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Can I Ask a Favia of You? By Eric Borneman October 1997 Aquarium.Net

This month Eric Borneman writes on favia sp. for the reef aquarium. Aquarium Net has numerous articles written by the leading authors for the advanced aquarist

Can I Ask a Favia of You?

By Eric Borneman

family: Faviidae genus: Favia common species: pallida, favus, mathaii, stelligera, and others common names: moon, pineapple, closed brain, moonstone, star

reef friendliness: 4 (1-10)

It's time to take a journey to the many moons of Favia. Pun intended. If there are spelling errors in this article, it is because my hands are none to nimble on my laptop. For the past three weeks, it has been computer chip meltdown for me, and the only word processor I have at my disposal right now is an eight year old copy of MacWrite....of course, the entire program is only 265K, so in that sense I suppose I should be grateful. Nonetheless, at that time spell checkers were not too common, so I must depend on my (heaven forbid) proofreading skills to find the errors....I hope it is OK.

Favia is a huge group of corals containing more genera than any other family of corals. Most of them are somewhat similar in gross appearance, but there is no mistaking their beauty. To me, Faviids are the corals which make a reef look like a reef. Perhaps it is because my first experience on coral reefs was spent looking at the tremendous orbs of Diploria in Jamaica back in 1972. Seven or eight genera of the family exist in the tropical Atlantic and West Indies, and they are often a dominant reef builder which commonly appear in huge colonies that dwarf almost all other species. At least seventeen genera exist in the tropical Pacific. In addition to their role in reef building and sheer numbers, they are also major contributors to Australian mass spawning events that usually occur in November and December following a full moon. Faviids spawn in June and July in other regions of the Pacific. All the species are symbiotic and hermatypic and the corallites of all genera are distinct with well defined septa, columella and wall structures.

But, I digress; for this is about Favia and not Faviidae.

Favia is the largest genus of Faviidae with more species and numbers in the wild than any of its relatives. In fact, Veron states that these are "the most common corals in shallow-water communities that are not dominated by Acropora." With at least 70 recorded species, this should be of no surprise.

They form mainly massive type flat or rounded colonies (rarely encrusting) with monocentric and plocoid corallites. Favia means "honeycomb," and this name certainly is applicable to the regular formation of the corallites covering their surface. The plocoid (having corallites with separate and distinct walls) Favia is what distinguishes this genus from its similar relatives of the genera Favites, Goniastrea, and Montastrea. In other words, when looking at a completely contracted colony or a part of visible skeleton, the corallites are separated from each other and are distinct oval, round, or amoeba-shaped structures which may be touching but never fusing.

They may be separated by a thin groove of coenosarc, although this feature is also common to Montastrea as well. However, the method of polyp division between these two genera is distinct and will be covered later. Although by no means a "rule," the tissue of Favia may often be seen to present accurate demarkations of the underlying skeletal features allowing for certain examples to be recognized even under full expansion. Identification to a species level is possible using a taxonomic reference to match skeletal features of the corallites and associated structures, as well as the corallite size.

The polyps emerge only at night to feed, and they can be quite dramatic. A full ring of prominent transparent to translucent tentacles emerges and surrounds the oral opening. They may even have colored or contrasting tips.

These tentacles are quite "sticky" and adept at prey capture, and Favia polyps can take surprisingly large food and devour it very rapidly. Most interesting is their ability to form surprisingly long sweeper tentacles.These corals are known in the aquarium hobby as moon corals partly for the often blindingly fluorescent greens that show under actinic light. Further, the round shaped colonies, coupled with the crater-like corallites, green colors and highlights certainly lends credence to this name. Pineapple coral is the common name given to Favia morphs which do not have the green polyps, and are strictly brown or have variations of other colors. Favia can be found in yellow, cream, brown, green, rarely orange/red tones, and in combinations thereof. The oral disk area may be a contrasting color, and occasional morphs containing several distinct regions of color within the same colony are quite common.

Favia reproduce sexually as hermaphroditic (possessing both male and female sex cells) broadcast spawners. This means that the coral releasing both gametes into the water column and they intermix and fuse in the open water to form a diploid cell which will grow and duplicate until settling some distance away from the parent colony. The actual settlement cues for Favia are not known, although it would appear that environmental conditions rather than chemical cues are likely for this coral. Asexual reproduction through the formation of "polyp balls" is common for these corals. An external bud develops on the surface, usually along the sides or bottom edge of the colony. A tiny amount of calcium skeleton is calcified in the center of the "ball" and gravity eventually causes its separation form the parent. It is notable that such daughter colonies do not necessarily immediately attach to the substrate, but may remain unattached for some time. This is likely a response behavior to avoid "crowding" and possible competition for the same substrate space occupied by the parent. Thus, while some buds may soon attach directly near the parent, others may roll along the substrate in the currents for a while before settling. Perhaps most notable in Favia is its intracolonial divisions of polyps. The polyps and corallites divide intratentacularly. This is a primary distinction between the related species of Montastrea. Montastrea polyps divide by extratentacular budding. The former process is characterized by polyps which adopt a figure eight shape and divide like a cell in a type of fission that cleaves the polyp in two halves, right across the oral opening. The latter process is like a bud that forms from the outer wall of the corallite and daughter polyps have distinct oral openings produced from an evagination of the polyp wall tissue.

Thus, these similar looking genera can be recognized by noting the dividing corallites, of which there are likely to be numerous polyps in the process of dividing across the surface of the coral colony.

In the aquarium, Favia is highly desirable. Its beautiful appearance, often striking coloration, and bold shape lends a very natural "look" to any reef.

