A quick internet search for “Favia for sale” will return a collection of encrusting large-polyp stony corals collectively grouped as such. However, if one were to take a closer look, they would notice that many of these “Favia” are nothing like one another. The disparity in corallite shape, structure, and size should indicate that perhaps there is more to identifying these corals than what retail names would lead one to assume.
The label “Favia” in the reef aquarium hobby is a bit of a misnomer. It’s true that at one point many of the encrusting large-polyp stony corals of Indo-Pacific origin were classified as Favia within the family Faviidae. These identifications were based largely on superficial macromorphological characteristics (i.e. gross similarity in corallite shape and colony growth form), that have since proven to be inadequate for diagnosing different coral genera.
By 2014, the widespread use of molecular sequencing data led to the genus Favia being largely torn apart. Many species once known as Favia were reclassified based on genetic, micromorphological, and microstructural data into nearly half a dozen different coral genera. Ultimately, Favia, a genus that once contained over a hundred nominal species, is now recognized as only having two species, F. fragum and F. gravida; which are endemic to the waters of the Caribbean and tropical Atlantic.
Given that the laws of several nations collectively prohibit the harvesting of stony corals from the Caribbean and tropical Atlantic, true Favia do not exist in captivity outside of a select few conservation facilities. Instead, many of the corals in the reef aquarium hobby commonly listed as Favia belong to the family Merulinidae. While this is undoubtedly a name that most reef aquarists are unfamiliar with, this family contains many of the hobby’s most popular corals. These include Trachyphyllia, Catalaphyllia, Platygyra, Cyphastrea, and all of the species that are often called Favia.
The identification of species within these merulinid genera and sometimes even the genera themselves can be incredibly complicated. While writing this article, I found countless online listings of misidentified merulinids, with some sites listing Dipsastraea as Goniastrea, others IDing Paragoniastrea as Platygyra, and of course “Favia” being slapped on to a variety of different coral species. However, I don’t necessarily fault hobbyists and vendors for getting their IDs wrong. In fact, for many years before its reclassification, many corals that would eventually become a part of the family Merulinidae were jokingly referred to by systematists as part of the “Bigmessidae” on account of how difficult they are to ID and how enigmatic their taxonomic relationships are. Consequently, precise IDs of merulinid specimens are usually beyond the means of the average aquarist. However, one can still draw upon some broad generalizations that will help to minimize coral warfare between merulinid species in reef aquariums. Below are some of the most common genera that tend to be labeled as “Favia” as well as some general traits to look for when telling one type apart from another
Dipsastraea
Dipsastraea make up the disproportionate majority of encrusting corals commonly called Favia. They are the most superficially similar to the true Favia of Caribbean and Atlantic origin based on their outward appearance. Species from this genus are encrusting, eventually adopting a massive or submassive corallum covered in exsert, monocentric corallites. Although there are some exceptions, these corallites are generally rounded and plocoid, having distinct walls not shared with adjacent corallites. Most Dipsastraea species bud intracalicularly, with each polyp elongating before separating into two distinct polyps. However, a few species of Dipsastraea exhibit extracalicular budding, wherein a polyp creates a smaller polyp on its outer periphery that grows until it attains the same size as the larger one.
The majority of commercially available Dipsastraea have polyps that are fairly “fleshy” which can hamper identifications by covering up important skeletal features. These polyps sport flashy colors, often with oral disks that are differentially pigmented than the rest of the polyps’s tissue. Some polyps bear radial stripes that correspond to the septa and costae of the underlying corallite, others a ring-like appearance, and others still with blotchy swathes of pigment across the colony. Common examples of Dipsastraea include popular corals with names like “Yellow Submarine”, “Wolverine”, “Mayan Sun”, “Raptor’s Peace”, and “Pot of Gold”.
Occasionally, Dipsastraea species may be sold under the name “Barabottoia” or “Barabottia”, the latter of which is a misspelling. Regardless, both are incorrect, as Barabottoia is a taxonomically defunct name that hasn’t been accepted for several decades. This name often refers to Dipsastraea with tall, widely-spaced exsert corallites that jut out from the corallum. The colonies are typically pastel colored (often pale shades of blue, orange, pink, or green) and sometimes exhibit darker mottling. While they might look drastically different from the aforementioned varieties of Dipsastraea, they still belong to the same genus and are just different species.
Favites
The next major group of corals that go by the pseudonym of Favia are from the genus Favites. With such similar spelling, I often see the two genera confused with one another, and sometimes these names are even used interchangeably. For example, the “Day-Glo”, a popular strain of Favites can be found sold under “Day-Glo Favia” and “Day-Glo Favites” with almost equal frequency. Name misapplication aside, Favites have traditionally included corals that resembled Dipsastraea but have ceroid corallites, meaning that adjacent corallites have a shared wall between them. In many (but not all) cases Favites are less fleshy than their Dipsastraea counterparts and their tissue seems to be more tightly drawn to their skeleton. Popular Favites varieties go by names like “Fascination”, “Day-Glo”, “Spicy Lemon”, and “War Coral”.
Most species of Favites have ceroid corallites with polyps that undergo asexual reproduction via intracalicular budding. Depending on the species, these corallites can be angular or rounded, which makes skeletal examination all the more important. However, Favites that were once in the now-defunct genus Phymastraea and Montastraea before that, have exsert, plocoid corallites that can make them very easy to confuse with Dipsastraea. Luckily, ex-Phymastrea Favites spp. exclusively undergo extracalicular budding which is fairly uncommon in Dipsastraea species, allowing for some degree of differentiation.
