Determining The Diet Of Two Jellyfish Species Using High-throughput DNA Sequencing Techniques

Jellyfish is one of the important groups of marine organisms in coastal waters.In recent years,jellyfish blooms have been reported in different sea areas around the world.Jellyfish,as a crucial ingester in marine food web,the increasing number of it has various effects on marine ecosystem,which affects the material and energy transfer of marine food web.However,the food composition of jellyfish in the natural sea area is the core issue of feeding ecology research,and at present,little is known about the feeding types and food structures of jellyfish,especially at the larval stage because of the limitations of traditional methods.Aurelia coerulea is a common large-scale scyphozoan in coastal waters of Yellow sea and Bohai sea.In recent years,blooms of A.coerulea,which erupts continuously in Qingdao,Yantai,Weihai and other places,causing great harm to local ecological environment and production and life.Sarsia tubulosa belongs to hydromedusae,which is a new recorded species in China.This research analyzes the field ingestion behavior of A.coerulea polyps and ephyrae,as well as S.tubulosa by using high-throughput sequencing.For adult A.coerulea,the traditional microscopy examination of stomach content was used.Results indicate that:(1)Adult A.coerulea in Weihai coastal water mainly ingests naupiar larva,which accounts for 75.87% of the detected species in its stomach content,and the ingestion structure is greatly affected by the species and abundance of the organism in the ambient environment.(2)Investigation of field ingestion structures of A.coerulea polyps and ephyrae showed that: they are all omnivorous and their food types are multitudinous,involving 10 categroies such as Annelida,Arthropoda,Chordata and so on,covering 15 orders such as Polychaete,Malacostraca,Maxillopoda and so on.But the food types of the two are different,polyps mainly ingest benthos and planktons,while ephyrae with planktons only.The dominant species of polyps and ephyrae is Rathkea octopunctata and Eurytemora pacifica separately,which accounts for 60.48% and 48.47% of the food source respectively.Besides,there are 12 identical ingestion food groups of the two,including S.tubulosa,E.pacifica and R.octopunctata,etc.(3)The ingestion food structures of S.tubulosa in Weihai coastal water is relatively simple,and 99.51% of its food sources are Cnidaria species.Among them,R.octopunctata is an absolute dominant species,providing 79.41% of the food sources for S.tubulosa.In this research,high-throughput sequencing technology is first used to study field ingestion food types of A.coerulea and S.tubulosa,and the food compositions of three different life stages: polyps,ephyrae and adults.The results showed that the feeding compositions of A.coerulea at different life stages are various,the polyps and ephyrae are all omnivorous and their food types are diverse and non-selective,compared to that of the S.tubulosa,whose food type is simple.Moreover,this research provides new methods for further study of jellyfish feeding,especially at the larval stage.