Staghorn Coral

   A primary reef-building coral, the Staghorn Coral holds the most important job in the Western Atlantic reefs!

   Although the Acropora genus has close to 400 nominal species, only three are found in the Atlantic Ocean. The Staghorn Coral Acropora cervicornis is one of these. They are dominant, of the two species of Caribbean Acroporas.

   The Staghorn Coral offers a variance on shape and structure in the Acropora genus. With branches that are more loosely spaced, they have a more “laid back” look to them. This is a big plus with Acros because they need that good water flow between their branches to stay healthy. This in turn makes it easier to care for, with less worry about debris build up.

   Being a primary reef building hard coral, the Staghorn Coral has a lot of work to do. They are currently listed as critically endangered as there has been a population reduction exceeding 80% over the past 30 years. This is due mostly to the effects of disease, but climate change and human-related factors are also suggested. The current populations today appear stable, and reefs are being rebuilt. But the progress is slowed by increased populations of urchins and other creatures that hinder growth.

   The A. cervicornis have been propagated in captivity, thus helping to spare the wild populations in the Atlantic reefs. It is illegal to harvest corals for commercial purposes In US waters. Buying captive propagated A. cervicornis also helps the aquarist, since they are a little more hardy than their wild siblings, but they can still succumb to diseases typical to Acros.

Scientific name

   Family: Acroporidae
   Species: Acropora cervicornis

Distribution / Background

   Acropora Coral Information: The Staghorn Coral Acropora cervicornis was described by Lamarck in 1816. They are the primary reef builder in the Caribbean. They are the dominant Acro of the two species found in the Caribbean. The less dominant species is Acropora palmata. Since El Nino in 1982-1983, their population has been slow getting reestablished.

   Where Acropora Corals Are Found:A. cervicornis are found in the Western Atlantic ocean, specifically, the Caribbean, Bahamas, Florida Keys, and Venezuela.

   Acropora Coral Habitat: The A. cervicornis are found at depths between 0 – 98 feet (0 – 30 m). They prefer warmer water and will not do well in water under 68° F (20° C).

Status

   The Acropora cervicornis is on the IUCN Red List for Endangered Species as Critically Endangered (CR).

Description

   What do Acropora Corals look like: All Acropora Spp. corals have very porous and lightweight skeletons. The A. cervicornis grows in a branching formation where branchlets “Y” off at right angles. It is not compact like A. prolifera, but loose and open, in an almost relaxed state. Their basal (bottom) parts are usually dead. Their bases are very dense. Acropora cervicornis along with the Staghorn Acroporal Acropora formosa, has the densest base skeletons ever recorded in stony corals. Their round cylinder shaped branches can reach from 3 feet (1 m) up to 6 feet (2 m), but only under ideal conditions. At night, they send out their tentacles and increase their girth by taking in water.

  Acropora cervicornis comes in colors of yellow, brown or gold. Acroporas with thick branches are said to be harder to keep than ones with thin branches. Also brown Acros are said to do better than the colored variety.

   Acropora corals are characterized by fast growing terminal (or axial) polyps at the tips of the branches. The polyps at the tips secrete this corallite, constantly forming new growth in a cluster shape. These terminal polyps do not have zooxanthellae. They grow quickly because the terminal polyps are fed by the rest of the colony. This allows Acropora to outgrow other corals on the reef.

   Acropora Coral Life Cycles: The Staghorn Coral A. cervicornis can grow up to 6 feet (2 m) in ideal conditions. It reaches sexual maturity within 3 to 5 years, with a branch diameter of 1.5-2.75″ (4-7 cm). They can live 4 to 7 years.

Difficulty of Care

   Acropora Coral Care: Acroporas are among the more difficult corals to keep, which is surprising as their natural habitats have a wide array of conditions. In captivity they require stable tank conditions, sudden changes may result in death. They are sensitive to temperature changes, sedimentation, chemical and other environmental stresses. They will stress very easily if the light is too low, or the water movement is not sufficient.

   Acropora need to be carefully acclimated to their new homes. They need to be placed in their permanent position within a tank after acclimation. It takes about 5 to 6 months for the A. cervicornis to regain their normal growth rates after being added to an aquarium. Moving Acropora from place to place will stress them, and possibly cause death.

   At times a healthy system has an additional Acro added and all the others die from polyp bail out or what people refer to as RTD (rapid tissue degeneration) and a whole tank of acros can be wiped out within a matter of hours. They are unsure why this happens, but it would probably be a good idea to have all the Acros you are going to want, and put them together at once while they are still young.

Foods / Feeding

   Acropora Coral Feeding: In the wild, Acropora corals have developed several feeding strategies. Through a symbiotic relationship with a marine algae, known as zooxanthellae, they receive the majority of their nutrients. They also capture planktonic organisms and microscopic food particles from the water column and can absorb dissolved organic matter.

   In captivity, feeding zooplankton once a week is the preferred choice. Copepods, Artemia, and nauplii are too large for them to ingest. But new forms of prey are being developed including invertebrate larvae and new strains of rotifers. Many feel that Acros in captivity need to be in a tank that has dissolved or solid organic matter to survive and thrive. Without this, they may seem fine for a while, but over a few months, without any visible indication, they may end up dead because of starvation. Signs of lack of food would be no new growth, polyps extending and some tissue recession.

Aquarium Care

   Excellent and stable tank conditions are required to keep all Acropora spp. corals. Doing water changes of 10% every 2 weeks is needed, although it is suggested that doing 5% water changes once a week will bring about amazing results. Keep the nitrate levels low. Tanks should offer high calcium levels and strontium should be added.

