Coral growth, retraction, defense, and regenerative strategies revealed by live microCT.

Abstract

Understanding how corals build and remodel their skeletons is key to explaining reef resilience, yet most insights come from static imaging. Using longitudinal live microCT, we tracked the same coral colonies over weeks to months at micrometer resolution. Coral skeleton formation is not a uniform accretion process but a dynamic integration of multiple programs, including vertical and horizontal patterned growth, previously undescribed defensive wall-building against competitors, exploratory edge behavior with reversible expansions and retractions, and skeletal regeneration favoring rapid, imprecise yet effective matrix expansion. Time-resolved imaging links colony-scale growth to microscale events, showing that all modes depend on balances between fusion of skeletal microparticles and layered matrix deposition, guided by tissue prepatterning. Beyond corals, this framework generalizes to studying skeletal dynamics across diverse biomineralizing organisms.