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ORIGINAL RESEARCH article

Front. Mar. Sci.
Sec. Coral Reef Research
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1512361

Polyp dimorphism in the Mediterranean Red Coral Corallium rubrum: siphonozooids are precursors to autozooids

Provisionally accepted
Guillaume Loentgen Guillaume Loentgen 1Scott K Parks Scott K Parks 2Denis Allemand Denis Allemand 3Sylvie Tambutté Sylvie Tambutté 4Philippe Ganot Philippe Ganot 1*
  • 1 Unité de Recherche sur la Biologie des Coraux Précieux CSM – CHANEL, 8 Quai Antoine 1er, Monaco, Monaco
  • 2 Biology Department, School of Arts & Science, Camosun College, Victoria, Canada
  • 3 Centre Scientifique de Monaco, Monaco, Monaco
  • 4 Department of Marine Biology, Centre Scientifique de Monaco, 8 Quai Antoine 1er, Monaco, Monaco

The final, formatted version of the article will be published soon.

    Polyp dimorphism, the presence of distinct autozooid (feeding) and siphonozooid (water circulation) polyps, has evolved multiple times within octocorals (class Octocorallia). Traditional anatomical descriptions have been limited to early hand-drawn publications. In precious corals (family Coralliidae), polyp dimorphism has been documented in the pacific species such as Corallium japonicum, Pleurocorallium elatius and Pleurocorallium konojoi, over the past century, yet in the Mediterranean red coral, Corallium rubrum, the literature has consistently referred to these structures generically as "polyps", neglecting the putative dimorphism and their respective roles in reproduction, growth, and development. A key distinction between red coral species lies in their reproductive strategies: Pacific species are broadcast spawners, with gametes developing in siphonozooids, while C. rubrum is a larval brooder, with gametes maturing in autozooids. In this study, we utilized laboratory-cultured C. rubrum and a custom video imaging system to document colony growth over extended time periods. Through histological analyses and long-term observations, we demonstrated that siphonozooids, previously thought to have purely structural roles, are precursors to autozooids, suggesting a novel mechanism for colony growth in C. rubrum. This finding has important implications for understanding the extraordinary lifespan of precious coral colonies, contributing a broader knowledge to octocoral biology.

    Keywords: Corallium rubrum, Polyp Dimorphism, Coral Reproduction & Development, Coral Anatomy, Red corals, Precious corals, Siphonoglyph, bilateral symmetry

    Received: 16 Oct 2024; Accepted: 08 Jan 2025.

    Copyright: © 2025 Loentgen, Parks, Allemand, Tambutté and Ganot. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Philippe Ganot, Unité de Recherche sur la Biologie des Coraux Précieux CSM – CHANEL, 8 Quai Antoine 1er, Monaco, Monaco

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