2007 Fiscal Year Final Research Report Summary
Auto-cleaning system in insects
| Project/Area Number |
18570069
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Animal physiology/Animal behavior
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| Research Institution | Okayama University |
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Principal Investigator |
SAKAI Masaki Okayama University, Grad Sch Natur Sci Tech, Professor (30027502)
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| Project Period (FY) |
2006 – 2007
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| Keywords | cricket / genitalia / cleaning / spermatophore / membrane / Scale / serotonin / motoneuron |
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| Research Abstract |
We have recently discovered that the male cricket Gryllus bimaculatus has a unique cleaning system in the genitalia. The inside of the genital chamber of the male is always clean irrespective of the fact that foreign substance seems to easily enters the chamber. Our investigation found that the floor of the genital chamber consisted of the flexible membrane with small scales (10 μm) and it showed particular arrangement over the floor. The scale arrangement was symmetric between right and left, and all the scales were continuously lined and directed toward the lateral pouch (trash container) which was located at either corner of the floor. This design suggested that any objects on the membrane are moved along the scale directions. In fact, we demonstrated that an artificial object (80 μm) placed on the floor was quickly conveyed to the lateral pouch within 10 min. lb understand the mechanism of this object translocation, Movement of the membrane was analyzed. The results indicated that
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the peristaltic movement (0.16 Hz) consists of two types: the large shift and the small crease-like movement. Denervation experiments showed that the crease-like movement is essential for object translocation. Light-microscopic observation demonstrated that the scales stood on end when the crease-like movement occurred. The crease-like movement is cased by contraction of a number of muscle fibers extending over the membrane which were arranged in parallel with the scale directions. The muscle fibers were innervated by only 4 motoneurons whose somata were located in the lateral portion of the terminal abdominal ganglion. Electrophysiological spike recording agreed to the anatomical results. To determine neurotrasmitters of the motoneurons, some biogenic amines (10^3-10^2M) were administered to patches of the genital membrane in vitro. Serotonin increased the frequency of the spontaneous twitching while serotonin antagonist mianserin decreased it. Octopamine had no effect on the movement. Finally, serotonin immuno-fluorescence survey indicated that only one of the four motoneurones innervating the genital membrane was serotonergic. These results revealed that genitalic autogrooming in the male cricket is regulated by serotonin. Less
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