Abstract

Acroporidae and Pocilloporidae are the predominant reef-building corals of Indo-Pacific coral reefs. Coral colony is the basic geometric construction of coral reef, while sustained formation of their calcium carbonate skeletons is the heart of healthy reefs. However, the reef forming strategies in coral growth is still obscure. In this study, we reconstructed 32 representative samples using high-resolution computed tomography and created canal networks inside skeletal data to investigate coral growth regulation and related parameters. In Acropora and Montipora colonies, the polyps are connected as an integral network by complex canals that perform and regulate physiological processes including budding, branching, and mineralising. Furthermore, we visualised coral growth axes and rings, revealing colony growth pattern regulation. We also drew a skeleton grey-gradient heat map and calculated coral skeleton ratios to reveal skeletal diversity, devising a method to quantitatively analyse coral growth. On the basis of the canal network reconstructions, we hypothesised coral growth strategies and compared the similarities and differences among the four genera. This work extends the knowledge of how corals grow their skeleton, what the major controls are and how skeletal growth varies amongst species, ensuring further protections of tropical coral reefs.