The ultimate challenge of reefkeeping is the closing of our captive animals’ life cycles. A fortunate few have witnessed a coral spawning in their aquariums and might be interested in what it would take to raise coral planula larvae. On the other hand, there may be dedicated hobbyists interested in captive spawning of a certain species. It is the goal of this series to assist those hobbyists. This time, we’ll examine reproductive habits of stony corals. Information on the reproductive habits of over 300 stony coral species (in almost 100 genera) is presented. It is the most complete single-source reference currently available. This article will begin to offer information other factors (puberty age and size, life spans, etc.) and should begin to answer questions hobbyists might have.

Figure 1. A female Sandalolitha robusta specimen spawns at the Waikiki Aquarium. Photo courtesy Dr. Bruce Carlson.

Witnessing coral reproduction, especially in an aquarium, is an exciting event. The first inclination is usually to find the camera and document the event. In the rush, some details may be (and often are) left unrecorded. Afterwards, many questions will inevitably arise. See the Figure 51 at the end of this article for suggestions on what to record.

There are several reasons why we don’t hear of corals’ sexual spawning in captivity, and the most likely reason is that few, if any, aquarists have specially tried to address issues pertinent to success. Another reason is that spawning events are simply not observed. It is also a fact that only a handful of dedicated aquarists have sufficiently researched requirements for captive breeding.

The goals of this third article on coral reproduction are simple. We’ll examine the information available on stony coral sexuality and reproductive habits. This, in turn, will allow us to decide how many corals we’ll likely need in order to have a pair (if necessary!). Sexual maturity is another issue. Unfortunately, we can not always judge the reproductive fitness of a coral simply by examining colony size – other factors are sometimes important (colony thickness is an important diagnostic tool in some small encrusting corals).

Be aware that benthic marine invertebrates as a group utilize almost every reproductive strategy imaginable, ranging from parthenogenesis (suggested by researchers to possibly occur in a few coral taxa) to other asexual means (including ‘popping’, ‘dripping’, ‘budding’, fragmentation, transverse fission, longitudal fission, stoloniferous growths, etc.) and, of course, sexual reproduction including broadcast spawning and brooding (both internally and externally). As usual, nature will continue to confound us as we realize that a particular coral species reproductive habit can, and often does, vary according to location and/or environmental conditions. However, this should not prevent us from reviewing reproduction data gathered from over 400 references (a complete reference list will appear at the end of this series).

To recap, our goals for this time are:

1. Discuss tools to ID your stony coral to the species level.
2. Understand its mode(s) of reproduction and with this information select the number and size of specimens to ensure a pair exists.
3. Enable you to select an appropriate aquarium size. (Be aware that many corals’ size at puberty might make them much too large for some home aquaria.)

Before continuing, perhaps a review is in order of terminology we’ll use.

Glossary

Brooding or Brooder – Brooding

Where fertilized eggs are held internally (or sometimes on the surface of a parent colony) and are released as planula larvae. Brooder: A coral that uses the brooding reproductive process.

Fecundity

Fertility; ability to produce abundantly.

Gonochoric

Possessing distinct male and female colonies where offspring are a result of fusion of gametes. Also referred to as dioecious, or unisexual. Gonochorism occurs in ~25% of coral species examined (Richmond, 1997).

Hermaphroditic

Possessing both male and female reproductive organs, sometimes referred to as monoecious. Self-fertilization (also called ‘selfing’) is an uncommon hermaphroditic trait among corals.

Oocyte

An immature egg (ovum).

Parthenogenesis

Development of a new individual from an unfertilized egg. This results in a female clone and is thought to occur in many invertebrates (including soft corals, gorgonians and possibly stony corals) and some vertebrates.

Planula larvae

The free-swimming, ciliated stage of coral larvae.

Polyspermy

Where more than one sperm fertilizes an ovum.

Protandrous hermaphrodite

Where male sex organs mature before those of the female.

Protogynous

(proto=first; gynous = female) – Where female sex organs mature before those of the male.

Self-fertilization or ‘Selfing’

Where gametes from a single parent colony are sufficient for successful reproduction. Relatively uncommon.

An Initial Recommendation

Unless you’ve witnessed a spawning of a particular coral species within your aquarium and want to investigate further, it is probably best to choose a coral that utilizes the brooding strategy. There are many advantages:

1. Brooding coral species are generally smaller in size than their broadcasting counterparts.
2. Planula larvae from brooders are relatively mature upon release and have the advantage of size.
3. Some hermaphroditic brooders do not broadcast gametes. This lessens the chance of the aquarium’s life support system suffering catastrophic failure.
4. Brooded larvae sometimes contain zooxanthellae upon release from the parent colony, and the larvae do not have to obtain them from the surrounding environment.