There are also corals commonly referred to as “Prism Favia” and “Reverse Prism Favia” which at a glance appear to be very similar to some of the larger-polyped Favites species. However, these are an atypical species of Dipsastraea called D. rosaria. Colonies of this species are often sold as flattened chunks with polyps composed of a peach-colored outer ring and a teal-colored inner ring surrounding a turquoise oral disk. D. rosaria seems to be endemic to Australia and particularly localized to the Queensland region where it is predominantly collected.
Another distinctive type of “Favia” are the ones sold by the name of “Dragon Soul”. These corals are likely some species of Favites, but not one of the more well-known large-polyp Favites spp. like F. vasta, F. flexuosa, and F. paraflexuosa. Given that the genus has yet to undergo any sort of major authoritative revision, it is near impossible to confidently say which species of Favites these are, especially without DNA. The more common phenotype of “Dragon Soul Favia” (pictured below) exhibits maroon corallites with neon green oral disks and seems to be endemic to the shallow waters of the Great Barrier Reef. A less colorful phenotype (lacks the reddish coloration) can be found in reefs of the Northern Territory but seems to be less common, perhaps due to infrequent collection or export.
“Dragon Soul Favia” are likely a species of large-polyp Favites but without conclusive DNA evidence, it’s hard to say for sure. (Image Credit: Reef Builders)
Goniastrea
Although Dipsastraea and Favites make up the bulk of corals sold as “Favia”, a few other genera sometimes bear the same misnomer. Goniastrea is one such genus, although they tend not to enjoy much popularity in the reef aquarium hobby. Goniastrea is perhaps one of the most misused names in the trade (along with Favia), and most corals offered for sale as Goniastrea are a species called Coelastrea palauensis (more on this later). In fact, when searching online for Goniastrea frags, none of the results were actual Goniastrea and almost all were images of C. palauensis.
True Goniastrea resemble Favites and have abortive, misaligned septa between adjacent corallite and a well-developed palliform crown. These traits, however, are not entirely unique to Goniastrea which can make distinguishing it from Favites rather difficult in some situations. Luckily, the only species of Goniastrea that enters the aquarium hobby with some degree of frequency is Goniastrea pectinata, which forms flattened, submassive colonies in shallow water reefs throughout the Indo-Pacific. G. pectinata comes in a few different colors, usually tan or a subdued pink, but the ones collected for the aquarium trade usually have an oral disk with bright green radial stripes, corresponding to its underlying palliform lobes. Unlike the majority of stony corals, this phenotype of G. pectinata does not seem to drastically change color under aquarium conditions and retains its “wild-type” appearance. These corals have been less common in recent years, but with the return of Fijian coral exports, they may start to trickle in again.
Coelastrea
Coelastrea is another common genus to be sold under the Favia category, sometimes referred to as “Alien Moon Brain Favia” or misidentified as a Goniastrea as I mentioned earlier. Coelastrea are infrequently seen in the aquarium hobby and despite members of the genus being found throughout much of the Indo-Pacific, most aquarium specimens seem to almost exclusively originate from Australia. Coelastrea species form massive, hemispherical coralla with large polygonal corallites. Each corallite has a deep calice with a well-developed crown of paliform lobes. At one point, Coelastrea were considered to be a member of the genus Goniastrea, but differ in one major aspect of their skeletal morphology, their septal alignment. Whereas the septa in adjacent Goniastrea corallites are misaligned, those of Coelastrea are confluent, lining up with the septa of other corallites. The only member of Coelastrea that enters the trade regularly is C. palauensis. This species almost always has large fleshy polyps that are varying shades of green with contrasting oral disks and mottled speckling across the colony.
A few other species like Paragoniastrea russelli and Astrea curta occasionally enter the hobby as “Favia”, but do not occur frequently enough on vendor listings to warrant much detail in this article. On some occasions, encrusting “maze brain” style merulinid corals like Platygyra and Paragoniastrea will be sold as Favia since small frags may or may not express the same meandering corallites as larger colonies. However, these are generally quite easy to tell apart with a bit of scrutiny.
While I certainly understand the utility of grouping corals with similar care requirements and growth forms under a single term, I also think that labeling so many of them as “Favia” is a disservice to the incredible diversity of scleractinian species. Sure, it may be easier for novice hobbyists to learn a single catch-all name for the sake of initial familiarity, but for those who seek to achieve a deeper and more nuanced understanding of the corals in their care, it becomes critical to learn how to recognize the subtle differences that make each genus distinct.
If you’re a vendor, I challenge you to attempt to properly identify the corals you sell. If you own a local fish store or an aquarium maintenance company, perhaps try to educate your clientele about the differences that separate these genera. And if you’re just a hobbyist, take a closer look at all of the “Favia” in your tank(s). You may have more coral diversity than you previously thought.
About the author
Sean Ono has been keeping corals for the better part of a decade, both at home and as a former volunteer aquarist at one of the largest public aquariums in the United States. He has a particular affinity for anthozoan cnidarians (including corals) but is passionate about echinoderms, marine worms, macroalgae, and more. Despite his familiarity with reef-associated organisms, his previous academic research is more elasmobranch-centric, aiming to quantify the biomechanical and behavioral aspects of stingray tail strikes. Having recently graduated with a Bachelor of Science in Marine Biology, Sean hopes to pursue a Ph.D. in ecology and evolution, focusing on the intersection of biomechanics, sensory capabilities, and comparative morphologies of marine taxa.
