Micromussa lordhowensis

Acanthastrea lordhowensis
Acanthastrea lordhowensis
Conservation status
Near Threatened  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Anthozoa
Order:	Scleractinia
Family:	Mussidae
Genus:	Acanthastrea
Species:	A. lordhowensis
Binomial name
Acanthastrea lordhowensis Veron & Pichon, 1982

Acanthastrea lordhowensis, the starry cup coral, is a species of stony coral in the family Mussidae. It is a widespread but uncommon coral with large polyps occurring on shallow reefs in the Indo-Pacific Ocean.

Description

Acanthastrea lordhowensis is a colonial coral forming low clumps that can be two metres (yards) across. The corallites are large, up to 15 mm (0.6 in) in diameter, with walls composed of closely packed septa with fine teeth. The columellae are well-developed. The colour varies widely and is often formed of two contrasting shades of red, orange, purple, blue or green.

Distribution

Acanthastrea lordhowensis occurs in the western Indo-Pacific on reefs at depths down to about 30 metres (98 ft). Its range extends from the Red Sea, the Gulf of Aquaba and the eastern coast of Africa to the East China Sea, Japan and Australia. It takes its specific name from Lord Howe Island, the most southerly coral reef in the Pacific. There it is found among about 83 recorded species of stony coral which include many tropical species at the southern limits of their range, along with subtropical species not found on the nearby Great Barrier Reef.

Biology

Acanthastrea lordhowensis is a hermaphrodite and a broadcast spawner. The larvae form part of the plankton and drift with the ocean currents, eventually settling on the seabed. In an experiment designed to find out how long the larvae could survive, Acanthastrea lordhowensis larvae were reared in an aquarium. It was found that the larvae could remain alive after they were fully developed for up to a further 78 days before settling. In the ocean, this allows the larvae to disperse widely and have greater chances of finding optimum sites for settling.

The polyps of Acanthastrea lordhowensis are large and fleshy. When the tentacles are extended, they search for zooplankton and small invertebrates which are transferred to the mouth when caught. Another source of energy is the symbiotic dinoflagellates, microscopic algae that live within the coral's tissues and which produce nutrients by photosynthesis. The coral is able to benefit from the carbohydrates produced by the algae and the algae for their part make use of the coral's nitrogenous waste products. Acanthastrea lordhowensis is an aggressive species of coral and defends itself against the possibility of being overshadowed. At night some polyps extend long filaments which secrete enzymes which digest the cells of other organisms with which they come in contact.

Status

The IUCN Red List of Threatened Species lists this coral as being "Near Threatened". It is an uncommon species but is widely distributed and seems to be more resilient than some other species. No studies of the population size have been done but the chief threat it is likely to face is from the degradation of its reef habitat. It may disappear entirely from some degraded reefs and, along with other coral species, is likely to be adversely affected by ocean acidification and climate change.