Colony architecture of Millepora dichotoma Forskal

In the Gulf of Elat, the hydrozoan coral, Millepora dichotoma Forskal exhibits four main morphotypes: encrusting, delicate lace-like, leaf-like bladed and robust “box-work”. The distribution of these morphotypes was found to vary with depth and between locations. The encrusting form was found in all sites and appeared to be the initial growth form adopted by M. dichotoma. The distribution of the other three growth forms suggested that further development from the encrusting form depends upon environmental conditions. The encrusting form was found at all sites but was dominant in highly energetic environments. The lace-like form develops from the encrusting form in low energy environments. In somewhat higher energy environments, repeated damage to the lace-like form moves development towards the bladed growth form and the box-work growth form. A model of this development is presented in which critical factors controlling the development of the different growth forms are sediment levels and damage to colonies. Both of these factors are linked with levels of turbulence in particular environments.