Transplantation experiments with Caribbean Millepora species (Hydrozoa, Coelenterata), including some ecological observations on growth forms

The historical background of the taxonomic problems in the fire-coral, Millepora, is reviewed. The growth forms of the Caribbean species: Millepora alcicornis Linnaeus, M. complanata Lamarck and M. squarrosa Lamarck are investigated in relation with environmental factors: water movement, current, light and turbidity. Several sites on Curaçao and Bonaire were visited and all forms of Millepora collected. The localities have been divided in biotopes and the relative frequencies of the growth forms in these biotopes were studied. Some relations between growth forms and environment were found: delicately branched forms appear in deeper, quieter waters, sturdy forms in sites with strong water movement, incrusting forms in turbid and also in turbulent sites. At sites with strong current Millepora corals are most abundant. The effect of transplantations on the growth forms of the three species has been studied. The transplantations caused changes in the growth form, which was most conspicuous in M. complanata. It is concluded that M. alcicornis and M. complanata most likely are distinct species. However, the materials from Curaçao and Bonaire commonly identified as M. squarrosa do not belong to that species, but probably represent variations of M. complanata.