OVIPOSITION BEHAVIOR OF THE CRICKET TELEOGRYLLUS-COMMODUS - MECHANOSENSORY CELLS IN THE GENITAL CHAMBER AND THEIR ROLE IN THE SWITCH-OVER OF STEPS

Sensory information interlinking two consecutive steps in the oviposition behaviour, egg progression and the rest phase, was investigated in the cricket Teleogryllus commodus. Two types of mechanosensory cells, several multipolar and many bipolar cells, were found in the posterior wall of the genital chamber. Females whose nerves from these sensory cells were severed failed to switch from the egg progression stage to the rest phase. The clustered multipolar cells spread their dendrites in the basement membrane of the epidermis of the genital chamber wall. More than 35 bipolar cells were scattered in the concerned area. Mechanical stimulation of these sensory cells evoked a tonic afferent response and a change in the efferent pattern. Consequently, the genital chamber contracted as a whole, and the frequency twitching of the spermathecal duct increased. The sperm may be squeezed out, by the intense twitch of the duct, to fertilize the egg. Contraction of the genital chamber forces the egg backwards. Thus, sensory information from the mechanosensory cells in the genital chamber terminates egg progression, and releases the rest phase, or the fertilization step. The link between the rest phase and the subsequent egg deposition step is also discussed.