From cells to skeletons: comparing octocorals and hexacorals
Tambutté, S.; Venn, A.A.; Ganot, P.; Tambutté, E.; Gilbert, P.U.P.A. (2026). From cells to skeletons: comparing octocorals and hexacorals, in: Fratzl, P. A WSPC Reference on Biomineralization. pp. 665-746. https://dx.doi.org/10.1142/9789819829705_0010
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| Authors | | Top |
- Tambutté, S.
- Venn, A.A.
- Ganot, P.
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- Tambutté, E.
- Gilbert, P.U.P.A.
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| Abstract |
Coral biomineralization underpins the formation of one of the most complex and ecologically important skeletal architectures in the marine environment. While the term “coral” encompasses phylogenetically and functionally diverse organisms, calcification is a unifying and defining feature of both reef-building hexacorallians (Scleractinia) and many octocorallians (notably Scleralcyonacea). In this chapter, we present a comparative analysis of coral calcification by integrating cellular, physiological, biochemical, and structural perspectives, with a particular focus on scleractinians and scleralcyonaceans.We review current knowledge of calcifying tissues, emphasizing the conserved epithelial organization of calcifying cells, their polarization, junction architecture, and interactions with the extracellular calcifying medium. Evidence for intracellular and extracellular mineralization pathways is discussed, including vesicle-mediated transport of amorphous calcium carbonate precursors, transcellular and paracellular ion transport, and pH regulation at the site of calcification. We further examine the composition, synthesis, and cellular origin of the skeletal organic matrix, highlighting major differences between aragonitic scleractinian skeletons and Mg-calcite octocorallian skeletons.At the skeletal scale, we compare the formation mechanisms and hierarchical structures of coral skeletons, from nanoscale amorphous precursors to mesoscale architectures. Scleractinian skeletons are shown to universally exhibit spherulitic growth, resulting in mechanically isotropic and space-filling structures, whereas much less is known about the formation mechanisms of octocorallian axial skeletons, which may involve distinct pathways including sclerite incorporation and mesocrystalline growth.By synthesizing data across biological scales, this chapter highlights both shared principles and lineage-specific strategies of coral biomineralization. Remaining knowledge gaps, particularly in octocorallians, underscore the need for integrative approaches combining in vivo imaging, molecular tools, and functional assays to fully elucidate the biological control of coral calcification. |
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