Abstract:Advanced metephyrae is one of the growth stages in the life cycles of Nemopilema nomurai and Rhopilema esculentum. In order to distinguish the advanced metephyrae (1～2cm) of N.nomurai and R.esculentum in early resources survey of giant jellyfish in every spring，The morphology of advanced metephyrae of N. nomurai and R.esculentum were studied.Their characteristics were compared and their main differentiae were summarized through laboratory cultivation and observation.The studies showed that the subgenital pits of N.nomurai are fuller and bigger than that of R.esculentum.For R.esculentum,the inside and outside radians of every subgenital pit are closer and the distance between two subgenital pits is greater.Two vertical lines of gastric cirrum are in the stomachic cavity of N.nomurai,with the longer one extending from subgenital pit to the central mouth.By comparison,the gastric cirrum of R.esculentum are distributed in four subgenital pits,and almost none of gastric cirrum is found in the stomachic cavity.When it is in the state of being contracted,the shape of central mouth of N.nomurai is crossed with smaller opening,and the cirrum are distributed anfractuously in the turbination-shaped oral canalis carpi. By comparison, the shape of central mouth of R.esculentum is eight-square,when it is in the state of being contracted, and the cirrum are distributed orderly in the column-shaped oral canalis carpi.The purpose of this study is to offer taxology evidence for investigating advanced metephyrae in natural field and forecasting of jellyfish blooming earlier, therefore to prevent jellyfish disasters.
