【作者】 杨帆；

【导师】 翟保平；

【作者基本信息】 南京农业大学 ， 农业昆虫与害虫防治， 2014， 博士

【摘要】 稻纵卷叶螟Cnaphalocrocis medinalis (Guenee)是亚洲水稻种植区一种局地间歇性发生的重大农业害虫,具有大区域、长距离、季节性的迁飞习性,2003年以来在我国连年全国性大发生,给我国水稻生产带来巨大的经济损失。20世纪70年代末的全国大范围多学科协作研究,业已证实了稻纵卷叶螟在我国东半部季节性南北往返迁飞的规律。但稻纵卷叶螟具有很强的再迁飞能力,其一次远距离迁飞常要经历多天的夜间飞行和白昼停息的过程,飞行过程极为复杂。目前尚不明确稻纵卷叶螟迁飞与生殖的关系以及再迁飞行为发生和终止的生理生态调控机制,因此无法准确提取蛾群迁飞的各项飞行时间参数。在轨迹分析未被普遍应用于该虫的研究之前,对稻纵卷叶螟的异地测报只能停留在大范围、大尺度的定性预报层面上,而对于中、小尺度内精细化迁飞路径的研究仍然束手无策。本论文将田间观测和室内试验相结合,对稻纵卷叶螟的起飞行为进行了较为系统的研究,并探讨了幼虫期拥挤和食物胁迫对成虫首次迁飞的诱导效应、实验种群的再迁飞能力及其与飞行强度、种群性质、环境因子(温度)和生殖系统发育的关系,取得了一些新的研究进展,以期探索包括起飞、首次迁飞和再迁飞在内的各迁飞阶段的发生机制和环境调控机制,为稻纵卷叶螟的轨迹分析提供可靠的实测参数,为异地预测提供科学的理论依据。主要研究结果如下：1.稻纵卷叶螟的起飞行为研究(1)根据田间系统调查及雌蛾卵巢系统解剖确定了2011年广西永福早稻田稻纵卷叶螟的主要迁出期,并通过大型罩笼观测,同步研究了田间自然状态下稻纵卷叶螟的起飞时刻、起飞比例和卵巢发育程度,分析了光照强度、天气条件(风、雨)等环境因子对起飞比例的影响。结果表明,稻纵卷叶螟的整个起飞过程一般在日落后20-40min内完成,并于昏影终时达到最高峰；日落前无起飞个体。稻纵卷叶螟具有大仰角起飞的特性,在起飞个体中,以落罩笼顶区的比例最高。降雨及2-3级风会显著降低种群的起飞比例。罩笼内起飞个体(迁飞型)与未起飞个体(居留型)的生殖系统发育程度表现出显著差异,表明稻纵卷叶螟在第一次远距离迁飞时存在“卵子发生与飞行共轭”的现象。(2)在室内条件下,通过自主设计的起飞观测装置,利用人工模拟的黄昏环境,分别对迁出种群以及本地繁殖种群的起飞、扩散行为与日龄、性别和环境因子(光照强度、温度)的关系进行了研究。结果表明,不同日龄稻纵卷叶螟的飞行比例存在显著差异,以羽化后24 h内成虫的起飞和扩散比例最低,2日龄的迁飞起飞比例最高。迁出种群雌蛾的产卵前期平均可达7.6 d,在羽化后较长一段时间内成虫均可保持远距离飞行的潜能和欲望。本地繁殖种群的起飞数量明显低于迁出种群,但仍占有一定比例,田间各代均有一定比例的外迁个体,这种种性特征不会因室内继代饲养而完全丧失。光照和温度是影响稻纵卷叶螟起飞的重要环境因子。成虫的起飞行为需要在一定光照强度的触发下才能发生,起飞高峰发生在0.1-1.01x,最适光强范围约为301x以下。起飞的适宜温度范围是20-30℃,最适温度为26.6℃。在一定范围内,起飞比例随着温度的升高而增加,并于26℃达到最大值；超过26℃起飞比例反而下降；10℃下没有个体起飞。不同性别个体的起飞行为对温度的响应有所不同,对于夏季北迁种群而言,在首次迁飞发生期,当具备适宜的光照、温度等适于起飞的环境条件时,雌虫的起飞欲望高于雄虫；但在低于20℃的条件下雄虫的起飞比例高于雌虫,说明起飞时雄虫对低温的耐受力更强。2.幼虫期拥挤和饥饿对成虫首次迁飞的诱导效应为了明确幼虫期拥挤和突发性饥饿处理对稻纵卷叶螟种群增长的影响以及是否存在迁飞的诱导效应,对室内条件下不同幼虫密度以及不同饥饿龄期、不同饥饿时间处理下饲养的稻纵卷叶螟的生长发育及繁殖力进行了研究。结果表明,幼虫期拥挤显著降低了蛹的重量、存活率以及雌虫繁殖力。随着幼虫密度的增加,幼虫取食速率加快,发育历期缩短,化蛹时间与单头饲养试虫相比提前2 d。与之相反,短时间的突发性饥饿处理及其随后的补偿性生长使幼虫的发育历期延长,化蛹时间与未饥饿处理试虫相比推迟3-4 d,蛹期延长1-2 d。幼虫饥饿同样降低了蛹的重量,但对雌虫繁殖力没有显著影响。不同龄期、不同时间的饥饿效应对稻纵卷叶螟的影响作用大小依次为4L-36h>5L-36h>4L-24h>5L-24h。尽管就不同性别而言,雌、雄个体拥有相似的发育策略,但雌虫面对种群拥挤和食物缺乏等不良环境时比雄虫更加敏感。所有处理对雌蛾的产卵前期均无显著影响。认为稻纵卷叶螟种群在面对拥挤和食物短缺时的发育应对策略有所不同；幼虫期出现的这两种胁迫因子不会诱导成虫迁飞行为的产生。3.稻纵卷叶螟实验种群的再迁飞能力在人工气候室内,利用计算机控制的昆虫飞行磨系统测定了稻纵卷叶螟2日龄首次起飞成虫的飞行能力和再迁飞能力,研究了夜间的主动飞行节律,明确了飞行强度对成虫起飞比例和再迁飞次数的影响,并对室内饲养不同世代后种群的再迁飞能力进行了比较分析。结果表明,在12h的人工暗期内,稻纵卷叶螟成虫的主动飞行主要集中在进入暗期后的前4-6个小时；其中强迁飞型个体的平均续航时间为7.6 h,迁飞型个体为4.9 h。飞行强度对再迁飞能力影响显著,每个夜晚吊飞8h成虫的再迁飞能力显著低于4h处理,表现为再迁飞次数的减少和再迁飞比例的下降。田间种群与室内种群的再迁飞能力存在显著差异,田间采集的稻纵卷叶螟种群在室内饲养一代以后,单次持续飞行时间、飞行距离以及飞行速度均没有明显的降低,仅表现出再迁飞次数的减少；但室内饲养二代后各项飞行参数与田间种群相比都显著下降。田间种群平均可进行4次再迁飞,最多8次；室内饲养一代种群平均可进行2次再迁飞,最多5次；而饲养两代以后大部分个体仅能连续飞行2天。在低强度飞行模式下雌、雄个体的再迁飞能力没有显著差异,但雌虫在高强度飞行模式下表现出更好的飞行“耐力”,发挥出明显强于雄虫的飞行潜能,表现为首次起飞夜晚的持续振翅时间较长、午夜后飞行活跃度较高,且每次吊飞8h处理下雌虫的再迁飞次数以及再迁飞3-5次个体的飞行比例和单次持续飞行时间、飞行距离、飞行速度均显著高于雄虫。4.温度对稻纵卷叶螟再迁飞能力的影响在未交配条件下,20℃-29℃范围内成虫均能进行正常的飞行活动,且雌、雄个体的飞行能力没有显著差异。260C条件下成虫的飞行时间最长、飞行速度最快、飞行距离最远,种群的再迁飞比例最高,再迁飞次数最多(平均2.42次,最多5次)；其它三个温度下大多数个体仅能完成一次连续飞行,无法进行再次飞行。虽然20℃、23℃和29℃下成虫的平均再迁飞次数(分别为0.53、0.81和0.75次)、再迁飞比例没有显著差异,但对飞行行为产生不同的影响。低温显著降低了成虫的飞行速度；而高温下成虫飞行后的死亡率大大增加,表现为29℃下个体的存活率明显低于其它温度。5.再迁飞过程中飞行与生殖的互作关系通过飞行磨吊飞和对飞行器官与生殖系统进行系统解剖,观察了雌蛾在再迁飞过程中的飞行肌与卵巢发育进度,比较了交配前后雌虫再迁飞能力的差异,并对飞行与生殖的相互作用关系进行了探讨。结果表明,在再迁飞过程中,随着飞行次(天)数的增加,飞行肌并没有发生明显降解,飞行器官与生殖系统的发育是同步进行的。再迁飞对生殖系统发育的影响受飞行时间长短的左右,飞行1-3个夜晚显著促进雌蛾的卵巢发育,飞行4-5个夜晚无显著影响,6个夜晚之后则表现为抑制作用,并且出现交配率降低、生殖力下降等负面影响。另一方面,生殖对飞行没有明显的负面影响效应,交配状态、产卵与否对再迁飞影响不大。综上所述,在本文以及原有研究的基础上,我们针对稻纵卷叶螟的迁飞模式提出一种新的概念：迁飞行为起始于个体性器官发育的未成熟阶段,但成虫在再迁飞过程中不符合“卵子发生与飞行共轭”现象,雌蛾的卵巢发育、交配、产卵可与再迁飞同步进行,并在迁飞途中可能会有一至多次交配,产卵之后可以继续飞行。更多还原

