Stony Corals

Seriatopora are abundant reef-building, or hermatypic, corals and harbour symbiotic algae (zooxanthellae) within their tissues. Zooxanthellae provide the coral with nutrients, obtained via photosynthesis (4). One of the most curious methods of asexual reproduction in corals was discovered in a Seriatopora coral when polyps were observed detaching themselves from a dying colony. The skeleton-less polyps were then able to form new colonies by normal budding. This phenomenon, termed 'polyp bail-out', is a unique escape response to environmental stress, and may also be considered a form of asexual reproduction (5). Seriatopora corals can also reproduce asexually by fragmentation, and sexually by brooding, in which larvae develops inside the polyps, and mature larvae is then released into the water column where it will disperse, eventually settling on the substrate and establishing a new colony (4). Parts of Seriatopora colonies sometimes show remarkable modifications caused by other organisms, most notably the gall-forming crab Haplocarcinus marsupialis. Female crabs of this species influence the growing tips of coral to form a 'gall' which is effectively a cage that permanently encloses the crab, (like a pair of cupped hands). Male crabs, which are much smaller than females, are able to enter the coral cage to mate. The female spends her whole life in this self-imposed captivity producing broods of larvae inside the protective walls of her cage (2).

Seriatopora 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). Seriatopora 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).

It was one of these pretty coral species that was first observed undertaking a unique method of reproduction (2). Colonies of Seriatopora generally form compact bushes with thin branches (3), although different species vary in their appearance depending on the water depth and wave action. In shallow water with strong wave action the branches are shorter and thicker than colonies that are situated in deep or turbid water (2). Colonies of Seriatopora may be brown, pink, yellow or cream in colour (4), and the many polyps which comprise a colony are only extended at night (2).

Seriatopora coral species can occur in protected reef environments or shallow reef environments (3).

Occurs in the Indo-Pacific Oceans (2).

Listed on Appendix II of CITES (1).

Seriatopora 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). Seriatopora may also be threatened by over-harvesting for use in aquariums, or as ornaments and jewellery. The potential impact of coral harvesting is illustrated by a study which focused on a heavily harvested site off Cebu in the Philippines. A demand for large, mature coral colonies for the ornamental trade resulted in a reduction in coral density and coral cover at the site, and Seriatopora, which was common in the region, was completely absent from the harvested site (7).

Seriatopora is a genus of colonial stony corals in the family Pocilloporidae. They are commonly known as needle corals, birdsnest corals or finger corals. They are native to the Red Sea, the Indo-Pacific region and some parts of the Central Pacific Ocean.