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A modern scleractinian coral with a two-component calcite–aragonite skeleton

Author(s): Stolarski, Jarosław; Coronado, Ismael; Murphy, Jack G; Kitahara, Marcelo V; Janiszewska, Katarzyna; et al

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Abstract: One of the most conserved traits in the evolution of biomineralizing organisms is the taxon-specific selection of skeletal minerals. All modern scleractinian corals are thought to produce skeletons exclusively of the calcium-carbonate polymorph aragonite. Despite strong fluctuations in ocean chemistry (notably the Mg/Ca ratio), this feature is believed to be conserved throughout the coral fossil record, spanning more than 240 million years. Only one example, the Cretaceous scleractinian coral Coelosmilia (ca. 70 to 65 Ma), is thought to have produced a calcitic skeleton. Here, we report that the modern asymbiotic scleractinian coral Paraconotrochus antarcticus living in the Southern Ocean forms a two-component carbonate skeleton, with an inner structure made of high-Mg calcite and an outer structure composed of aragonite. P. antarcticus and Cretaceous Coelosmilia skeletons share a unique microstructure indicating a close phylogenetic relationship, consistent with the early divergence of P. antarcticus within the Vacatina (i.e., Robusta) clade, estimated to have occurred in the Mesozoic (ca. 116 Mya). Scleractinian corals thus join the group of marine organisms capable of forming bimineralic structures, which requires a highly controlled biomineralization mechanism; this capability dates back at least 100 My. Due to its relatively prolonged isolation, the Southern Ocean stands out as a repository for extant marine organisms with ancient traits.
Publication Date: 15-Dec-2020
Citation: Stolarski, Jarosław, Ismael Coronado, Jack G. Murphy, Marcelo V. Kitahara, Katarzyna Janiszewska, Maciej Mazur, Anne M. Gothmann et al. "A modern scleractinian coral with a two-component calcite–aragonite skeleton." Proceedings of the National Academy of Sciences of the United States of America 118, no. 3 (2020). doi:10.1073/pnas.2013316117.
DOI: doi:10.1073/pnas.2013316117
ISSN: 0027-8424
EISSN: 1091-6490
Language: eng
Type of Material: Journal Article
Journal/Proceeding Title: Proceedings of the National Academy of Sciences of the United States of America
Version: Final published version. This is an open access article.

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