Suspected Parthenogenesis

Parthenogenesis (definition above) is known to occur in a few invertebrates and even some vertebrates. It is suspected to occur in these stony corals:

• Pocillopora damicornis (Permata et al., 2000)
• Porites lobata (Fadllalah, 1983)
• Porites lutea (Fadllalah, 1983)
• Fungia scutaria (Krupp, 1983)

Self-fertilization (‘selfing’)

• Acropora (Isopora) brueggemanni (Okubo et al., 2007)
• Acropora tenuis (Heyward and Babcock, 1986)
• Agaricia agaricites (Gleason et al., 2001).
• Balanophyllia europaea (Goffredo et al., 2005).
• Diploria strigosa (Hagman et al., 1998, in Alvarado et al., 2003)
• Favia fragum (numerous references)
• Goniastrea aspera (Heyward and Babcock, 1985)
• Goniastrea favulus (Stoddart et al., 2004; Miller & Mundy, 2005)
• Mycetophyllia species, suspected (Tirado, 2006)
• Pocillopora damicornis (numerous references)
• Porites astreoides (Gleason et al., 2001).
• Seriatopora hystrix (Sherman, 2008)
• Siderastrea radians (Neves et al., 2008)
• Tubastraea coccinea (numerous references)

Gonochoric Brooding

Gonochoric brooding involves broadcast spawning by males and internal or external (surface) fertilization of oocytes, followed by internal or surface brooding:

• Balanophyllia regia (Goffredo et al., 2005)
• Dendrophyllia sp. (Babcock et al., 1986)
• Goniopora queenslandiae (Yamazato et al., 1975, in Fadlallah, 1983)
• Isophyllia dipsacea (Duerden, 1902, in Fadlallah, 1983)
• Leptopsammia pruvoti (Kruzic et al., 2008)
• Porites brighami (Richmond & Hunter, 1990)
• Porites clavaria (Fadlallah, 1983)
• Porites furcata (Soong, 1991)
• Porites murrayensis (Neves, 1998)
• Porites panamensis (Glynn et al., 2008)
• Scolymia wellsi (suspected; Pitombo, 1992)
• Tubastraea faulkerni (Babcock, 1986)

Brooders (stony corals)

• Acrhelia horrescens (Kawaguti, 1941)
• Acropora (Isopora) brueggemanni (see Richmond & Hunter, 1990)
• Acropora corymbosa (Stimson, 1978)
• Acropora (Isopora) cuneata (Wallace et al., 2007)
• Acropora humilis (Stimson, 1978)
• Acropora palawensis (see Richmond & Hunter, 1990)
• Acropora (Isopora) palifera (Kojis, 1986)
• Acropora striata (Stimson, 1978)
• Acropora (Isopora) togianensis (Wallace et al., 2007)
• Agaricia agaricites (Thornhill et al., 2006)
• Alveopora daedalea (Schlesinger & Loya, 1985)
• Balanophyllia europaea (Mezzomonaco et al., 2002)
• Caryophyllia cyathus (Koch, 1897)
• Cyphastrea ocellina (Stimson, 1978)
• Dendrophyllia manni (see Richmond & Hunter, 1990)
• Diploria strigosa (Hagman et al., 1998)
• Euphyllia glabrescens (Kawaguti, 1941)
• Favia fragum (Szmant, 1986)
• Galaxea aspera (see Richmond & Hunter, 1990)
• Goniopora queenslandiae (Loya, 1976)
• Heliofungia actiniformis (see Richmond & Hunter, 1990)
• Isophyllia dipsacea (Fadllalah, 1983)
• Isopora togianensis (Wallace et al., 2007)
• Madracis carmabi (Vermeij et al., 2004)
• Madracis decactis (Vermeij et al., 2004)
• Madracis formosa (Vermeij et al., 2004)
• Madracis mirabilis (Vermeij et al., 2004)
• Madracis pharensis (Vermeij et al., 2004)
• Madracis senaria (Vermeij et al., 2004)
• Manicina areolata (Johnson, 1992)
• Mycetophyllia ferox (Babcock et al., 1986)
• Pocillopora damicornis (Stimson, 1978)
• Pocillopora elegans (Stimson, 1978)
• Pocillopora verrucosa (Stimson, 1978)
• Porites astreoides (Thornhill et al., 2006)
• Porites panamensis (Glynn et al., 2008)
• Scolymia wellsi (Pitombo, 1992)
• Seriatopora caliendrum (Rinkevich & Loya, 1979)
• Seriatopora hystrix (multiple references)
• Siderastrea radians (Thornhill et al., 2006)
• Tubastraea coccinea (Glynn et al., 2008)

Protandrous and Protogynous Hermaphrodites

Protandrous Hermaphrodites

• Flabellum rubrum (Moseley, 1881, in Fadlallah, 1983)
• Goniastrea favulus (Kojis and Quinn, 1981)
• Stylophora pistillata (Loya, 1976)

Protogynous Hermaphrodite

• Siderastrea radians (Duerden, 1902, in Fadlallah, 1983)

Degree of Difficulty

As we have seen, aquarists have been successful in propagating a number of coral species. There are a number of factors involved in these successes, beginning with the skill and dedication of the aquarist. Seasoned veterans often report ‘easy’ asexual reproduction of species difficult to maintain long-term in captivity (some Goniopora species are good examples, while there are no reports of reproduction of easily maintained species).

With that said (and avoiding the issues and degrees of difficult in husbandry of some coral species), I will unilaterally list my perception of how challenging captive breeding of corals could be (beginning with the least difficult):

1. Those capable of Parthenogenesis.
2. Programmed fragmentation. This method is essentially left to the coral (it is genetically programmed to produce colonies in this manner), and fragments ‘drip’ or ‘pop’ away. The only thing required from the hobbyist is securing the cloned colony to a suitable substrate.
3. Intentional fragmentation. This technique requires little from the hobbyist. Small fragments, or nubbins, or snipped, clipped, sliced or cut away from brood stock and attached to any of a number of substrates for grow-out.
4. Brooding coral colonies capable of self-fertilization or ‘selfing’. Since ‘selfing’ is due to fertilization of an egg produced by a female by a sperm produced by a male within the same colony or sometimes the same polyp (hermaphroditic), these bisexual coral colonies can reproduce with only one colony present.
5. Hermaphroditic brooding corals.
6. Hermaphroditic broadcast spawners. In theory, only two coral colonies would be required to ensure cross-fertilization. However, many variables come into play such as sperm concentrations, polyspermy, egg buoyancy, impact of spawning on aquarium water quality, mode of zooxanthellae acquisition (vertical or horizontal), etc.
7. Gonochoric broadcast spawners. In addition to the challenges presented by hermaphroditic broadcast spawners (above), we have to consider sex ratios (sometimes heavily skewed towards males) and the impact this has on sizing the aquarium.

