| Budget Amount *help |
¥20,700,000 (Direct Cost: ¥20,700,000)
Fiscal Year 2001: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2000: ¥9,000,000 (Direct Cost: ¥9,000,000)
Fiscal Year 1999: ¥6,200,000 (Direct Cost: ¥6,200,000)
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| Research Abstract |
To approach the matter of consciousness in insects, mechanisms of thanatosis and its functional significance were investigated in the cricket Gryllus bimaculatus DeGeer. Tb examine the neural mechanism, responses of ascending and descendin interneurons through the connectives were recorded during the resting state and thanatotic state with a chronic electrode. Stimulation was noticeptive in general which caused a startle response in males in the resting state, 1) Sensory response : Behavioral responses to mechanical shocks onto the antenna, ultra-sound to the ear, or strong contact to the tips of the hindwings were completely lost during thanatosis. According to neural recording, responses of ascending interneurons were not different between the resting state and thanatosis, while those of descending interneurons were blocked, in particular, those of the brain neurons, suggesting the behavioral unrespoonsivenss is due to inhibition in the brain. On the other hand, behavioral responses
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to a wind onto the cerci were inhibited when the legs had a contact with the substrate, but rather fecilitated when they had no contact, suggesting that mechano-sensory afferent is normally processed even under thatatosis. 2) Reflex during thanatosis : The cricket shows catalepsy, a state without resistance reflex, during thanatosis. It was found that this occurs at the loss of balance between two antagonistic groups of scoloparial neurons in the femoral chordotonal organ. 3) Comparative study of thanatosis : It was found that thanatosis did not occur in Teleogryllus emma, while it occurred in Gryllus bimaculatus. The examination of the mechanoreceptors on the pronotum indicated that the latter had short hairs which did not respond to contact but did to the deformation of the cuticle, while the former had longer haris which responded to contact. These differences possibly underlie the differene in behavioral responsiveness. In fact, Gryllus bimaculatus falls on thanatosis during struggling to creep into a small space between stones in their habitat, which is triggered by compression of the prontum as a result of the self-produced movement. These results gave an insight into the neural mechanism of thanatosis and its adaptation to environments. Less
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