   Suggested levels for Acropora species are:

• Calcium:  400 to 450 ppm (closer to 450). If the Acro does not have enough calcium, it will not grow. There will be no tissue recession, but the polyps will be extended.
• Alkalinity:  3.2 TO 4.5 MEQ/L (8 to 10 dKh – 10 is recommended)
• Phosphates:  0, zero. Phosphates are the worst of all and all corals hate them.
• Magnesium:  1350-1500. Magnesium makes calcium available, so if your calcium is low, check your magnesium levels before adding any more calcium.
• Strontium:  10

Aquarium Parameters

Quick Reference Chart
Lighting:
Water Flow:
Temperament:

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   A typical live rock/reef environment is what is needed for your Staghorn Coral, along with some fish for organic matter production. A mature tank (well over a year old) is advised to increase the chance of successfully keeping Acropora.

• Minimum Tank Size / Length: 100 gallons (380 L) or larger
• Marine Lighting: High, metal halides are suggested.
• Temperature: 68° – 83° F (20° – 28° C)
• Salinity / Specific Gravity: 1.023 – 1.025
• Water Movement: Moderate and surge-like. They prefer a strong, random, mixing-type current, therefore a rotating powerhead or wavemaker setup is recommended. Tunze stream pumps, though they have a comparatively high initial purchase price, are popular with Acro keepers.
• Water Region: Top or middle of the aquarium

Compatibility and Social Behaviors

   The Acropora corals are peaceful, but watch out for crabs. Many experienced aquarists do not believe any crab should be kept in a closed system with Acros. Crabs are opportunistic predators, with the exception some of the symbiotic crabs like commensal crabs, and gall crabs.

   Acroporas are best kept in a small polyp stony (SPS) tank with only other SPS corals. They can send out digestive strands called ‘acontia’ that are actually used to digest neighboring corals, so keep an eye out for any problems. The exception to this would be if your system has an incredible filtration system and the Acros are at least 10″ away from other corals such as zoanthids, large polyp stony (LPS) corals, and other invertebrates.

   Do not keep soft leather corals with your Acropora species as they are aggressive and release terpins that will eventually kill your expensive investment. Leather corals are dangerous to Acros, even in the best filtered aquariums. Some large polyp stony (LPS) corals can stretch out their tentacles and kill your Acros too, so caution is needed if you have a mixed reef.

Sex – Sexual differences

   No sexual difference in appearance is known.

Breeding and Reproduction

   Acroporas grow rapidly and are considered to be among the most rapid growing of the stony corals. They will reach sexual maturity within 3 to 5 years, with a branch diameter of 1.5 – 2.75″ (4 – 7 cm). They fragment easily and the fragments can form new colonies. This makes them ideal candidates for captive breeding/propagation.

   The Acropora Spp. are male and female and can reproduce both sexually and asexually. In the wild they reproduce sexually by releasing eggs and sperm at the same time, resulting in a fertilized egg which then forms into a free-swimming planula larva. Eventually the planula larvae settles onto the substrate, becoming plankters. This then forms a tiny polyp which begins to excrete calcium carbonate and develops into a coral. Planula larvae are extremely vulnerable to predation, and very few survive. In the wild Acros reproduce asexually as well. The polyps at the tips of branching species secrete corallite around itself, forming longer branches. Acros also spread from breakage due to storms and fragmentation.

   Propagation is rather simple for Acropora corals. First you need to choose a healthy coral that is not showing any signs of distress. Then, simply cut a branch at least 2″ long and glue the frag to a plug or rock. You can use the 2-part epoxy or underwater putties. A little tip, don’t glue frags upright since they will grow faster on their sides.The slime that the coral will exude should not come in contact with any other corals and gloves are suggested. Give the frag ample water flow.

Potential Problems

   Signs of stress are bleaching and receding and they will diminish and die rapidly. Transporting Acropora spp. corals can be a problem because of their shapes, the easily broken outer edges of the coral skeleton, and the ease with which they become stressed. They are also susceptible to almost every coral disease including white-band disease, black-band disease, necrosis, etc. Acropora is particularly susceptible to rapid tissue necrosis (RTN), especially specimens from the wild.

   For more information on disease see Keeping Acropora Corals: SPS Coral Ailments

   There are many animals that will prey on Acropora spp. corals. Some Acropora have symbiotic relationships with crabs and shrimps that may help them against predators. Other hitchhikers may actually be predators so careful observation must be done.

Availability

   Acropora Corals for Sale: The Staghorn Coral A. cervicornis are very hard to find at pet shops and on line. More than likely they will be under “Acropora sp.” or “Acropora spp.”. In US waters, it is illegal to harvest corals for commercial purposes, so make sure your coral is captive propagated.

   Many Acropora spp. corals have been propagated by fragmentation. It is not difficult to find captive-bred colonies of Acropora corals for sale or trade. Captive-bred corals may tolerate less intense lighting and water movement as well as possibly being easier to care for than those taken from the wild.

References

• Animal-World References: Marine and Reef
• Eric Borneman, Aquarium Corals : Selection, Husbandry, and Natural History , TFH Publications, 2001
• Anthony Calfo, Book of Coral Propagation, Volume 1 Edition 2: Reef Gardening for Aquarists, Reading Trees; 2nd edition, 2007
• Ronald L. Shimek, Guide to Marine Invertebrates: 500+ Essential-to-Know Aquarium Species, Microcosm, 2005
• Acropora cervicornis, Coralpedia, Your Guide to Caribbean Corals and Sponges
• Krystyn Alter, Acropora cervicornis, Staghorn Coral, Animal Diversity Web, University of Michigan Museum of Zoology, Copyright 1995-2008
• Staghorn Coral (Acropora cervicornis), NOAA Fisheries, Office of PRotected Resources

Featured Image Credit: John A. Anderson, Shutterstock