Comments on Data Bases

While research this article, I found it best to maintain two data bases, and both are presented in this article. First, reproductive information about stony corals is listed in taxonomic order – by Family, Genus and Species along with comments, photographs, etc. After that, a quick reference sheet (along with the reference) presents reproductive information sans photos and comments (See Table 108).

A Note on Caribbean Corals

There have been rumors for a number of years that Caribbean corals would become legally available to hobbyists. After a number of false starts, this seems to be a reality. Rose corals (Manicina areolata) are available, and Siderastrea species may soon follow (Michael Janes, personnel communication. See www.aquatouch.com for details). Acropora palmata spats (grown from legally collected eggs and sperm from spawn slicks) are now in public aquaria. Perhaps this endangered species will someday be in home reef aquaria.

It has been estimated that 60% of Caribbean corals are brooders; some are of relatively small size and may be available in the future. For these reason, I have included Caribbean species in this article.

The Aquarium

Almost every article written on home-based fish propagation begins with aquarium selection. So, it is seems reasonable to start there, right? “Let’s see – I’ve got that old 40 gallon breeder tank just gathering dust. I could use it…”

Whoa, cowboy! This line of reasoning has already dismissed the idea of logically thinking this project through from concept to reality. Fish breeders can choose the correct aquarium because they know much more about their fishes’ reproductive habits than coral farmers know about their corals’. It is fairly easy to quickly research size of adult fish and how to sex them. So, let’s start over.

Selecting Your Coral

Before you select your candidate coral, you should be able to identify it. There is a great deal of published research available (some of it presented in this series of articles), but utilization of this information depends upon correct identification of the coral. In some cases and with enough experience, this is simple. Some corals, such as the Elegance coral (Catalaphyllia jardineri), are not easily confused with any other species. Other corals will demonstrate a plasticity in shape and appearance according to environmental factors (water motion and lighting being two major influences), or naturally resemble very closely another coral species. For instance, there are several Acropora species that have pronounced corallites that appear to the casual viewer to be Acropora millepora, when in fact they are not.

Coral Identification Resources

Coral ID Software

Unless your stony coral identification skills are well-honed, I recommend the purchase of Veron’s Coral ID software. See the Media Review on this excellent resource for stony coral species identification here (http://www.advancedaquarist.com/2008/4/review ).

Internet Resources

For Acropora species, there is an excellent free resource on the internet (www.coralsee.org).

Veron’s Corals of the World is available for free at this website: http://whelk.aims.gov.au/coralsearch/coralid-search.php

Note this website is easier to use if you already know the coral ID to genus level. Then it is a matter of looking at each species. This can be a time consuming matter, and definitely is not as easy to reference as the print version.

If getting an ID to the genus level is acceptable, see CoralIdea (www.coralidea.com).

Books

There is no better book than Veron’s Corals of the World (2000). See the review of this book here (http://www.advancedaquarist.com/2008/4/review).

With a little practice and a few basic laboratory tools (magnifying glass, dissecting microscope) you should be able to get a reasonable idea as to the correct species (it helps if you know where the corals were collected – keep this in mind if you order through any of the major distributors. They know!).

Can I Use Fragments? Effect of Damage (Fragmentation) on Fecundity

Figure 2. Anatomy of a ‘typical’ stony coral polyp. Eggs (oocytes) and spermaries (male gonads) – either separately or together – can be found on mesenteries within sexually mature polyps.

It is generally believed that growth, reproduction and maintenance are processes competing for a limited amount of energy. The effects of breakage on a particular colony depend upon the amount of damage, colony size, energy reserves (such as lipids), environmental conditions and other factors. Limited resources could be devoted to repair traumatized areas. It is also possible that corals will re-absorb oocytes/eggs to obtain their high-calorie yolks for use in tissue repair.

There are several published papers on the subject. Zakai (1997) found that breakage of Pocillopora damicornis exceeding 25% of colony area reduced planulation by 63% while having no effect on the size (but obviously the number) of planulae. Smith and Hughes, 1999 examined the effects of breakage on Acropora intermedia, Acropora millepora, Acropora hyacinthus and found that fecundity was greatly reduced.

However, fragmentation does not necessarily reduce fecundity. Daughter colonies produced by programmed fragmentation by Diaseris distorta are sexually functional at sizes as small as 1 cm² (roughly ½” square). See Part 1 of this series for photos of Diaseris.

In general, fragments can be used, but expect fecundity to be reduced or delayed.

Polyp Anatomy

Figure 3. Modes of coral reproduction. ‘Selfing’ and ‘gonochoric brooding’ are relatively uncommon, while the two forms of broadcast spawnings are not.

The sexual organs of corals are usually on mesenterial filaments within the polyp. See Figure 2.

