Marine Biology

, Volume 143, Issue 6, pp 1175–1183 | Cite as

The hydrozoan coral Millepora dichotoma: speciation or phenotypic plasticity?

  • Efrat Meroz-Fine
  • Itzchak Brickner
  • Yossi Loya
  • Micha IlanEmail author
Research Article


This article describes ecological and biological differences between two morphs of the Red Sea fire coral Millepora dichotoma. The species is divided into two main morphs: branching and encrusting, which were found to differ both in color and morphology. Each morph has two or more sub-morphs. A total of 372 M. dichotoma colonies were examined in a census at two study sites in the Gulf of Elat. Colony size and abundance of the two morphs were found to differ significantly between sites. Experimental examination of each morph's morphological plasticity revealed different growth rates and difference in growth plasticity between the branching and the encrusting morph. Most of the fragments from the branching colonies (94%) attached to experimentally placed Plexiglas substrate, compared with much less attachment by the encrusting fragments (11%). The growth form of the branching morph on the Plexiglas switched to encrusting, spreading over and covering the substrate. When the new encrusting colony reached the edge of this substrate, it started to produce tips, and returned to growth in the classic branching form. The encrusting morph did not change its growth form. Following attachment of the original fragments of the branching morph to the substrate, 8.1% of them produced new tips. When the original branches were removed, after converting to encrusting growth form, 19% of the fragments produced new tips. The capsule size of nematocysts of the two morphs was also significantly different (t-test, P<0.05). Molecular data (ITS region) clearly demonstrate that these two M. dichotoma morphs differ considerably. Molecular evidence (srRNA) from the symbiotic zooxanthellae also shows a different pattern of clades in the hosts. The ecological, biological and molecular data thus attest to the two morphs being distinguishable. Contrary to previous reports, we consequently suggest that the two morphs of M. dichotoma found in the Gulf of Elat are actually two distinct species.


Internal Transcribe Spacer Growth Form Colony Size Nest ANOVA Plexiglas Plate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank E. Geffen for assistance with the statistics, construction of the phylogentic trees and his important comments on the manuscript. We are grateful to I. Lerer for his invaluable technical assistance. A. Daya assisted with photography. We thank L. Fishelson for his help with the study of the nematocyts. S. Sheffer assistance with DNA extraction is acknowledged. Parts of this research were supported by the Israeli Diving Federation.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Efrat Meroz-Fine
    • 1
  • Itzchak Brickner
    • 1
  • Yossi Loya
    • 1
  • Micha Ilan
    • 1
    Email author
  1. 1.Department of ZoologyTel Aviv UniversityTel AvivIsrael

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