# Skeleton Precedes Polyp: Visualization of Structural Changes During Coral Growth in Montipora capricornis

## TL;DR

This study uses micro-CT to show how coral skeletons form before polyps in Montipora capricornis, revealing a transit area that guides polyp migration and growth.

## Contribution

The study identifies a 'transit area' in coral canals as a morphological marker for polyp budding and migration.

## Key findings

- Skeleton–canal network formation precedes polyp budding in Montipora capricornis.
- A transit area with specific skeleton-to-void ratios serves as a pathway for polyp migration to new calices.
- The polyp–canal system shows dynamic changes with concurrent skeleton formation and dissolution.

## Abstract

Scleractinian corals are foundational to coral reefs, vital marine ecosystems under threat from climate change. Montipora, a widely distributed reef‐building genus, contributes through continuous corallum mineralization, yet polyp budding and skeleton formation processes remain elusive. This study elucidates temporal and spatial dynamics of skeletal formation and polyp budding in
Montipora capricornis
using high‐resolution micro‐computed tomography (micro‐CT). We demonstrate that skeleton–canal network formation precedes polyp budding at colony margins, identifying a “transit area” (volumes ~1 mm3, skeleton‐to‐void ratio 20%–35%) within tubular canals as a pathway for polyp migration to new calices. This feature serves as a morphological budding marker, enabling visualization of polyp trajectories and growth axes. The polyp‐canal system undergoes dynamic changes, including concurrent skeleton formation and dissolution. These insights establish a structural framework for biomineralization regulation and colony expansion, contributing to the development of coral growth models, and informing environmental impacts on reef‐building in
M. capricornis
.

Using high‐resolution micro‐computed tomography, this study demonstrates that in
Montipora capricornis
, skeleton–canal network formation precedes polyp budding at colony margins, with a “transit area” (volumes ~1 mm3, skeleton‐to‐void ratio 20%–35%) in tubular canals serving as a pathway for polyp migration to new calices. This feature acts as a morphological budding marker, enabling visualization of polyp trajectories, growth axes, and dynamic changes involving concurrent skeleton formation and dissolution. These findings provide a structural framework for biomineralization regulation, colony expansion, and modeling environmental impacts on reef‐building corals.