Sexing Your Coral

After selecting your target species, we can continue. Unfortunately, you can’t just look at a coral and determine if it is male or female (unless you have the good fortune to witness it in the act of spawning, or have a small laboratory devoted to histology and can examine coral gonads). We’ll need to understand a couple of terms before we continue.

Spawning Ratios – How Many of Each Species in an Aquarium?

Most corals are hermaphroditic and only in relatively few cases do we have to concern ourselves with the issue of sex ratios. Sex ratios, when available, are included in the initial reports (below). Be aware that sex ratios are not fixed and can vary from location to location, but this is the best information we currently have.

Notes on Colony Size, Sexual Maturity and Life Span

Colony size and sexual maturity has been linked in some cases, but many factors other than colony area should be considered. In some cases, it is not the size of the colony but the thickness of the coral’s encrustation over the substrate that is the telling factor. In other cases, corals can asexually reproduce by fission, where a portion of the colony becomes isolated from the parent. In some cases, total mass of the colony (such as gorgonians) should be considered in lieu of colony height.

Generally, corals are a long-lived bunch and it is not uncommon to hear reports of corals believed to be hundreds of years of age. However, local patterns (number of storms, temperature, anthropogenic impacts, etc.) can limit survival rates.

On the other hand, brooding corals tend to have relatively brief lives. They mature at an earlier age and smaller size. They produce fewer young, but these tend to be well developed with a higher chance of survival. In some cases, brooders are opportunistic colonizers.

We’ll now begin our review of stony coral reproductive habits. They are listed by in alphabetical order by Family, followed by Genus (also in alphabetical order). Information on species is presented in any of the Tables and some of the Figures.

For those wanting a quick reference, see the end of this article for Table 108 – The Quick and Easy Reference. There, corals are listed alphabetically by Genus.

Family Acroporidae

Genus Acropora (Staghorn and Antler Corals)

Figure 4. Acropora species are easily propagated via intentional fragmentation by hobbyists, but there are reports of sexual spawning in aquaria. Photo by the author.

Puberty Age for Acropora Species

Wallace (1985) estimates Acropora granulosa, A. hyacinthus, A. loripes and A. valida first spawn when they are 4-5 years of age. See Table 2 for more information.

Subgenus Isopora

Some controversy exists over ‘subgenus’ status of Isopora (some feel it should be elevated to genus status), but I’ll present information as subgenus -as it is listed in the references – until this matter is resolved.

Genus Anacropora

Genus Astreopora

Genus Montipora

Montipora species are very popular among reef hobbyists and for good reason. As a group, they are hardy and can grow quickly. In addition, some species contain colorful fluorescent and chromoprotein pigments (see Figure 5).

Figure 5. The fluorescence of Montipora danae. Photo by the author.

Puberty Size of Montipora Specimens

Bassim (1997) reports that Montipora verrucosa (now M. capitata) colonies are sexually mature when they are 18 cm (7.2″) on the longest axis.

Family Agariciidae

Members of Agariciidae are a mixed bag, reproductively speaking (Veron, 1986) – Agaricia species are brooders, while Pavona species are broadcast spawners. We don’t have enough information on other genera to make generalizations. Unfortunately, there is presently a ban on collection of Agaricia species, but Pachyseris and Pavona specimens are common in reef aquaria.

Genus Agaricia(Lettuce Leaf Corals)

Puberty Size of Agaricia humilis

Figure 6. Diameters of adult Agaricia species (Van Moorsel, 1981).

Agaricia species are found only in the Caribbean (Veron, 1986). As far as we know, all Agaricia species are hermaphroditic brooders. Agaricia humilis specimens are sexually mature when they are ~28mm in diameter (van Moorsel, 1983). A. humilis is known to planulate year round. See Figure 6 for details on adult colony sizes.

Genus Coeloseris

No information on reproductive habits available.

Genus Gardineroseris

Genus Helioseris

Genus Leptoseris (Ridge Corals)

No information on reproductive habits available.

Genus Pachyseris

Genus Pavona (Pork Chop or Corrugated Corals)

Figure 7. Pavona varians, from Hawaii. Photo by the author.

Family Astrocoeniidae

Genus Madracis

Madracis species are cosmopolitan – they are found in the Pacific (including Hawaii), Atlantic and Mediterranean.

Genus Palauastrea

Biologists seem to have overlooked this coral (it strongly resembles the common Porites cylindrica) and I have been unable to locate any information concerning its reproductive habits.

Genus Stephanocoenia

Genus Stylocoeniella

Family Caryophylliidae

Genus Heterocyathus

A zooxanthellate coral (Veron, 2000). No information is available about reproductive habits.

Genus Caryophyllia

Genus Goniocorella

Genus Lophelia

Family Dendrophylliidae

Some of the members of Dendrophylliidae are non-photosynthetic (they do not contain zooxanthellae). Since they are not autotrophic, some Balanophyllia, Dendrophyllia, Tubastraea and others require good water motion to deliver enough food, or require regular feedings. Those aquarists willing to meet the demands of these often brightly colored animals are often rewarded by their corals’ captive spawnings (usually in the form of planula larvae).

Genus Balanophyllia

Balanophyllia europea (a Mediterranean coral) contains zooxanthellae. Other Balanophyllia species do not.

Age of Puberty, Sex Ratio and Life Span for Balanophyllia species

Balanophyllia elegans colonies are capable of reproduction (brooding) at 1.5 years of age and have an expected life span of about 10 years (Gerrodette, 1981).

The gonochoric Balanophyllia pruvoti has a sex ratio of 1:1 (Radetic et al., 2002).

