News / Species Spotlight / Revisited - Duncan Corals (07/23/15)

Revisited - Duncan Corals



by Charles J. Hanley

Species Name: Duncanopsammia axifuga
Common Name: Duncan Corals, Duncans Corals, Duncans Corals, Whisker Corals, Aussie Corals, Aussie Duncans, Daisy Corals

Taxonomy:

Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Scleractinia
Family: Dendrophylliidae
Genus: Duncanopsammia
Species: Duncanopsammia axifuga

Introduction:

There is just something about a Duncan Whisker coral (Duncanopsammia axifuga). They are like a weird fusion of a euphylliad and a zoanthid. These stony corals are Large-Polyped Scleractinians of the genus Duncanopsammia and are a relatively newcomer to the hobby in the US. Though a large colony can fetch a premium price, a single head is much less expensive and can quickly grow into its own new colony.

As I mentioned, whiskers are oddballs. They stand tall, growing columnar skeletons with terminal polyps. On the top of each corallite, each polyp has a single mouth set in the center of a fluorescent green oral disc. Around the edge of the disc, there are two rows of pink or tan tentacles. In a manner reminiscent of button polyps (Palythoa and Protopalythoa spp.), each tentacle is actually associated with a single radial ridge. Every ridge ends in a tentacle but the ends are irregularly offset from one ridge to the next, giving the distinct impression of multiple concentric rows. Below the tentacular crown, which is roughly one inch in diameter, the Duncan coral features a velvety-looking coenosarc that connects all the heads of the colony. This tissue layer is usually a brownish-green color, but can fluoresce bright green under actinic and metal halide lighting.

A colony of Duncan corals can take on several looks over its life. As it fills out, it will take on a domed, bushy appearance. Duncans are similar to hammer corals in that the tentacular crowns fill in the spaces between themselves with new heads and densely packed tentacles. They almost seem to form a continuous mat, which belies the branched skeleton underneath. Duncan corals also demonstrate variability in tentacle length. Most I have seen have short tentacles, on the order of about one quarter to one half of an inch in length. However, I have seen pictures and read anecdotes of Duncans having tentacles several inches long. Though there may be a connection to light levels or flow rates, at this point that is all strictly conjecture.


Ecology:

Unfortunately, there is very little scientific literature that discusses Duncans Corals. In fact, I searched several comprehensive databases and came up with virtually no hits for the species name Duncanopsammia axifuga. The only mentions came from estimates of species abundance and exploitation statistics. There was nothing that described the ecological role played by these corals, nor were there any details of their general habitat needs. They are believed, but not conclusively known, to be more robust to environmental changes that threaten such reefs and certainly their hardiness in the aquarium can attest to that.

Obviously with such sparse scientific attention given to this species of coral, nothing has been written about their reproductive tendencies. However, generalistic trends amongst regionally-proximal scleractinians and growth rate records can be used to infer that colonies may be eight to ten years old before reaching sexually maturity. It is thus reasonable to assume that these corals can be long-lived in captivity, and may survive tank life for a decade or more.

One reason Duncan corals are not well described is that they exist only in a relatively small part of the world. They are restricted to a smallish range in the southwest Pacific Ocean. They are endemic to coastal Australia and the South China Sea, typically being found in waters of 60 feet deep or more.

In the wild, Duncan corals are typically found on muddy or sandy bottoms in lagoonal environments. Thus, they have a fair amount of resistance to turbid waters and elevated nutrient levels.


Aquarium Care:

Duncans have been available to the aquarium livestock market in Australia for many years and aren't nearly as popular there. Nonetheless, in the states there has been a very positive reaction to these as it has only been relatively recently that Duncanopsammia axifuga has been widely available. The reason why these are so new to the US market is due to the lifting of a ban on exports of all coral out of Australia, which occurred a few years ago.

Fortunately, Duncans are relatively easy to propagate and so they have become more readily available as aquacultured pieces. In fact, whenever possible it is a good idea to buy cultured frags. Doing so helps to ensure that these animals are not over-harvested. Propagated fragments are also good because they already have been demonstrated to live and survive fragmentation in a captive environment. As such, they can be expected to be hardier individuals. Their conveniently branched corallites present excellent opportunities to snip the heads apart with a sharp pair of bone shears or a wet band saw for even more precision. Because they are easily propagated, the extreme cost of large colonies can be mitigated by buying a single head and growing it out into its own colony.

