Taxonomic And Ecological Studies On Epibiotic Diatoms On Typical Living Substrata In Coastal Waters Of China

Epibiotics on living substrata are important ecological populations,and they are very common in nature.Among them,epiphytic and epizoic diatoms are two important groups of marine diatoms and play important roles in the structure and function of marine ecosystem.However,thses two diatom groups have not received enough attention from researchers.The distribution of epizoic diatoms on animals containing marine copepods and turtles in China seas is particularly unclear.In this study,we collected samples of common seaweeds,copepods,turtles,crabs and brittle stars from China seas,as well as the seaweeds from Australia coast.The taxonomy and ecology of epibiotic diatoms on these living substrata were investigated by light microscopy,as well as scanning and transmission electron microscopy.Results are as follows.1.A total of 135 diatom species and varieties belonging to 2 classes,7 orders,16 families and 59 genera were identified in the samples from China seas,as well as 53 diatom species and varieties belonging to 2 classes,6 orders,11 families and 30 genera were identified in the samples from Mooloolaba Beach of Sunshine Coast in Australia.2.In the samples of seaweeds,a total of 117 epiphytic diatom species and varieties belonging to 2 classes,7 orders,14 families and 50 genera were found.The most species-rich genus was Nitzschia Hassall,which had 11 taxa.In the samples of marine copepods,a total of 66 epizoic diatom species and varieties belonging to 2 classes,6 orders,15 families and 32 genera were found.The most species-rich genus was also Nitzschia,which had 10 taxa.In the samples from sea turtles,a total of 20 epizoic diatom species belonging to 1 class,4 orders,5 families and 10 genera were observed.Among them,Nitzschia was the most species-rich genus,which had 6 species.Epizoic diatoms on crabs and brittle stars were less species rich,containing 8 and 7 species respectively.3.In the offshore waters,the species number of epizoic diatoms on marine copepods from the East China Sea and the Taiwan Strait is the greatest(15 species and variety),while those from the Bohai Sea is the least(only one species).In general,there are less species number of epizoic diatoms on marine copepods in offshore waters than those in coastal and aquaculture waters.In addition,marine copepods infested with epizoic diatoms are common in spring,early summer and winter,but few epizoic diatom can be observed in the months of hot weather.4.Three epizoic diatom species specific to marine copepods were observed in this study.They are Pseudofalcula hyalina(Takano)Gomez,Wang&Lin,Protoraphis hustedtiana Simonsen and Pseudohimantidium pacificum Hustedt&Krasske.Among them,Pf.hyalina can be epizoic on any part of copepod bodies by mucilage pads,while cells of Pr.hustedtiana were usually found on the posterior body appendages and segments of the planktonic copepods with mucilage stalks.The attachment sites of epizoic diatoms on copepods may be related to the life mode of copepods,the cell size of diatoms and the length of mucilage stalks(pads).5,The diversity of epizoic diatoms on the sea turtles was related to the turtle species.There was no significant difference in diatom species on the same species of turtles,but the diatom species on the adult were more than those on the subadult and larva.6.A new epiphytic diatom species,Rhoicosphenia pseudogenuflexa Li,Gao&Chen,was found on Sargassum horneri(Turner)Agardh,which was collected from the north of Yellow Sea.This diatom features by very short pseudosepta,exposed helictoglossae,circular pores on the girdle bands and denser striae than similar species7.A total of 6 diatom genera(Rhoiconeis Grunow,Pteroncola Holmes&Croll,Protoraphis Simonsen,Nagumoea Kociolek&Witkowski,Gomphoseptatum Medlin and Pseudogomphonema Medlin)and 28 diatom species were newly recorded for China.This paper has studied the species diversity of epibiotic diatoms on typical living substrata in China systematically,including epiphytic diatoms on seaweeds and the epizoic diatoms on marine animals.It will provide abundant data and technical methods for future research concerning epiphytic and epizoic diatoms and contribute to the taxonomic and ecological studies of marine diatoms in China.The study can also be used as an important reference for the investigation of marine biodiversity and ecosystem in China seas.