Genus Cladopsammia

Genus Dendrophyllia

Genus Duncanopsammia

No information available on reproduction of the single member of this genus – Duncanopsammia axifuga (Veron, 1986).

Genus Enallopsammia

Genus Leptopsammia (Sunset Cup Coral)

Genus Heteropsammia

These small (25mm diameter) corals live at depths of ~25 meters or more and are free-living on soft bottoms (Veron, 2000). They may or may not contain zooxanthellae.

Genus Rhizopsammia (Wellington’s Solitary Coral)

Genus Tubastraea(Sun Corals)

Figure 9. This Tubastraea colony originated from a planula larva that settled in an area of high flow – an overflow in a reef aquarium.

Tubastraea (or perhaps Dendrophyllia) specimens reproduce readily in an aquarium when conditions are right.

Fully developed planula larvae are released and the number of reports of this occurrence in aquaria rivals that of another brooding coral – Pocillopora damicornis.

Figure 10. These Tubastraea and Balanophyllia species are sexually mature at an early age.

Puberty Size and Age of Tubastraea coccinea

Tubastraea coccinea (Glynn et al., 2008) Reproductive at 1.5 years, equating to colony size of ~5 cm in diameter, although Glynn et al., 2008 reports colonies can be reproductive when only 2 to 10 polyps are present (possibly due to stoloniferous growths). Paz-García et al. (2007) also reports reproduction in colonies only 5 cm in diameter (see Figure 11).

Genus Turbinaria (Pagoda Corals)

Veron, 1986 states that Turbinaria species are all gonochoric broadcast spawners.

Figure 11. The distinctive yellow-green coloration of Turbinaria reniformis is visible in this specimen. Photo by the author.

Family Euphyllidae

Family Euphylliidae contains some of the most popular aquarium corals including Euphyllia species (commonly called Anchor, Hammer, and Frogspawn corals) as well the Elegance coral (Catalaphyllia jardinei), Bubble and Grape corals (genera Plerogyra and Physogyra, respectively) and the Fox coral (Nemenzophyllia).

Euphylliidae corals, as a group, use various reproductive strategies as the following tables demonstrate.

Genus Catalaphyllia (Elegance Coral)

There is only one known Catalaphyllia species.

Figure 12. Euphyllia ancora, a gonochoric broadcast spawner. Photo by the author.

Genus Euphyllia (Hammer, Anchor, and Frogspawn Corals)

Euphyllia species are of separate sexes (gonochoric) and broadcast gametes, except for the hermaphroditic brooder E. glabrescens. There are reports of E. glabrescens planulating and successful settlements of larvae within aquaria (Mitch Carl, personal communication).

Figure 13. Release of planula larvae by a Euphyllia glabrescens at the Henry Doorly Zoo, Omaha, Nebraska. Photo courtesy Mitch Carl.

Maximum Colony Sizes of Brooding and Broadcasting Euphyllia Species

Figure 14. Euphyllia glabrescens is a hermaphroditic brooder, and is smaller than its broadcasting relatives. Note that 100 cm diameter may not be the largest colony size, it is the largest category listed by the researcher (Soong, 1993).

Genus Nemenzophyllia (The Fox Coral)

Some of the corals sold as Nemenzophyllia are likely Plerogyra discus. Nemenzophyllia is often listed as rare, and no information is available on its reproductive habits.

Genus Physogyra (Grape Coral)

The Grape coral is commonly seen in reef aquaria. It is a gonochoric, broadcast spawner.

Figure 15. Nemenzophyllia turbida or Plerogyra discus? Only its taxonomist knows for sure. Photo by the author.

Genus Plerogyra (Bubble Coral)

The Bubble coral is another popular reef aquarium inhabitant. It is probably gonochoric, and definitely a broadcast spawner.

Figure 16. Hobbyists have reported that Bubble Corals (Plerogyra sinuosa) are broadcast spawners. Photo courtesy of Steve Ruddy.

Genus Solenosmilia

Family Faviidae

Genus Astreosmilia

Limited to the western Indian Ocean (Veron, 1986), few researchers have paid much attention to these corals, and no information on spawning habits is available.

Genus Australogyra

Genus Barabattoia

Genus Caulastrea (Candy Cane Corals)

Genus Cladocora (Tube Corals)

Cladocora specimens are often found on Florida live rock but their patchy spots or clusters of small polyps are not particularly spectacular. Some do not possess zooxanthellae making their small tentacles colorless. Their ‘tubes’ are ~1/8″ in diameter.

Figure 17. Colpophyllia species. Photo courtesy Jake Adams and www.coralidea.com

Genus Colpophyllia(Grooved Brain Coral)

This genus is found only in the Atlantic (Veron, 1986).

Genus Cyphastrea

Figure 18. The brooder Cyphastrea ocellina has a smaller adult colony size than the Cyphastrea species that are broadcast spawners.

Maximum Colony Sizes of Various Cyphastrea Species

Information on maximum colony sizes of various Cyphastrea confirms once again that brooding corals are smaller in size than their broadcasting relatives. See Figure 18.

Genus Diploastrea

Figure 19. Adventurer and reef hobbyist John Dawe watches a Diploria spawn at the Flower Garden Banks, Gulf of Mexico. Egg/sperm bundles are visible as white dots throughout the picture. Photo courtesy of Michael P. Janes.

Genus Diploria (Brain Corals)

This genus is found only in the Atlantic (Veron, 1986), and it is possible that specimens could hitchhike in on legally collected live rock.

