Time dependence is an important aspect of the reproductive behaviour of male crickets (Loher and Rence, 1978; Nagao and Shimozawa, 1978;Sakai et al., 1991). It usually occurs as follows. The male begins to sing a calling song to attract females when he becomes sexually active. The calling song soon changes into a courtship song when a female approaches. When the female steps onto the male's back, the male begins to perform copulatory actions by slipping backwards underneath the female. After success in genital coupling, the male extrudes the spermatophore and transfers it to the genital chamber of the female. As soon as the male finishes copulation, his behaviour towards the female changes from courtship to aggression, that is, he enters the sexually inactive state. Subsequently, the male performs spermatophore preparation to make a new spermatophore for the next copulation. Spermatophore preparation consists of the secretion of spermatophore materials from the accessory glands and testes, their transport through the ejaculatory duct and their ejection onto the ventral lobes of the phallic complex in the genitalia. Once spermatophore preparation is initiated, the calling song occurs after a fixed time, and he again enters the sexually active state.Thus, the male cricket has a reproductive cycle consisting of the pre-copulatory mating stage (MS) and post-copulatory sexually refractory stage (RS). The mating stage is here defined as the interval from the onset of the calling song to spermatophore extrusion in copulation. The sexually refractory stage is the interval from spermatophore extrusion to the onset of the calling song. This refractory stage is further divided into the two substages: the first refractory stage (RS1) between spermatophore extrusion and spermatophore preparation, and the second refractory stage (RS2) between spermatophore preparation and the onset of the calling song. In Gryllus bimaculatus, RS1 is normally several minutes if a female is readily available. However, it is considerably prolonged, occasionally more than 1·h, if no female is present or the male is subject to stressful conditions (Nagao and Shimozawa, 1987;Ootsubo and Sakai, 1992). In contrast, RS2 is time-fixed (about 1·h) and is unaffected by the female or by stress. Thus, it is called the time-fixed sexually refractory stage, and is presumably under the control of a reproductive timer (Nagao and Shimozawa, 1987;Sakai et al., 1995;Ureshi and Sakai, 2001). The reproductive cycle of the male cricket consists of the mating stage and the sexually refractory stage. The latter is further divided into the first refractory stage (RS1) from spermatophore extrusion in copulation to spermatophore preparation after copulation, and the second refractory stage (RS2) from spermatophore preparation to recommencement of a calling song. RS2 is time-fixed and unaffected by the female or by stress, hence RS2 is assumed to be controlled by the reproductive timer. Previously, we suggested that the timer is located in the terminal abdominal ganglion...
Pycnospores of Mycosphaerella pinodes, a non-obligate parasite of pea plant did not induce pisatin accumulation until they established infection, probably suppressing defense reaction of the host.This fungus was highly tolerant to pisatin as assessed by the inhibitory activity to spore germination or germ-tube elongation (ED50=500ppm). The fungus, however, could not establish infection on pea if a very low concentration (less than 50ppm) of pisatin was administered artificially into the spore inoculum. The perforation of cellophane-sheet by germ-tube of M. pinodes was also inhibited by the same concentration of pisatin that inhibited infection on the host. These results suggest strongly that the importance of phytoalexin as an anti-infectional factor in defense reaction of host rather than antifungal substance and pea pathogen, M. pinodes suppresses pisatin production in early stage of infection in order to avoid its inhibitory effect on infection.
Insects groom almost all parts of the body surface with their legs and mouth parts. However, some body regions are difficult to reach and keep clean. One is the genital chamber located in the last abdominal segment in males which houses the phallic complex for copulation and production of the spermatophore. In the male cricket, foreign substances can enter the genital chamber when it is opened during copulation and spermatophore formation. Moreover, the dorsal pouch and ventral lobes of the phallic complex, which mould the attachment plate, tube, and ampulla of the spermatophore, are inevitably soiled as a result of spermatophore production. We found a unique cleaning system in which foreign substances accumulated during copulation and spermatophore debris left in the dorsal pouch after copulation are quickly removed and collected in special pockets in the genital chamber. This trash is collected by undulation of the genital chamber's membranous floor which is entirely covered by small scales ( approximately 10 microm) similar to those in the ovipositor of female crickets. This self-filling trash collecting system may be used in some other insects which produce the spermatophore in a similar manner to that of crickets.
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