Impact Factors Of Wing Morph Determination And Trade-off Of Nutrient Between Flight Capability And Reproduction In Wing Diomrphic Crickte Modicogryllus Confirmatus

Environmental heterogeneity and trade-off of energy distribution between different life history traits caused differentiation of the flight strategies in insects. Many kinds of insects have degenerate the ability to fly, and exist the so-called phenomenon of wing polymorphism or wing dimorphism. The cricket species Modicogryllus confirmatus has distinct wing dimorphism, and nymphs emerged either as macropters or micropters. The macropters have obvious difference in morphological characteristics, including body weight, front and hind wing length, and head width.In this paper, effects of photoperiod, temperature, and density on wing differentiation in a subtropical population of M. confirmatus were studied in order to find out possible relationship between wing development and environmental factors. The results showed that neither constant photoperiod nor changing photoperiod could influence its wing differentiation. The macropterous rate did not change significantly when nymphs were reared under25℃and30℃, but it decreased significantly when nymphs were kept under exceeding high temperature (35℃). These results indicate that seasonal adaption may not be the reason of wing differentiation of M. confirmatus, but high temperature stress may have a strong micropters inducing effect. The macropterous rate also did not change significantly when nymphs were kept under different density suggesting the density could not affect the wing differentiation too. In order to investigate whether genetic factors could influence the wing morph of offspring, and what is genetic mechanism? We selected LW and SW morphs for three generations, and we also investigate the macropterous rate of offspring produced by L♀×L♂,L♀×S♂, S♀×L♂, or S♀×S♂parents. The results showed that the frequency of micropters in a SW selected line increased significantly, whereas it remained at a low level in a LW selected line. This indicates that genetic factors could influence the wing morph of offspring. Crossing experiments indicated that wing morph was under polygenetic control. It is often thought there is a trade-off between flight capability and reproduction in wing dimorphic insects. In this paper, we compared the weight of flight muscles and reproductive organs between macropters and micropters in first and7th days after adult emergence. The macropterous females have well developed flight muscles, and developed flight muscles dramatically in early adulthood. By contrast, the micropterous females have poorly developed flight muscles, but developed ovaries faster than the macropters. We also investigated egg production in first20days of adulthood, the results showed that the micropters ovisposited earlier, and laid more eggs than the macropterous females. These results strongly suggest trade-off between flight capability and reproduction exists in female M. confirmatus. For the males, we found the macropters also had better developed flight muscles than the micropters. However, no significant difference was found in testes and accessory glands mass between these two wing morphs. So it seems there is no trade-off between flight and reproductive development in male M. confirmatus.In order to find out whether trade-off between flight capability and reproduction is underlied by trade-off of nutrients allocation between flight apparatus and reproductive organs, we investigated food consumption, digestibility and assimilation ratio of macropters and micropters during the first7days of adulthood. The results showed that food consumption and assimilation ration of micropterous females were both significantly higher than the macropters, and no difference existed in digestibility between macropters and micropters. It suggests that nutrients allocation between flight apparatus and ovary is different in macrpterous and micropterous females, but the food consumption also play an important role in development of ovary. For the males, no difference was observed in food consumption and digestibility, but macropters had lower assimilation ratio. This result indicates that the nutrients allocation between flight apparatus and other organs rather than reproductive organs is different in macrpterous and micropterous males.In nature environment not all insects could get enough food. In order to explore flight and breeding mode under limited food conditions, crickets were provided100%,50%,25%, and0feed during the first7days after emergence. The results showed that as the food supply decrease, ovary weight of the short winged female and flight muscle weight of long winged female insect showed a trend of reduction. Testis weight of both long winged and short winged males did not change obviously; accessory gland weighs of both long winged and short winged males showed a trend of reduction, and flight muscle weight of long winged male showed a trend of reduction. These results suggest that flight and reproductive trade-off is regulated by the nutrition conditions.