| The amount and frequency of the jellyfish blooms in the highly productive offshorewaters all over the world increased because of human activities, global warming,eutrophication and so on in recent years. In China, the blooms of Aurelia auritaNemopilema nomurai and Cyanea nozakii, in the northern East China Sea, Yellow Seaand Bohai Sea increased in the scale and frequency and affected the normal fisheryactivities heavily, as well as local aquaculture, tourism trade and offshore industry.The growth model during sexual reproduction, development of radial canals，ovarian development, and fertilizing process of moon jellyfish which bloomedfrequently in china offshore waters were observed and measured in the laboratory. Thecultured moon jellyfish can offer material for the experiment of the predation of filefishto jellyfish. The predation of filefish to four kinds of giant jellyfish species, R.esculentum, N. nomurai, A. aurita and C. nozakii, was explored in laboratory condition.The results could contribute to the relationship between fish population changing andgiant jellyfish blooms along Chinese coastal areas.The growth models of the diameter, wrist length and weight of the moon jellyfishmedusa stage in Yantai waters were studied in this present study, and the developmentof radial canals was observed in details for the first time. Our results showed that thecultured moon jellyfish (15-150mm of the umbrella-part diameter) displayed a powerfunction growth equation between weight and diameter（W=6×10-5D3.0178R2=0.992）,and a linear relationship between the wrist length and diameter（L=0.6208D-2.8393R2=0.9871）. The growth curve equation of diameter of the moon jellyfish medusa is Dt=4×10-6t4-0.0014t3+0.1087t2+0.5079t+9.428(R2=0.9993). The perradial canals andinteradial canals appeared in the newly released ephra. The adradial canals formed inthe3-day ephyra. And the ring canal formed in the11-day ephyra with the divergences. The number of convergences and divergences increases with the development of themoon jellyfish medusa diameters. Moreover, the maximum number of convergences anddivergences in1/4umbrella of mature moon jellyfish medusa was66and32,respectively.The ovarian development and fertilizing process of Aurelia aurita were studied inthe laboratory. The ovarian development of Aurelia aurita was divided into four stages:the early development, the quick development, the maturation, and the shrink anddisappearance stages.①In the early development stage, gonads appeared in moonjellyfish whose umbrella diameter was about7cm, and were thin as20%of gastric cirriand gray. The gonads at this stage could not be identified sexually with germ cellsdispersing in the middle.②In the quick development stage, the translucent gonadswhich were1.5mm in width could be identified sexually. The oocytes in the ovary wereoval and in regular shape whereas the male gonad should be verified in the microscope.In this stage, the diameter of the oocytes were30~90μm.③In the maturation stage,the50%~67.7%of the ovaries which were ligh brown with2~3mm in width wereoccupied by maturated eggs whose diameters were100~120μm.④In the shrink anddisappearance stage, the oocytes of different phases released in bitches from ovarieswhich were loosen and dim and the remained occytes mostly were under90μm in thediameter with loosely arranged. Then ovaries recessed and disappeared and gastric cirriremained in stomach. Moreover, the ovaries of moon jellyfish which cultured under thesame conditions did not developed again.In this study, the predation of filefish to four kinds of giant jellyfish species, R.esculentum, N. nomurai, A. aurita and C. nozakii, was explored in laboratory condition.Filefish weighted215±20g actively preyed on these jellyfish species, and its dailymedusae consumption were150.7±18.6,129.7±11.6,120.0±19.3, and92.5±11.3g/dto A. aurita, R. esculentum, C. nozakii, and N. nomurai, respectively. The medusaebiomass, not bell diameter, affected the fish daily consumption when medusae of A.aurita and R. esculentum were feed to filefish. All medusae were preyed when thebiomass no more than its maxed consumption. However, the remains were all deadbecause of the eaten tentacles and edges of umbrella when the biomass was more thanthe max consumption, though the consumption was no more than the maximum.Moreover, the filefish also showed preference for jellyfish as food when sand lance was fed to filefish along with medusae of A. aurita and R. esculentum, respectively. And thedaily consumption of A. aurita and R. esculentum only reduced20.2%and16.9%. |
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