Lace Corals

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).

Lace corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that trade in this species should be carefully regulated (1). Indonesia and Fiji both have quota systems for corals, including lace corals, monitored though CITES (1). Lace corals will form part of the marine community in many marine protected areas (MPAs), which offer coral reefs a degree of protection, and there are many calls from non-governmental organisations for larger MPAs to ensure the persistence of these unique and fascinating ecosystems (6).

Lace corals form ornate tree-like structures, with all the fine, tapered branches growing in one plane. These delicate fan-like corals are remarkable for their bright colours (2). The colour is deposited within the limestone skeleton and remains even after the animal tissue is gone, unlike reef-building corals which have white skeletons and the only colour is found in the living tissue (3). Clusters of small pores, gastropores and dactylopores, can be seen on alternating sides of the branches (2).

Widely distributed in temperate as well as tropical latitudes, and also occur at abyssal depths. Commonly found in caverns where it may occur as clumps, and under overhangs in shallow reef environments (2).

Occurs throughout the Indo-Pacific and Atlantic Oceans (2).

Listed on Appendix II of CITES (1).

Lace corals face the many threats that are impacting coral reefs globally. It is estimated that 20 percent of the world's coral reefs have already been effectively destroyed and show no immediate prospects of recovery, and 24 percent of the world's reefs are under imminent risk of collapse due to human pressures. These human impacts include poor land management practices that are releasing more sediment, nutrients and pollutants into the oceans and stressing the fragile reef ecosystem. Over fishing has 'knock-on' effects that results in the increase of macro-algae that can out-compete and smother corals, and fishing using destructive methods physically devastates the reef. A further potential threat is the increase of coral bleaching events, as a result of global climate change (6). Lace corals are also potentially threatened by the global coral trade, for use in aquariums, or for jewellery and ornaments, however, the amount in trade is significantly smaller compared to many other coral genera (7).

Stylaster is a genus of hydroids in the family Stylasteridae.

1-1485 m

Calcareous skeleton with fine, tapering branches which are rounded in section. Pores grouped along outer edges. White, purplish to yellow. Habitat: shallow to deep water. Distribution: all warm seas (Richmond, 1997).

Known from seamounts and knolls