Figure 20. Diploria clivosa is a hermaphroditic broadcast spawner.

Sizes and Sexual Maturity of Diploria clivosa and D. strigosa

Genus Echinopora

Figure 21. Diploria strigosa is a hermaphroditic brooder.

Genus Erythrastrea

This genus’ distribution is limited to the Red Sea (Veron, 1986) and no information on its reproductive habits is available.

Genus Favia (Star Corals)

Figure 22. A Favia specimen releases an egg or sperm bundle in the aquarium of master aquarist Tony Vargas. Photo courtesy of Tony Vargas. This Favia has been maintained in captivity since 2000, and is 8 inches in diameter. Spawning occurred in June 7, 2004 in the early morning, and the event lasted for ~1 hour. This coral had recently endured a move from New York to Florida.

Favia corals have been a mainstay in the reef aquarium hobby for many years. There are scattered reports of reproduction in aquaria.

Figure 23. Favia fragum is known to reproduce in public aquaria. It is a brooder, matures at a small size (~ 50mm in diameter) and can be very attractive. Unfortunately, it is an Atlantic coral and is not readily available to hobbyists.

Notes on Favia Puberty Size and Age

• Favia doryensis specimens are sexually mature at 8 years of age (Connell, 1974).
• Favia fragum has reproduced in aquaria. It is a small coral (no more than 2″ in diameter and broods its young).

Figure 24. The trend continues… the brooding coral F. fragum is smaller than its broadcast spawning counterparts. Note that 100 cm diameter may not be the largest colony size, it is the largest category listed by the researcher (Soong, 1993).

Genus Favites

Genus Goniastrea (Honeycomb Coral)

Puberty Size and Age of Goniastrea Specimens

• Goniastrea aspera – less than 3″in diameter have only a slim chance of containing gonads, and proportion of mature colonies increases with colony size (Babcock, 1984)
• Goniastrea aspera and G. favulus reached reproductive age in about 5 years (Babcock, 1991).

Genus Leptastrea

Genus Leptoria

Figure 25. The Caribbean Rose Coral (Manicina areolata) is now legally available for purchase by hobbyists. Photo courtesy Jake Adams and www.coralidea.com

Genus Manicina(Common Atlantic Rose Coral)

These beautiful Caribbean corals are being legally reared and are beginning to find there way to market in the U.S. Their small size and reproductive habits make them an idea candidate for captive propagation efforts. See this website for details on obtaining Manicina specimens: www.aquatouch.com

Comment on M. areolata Adult Size

Adult Manicina specimens are ~3 inches long.

Figure 26. Montastrea cavernosa. Photo courtesy Jake Adams and www.coralidea.com

Genus Montastrea (Boulder Coral)

Montastrea corals are found in the Atlantic and Pacific Oceans.

Figure 27. The Caribbean faviid Montastrea cavernosa has a sharply defined sexual maturity size.

Age of Puberty for Montastrea annularis

Szmant (1986) estimates the age of puberty for Montastrea annularis is 5 to 6 years.

Genus Moseleya

Genus Oulastrea (Zebra Coral)

Puberty Size of Oulastrea crispa

Colonies greater than 20mm in diameter are sexually mature (Lam, 2000).

Genus Oulophyllia

Genus Parasimplastrea

There is only one species (Parasimplastrea sheppardi). It has a very limited distribution, and no information is available on its reproductive habits.

Genus Platygyra

Puberty Age of Platygyra sinensis

Platygyra sinensis reaches a reproductive state at ~5 years of age (Babcock, 1991).

Genus Plesiastrea

Genus Solenastrea

Solenastrea is an Atlantic species (Veron, 1986).

Family Flabelliidae

Genus Flabellum

Notes on Flabellum rubrum Sexuality and Size

Flabellum rubrum – small colonies (13-20mm) are males; larger colonies are hermaphroditic (Gardiner, 1902, in Fadlallah, 1983).

Genus Gardineria

Azooxanthellate. No information on reproduction is available.

Genus Monomyces

No information on reproduction is available.

Genus Placotrochus

No information on reproduction is available.

Figure 28. A female Fungia scutaria spawning at the Hawaii Institute of Marine Biology, Oahu, Hawaii. Note the tiny orange eggs being released. Photo courtesy of Jake Adams.

Family Fungiidae

As a rule, all Fungiids seen to be gonochoric with the exception of one report of Heliofungia actiniformis being a brooder.

Genus Cantharellus

This Fungiid has a wide geographical range, but is rarely seen. It sometimes lives attached to the substrate (Veron, 2000). No information is available on reproductive habits.

Genus Ctenactis

No information is available on reproductive habits.

Genus Cycloseris

YouTube has some interesting video clips showing a Cycloseris (tentative ID) broadcast spawning. It is tempting to state that Cycloseris, like other Fungiids, is a gonochoric broadcast spawner.

Genus Danafungia

No information is available on reproductive habits.

Figure 29. Sex ratios of Diaseris distorta in Galapagos Islands, Ecuador, where there are 5 males to every female colony.

Genus Diaseris

Puberty Size and Sex Ratios of Diaseris distorta

Diaseris distorta (Colley et al., 2000) – Satellite colonies possess sex organs when colony size is ~1 cm², while colonies produced sexually do not reach puberty until they are of larger size . Male colonies outnumber females by a ratio of 5 to 1 (in Ecuador).

