Unlike many coral species, lace corals do not have the symbiotic algae zooxanthellae living within the coral tissue; they are azooxanthellate (2). They are therefore not dependent on light and thus can live where the reef-building corals, dependent on photosynthetic algae, can not.
Lace corals are hydrozoans, and thus have different type of polyps with different functions than anthozoan corals. The polyps of hydrozoans are near microscopic size and are mostly imbedded in the skeleton, connected by a network of minute canals. All that is visible on the smooth surface are pores of two sizes; gastropores surrounded by dactylopores. Dactylopores house long fine hairs that protrude from the skeleton. The hairs possess clusters of stinging cells (nematocysts) that can inflict stings on human skin. These hairs capture prey, which is engulfed by gastrozooids, or feeding polyps, situated within the gastropores (2).
Reproduction in lace corals is more complex than in reef-building corals. The polyps reproduce asexually, producing jellyfish-like medusae, which are released into the water from special cup-like structures known as ampullae. The medusae contain the reproductive organs, which release eggs and sperm into the water. Fertilised eggs develop into free-swimming larvae that will eventually settle on the substrate and form new colonies. Lace corals can also reproduce asexually by fragmentation (4) (5).