温度、投饵频次对白色霞水母无性繁殖与螅状体生长的影响
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辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院,辽宁省海洋水产科学研究院

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国家973重点基础研究发展计划项目(2011CB403601);海洋公益性行业科研专项(200905019, 201005018)


Effect of temperature and feeding frequency on asexual reproduction and polyp growth of the scyphozoan Cyanea nozakii Kishinouye
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Liaoning Ocean and Fisheries Science Research Institute,Key Laboratory of Marine Biological Resources and Ecology,Liaoning Province,Liaoning Ocean and Fisheries Science Research Institute,Key Laboratory of Marine Biological Resources and Ecology,Liaoning Province,Liaoning Ocean and Fisheries Science Research Institute,Key Laboratory of Marine Biological Resources and Ecology,Liaoning Province,Liaoning Ocean and Fisheries Science Research Institute,Key Laboratory of Marine Biological Resources and Ecology,Liaoning Province

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    摘要:

    白色霞水母是我国近海主要大型灾害水母种类之一,其暴发性增殖严重破坏了海洋生态系统平衡。在室内控制条件下,研究了温度(7.5、11、14.5、18、21.5和25 ℃)和投饵频次(1次/2d、1次/8d和1次/16d)对白色霞水母无性繁殖与螅状体生长的影响。结果显示,白色霞水母足囊繁殖的适宜温度为18-25 ℃,足囊繁殖随温度和投饵频次的增加而增加。温度对白色霞水母横裂率和横裂次数的影响显著,温度越高,白色霞水母发生横裂生殖的时间越早,横裂生殖速度越快,重复横裂次数越多,释放的碟状体数量也越多。横裂率和横裂次数随投饵频次的增加而递增。白色霞水母螅状体在7.5-25 ℃范围的成活率均为100%,其生长速度随温度和投饵频次的增加而增加。温度和投饵频次对白色霞水母螅状体足囊繁殖、横裂率和螅状体生长具有明显的交互效应。螅状体的横裂次数和初生碟状幼体伞径随螅状体柄径增大而递增,呈线性相关。研究表明,温度、投饵频次即营养条件显著影响着白色霞水母的种群数量,说明海水水温上升、富营养化或渔业资源锐减导致的浮游动物量增加均可能诱发白色霞水母暴发性增殖。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。

    Abstract:

    When jellyfish aggregate in great abundance and form large swarms, or 'blooms’, they often cause significant environmental and economic impacts. Cyanea nozakii Kishinouye is one of the jellyfish species causing problems in the waters of China. C. nozakii has a life cycle consisting of a planktonic sexually-reproducing medusa and a benthic asexually-reproducing polyp. Polyps produce young medusae (ephyrae) through strobilation. Increasing medusa populations may reflect the increasing success of asexual polyp reproduction. Environmental factors (temperature, salinity, light, food, etc.) significantly affect the population size of both polyps and medusae. Therefore, studying the effects of environmental factors on the asexual reproduction of C. nozakii is important for exploring the reproduction potential of this jellyfish and to forecast jellyfish blooms. In this study, polyps of C. nozakii, from Liaodong Bay, Bohai Sea, were tested in six temperature gradients (7.5℃, 11℃, 14.5℃, 18.5, 21.5 ℃and 25℃) and nine temperature (14.5℃, 18℃ and 21.5 ℃) and feeding frequency (1/2d、1/8d and 1/16d) combinations in laboratory experiments. The influences of the two environmental factors and their interactions with asexual reproduction and polyp growth were observed. The results showed that polyps did not produce podocysts at low temperatures (7.5-14.5 ℃). The percentage of polyps that produced podocysts and the number of podocysts produced by each polyp increased with increasing temperature at warm temperatures (18-25 ℃). Podocysts germinated only in the 21.5 ℃ and 25 ℃ groups, but the difference was not significant (P>0.05,n=3). Optimum temperatures for podocyst reproduction were from 18 ℃ to 25 ℃. Strobilation occurred only at 21.5 ℃ and 25 ℃. At 25 ℃, strobilation occurred earlier, the strobilation rate was always higher, the polyps strobilated more times, and the time between strobilations was shorter than that at 21.5 ℃. The results of the temperature and feeding frequency combinations showed that the maximum percentage of polyps that produced podocysts and the highest number of podocysts produced by each polyp occurred at the 21.5 ℃ and 1time/2d feeding frequency combination. Podocyst reproduction (P<0.01,n=45) and strobilation rates(P<0.05,n=45)differed significantly with temperature, feeding frequency, and their interaction. Strobilation times differed significantly with temperature(P<0.05,n=45). The polyp survival rate was 100% in all temperatures (7.5-25 ℃). The relative growth rate and the specific growth rate of polyps increased with increasing temperature. The results of the combination of temperature and feeding frequency showed that polyp growth differed significantly with temperature, feeding frequency, and their interaction (P<0.01,n=45). Strobilation times and ephyra primary diameter increased with larger polyp diameter. The cumulative number of ephyrae released by polyps at the combination of 25 ℃ and 1time/2d was about 293 times that released at 21.5 ℃ and 1time/8d, suggesting that temperature and nutritional conditions strongly affect ephyra numbers for C. nozakii. Temperature, feeding frequency and their interaction significantly affected the potential production of polyps and medusa, indicating that both increases in water temperature and increases in zooplankton prey abundance because of eutrophication and declining fisheries may encourage prominent blooms of C. nozakii medusae.

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孙明,董婧,柴雨,李玉龙.温度、投饵频次对白色霞水母无性繁殖与螅状体生长的影响.生态学报,2013,33(10):3222~3232

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