【Abstract】 The rice leaf roller, Cnaphalocrocis medinalis (Guenee), is one of the most serious pests in the Asian rice production and is confirmed to be a high-altitude nocturnal windborne migrant. The outbreak frequency of this species continued to increase in the whole China since 2003 and caused huge loss on rice production. It has been proved that the moths migrate annually from southern to northern areas in the spring and summer and then return to the southern areas in the autumn. However, the C. medinalis adults have strong re-emigratory flight capacity. Moreover, the migration process is composed of a series of night-time flights rather than one continuous flight. Moths usually land at dawn and emigrate in the following evening. All of these reasons made the complex aerial flight process of this pest. At present, the flight-oogenesis relationship in the process of re-emigration and its ecological and physiological mechanisms were not quite so clear-cut. So exact time parameters set in migratory phase were still unable to be determined. It is a real problem to accurately forecast the occurrence of C. medinalis compared with those species flying once only. Before trajectory analysis was widely used in C. medinalis, we always felt helpless to provide precise estimates for a middle or small-scale flight path and the forecasting on occurrence could just stay in the qualitative level at large scales.In the present study, the take-off behavior of caged C. medinalis both in field conditions and climate chamber were observed, and the effects of light intensity and ambient temperature on take-off proportion were investigated. Larval and adult developmental responses to crowding and food stress were analyzed. The re-emigratory flight performance and its relation to flight intensity, population characteristics, environmental factors and reproductive development were examined by tethered flight using computer-interfaced flight mills. The ecological mechanisms of taking-off, first migration and re-emigration were explored. These results may provide reliable parameters for trajectory analysis and help develop effective population monitoring and forecasting measures. The main results were summarized as follows:1. Take-off behavior of C. medinalis(1) The emigration peak period of C. medinalis in double-cropped early-season rice field in Yongfu, Guangxi were confirmed by systematic field surveys and female ovarian dissection in 2011. The take-off behavior, time, proportion and ovarian development of emigrants in the field of natural state were studied through large-size cage experiment. And its relation to environmental factors such as light intensity and weather condition (wind and rain) were also analyzed. The whole process of take-off behavior of C. medinalis occurred in 20-40 minutes after sunset and reached a peak period at the endiri’g of evening twilight. There were no individuals taking-off before sunset. The highest landing proportion in top area of the cage was observed. Heavy rain and wind at 2-3 grades could obviously reduce its take-off propensity. The ovarian development showed significant difference between emigrants and residents, which meant that the oogenesis-flight syndrome occurred in its first long distance migration.(2) Take-off behavior of C. medinalis was also observed with unmated females and males of 1 to 6-day-old in climate chamber. The relationships between take-off activity of emigrant and local breeding population, moth ages, sexes and environment factors were investigated. Simulated dusk and a self-developed observation device were used in this study. There was significant difference in flight frequency of virgin moths at different ages. The number of take-off was lowest during the first 24 hours after eclosion and reached peak period quickly at the second day. The emigrant population had a long pre-oviposition period for 7.6 days, which meant that C. medinalis had a long migrating period and their propensity and capacity to migrate could be maintained for a quite long time after eclosion. The local breeding population had significantly lower average take-off frequency than emigrant population, but it still occupied a certain proportion of emigrants. This result suggested that migration was the hereditary character of C. medinalis with species specificity, which would not be lost completely even under laboratory