Research Press Release | February 14, 2014
|Key Points||・The gene that causes sexual dimorphism in stag beetles has been identified.
・When the function of this gene is inhibited stag beetles showed neutral characteristics between male and female.
・The gene regulates mandible*1 growth, which differs significantly in size between males and females.
・This gene may regulate the responsiveness to hormones that promote mandible growth.
・Experimental evidence of morphogenetic regulation by sex-determination gene via hormone signaling in insects is rare so far.
・These results are considered to be important in the understanding of the mechanism which causes sexual differentiation in insects.
*1 Mouth parts of insects. Significant mandible growth is observed in male stag beetles. In Japan, these parts are commonly called “hasami” (meaning scissors in Japanese).
The morphological difference between male and female stag beetles is widely known. Male stag beetles have a pair of fully developed mandibles that are commonly called “hasami,” while females do not exhibit such mandible growth. What is the mechanism that causes such significant difference within the same species? In order to understand this mechanism, a developmental study was carried out on Cyclommatus metallifer, focusing on sex-determination genes and juvenile hormone*2 signaling pathways.
Results indicate that the dsx gene, a sex-determining gene for insects, regulates sexual dimorphism in stag beetles. It is also suggested that a large difference in sexual dimorphism of mandible growth is due to the dsx gene that regulates juvenile hormone responsiveness in different directions depending on whether the individual is male or female. These results are a major milestone, and mark the discovery of the “sexual differentiation regulatory mechanism by the dsx gene via hormone responsiveness,” which is relatively unknown in the insects. This finding is also important in the understanding of the mechanism which causes phenotypic sexual dimorphism in other insects as well.
*2 A type of insect hormone which is known to be involved in various biological phenomena in insects, such as development and metamorphosis. In addition, the growth-promoting function of this hormone on the mandibles of the stag beetle has been identified.
Toru Miura, Associate Professor, Graduate School of Environmental Earth Science, Hokkaido University
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PLoS Genetics (2014.1.16)