Fig. 1 Vetulicola and the symbiotic social trumpetworm (Vermilituus gregarius) that symbiotic on its inner surface, the specimen comes from the Cambrian Chengjiang biota in eastern Yunnan. Image modified from Li et al., 2020, Communications Biology
Fig. 2 Illustration of the preservation method of ancient insects and symbiotic social trumpetworms. Top left: Archaea are buried in rock formations; Bottom left: The rocks are cracked through fossils, so that the inner and outer surfaces of archaea are preserved on both plates -; Right: After opening, the gregarious trumpetworms are visible preserved on the inner surface of the archaea. Photo: Wang Xiaodong
Fig. 3 Hand-drawn restoration of wedge-shaped archaea (left) and rectangular archaea (right), showing that the inner surface of the precursor shell is contaminated with Qunjun trumpetworm. Image courtesy of Li et al., 2020, Communications Biology, courtesy of Xiaodong Wang
(Mysterious Earth uux.cn) According to the Institute of Paleontology of Yunnan University and the Key Laboratory of Paleontology Research of Yunnan Province: On September 18, 2020, Dr. Li Yujing of the Institute of Paleontology of Yunnan University and the University of Leicester in the United Kingdom conducted a new paleoecological study of archaea, a typical representative of the chengjiang biota of the World Natural Heritage Site, with the result of "Symbiotic fouling of early Cambrian swimming animal archaea." Vetulicola, an early Cambrian nektonic animal) is published in the journal Communications Biology. Thesis link: https://doi.org/10.1038/s42003-020-01244-1.
Symbiosis between species is one of the most important ecological relationships in ecosystems and an important driver of ecosystem complexity. The radiation evolution of early Cambrian post-mezoans constructed the earliest marine ecosystems dominated by the phyla. Previous studies have suggested that the complexity of marine ecosystems in the early Cambrian period may not be high, and that interactions between species are mainly based on predators and episymbiosis (such as brachiopods growing on each other's hard shells). Dr. Li Yujing's study found that there are symbiotic hard-shell tubular organisms clustered in its body, representing the earliest fossil record of symbiotic relationships in the body of the currently known postbiotic animals; this discovery reveals that the early Cambrian marine ecosystem has evolved into ecological dimensions such as endosymbiosis, indicating that the complexity of the early Cambrian marine ecosystem is far more than previously recognized.
This intractable fossil attached to the precursor shell of the archaeoptera is named Vermilituus gregarius (Fig. 1), whose body is conical in the shape of a conical tube, only 0.8 to 7.2 mm in size, and the surface of the body has a transverse ring pattern, which is preserved in groups. Dr. Yujing Li first observed this phenomenon in archaea in 2015. In recent years, Dr. Li Yujing has examined thousands of archaeological specimens in the Chengjiang biota and confirmed that a total of 192 gregarium hornworms have been found on 10 archaeopteric specimens, and the most infected single archaeopteric body carries as many as 88 symbiotic individuals.
Archaea are a class of extinct intractable fossil taxa endemic to the Cambrian. Gregarium trumpetworms grow mainly near the water outlets of precursors of archaea and may compete with host archaea for food particles and oxygen. A single host archaea can infect nearly a hundred symbiotes with typical biosymbiotic pollution characteristics.
Co-author Professor Mark Williams of the University of Leicester commented: "We were very surprised by this phenomenon of in vivo symbiosis. The discovery traces this ecological relationship back to Cambrian marine fauna 518 million years ago, suggesting that complex symbiotic relationships have become one of the driving forces behind the radiation process of early Cambrian post-medustics. ”
Dr. Yujing Li of the Institute of Paleontology of Yunnan University is the first author of the paper, and his co-supervisor, Researcher Cong Peiyun, is the co-corresponding author. In recent years, Cong Peiyun's team (difficult fossils and early radiative evolution of animal phylums) has continued to focus on the interactions between species in the Chengjiang biota, and in 2017 it was first reported that the earliest symbiotic demodex found in the Chengjiang biota (Cong et al. Host-specific infestation in early Cambrian worms. Nat Ecol Evol 1, 1465–1469. https://doi.org/10.1038/s41559-017-0278-4), revealing the earliest host-specific and host migration ecological phenomena. This study is another important result of the team's research on the complexity of Cambrian marine ecosystems.
The project has been supported by the Key Laboratory of Paleontology Research of Yunnan Province, the Joint Laboratory of International Cooperation on Major Biological Evolution Events and Paleoenvironment in Yunnan of the Ministry of Education, the Postdoctoral Research Station of Ecology of Yunnan University, the "Double First-class" Construction of "Plateau Mountain Ecology and Earth Environment" discipline group of Yunnan University, and other platforms and departments, as well as the National Natural Science Foundation of China, the Department of Science and Technology of Yunnan Province and other projects.