Genus Fungia (Mushroom Coral)

Figure 30. All Fungia species are gonochoric broadcast spawners. Sex ratios vary among species, and then even with environmental conditions. Based on information from Kramarsky-Winter and Loya (1998) and others.

Puberty Size, Age and Lifespan of Fungia Species

Fungia concinna and Fungia fungites are capable of reproduction at 4 years of age (equaling a size of ~6 cm in diameter; Harrison and Wallace, 1990). This information is in good agreement with that of Goffredo and Chadwick-Furman (2004) who report Fungia scutaria specimens are approximately 5 years of age when obtaining a diameter of 7 cm.

Further, these researchers report F. scutaria specimens are about 14 years old when they obtain a diameter of 22 cm. The estimated life span of F. scutaria is about 50 years.

Figure 31. Fungiids can be reproductive over a broad range of sizes.

Genus Fungicyathus

This azooxanthellate coral can live at extreme depths – over 6,000 meters – the deepest of any coral (Veron, 2000). Needles to say, this coral is not likely to be found in your average reef aquarium!

Genus Halomitra

No information available.

Genus Heliofungia (Plate Coral)

Heliofungia Puberty Size and Age

Heliofungia actiniformis is reproductive at 10 years of age with a corresponding diameter of 8cm (Connell, 1973).

Genus Herpetoglossa

Genus Herpolitha

Genus Lithophyllon

No information available.

Genus Podabacia

Genus Polyphyllia

Genus Sandalolitha

Genus Verilliofungia

No information available.

Genus Zoopilus

No information available.

Family Meandrinidae

This family has 4 genera found only in the Atlantic. For the purist, the Meandrinidae is sometimes spelled differently from the way it is listed in Veron’s Corals of the World (2000).

Genus Ctenella

No information available on the reproduction habits of the one known species (C. chagius) from the western Pacific. This coral has a limited distribution (Veron, 2000).

Genus Dendrogyra (Pillar Coral)

Only one known species (D. cylindrus), an uncommon coral from the Caribbean.

Figure 32. This Dendrogyra is reproducing asexually via ‘budding’ but it is also a gonochoric broadcast spawner. Photo courtesy of Julian Sprung.

Genus Dichocoenia (Caribbean Starlet Coral)

Dichocoenia stokesi has been shown to spawn in September and October of each year (Hoke et al., 2002).

Genus Eusmilia(Flower Coral)

A beautiful Caribbean coral which makes it a rarity in captivity.

Genus Gyrosmilia

Gyrosmilia has a relatively small geographical range and is found only in the West Indian Ocean & Red Sea. No information available on the one species known.

Genus Meandrina (Tan Brain Coral)

Genus Montigyra

No information available on the one species known.

Family Merulinidae

Veron (1986) reports these corals are hermaphroditic broadcast spawners.

Genus Boninastrea

No specific information is available on reproductive habits.

Genus Hydnophora

Genus Merulina

Genus Paraclavarina

Paraclavarina specimens are occasionally seen in the trade. Although usually colored tan, their distinct shape makes them a worthwhile addition to a SPS tank. Table 61 uses the outdated name of Clavarina, per Babcock and Heyward’s 1986 description.

Genus Scapophyllia

Family Micrabaciidae

Genus Stephanophyllia

Family Mussidae

Genus Acanthastrea

Recent imports from Australia’s Great Barrier Reef have included a number of spectacular Acanthastrea specimens. Their fluorescent pigments are showcased in reef aquaria and, not surprisingly, are popular and command high prices – making them a good candidate for captive propagation efforts.

Figure 33. Imagine a tank full of settled Acanthastrea ‘spats’. Photo courtesy of Steve Ruddy.

Genus Micromussa

Veron (2000) created this genus to distinguish corals containing certain skeletal details from those previously listed as Acanthastrea, and states that these corals are rare. His book lists 3 species. To my knowledge, there is spawning information on only one species.

Figure 34. The reproductive habits of Micromussa species have only recently been described. Photo courtesy Jake Adams and www.coralidea.com

Genus Mussismilia

Genus Mussa(Flower Coral)

Genus Isophyllia(Stalked Cactus Coral)

Isophyllia sinuosa Puberty/Adult Colony Size

Adult I. sinuosa specimens are about 6 inches in diameter.

Genus Isophyllastrea (Rough Star Coral)

Veron (2000) states this coral’s proper name as Isophyllia rigida, but I have listed it as the Coral Reef Task Force originally described it.

Genus Mycetophyllia (Large Cactus Coral)

Genus Australomussa

No information available.

Genus Blastomussa

No information available.

Genus Cynarina

Genus Lobophyllia

Genus Scolymia (Fungus Coral)

Figure 35. A strikingly beautiful Scolymia specimen. Photo courtesy Jake Adams and www.coralidea.com

Genus Symphyllia

Family Oculinidae

Genus Acrhelia

This genus was discontinued by Veron (2000), who considers Acrhelia horrescens to now be Galaxea horrescens. I include this information to avoid confusion.

It does not change the fact that Galaxea/Acrhelia horrescens is a brooder (Kawaguti, 1941).

Genus Galaxea (Galaxy Corals)

Genus Neohelia

Genus Oculina (Bush Corals or Ivory Tree Coral)

Oculina varicosa spawns in late summer and early fall. Planula larvae settle at about 21 days of age (Brooke et al., 2002).

Genus Madepora

Genus Schizoculina

No information available on reproductive habits.

Genus Simplastrea

No information available on reproductive habits.

