogues can induce male offspring in female Daphnia, forming the basis for a JH-activity screening assay.
- Understanding JH-responsive pathways in the Daphnia ovary is crucial for elucidating mechanisms of sex determination and potential endocrine disruption.
Purpose of the Study:
- To investigate JH-responsive gene expression in the Daphnia magna ovary, including developing oocytes.
- To compare the transcriptomic responses to an artificial JH agonist (fenoxycarb) and a putative innate JH (methyl farnesoate) in the ovary.
- To elucidate tissue-specific modes of action for JH agonists in Daphnia.
Main Methods:
- Comparative microarray analysis of Daphnia magna ovaries.
- Treatment of adult female Daphnia magna with fenoxycarb (Fx) and methyl farnesoate (MF).
- Analysis of gene expression profiles during a JH-sensitive period for male sex determination.
Main Results:
- Hemoglobin gene induction was identified as a conserved response to JH in the Daphnia ovary.
- Suppression of vitellogenin gene expression was observed as a potential adverse effect of JH agonists, possibly reducing offspring number.
- Distinct transcriptomic profiles were observed between methyl farnesoate and the artificial JH agonist fenoxycarb in the Daphnia ovary.
Conclusions:
- JH agonists induce conserved responses like hemoglobin gene expression in the Daphnia ovary.
- JH agonists may negatively impact reproduction by suppressing vitellogenin expression.
- This study provides the first comparative transcriptomic data for different JH agonists in the Daphnia ovary, enhancing understanding of JH's tissue-specific effects.
