Simplified polyp-canal system of stony coral Seriatopora hystrix
protects its branching areas in the flow field
Abstract
The polyp-canal system is vital for the growth, budding, and
mineralization of scleractinian corals. Seriatopora hystrix displays a
unique structural trait, with its calices and canals making up only
about 15% of the colony volume, significantly lower than the 40-50%
observed in other widely distributed genera such as Acropora, Montipora,
Pocillopora, or Stylophora. We used micro-computed tomography to
visualize the polyp-canal system of S. hystrix, quantify its growth
parameters, and simulate the dynamic processes of polyp budding and
movement. It reveals that the polyps in S. hystrix follow the budding
pattern of unilateral extension along the growth axis and radiates
within the horizontal plane, which simplifies its polyp-canal system.
Through the finite element analyses under average and maximum wave
velocities of South China Sea, we measured the stress distribution in
coral models with varying canal volume proportions. We found that the
lower volume proportion of polyp-canal system in S. hystrix reduces the
VonMises stress at the branching areas by approximately 40-50%,
ensuring the continual construction of branchlets in high speed flow
field. This study enhances our understanding of Seriatopora coral growth
patterns and their adaptation to marine environments, contributing to
the species selection in coral reef restoration.