沙海蜇（Nemopilema nomurai）繁殖策略研究

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题名	沙海蜇（Nemopilema nomurai）繁殖策略研究
作者	冯颂
学位类别	博士
答辩日期	2015-05-10
授予单位	中国科学院大学
授予地点	北京
导师	孙松
关键词	沙海蜇生活史有性生殖无性繁殖水螅体
其他题名	Study on reproduction strategy of Nemopilema nomurai Kishinouye (Scyphozoa: Rhizostomeae)
学位专业	海洋生态学
中文摘要	近年来，全球水母暴发备受人们关注。东亚海域是水母暴发的“重灾区”之一。自20世纪90年代末起，大型水母沙海蜇频繁地在我国东海北部、黄海、渤海、日本海及韩国海域暴发。沙海蜇的暴发对东亚海域的旅游业、渔业资源与生产及海洋生态安全造成巨大的威胁。目前，野外调查已经对东亚海域沙海蜇浮游阶段水母体的种群动态、季节性变化进行了详细系统地研究。然而，水母生活史中，底栖水螅体阶段的繁殖策略可能被认为是水母暴发的关键环节。由于沙海蜇伞径较大，对其人工繁殖比较困难，因此很难获得实验材料对水螅体进行室内实验，严重阻碍了对水母体有性繁殖和水螅体无性繁殖策略的研究。本文在人工繁殖的基础上，描述了沙海蜇的室内生活史过程：受精卵形成8h后，发育为浮浪幼虫。浮浪幼虫1-7d内附着变态为2-4触手水螅体，约10d后发育为8触手水螅体。2-4触手水螅体1个月后，生长为16触手成熟水螅体。水螅体在春季发生横裂。横裂体形成2-6d后开始释放碟状体，碟状体15-20d后发育为后期碟状体及水母幼体，大约经过4个月，水母体生殖腺发育成熟，适宜条件下产卵受精，进入下个世代。通过室内受控实验，研究了沙海蜇水螅体在不同温度、饵料浓度下的足囊繁殖和横裂生殖策略。结果表明，沙海蜇水螅体横裂最适温度范围为10-13˚C。长低温持续时间缩小了水螅体第一次横裂温度范围，增加了二次横裂温度范围。长低温持续时间加速了升温后，横裂体形成，提高了水螅体对升温的敏感性。碟状体最大产量发生在长低温持续时间水螅体升温到10 ˚C时，其次是短低温持续时间水螅体升温到13˚C时。水螅体倾向于在≥19˚C时进行足囊繁殖；温度越高，产生的足囊数量越多；长低温持续时间，显著增加了足囊产量。暖年夏季，18-25ºC的延长显著增加了沙海蜇足囊产量；暖年秋季18-10ºC的延长促使更多沙海蜇水螅体横裂，导致来年春季更少横裂生殖的发生，同时由于冬季碟状体低的存活率，因此不利于来年夏季水母体暴发。饵料供应对春季沙海蜇水螅体横裂百分比及碟状体产量影响不显著；但是对秋季碟状体和足囊产量，以及夏季足囊产量影响显著。我们得出了可能导致沙海蜇暴发的温度变化模式：秋季更短18-10ºC时间，冬季更长的低温持续，以及春季10-13ºC的维持。通过对水螅体的野外挂板原位实验，模拟追踪了自然海区水螅体横裂生殖过程，结果表明，横裂生殖开始于4月中旬，终止于6月初，现场水温为9-18℃。实验中观察到二次横裂发生，成熟二次横裂体形成于5月初，水温为13.6℃。最终，每个水螅体平均产生2.0个碟状体。根据本实验结果和以往研究，我们初步推测，自然海区每只沙海蜇水螅体可能平均产生≤0.02只水母体。通过青岛近岸潜水搜寻水螅体的方法，寻找沙海蜇水螅体，到目前为止虽然没有探索到沙海蜇水螅体，但是我们率先发现了海月水母水螅体自然种群，并描述了野外水螅体的附着特征及分布规律。结果表明：水螅体不但可以倒挂附着于一些自然基质如牡蛎壳、贻贝壳上，而且可以大量生长在人工基质船底、混凝土块等上。室内实验也表明人工基质适合水螅体生长及迁移，对渔网、PVC板及木板偏好性最高。这些为未来沙海蜇水螅体野外搜寻提供了重要的基础研究。潜水调查和室内实验也表明了日益增加的海洋人工基质如人工建筑和固体垃圾等，为水螅体附着、生长和迁移提供了新的基质，可能是近年来水母暴发的一个关键驱动因子。总之，本文主要围绕沙海蜇的无性生活史，通过室内实验探讨了沙海蜇水螅体横裂生殖和足囊繁殖的温度、饵料受控机制；通过水螅体挂板原位实验追踪了自然海区沙海蜇水螅体横裂生殖过程，估算了野外水螅体对水母体的贡献；并通过对比研究我国近海其他钵水母的无性繁殖策略之间的差异，重点研究了沙海蜇的无性繁殖策略，为研究近年来东亚海域沙海蜇的暴发机理、机制提供了重要的理论基础。通过潜水搜寻水螅体的方法，寻找沙海蜇水螅体，到目前为止虽然没有探索到沙海蜇水螅体，但是率先发现了海月水母水螅体自然种群，描述了野外水螅体的附着特征，为下一步沙海蜇自然海区水螅体的成功搜寻积累了重要的经验。
英文摘要	Recently, jellyfish blooms have arisen worldwide attention. In East Asian Sea, severely afflicted by jellyfish, giant jellyfish Nemopilema nomuai Kishinouye frequently outbroke in northern East China Sea, Yellow Sea, Baohai, in China, in the Japan Sea and in the Korean waters since 1990s. Blooms of N. nomurai brought about a deleterious socioeconomic and ecological impacts, such as the tourisms, fishery resources and production activities, even marine ecosystem. Long-term N. nomurai outbreaks may pose an ongoing ecosystem shift from dominance by fish to dominance by jellyfish. The spatial and temporal distribution of N. nomurai medusae have been investigated in detail so far. In the life cycle of scyphozoan, benthic polyps may determine the medusa population size. Due to the large umbrella of N. nomurai, the breeding of polyps was difficult, which seriously hinders the study on sexual reproduction process of medusae and asexual reproduction of polyps. In our study, we successfully cultivated millions of N. nomurai polyps, and detailedly described the life cycle of N. nomurai. Fertilized eggs developed into planulae after 8h. The polyps with 2-4 tentacles were formed in 1-7days, which then grew into 8-tentacle polyps after 10 days. The polyps with 2-4 tentacles developed into 16-tentacles polyps in one month. Ephyrae were liberated in 2-6 days after strobilae were formed. Ephyrae were developed into metephyrae or young medusae after 15-20 days. After four months, mature medusae were formed, and spawned in favor conditions. In the laboratory experiment, we discussed the podocyst reproduction and strobilation strategy of N. nomurai polyps at different temperatures and food supplies. The results demonstrated that the optimum temperature of N. nomurai strobilation ranged from 10-13 ˚C. Longer duration at low temperature narrowed the temperature range for the first strobilation, which was then broader for the second strobilation. Longer duration