A Study On Ecology Of Symbiosis In The Cambrian Chengjiang Biota

This thesis reviews the symbiotic ecology of the early Cambrian Chengjiang biota in South China and summarizes symbiotic phenomena between 12 categories of epibionts and hosts,including “Inquicus-priapulids”,“Unknown organsim-priapulids”,“ArchotubaHosts”,“Cotyledion-Hosts”,“Cheungkongella-Trilobites”,“Brachiopods-Brachiopods”,“Brachiopods-Hosts”,“Sponges-Algae”,“Phlogites-Hosts”,“Eldoniids-Hosts”,“Unidentified tubeworm-Lobopodians”,and “Unkown worm-Vetulicolians”.A systematic study on the symbiosis between the enigmatic epibiont Inquicus and the host priapulid Cricocosmia supports that Inquicus was likely commensal to the priapulid.However,the possibility of parasitism or non-symbiosis(i.e.,only scavenging on dead priapulids)cannot be completely ruled out.The phylogenetic position of Inquicus remains undetermined,but most likely a modified priapulid.A systematic study on the symbiotic relationship between an unidentified tubeworm epibionts and the host lobopodian Onychodictyon suggests that,although much smaller in size,the unidentified tubeworms were most likely early juveniles of the described tubeworm Archotuba,based on their similar morphometrics.A systematic study on the symbiotic relationship between an unknown vermiform epibiont and the vetulicolians Vetulicola rectangulata and V.cuneata reveals distinctive morphological characteristics of the epibiont(Vetulicolinquilinus flexibilis gen.et sp.nov.)and demonstrates the epibiont as an obligatory parasite.However,the phylogenetic position of the parasite remains undetermined.Commensalism and parasitism,two of the three main types of symbiotic relationships of modern marine organisms have appeared in the Chengjiang biota.In addition,both obligatory and facultative relationships in symbiosis have also evolved in the Chengjiang biota.Hence,the early Cambrian marine ecosystem,as represented by Chengjiang biota,has evolved a modern-type symbiotic community.