continuous breeding. A certain proportion of emigrants always existed in any field generation. Light intensity and ambient temperature had significant effects on flight and landing behavior of C. medinalis adults. Occurrence of the take-off behavior needed the triggering of optimum light intensity below 30 Ix, and the proportion of take-off reached a peak at the light density ranged from 0.1 to 1.0 1x. The ambient temperature suitable for take-off was ranged from 20℃ to 30℃ and the optimum temperature was 26.6℃. Take-off proportion reached a peak at 26℃ whereas a high temperature above 26℃ would inhibit take-off. There were no individuals taking-off at 10℃. The response of taking-off to ambient temperature was a bit different between females and males. A significantly higher proportion of females would take off at optimum temperature and illumination conditions compared with males during the first long distance migration. However, males showed higher take-off propensity when temperature was lower than 20℃ than females, indicating that low temperature threshold for take-off of males was lower than that of females.2. Effects of larval density and food stress on migration of C. medinalis adultsIt has been known that the temperature and photoperiod were the cues to trigger the migrating behavior of C. medinalis. However, the effect of food conditions on the migration of this insect is still unclear. In the present study, larval and adult developmental responses to crowding and food stress were investigated. The results showed that a high larval rearing density significantly reduced pupal mass, survival rate and female fecundity. Larvae developed rapidly under crowding conditions, and time to pupation was 2d earlier than individuals reared alone. By contrast, short-term starvation and associated compensatory growth prolonged larval development time by 3 d to 4 d and pupal development time by 1 d to 2 d. It also reduced the pupal mass, but showed no detectable effects on female reproductive performance. The effect of starvation treatment on larval development was highest in the 4L-36h group, followed by the 5L-36h,4L-24h and 5L-24h-groups. Both sexes had similar development strategies; however, females seemed to be more sensitive to crowding and food shortage than males. All treatments did not significantly increase female pre-oviposition period. Therefore, we concluded that life developmental responses to crowding and food shortage in this species were different. Adult migration propensity was not enhanced under such stress conditions during the larval phase.3. Re-emigratory flight performance of C. medinalisThe flight and re-migration performance of C. medinalis were examined by tethered flight using computer-interfaced flight mills in 2-d-old virgin females and males when taking-off behavior occurred for the first time. We investigated the nocturnally active flight rhythm. Effects of flight intensity on take-off proportion and re-migration times were analyzed. Flight and re-migration capacity of C. medinalis origin from field and laboratory populations were compared. The results showed that nocturnally flight activity of migratory individuals occurred throughout the 12 h scotophase and peaked at 4-6 h after artificial dusk. Flight duration for strong migratory type of moths at one night was 7.6 h and migratory type was 4.9 h. Re-migratory times and take-off proportion in the treatment of testing for 8 h every night were lower than that of 4 h treatment. There were significant differences in re-emigratory flight capacity between field and laboratory-reared insects. Strong re-migration propensity of field populations had been observed, which could fly for five successive nights on average, and nine nights maximum. Rearing for just one generation had no negative influence on their flight performance except