at low temperature accelerated the formation of strobilae when temperature rose, and enhanced the sensitivity of elevated temperature. The maximum number of ephyrae appeared after polyps of longer duration at low temperature were placed at 10˚C, followed by polyps of shorter duration at low temperature at 13 ˚C. Polyps preferred to carrying out podocyst reproduction at ≥19˚C. More podocysts occurred at higher temperature. Longer duration at low temperature significantly increased the podocyst production. The prolongation of 18-25˚C significantly increased the N. nomurai podocyst production in summer during warm years. And the prolonging duration of 18-10ºC contributed more polyps strobilating in autumn during warm years. Owing to low winter survival rate in winter and fewer polyps strobilating in the following spring, it thus proved adverse to the outbreaks of N. nomurai in the following summer. Food supply did not significantly affect the strobilation percentage and ephyra production for the over-wintering polyps in spring. But it had a remarkable influence on ephyra and podocyst production in autumn, as well as podocyst production in summer. A N. nomurai bloom year was expected when a shorter duration of 18-10ºC in autumn, longer duration at low temperature in winter, and a continuous 10-13ºC period in the following spring appeared. We clarified the strobilation process in the natural environment by the incubation in situ of polyps on settling plates. Strobilation occurred in the middle of April, and ceased in primary June. The seawater temperature was 9-18℃. The second strobilation was observed in the experiment in situ, whose strobilae were developed on early May and seawater temperature was 13.6℃. Finally the ephyra production was 2.0 ephyrae polyps^-1. According to our experimental results and previous study, we estimated that ≤0.02 medusae were produced from the original polyps in the natural environment. We have not still discovered the N. nomurai polyp population in natural environment in Qingdao coast. However, the Aurelia sp.1 population was firstly observed there. Polyps not only settled in some natural hard substrates upside down such as oyster shells, mussel shells or live mussels, but also massively grew underside the artificial substrates (floating wharf, concrete etc). The laboratory experiment also demonstrated that artificial substrates were favorable to the growth and immigration of polyps. The highest preference appeared at fish nets, PVC plastic and moods. These results provided crucial experiences for discovering the N. nomurai polyps. Besides, they also indicated that increasing marine artificial substrate such as marine constructions and plastic garbage may afford new substrates to polyps, and become a vital driver of jellyfish blooms. In summary, the thesis dominantly focus on the asexual reproduction of N. nomurai. We discussed the regulatory mechanisms of temperature and food supply on the asexual reproduction of polyps via the laboratory experiment. The process of asexual reproduction of polyps was approximately simulated by incubation of polyps in situ on settling plates in Jiaozhou Bay, China. And the contribution of polyps to medusae in natural environment was estimated. We emphasized the asexual reproduction strategy of N. nomruai, in comparison with other scyphozoan. The results provided a crucial theory for the N. nomurai blooms in East Asian Sea. Although we did not discover the N. nomurai polyp population in natural environment by scuba diving so far, massive Aurelia sp.1 population were firstly recorded. The distribution of population was described, which accumulated successful experience for the search of N. nomruai population in the future.
语种	中文
学科主题	海洋生态与环境科学
公开日期	2015-06-11
内容类型	学位论文
源URL	[http://ir.qdio.ac.cn/handle/337002/22797]
专题	海洋研究所_海洋生态与环境科学重点实验室
作者单位	中国科学院海洋研究所
推荐引用方式 GB/T 7714	冯颂. 沙海蜇（Nemopilema nomurai）繁殖策略研究[D]. 北京. 中国科学院大学. 2015.