Red fox (provided by Dr. Yuji Ishikawa, Ishikawa Clinic, Asahikawa City)
The Zoological Society of Japan, Hokkaido Branch, 604th Branch Lecture
Date and Time: Friday, March 7, 2025, 5:00 PM – 6:30 PM
Location: Hokkaido University, Faculty of Science Building No. 5, 4th Floor, Room 407
Speaker: Dr. Takayuki Watanabe (Assistant Professor, Research Center for Integrative Evolutionary Science, The Graduate University for Advanced Studies, SOKENDAI)
Title: How are sex differences in insect brains and behavior generated?
Looking at the mechanisms of sexual differentiation in the brain and neural circuits from an evolutionary biological perspective
Abstract: Sex-specific behaviors are widely observed across the animal kingdom, both in vertebrates and invertebrates. The existence of behavioral sex differences implies underlying sex differences in the nervous system. Among insects, Drosophila melanogaster—a model organism that allows the use of powerful genetic techniques—has provided numerous insights into the molecular mechanisms underlying sex differences in the brain and behavior. While insects possess a cell-autonomous sex determination mechanism controlled by a sex-specific splicing cascade, it has been revealed that the transcription factor-encoding fruitless and doublesex genes function as “terminal differentiators” in the Drosophila brain. The fruitless and doublesex genes undergo sex-specific splicing regulation, producing sex-specific gene products. Neuronal populations expressing these genes exhibit prominent morphological sex differences, and as a result of more than 30 years of neurogenetics research, it has become clear that the sex-specific neural networks woven by fruitless- and doublesex-expressing cells play crucial functions in sexual behavior.
On the other hand, a broad overview of insect phylogeny reveals that the model organism *Drosophila melanogaster* belongs to the most phylogenetically derived group. Over 500 million years of evolution, insects have diversified through various evolutionary innovations, such as the acquisition of wings and pupae. Naturally, sex-specific behaviors are universally observed in insects as well, yet the actual neural circuits governing sexual behavior and their sex differences have remained largely unexplored in non-Drosophila insects. Furthermore, it remains unclear to what extent the brain and neural circuit sex-differentiation mechanisms dependent on the *fruitless* and *doublesex* genes, which have been elucidated in *Drosophila*, are universal across insects; even this fundamental question still lacks a clear answer.
In this seminar, we will introduce the latest findings on the sex differentiation mechanism of the insect brain, obtained from neurogenetic studies using the two-spotted cricket (Gryllus bimaculatus)—a hemimetabolous insect that diverged from a common ancestor with Drosophila about 400 million years ago.
The 604th Annual Meeting of the Zoological Society of Japan, Hokkaido Branch
