基于螅状体种群两种有效补充途径的渤海沙蜇暴发增殖策略研究

Based on our preliminary research result, we will throughout this project, explore the recruitment modes of polyp population based on sexual and asexual reproduction, and blooming potential of the giant jellyfish Nemopilema nomurai in Bohai Sea: (1) Clarify the spatiotemporal distribution and pattern of horizontal migration of N. nomurai mature parent in Liaodong Bay using synchronously surveyed data on abundance and gonadal maturity, by means of molecular characteristics (COI and ITS-5.8S rDNA). (2) Find out the favorable conditions of metamorphosis for planula produced by sexual reproduction through experiments on substrate choice and settlement preferences, and on the effects of temperature, salinity and light on survival rate and adhesion rate. (3) Evaluate the capacity of the sexual reproduction recruitment of adult to polyp population basing on the fecundity data of natural mature medusa obtained from field investigation and on the conversion rate from fertilized eggs to developed polyps with 8-tentecle in laboratory. （4）Compare the capacity of sexual (mature medusa) and asexual reproduction (polyp) and estimate their relative contribution to the original polyp population through a two-year’s synchronous observation on the annual life cycle of two generations of polyp from N. nomurai population, combining field experiment with polyps attached on hanging polyethylene plates and laboratory experiment simulating natural condition in terms of temperature, salinity and light intensity, etc. The results of this study should be essentially used in clarifying the recruitment mode of polyp population based on sexual and asexual reproduction, and would help in determining the probability of future bloom development and in installing effective means and ways of countermeasures.

本项目在前期研究基础上，拟从螅状体有性繁殖和无性繁殖两种补充途径研究大型致灾水母沙蜇底栖螅状体种群的最有效补充途径与机制。通过同步调查辽东湾沙蜇产卵亲体的时空分布和性腺成熟度、辅助以分子标记技术(如线粒体COI、ITS-5.8S rDNA)查清渤海沙蜇产卵群体的时空分布与移动特征；通过浮浪幼虫对不同附着基的偏好实验以及环境因子对浮浪幼虫变态附着率的影响实验，查清有性繁殖补充途径对螅状体种群补充的最适宜生境条件；通过对自然水域调查和繁育实验观察，从怀卵量-受精卵-8触手螅状体之间的数量转换率角度综合分析沙蜇的有性繁殖对螅状体种群的补充能力。首次通过野外螅状体挂板与室内同步模拟对照结合的方法，进行两代螅状体种群的周年生活史观察，阐明有性繁殖与无性繁殖对渤海沙蜇螅状体种群的相对贡献差异，本研究将进一步揭示沙蜇的暴发机理，为灾害预测及有效治理提供新思路。

本项目聚焦黄渤海海域大型致灾水母种类中个体最大、生物量最高、影响范围最广的沙蜇（N.nomurai），采用螅状体室内生态实验与野外多点挂板相结合的方法，从有性繁殖和无性繁殖两种途径探究了沙蜇螅状体种群的有效补充机制，通过同步调查辽东湾沙蜇产卵亲体的时空分布和性腺成熟度、辅助以分子标记技术查清了渤海沙蜇产卵群体的时空分布与移动特征,证明沙蜇的发生地是多缘、多点的，沙蜇的生活区域从其初始发源地扩散到辽东湾南部海域，沙海蜇在辽东湾和辽东半岛南部水域可以完成野外生活史的全过程。通过浮浪幼虫对不同附着基的偏好实验以及环境因子对浮浪幼虫变态附着率的影响实验，科学界定了沙蜇浮浪幼虫变态附着的最适温度、盐度和饵料条件，揭示沙蜇浮浪幼虫附着偏好。查清了有性繁殖补充途径对螅状体种群补充的最适宜生境条件；通过对自然水域调查和繁育实验观察，从怀卵量-受精卵-8触手螅状体之间的数量转换率角度综合分析了沙蜇的有性繁殖对螅状体种群的补充能力。首次通过野外螅状体挂板与室内同步模拟对照结合的方法，进行两代螅状体种群的周年生活史观察，阐明了在渤海海域沙蜇有性繁殖新产生的螅状体和无性繁殖萌发的子代螅状体共同维持原发生地的螅状体种群数量,贡献率会受到环境异常变化、敌害生物栖息地竞争等复杂环境因素影响，沙蜇相对其它大型水母种类（如海月水母等）更依赖于有性繁殖进行种群的有效补充。本研究将进一步揭示沙蜇的暴发机理，为灾害预测及有效治理提供新思路。