Tubule system of earliest shells as a defense against increasing microbial attacks
Luoyang Li,
Timothy P. Topper,
Marissa J. Betts,
Gundsambuu Altanshagai,
Batktuyag Enkhbaatar,
Guoxiang Li,
Sanzhong Li,
Christian B. Skovsted,
Linhao Cui,
Xingliang Zhang
Affiliations
Luoyang Li
Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Mineral Resources, National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China
Timothy P. Topper
Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China; Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden
Marissa J. Betts
Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China; Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
Gundsambuu Altanshagai
Institute of Paleontology, Mongolian Academy of Sciences, Ulaanbaatar 15160, Mongolia; School of Arts and Sciences, National University of Mongolia, Ulaanbaatar 14200, Mongolia
Batktuyag Enkhbaatar
Institute of Paleontology, Mongolian Academy of Sciences, Ulaanbaatar 15160, Mongolia
Guoxiang Li
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
Sanzhong Li
Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Mineral Resources, National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China
Christian B. Skovsted
Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden
Linhao Cui
Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China
Xingliang Zhang
Shaanxi Key Laboratory of Early Life and Environments, State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; Corresponding author
Summary: The evolutionary mechanism behind the early Cambrian animal skeletonization was a complex and multifaceted process involving environmental, ecological, and biological factors. Predation pressure, oxygenation, and seawater chemistry change have frequently been proposed as the main drivers of this biological innovation, yet the selection pressures from microorganisms have been largely overlooked. Here we present evidence that calcareous shells of the earliest mollusks from the basal Cambrian (Fortunian Age, ca. 539–529 million years ago) of Mongolia developed advanced tubule systems that evolved primarily as a defensive strategy against extensive microbial attacks within a microbe-dominated marine ecosystem. These high-density tubules, comprising approximately 35% of shell volume, enable nascent mineralized mollusks to cope with increasing microbial bioerosion caused by boring endolithic cyanobacteria, and hence represent an innovation in shell calcification. Our finding demonstrates that enhanced microboring pressures played a significant role in shaping the calcification of the earliest mineralized mollusks during the Cambrian Explosion.