the reduction in re-migration times, which had three successive flights on average and 6 maximum. But parameters included duration, distance, velocity and successive flight times were significantly decreased when insects were reared for two generations in laboratory. Most of the moths could fly for twice only. The long-duration flight behavior of unmated females was similar to that of unmated males under the flight patterns of low intensity. Their propensity and capacity to flight, however, were still different. Females showed better flight endurance and greater flight potentials than males under the flight patterns of high intensity. Longer wing-beating duration and higher flight willingness after midnight were performed in females in the first testing night. There were also significant differences in re-emigration times, take-off proportion and flight parameters between females and males flying for 4-6 nights and tested for 8 h every night.4. Effects of temperature on re-emigratory flight performance of C. medinalisAmbient temperature had a significant influence on re-emigratory flight behavior, although flight activities could be performed normally at all temperatures ranged from 20℃ to 29℃ and there were no significant differences in all measured flight parameters between females and males under the same treatment. Longest flight duration, fastest flight speed and greatest flight distance were performed at 26℃, as well as the highest take-off proportion and re-emigration times. Adults could fly for 3.42 successive nights on average and six nights maximum at 26℃. By contrast, most individuals could only complete a continuous flight for one night and could not take off for the second night under other three temperatures. Although re-emigration performance tested at 20℃ and 23℃ were similar as 29℃, different influences on flight behavior were observed. Flight velocity was greatly reduced at lower temperatures, while mortality rate of moths after successive passive flights at 29℃ was significantly higher than any other temperatures, showing that high temperature had greater impact on survival rate of moths and resulted in a long-duration flight than low temperature.5. Interrelationship between migration and reproduction in C. medinalisDaily flight muscle and ovarian development of virgin females were investigated by tethered flight and systematic dissection. We compared the re-emigratory flight performance between mated and unmated females. The interactions between flight and reproduction in the process of re-emigration were analyzed. The flight muscle histolysis did not take place after a series of night-time flights. The development of flight apparatus and reproductive system were synchronized in the process of re-migration. Effects of re-emigratory flight on reproduction of moths were strongly dependent on the flight duration. Continuous flight for 1 to 3 times significantly accelerated the ovarian development, and inhibitory effect appeared with the onset of the sixth flight. It is suggested that a short period of flight may stimulate the reproductive development, whereas passive flight to exhaustion incurs a reproductive cost caused by a prolonged pre-oviposition period, decreased mating percentage and frequency. Furthermore, mating status and oviposition did not seem to influence the re-emigratory flight performance. Together, we propose a new conceptual migratory model for this species based on the results of this and previous studies:The first long distance migration initiates in the stage when adults are sexually immature, however, ovarian development and flight are synchronized in the process of re-migration, showing the apparent absence of the oogenesis-flight syndrome. We hypothesize that C. medinalis may pursue mating during the migratory phase and oviposit a part of eggs en route.更多还原