| The cricket species Velarifictorus ornatus displays distinct wing dimorphism-individuals are either micropterous with much degenerate wings or macropterous with fully developed wings. In previous study, we found that long-winged (LW) females had better developed flight muscle, but less egg production than short-winged (SW) females. Dealation could change development pattern of flight muscle and ovary. LW males also had better developed flight muscle than SW males, but no significant difference existed in development of testis and accessory gland among morphs. It was suggested that there was a trade-off between flight muscle and reproductive development in female V. ornatus, but not in male crickets, In this study, we further investigated effect of food shortage on flight muscle and reproductive development of V. ornatus to find out whether LW adults preferentially allocate limited resources in flight muscle development, while SW adults allocate them in reproductive development firstly. We also tested whether SW males had a mating competitive advantage over LW males by comparing female preference in mating competition trial. To test whether this trade-off is under control of juvenile hormone, effects of juvenile hormone Ⅲ (JH Ⅲ), juvenile hormone analogue (JHA), and precocene Ⅱ (P Ⅱ) on flight muscle and reproductive development were examined. Finally, food utilization pattern and enzyme activity were compared between LW and SW adults so as to discuss nutrient regulation of this trade-off.The results are as follows:1. Food shortage significantly suppressed flight muscle development of SW female, but did not affect flight muscle development of LW female. By contrast, ovarian development of LW female was inhibited dramatically by food shortage, but ovarian development of SW female maintained at high level when food supply was reduced. It was suggested that there was a trade-off between flight muscle and reproductive development in female V. ornatus. Like the female, food shortage also significantly inhibited flight muscle development in SW male, but not in LW male. Fresh weight of testis did not change significantly in both of LW and SW male when different amount of food was given. However, dry weight of testis was significantly decreased in LW male, while dry weight of testis of SW male did not change significantly when food supply was reduced. This result indicated that trade-off between flight muscle and reproductive development also existed in male V. ornatus.2. In a mating competition trial-one SW male and one LW male were hold together to compete for one female, females chose SW males to copulate at a probability of71.1%, while they chose LW males to copulate at a probability of29.9%. When one SW male competed with two LW males, the females also preferred to copulate with the SW male (63.2%) rather than the LW male (36.8%). These results strongly suggested that SW males had a mating competitive advantage over the LW rivals. Sound disability of SW males by removal of scraper significantly decreased their chance to copulate and mating probability of disable SW males and intact LW males were23.3%and76.7%respectively when they were competing for female. When both of LW and SW male were sound disabled, mating probability did not changed significantly between morphs (54.8%for LW male, and45.2%for SW male). It is suggested that sound of the male play an important role in courtship with female.3. LW and SW females were treated with different dose of JH Ⅲ and P Ⅱ respectively at the first day after emergence. Topical applications of JH Ⅲ within range of5-25μg/♀suppressed development of flight muscle of LW females, but they promoted development of ovary and synthesis of eggs of the LW females. The strongest effect was found in LW females treated with5μg JH Ⅲ. However, no effect was observed when LW females were treated with50μg JH Ⅲ. JHA had a similar effect on development of ovary and flight muscle of the LW females, and the strongest effect was found in LW females treated with10μg JHA. A single treatment of PⅡ could not affect development of ovary and flight muscle in SW females. However, when SW females were treated with0.5-12.5jig P Ⅱ at the first day after emergence and once again at5d after emergence, development of flight muscle apparently increased, and development of ovary and synthesis of eggs were suppressed to some degree. Development of ovary and synthesis of eggs were significantly suppressed when SW females were treated twice with25μg P Ⅱ. These results indicated that physiological trade-off between flight muscle and reproductive development of female V. ornatus might be regulated by juvenile hormone.4. Topical application of1-50μg JH Ⅲ on first day of adulthood could promote development of flight muscle, testis, and accessory glands of LW males to some extent. Topical application of JHA had similar effect on development of flight muscle, testis, and accessory glands of LW males. A single treatment of P Ⅱ to SW males on first day of adulthood could dramatically decreased development of flight muscle, but not affect development of testis and accessory glands. When SW males were treated twice with2.5-5ug P Ⅱ, development of testis was apparently decreased, but no effect on development of flight muscle and accessory glands was found. When they were treated twice with5-25ug P Ⅱ, only flight muscle development was significantly suppressed. These results did not support the hypothesis that physiological trade-off between flight muscle and reproductive development of males are under control of juvenile hormone.5. LW and SW females of V. ornatus were different in digestibility of food. Although efficiency of conversion of ingested food to body matter (ECI) and approximate digestibility (AD) were similar in SW and LW females, SW females ate significantly more food than LW females, and they also had a higher efficiency of conversion of digested food to bodyⅡmatter (ECD). For this reason, absolute growth (GR) and relative growth (RGR) of SW females were both significantly higher than that of LW females. Unlike the females, we found no significant difference in food consumption, AD, ECI, ECD, GR, or RGR between LW and SW males. Digestive enzyme activity also varied between morphs. Total protease and trypsin activity reached a peak at4d after emergence, and both of them were significantly higher in LW adults than in SW adults. Amylase activity increased during first12d of adulthood, and it did not change dramatically between LW and SW females, but a higher amylase activity was found in SW males than in LW males at4d of adulthood. Lipase activity was similar in SW and LW females at first day of emergence, and it was significantly higher in SW females than in LW females at4d of adulthood, but lower in SW females than in LW females at12d of adulthood. Protein content decreased after emergence, and no significant difference was found between LW and SW females at all three ages. However, SW males had significantly higher protein content than LW males at4d after emergence. These results indicate that food utilization patterns vary between morphs, and it may be correlated with physiological difference of digestive enzyme activity in midgut. |
PDF Full Text Request