A new colony should be placed securely in the sand or anchored to a base of bare rock. It is important to make sure the colony is securely supported. If it is not already, it will soon become top-heavy. The skeleton in most cases grows more upward than outward, and will not attach itself to any surfaces. Cyanoacrylate glue or reef-safe epoxy putty can be used to safely bond the corallite to a rock or a ceramic plug. Ideally, the base should be large and heavy enough to support the collective weight of the tentacular crowns without tipping over. Nicks and wounds caused by toppling over can quickly become infected, so it is important to make a point of securing these specimens down. Also, be sure to give the colony plenty of space to expand during the day, as well as grow over time. Unlike many other types of LPS corals, Duncans do not possess sweeper tentacles. They don't have a very potent sting, and will usually lose fights with other corals.

Aquarium placement is another important consideration. Since they hail from deeper, more turbid waters, Duncans require only moderate lighting. They are known to adapt well to various lighting conditions, but should still be placed away from the direct path of higher wattage metal halide bulbs. Bluer wavelengths of T5 fluorescent will do these corals very well, especially if they are kept in +12,000 K range. They will also do better when water flow is kept to a moderate rate; strong currents can injure the animal on its own sharp septa or knock the awkward colony over.

Duncan corals feed from the water column, usually trapping small meaty particles. Typical offerings include the usual subjects, such as mysid shrimp, Nauplii larvae, cyclops or Tigropius copepods, and Artemia (brine shrimp). Just keep it mixed up, and feed every head a tiny squirt 3-4 times each week. I suggest using a turkey baster or aquarium syringe to control the placement and quantities of the feedings. Water flow can be reduced or turned off while feeding to ensure that the food is not blown away. It is also effective to use a plastic container, placed upside down over the colony immediately after offering food. The container will not only reduce current over the colony, it will also protect it from your other marauding livestock. Typically, no more than about five minutes of the lid is needed to get the job done. It should be removed as soon as all the food is consumed.

Duncans are also hermatypic zooxanthellates, meaning they photosynthesize and build substantial calcium carbonate skeletons. They use plenty of calcium, strontium, and other micronutrients in a reef aquarium, so supplementation is a must.

In my mind, Duncan corals are exceptionally likeable. They have cool colors and a unique look. They grow fast, and reward good care with rapid reproduction and excellent coloration. They are hardy and can live for long periods of time. Duncans are just plain good fun.


Quick Notes:

  • Duncans need medium-to-medium strong lighting and low-to-medium water flow
  • They are hardy corals that grow quickly when happy
  • Regular feedings of meaty foods and micronutrient supplementation are necessary and help spur faster growth
  • Fragging without damaging the coral is relatively easy, so aquacultured specimens are increasingly more available


Works Cited:

Gay, J. Duncans Coral, Duncanopsammia axifuga. Practical Fishkeeping Magazine. 2009. URL: < http://www.practicalfishkeeping.co.uk/content.php?sid=57 >

Staff. Duncanopsammia axifuga. ITIS Report. 1999. URL: < http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=53828 >

Perun, B. Duncanopsammia Axifuga. The Sea Online. Undated. URL: < http://www.thesea.org/duncanopsammia/duncanopsammia-axifuga.htm >

Wijgerde, T. Duncanopsammia axifuga. Coral Publications. 2009. URL: < http://www.coralscience.org/main/videos/cnidaria-11/hexacorallia-9/scleractinia-8/duncanopsammia-axifuga >

Photo Credits:

Anonymous. CoralsPhotos, Duncan Coral (Duncanopsammia axifuga). Nature Pictures Online. Undated. URL: < http://www.nature-pictures.org/image/457/2051/ > DeCloux, R. Duncan Coral Colony. ARKive Online. Undated. URL: < http://www.arkive.org/duncan-coral/duncanopsammia-axifuga/ >

Hepworth, N. Practical Fishkeeping Magazine. 2009. URL: < http://www.practicalfishkeeping.co.uk/content.php?sid=57 >

Unissuh. Duncanopsammia axifuga. Aquahobby Online. Undated. URL: < http://www.aquahobby.com/corals/e_Duncanopsammia_axifuga.php >

Verun, C. Duncan Coral Colony. Coral ID. ARKive Online. 2002. URL: < http://www.arkive.org/duncan-coral/duncanopsammia-axifuga/ >