Coral nutrient requirements are met by 2 methods. In the first, small single-celled photosynthetic animals that live within tiny sacs (vacuoles) in the cells lining the coral gut provide carbohydrates, amino acids, small peptides and sugars. In the second, the coral itself takes in microscopic aquatic animals and other organic materials in the environment into the gut and digests them to extract nutrient value. Reef building corals, such as Acropora millepora, can reproduce sexually in an event called "mass spawning". This occurs once a year, around 3 nights in early summer when the moon is nearly full. Mass quantities of eggs and sperm are released simultaneously from the huge numbers of coral colonies, many belonging to different species and genera. Acropora millepora eggs that have spawned have within them high levels of UV blocking agents. More than likely, this agent protects the eggs from UV radiation during an early developmental stage. After the gametes are released into the water by adult coral, they must undergo 3 general stages of development before they may grow into newly settled coral. These stages are: 1) Fertilization and embryonic development; 2) Larval growth; 3) Settlement and metamorphosis. In each of these stages, the percentage survival of each is low. This is due to both physical (wind, wave, salt concentration) and biological (predator abundance) factors. Coral reefs are experiencing great stress; biological, physical, and chemical. It has been predicted that 40% to 60% of the present coral reefs will decline in the next 50 years, unless remedial measures are taken soon. -- Adapted from Animal Diversity Web, University of Michigan Museum of Zoology; Science News Online
Acropora millepora, along with other members of the genus Acropora, dominates the Indo-Pacific coral reefs. Acropora millepora are social, sessile animals. As social animals, they form a coral reef. This is mainly made of material which has its origin in live coral, coral rubble, dead standing coral, and coral-like rock (86% of the rest is sand). Acropora millepora is a hard coral, and it has been found to reach 5.1 mm in diameter during a period of 9.3 months. This species grows mostly vertically, which leads to a bushy morphology that is semi-erect. Polyps extend from vertical branch tips on an average of 1.2 to 1.5 cm. Many reefs that have a high coral cover also have surprisingly turbid conditions, but this does not appear to be detrimental to coral. A second issue that affects habitat is sedimentation. High sedimentation lowers coral diversity and allows the habitat to become dominated by sediment-resistant species. These reefs have slower colony growth rates, which results in reduced colony size and shape as compared to reefs that experience lower levels of sedimentation. Sedimentation not only affects growth, but also metabolism and reproduction. One way in which sediment is a stress factor is that it reduces the amount of light that can penetrate to the coral for photosynthesis. Sediment also smothers coral tissues. Acropora millepora must have adequate light. This light is often regarded as the factor that limits maximum depth of coral growth. Studies of Acropora species show that light intensity may have an effect on settlement orientation, determining whether the larvae settle on the upper or lower surfaces.
This organism was sent to the McDonnell Genome Institute for survey sequencing (25,152 whole genome shotgun reads) to attempt to make an initial assessment of the genomic landscape as an aid in determining which coral genome would be sequenced. The survey sequence is complete. The National Human Genome Research Institute (NHGRI), National Institutes of Health (NIH), provided the funding for the Acropora millepora genome survey sequence.