The Wing Variation And Control Mechanism Of Physiological Trade-offs In The Wing-dimorphic Cricket, Velarifictorus Ornatus

Diapause and wing dimorphism is the two major season adaptation strategy of insect. Velarifictorus ornatus overwinter in the form of nymphs and has two types of wings in adult. In this paper, we studied the effect of photoperiod on the development of nymphs and the effect of environment factors and injury on the variation of wings. Meanwhile, the physiological trade-off and endocrine control the physiological trade-off between long-winged individuals and short-winged individuals were investigated. The difference in allocation of resources to egg production and flight muscle development between wing dimorphism were also studied. The results are as follows:1. Nymphal development was slow under constant photoperiods at25℃. The shortest mean duration of nymphal development was (206.2±44.0)(mean±SD) days at LD16:8h, followed by (230.3±47.4) days at LD12:12h and (236.5±93.3) days at LD14:10h. No significant difference was observed in the nymphal durations among different constant photoperiods at25℃. Nymphal development was further prolonged when nymphs were exposed to LD16:8h during the first60days and then transferred to LD14:10h or LD12:12h at25℃. Similar results were obtained when nymphs were transferred from LD14:10h to LD12:12h at60days after hatching at25℃. However, in the reverse transfer, i.e. from short days to long days, the durations of nymphal development was dramatically shortened. When nymphs were transferred from LD12:12h to LD16:8h at10,30,60or90days after hatching, the mean nymphal durations were (135.9±88.5),(80.0±5.9),(110.4±10.4) and (142.9±10.8) days respectively. When photoperiod was shifted from LD12;12h to LD14:10h at60days after hatching, the nymphal duration was (120.9±7.7) days. Nymphs exposed to those photoperiod shift developed faster than those kept at constant photoperiods. Although adults emerged more rapidly under long days than those reared under short days at30℃, changing photoperiods showed similar results on nymphal development as those at25℃. These results suggested that seasonal changing day-length controls nymphal development of V. ornatus to synchronize their life-cycle with the season.2. The percentage of brachypterous morph was more than95%when nymphs were reared at constant LD16:8h、 LD14:10h and LD12:12h at25℃or30℃. The percentage of macropterous increased when nymphs were first exposed to short photoperiod and then transferred to long photoperiod. But there was no statistics difference between the above experiments. However, in the reverse transfer, i.e. from short day to long days, The percentage of brachypters was similar to the nymphs which were reared at the constant photoperiod. In crowding experiment, percentage of macropters was11%when rearing of nymphs separately at25℃. The number of macropters increased obvious, which is higher than the nymphs reared separately, as the per container density was increased to2nymphs. But the number of macropters decreased as the per container density was increased to5or10nymphs. The results indicated that the density played an important role in the determination of wing morphs. Meanwhile, injury could induce brachypters in the phase of nymphs especially in the last instar.3. There was no difference in body weight and pre-oviposition between the two morphs, but long-winged individuals had better-developed flight muscles than short-winged individuals during and after emergence of the adult. The flight muscles at adult emergence represented11.9%of the total body weight in the long-winged female and4.9%in the short-winged female. In addition, the weight of the flight muscle of long-winged females increased by50%during the first5days, whereas the flight muscle of the short-winged variant increased only slightly after adult emergence. The process of oviposition in long-winged, short-winged, and de-alated females varied:short-winged females produced more eggs at the early stage than long-winged females, but de-alation could shorten the time until the peak of egg laying and caused histolysis of flight muscles of long-winged females. There was no significant difference in total egg production between the above three groups. In the male, unlike the female, the accessory glands of the two wing morphs enlarged continuously at the same rate. There was no difference between the two wing morphs in the mass of the testes during the first7days after adult emergence.4. Juvenile hormone and precocene were injected to long and short individuals respectively at the day of adult emergence. Topical application of juvenile hormone increased ovary and incident of flight muscle histolysis in long-winged female. Exogenous juvenile hormone stimulated ovary development but failed to elicit any significant effect on egg production. Injection of precocene restrained the ovary development of short-winged female when the dose was over50ug, but there was no effect on the ovary development when the dose was less than50ug. There was no difference in the testis, accessory gland and flight muscle development between the males which were injected acetone and the males which were injected JH. Injection of precocene elicited no influence on the testis, accessory gland and flight muscle development of short-wing male.5. Differences in resource allocation to flight muscle and reproduction organs between wing dimorphism individuals were studied by means of protein, glycogen and total lipid analysis. Long-winged females first devoted the energy to their flight muscle, while short-winged females allocated the energy to their ovary firstly. The long-winged female could reutilize the energy from the histolysis of flight muscle to development of ovary after the hind-wing was removed at the day of adult emergence. The amount of protein, glycogen and total lipid in flight muscle of long-winged male were much more than that of short-winged male, but there was no difference in testis and accessory gland between long-winged and short-winged morph. These results indicated that it was different in allocation of resources to flight muscle and reproduction organs between long-winged and short-winged individuals. On the other hand, the total lipid in flight muscle was much more than the protein and glycogen, that means lipid was the major energy for flighting.6. Topical application of juvenile hormone increased ovary and incident of flight muscle histolysis in long-winged female. Exogenous JH only raised the amount of protein, glycogen and total lipid in ovary, but failed to elicit any effect on the amount of protein, glycogen and total lipid in flight muscle. There was no effect on the amount of protein, glycogen and total lipid in flight muscle and reproduction organs after the long-winged male were injected JH and short-winged male were injected precocene.