These are very hardy corals that tolerate a wide variety of water conditions. Of course, it is always best to provide the best possible water quality in any closed system, but in terms of ease of care, Favia are excellent "starter stony corals." They are tolerant of lighting conditions and may even thrive under comparatively low normal output fluorescent bulbs.

Yet, none that I have personally seen have had any adverse reaction to the intense lighting found in many small polyp style tanks. In fact, they seem equally at ease under either regimen. In terms of water flow, Favia prefer a moderate current to wash over their surface. I have found that extremely slow currents do not seem to be particularly detrimental except that the nighttime feeding tentacles do not seem to emerge as readily under such conditions. Conversely, stronger currents seem to induce the formation of sweepers. I have also found that while Favia may appear "happy" during the day, the less than dramatic nightime feeding response is a good indicator of some deteriorating water quality. It is also notable that Favia maintain the same pattern of feeding behavior (at night) as they do in the wild. This contrasts with many of our captive corals which adopt a reverse feeding schedule in captivity.

Some authors have stated that Favia do not need to be fed. In fact, these corals are quite heterotrophic, with only approximately 60% of their daily nutritional needs being met under ideal natural photosynthetic conditions.

It is quite possible that in aquariums that do not have light levels that approach natural reef conditions for their collection area ( i.e. likely most aquariums), that even less photosynthate will be produced for their metabolic needs. Favia does feed on dissolved organic material, plankton, and particulate organic matter. However, in aquariums with heavy use of foam fractionation or in tanks with extremely low nutrient water, this may not be enough to supply the corals with their daily needs. Therefore, it is recommended that occasional feedings of suitable foods be blown across the extended tentacles at night. Mysis shrimp and brine shrimp seem to be favorites. Even if photosynthetic and in-tank nutrition are adequate, supplemental feedings are highly likely to supply nutrients that may be missing from closed systems, including certain fatty acids and amino acids.

Favia do not grow quickly. They increase their mass substantially, but are not perceived as contributing much in terms of outward growth rates. Part of this is due to the small surface area of massive type corals. They grow from within. Certainly, though, the tissue expansion during the day can be surprising and alludes to a much larger coral than actually exists by measure of the skeleton. Favia are one of several massive type corals who seasonally add strontium to their skeletons in ratios that approach or exceed natural sea water levels. The substitution of strontium for calcium in their skeleton at such yearly times has allowed for fairly accurate ages to be determined for colonies in the wild. Strontium also results in a denser skeleton. An interesting feature of Favia (and most faviids) is that while their skeleton appears to be very solid underneath the colony with no apparent tissue where he colony had formerly been attached to substrate, these colonies often attach from their base if left undisturbed for a prolonged period of time. I am unsure of the method, but in situ observations of my own colonies shows that a translucent thick gelatinous tissue or secretion seems to exude from the porous skeleton underneath.

This seems to act as a cement that eventually leaves the colony permanently attached to the substrate. I would be interested in hearing if anyone has more information on this phenomena.

In terms of disease, Favia is quite resistant. Perhaps this is due to the fact that the tissue lies deep within the corallites and a large portion of living tissue is relatively unexposed to irritants and external noxious stimuli and pathogens. Nevertheless, Favia is regularly reported to show susceptibility to most coral diseases including Black band, White Band, Brown Jelly, White paste and other maladies. It is also commonly found to have expelled its zooxanthellae fairly early-on in local and widespread bleaching events. Often, only the top portion of the colony bleaches since the sides and bottoms are not exposed to full light and radiation. There are no genus specific predators to my knowledge outside those animals which are simply corallivorous. Favia specimens in the aquarium may also tend to recede from the margins of edges of tissue coverage. Although often found with a few isolated empty corallites, this loss of colonization is common and well tolerated in most cases. However, a progressive recession towards the top of the colony is usually indicative of poor water quality and often high phosphate levels. Furthermore, the colony may be receiving inadequate light or nutrition. Protocol to systematically remove or deal with any of these stressors or conditions is self evident and should be attempted without trepidation after noticing the loss of polyps. These coral are tolerant species and not so fragile that some amount of handling and treatment cannot be accomplished without harm. Unlike thinner tissued corals, Favia does not usually recede quickly, so that the urgency with which many small polyp problems must be attended to are not necessary. The brown jelly infections are likely to be the most quickly fatal problem seen in these corals, and freshwater dips or siphoning off the mass of decaying tissue are both effective means of combating this affliction with Favia.

In conclusion, the corals of the genus Favia are highly recommended hardy and beautiful additions to the reef aquarium. I have only assigned an reef friendliness rating of four to these corals. This is because their slow growth rate makes captive propagation an unlikely possibility in terms of realistic numbers that can be provided. They are not easily "fragmented" and it is not possible to "induce" polyp balls. Consequently, their growth rate also makes their recovery in natural communities a tedious process. Furthermore, these corals must be cleaved from the reef itself to collect them, which causes some collateral damage to the reef. Fortunately, the very common and prolific number of Favia makes it unlikely that the specimens collected for the hobby will have any significant impact on reef communities. The first coral I ever purchased was a Favia, and its beauty is every bit as wondrous today as it was so many years ago.

Eric Borneman EricHugo@aol.com

References:

Borneman, 1997. In press.

Houck, James E., and Robert Buddemeier. 1977. The response of coral growth rate and skeletal strontium content to light intensity and water termperature. Proc. 3rd Intl. Coral Reef Symp. 425-31.

Rasmussen, C.E. 1988. The use of strontium as an indicator of anthropogenically altered environmental factors. Proc. 6th Intl. Coral Reef Symp. 325-30.

Veron, J.E.N. 1986. Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu. 644 pp.

Wood, Elizabeth M. 1983. Corals of the World. T.F.H. Publications, Inc. Ltd. 256 pp.

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