|Budget Amount *help
¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 1998 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1997 : ¥3,200,000 (Direct Cost : ¥3,200,000)
We reexamined the brain and suboesophageal ganglion (SOG) to determine which was essential for inhibition of mating behavior in the male cricket Gryllus bimaculatus DeGeer. The elimination of the brain influence on the central pattern generator (CPG) for copulation actions was done by removing the brain, and that of the SOG influence was made by splitting the SOG.Noxious stimulation, leg pinching or head injury, was introduced to cause the change of the male internal state temporarily from the sexually responsive state to the sexually unresponsive state. The results showed that decerebrated males exhibited the copulation response consistently to mimetic stimulation at least for 1 hour and their responsiveness did not change after additional removal of the SOG, while SOG-split males exhibited copulation actions sporadically and increased their responsiveness drastically after additional removal of the brain, These suggest that the brain but not the SOG plays a key role in inhibition of
copulation actions of the male cricket in the mating stage. Partial cut of a single connective (hemilateral connective-cut) combined with a copulation response test and an axonal backfilling revealed that approximately 40 brain neurons (per one connective), whose somata were located in the posterior region of the protocerebrum and mainly contralaterally to their descending axons running through the dorso-medial part of the connective, were candidates for inhibition of copulation actions in the mating stage. In addition, we report here for the first time that copulation actions can be elicited soon after copulation even in intact males. This unusual behavior emerged frequently in fledglings shortly after the final molt. The results were discussed from the viewpoint of operation of brain inhibition system on the central pattern generator (CPG).