Family Pectiniidae

All corals in Pectiniidae are hermaphroditic broadcast spawners (Veron, 1986).

Genus Echinomorpha

Contains one species, Echinomorpha (formerly Echinophyllia) nihihirai (Veron, 2000).

Genus Echinophyllia

Some Echinophyllia species are particularly colorful and command extreme prices. Unfortunately, observations of spawning within aquaria have not been made.

Figure 36. An Echinophyllia species. Photo by the author.

Genus Mycedium

Genus Oxypora

Genus Pectinia

Figure 37. Pocillopora eydouxi is a hermaphroditic broadcast spawner. Kauai, Hawaii. Photo by the author.

Family Pocilloporidae

Family Pocilloporidae contains 3 genera – Pocillopora, Seriatopora and Stylophora.

Genus Pocillopora (Wart Corals)

Figure 38. In this photo by David Kearnes, the normally clear waters off Kailua-Kona, Hawaii become cloudy with gametes during the seasonal Pocillopora meandrina spawnings.

Figure 39. Within hours, the water will swarm with billions of planula larvae. Only a few will survive long enough to settle. Photomicrograph by the author.

Puberty Sizes of Two Pocillopora Species

Pocillopora damicornis is probably the most researched species of any stony coral.

Jokiel (1997) states that Pocillopora damicornis at a size of 10 cm (~4″) diameter releases 220 planula larvae per month. Harrigan (1972) found P. damicornis as small as 5 cm in diameter can produce planulae (estimated to be 1-2 years old).

Ricmond (in Richmond and Hunter, 1990) states Pocillopora damicornis takes at least two years to mature. P. damicornis colonies in the eastern Pacific can live to at least 70 years of age (Richmond & Hunter, 1990).

During the 2008 Pocillopora meandrina mass spawning in Hawaii, the smallest colony observed spawning was ~6″ in diameter (personal observations), which is about 2″ less in diameter than the smallest mature colony observed by Stimson (1978).

Figure 40. Again, this figure demonstrates that a brooder (P. damicornis) is reproductive at a smaller size than the broadcast spawner (P. meandrina).

Genus Seriatopora (Bird’s Nest Corals)

Genus Stylophora (Club Coral)

Figure 41. The red morph of Seriatopora hystrix. It is a hermaphroditic brooder, making it a prime candidate for aquarium spawning, yet reports of reproduction in captivity are practically non-existent. Why? (This photo was taken during a recent visit to Salt Lake City. If this is your coral, please contact me and I’ll post a tardy photo credit).

Notes on Stylophora pistillata Sexuality

Stylophora pistillata is a male in its first year and then becomes hermaphroditic, capable of self-fertilization and brooding in its second year (Loya, 1976). Later, Rinkevich and Loya stated that Stylophora pistillata reaches puberty at 1.5 to 2 years of age.

Family Poritidae

Genus Alveopora

Figure 42. These two brooding corals mature relatively quickly.

Genus Goniopora (Flower Pot Corals)

Figure 43. A Porites lutea, from a shallow tide pool in Keauhou, Hawaii. Photo by the author.

Genus Porites (Lobe and Finger Corals)

Figure 44. Sex ratios of various Porites species.

Notes on Porites Puberty Size and Sex Ratios

Porites andrewsi: 2:1 male/female, with a small percentage (~4%) being hermaphroditic.

Porites astreoides: A Caribbean coral, and within specimens containing gonads – some do not!) are found in percentages of 48% hermaphroditic to 52% female, giving a ratio, of course, ~1 to 1 (Chornesky and Peters, 1987). McGuire (1998) states that Porites astreoides capable of reproduction at 70 cm² (approx. 14″ square).

Figure 45. Brooders are in green, Broadcasters in orange. Note that adult size of brooders is always smaller that broadcasting species. Also note that 100 cm diameter may not be the largest possible colony size, it is the uppermost category listed by the researcher (Soong, 1993). For true maximum colony sizes of Porites lobata and P. lutea, see Figure 45. Note that P. brighami is endemic to Hawaii.

Porites lobata: Spawning ratios were 1:1 in Hawaii (Mate, 1997); ~1:1 at the Great Barrier Reef, Australia (Kojis and Quinn, 1981) and 1:1 in the eastern Pacific (but 14% of Costa Rican P. lobata colonies were hermaphroditic – Glynn et al., 1994).

Porites lutea: Roughly 1:1 at the Great Barrier Reef, Australia (Kojis and Quinn, 1981).

Harriot (1983) estimates Porites lutea reaches puberty at 4 years of age.

Porites murrayensis: Reproductive at 1.3 – 5.5 cm diameter (adult colonies are <20 cm in diameter) at Australia’s Great Barrier Reef (Kojis and Quinn, 1981).

Genus Poritipora

This genus, erected by Veron, 2000, has a limited distribution from the east coast of Africa and northeast to the Indian coast and nothing is known of its reproductive habits.

Figure 46. True maximum colony size of various Porites species. Information from Doug Fenner, 2005.

Genus Stylaraea

This genus contains but one species (S. punctata), and it is small (<15mm across). We could expect its reproductive size to be very small. It refers carbonate biofilms for settlement (Golbuu & Richmond, 2007). Information is available for S. punctata, but I lost the reference and am supremely disappointed that I cannot find that information in a stack of over 500 reference papers.

Subgenus Synaraea

Controversy about the validity of subgenus Synaraea exists (Veron 2000 lists Porites (Synaraea) rus as simply P. rus, but acknowledges the previous classification).

Figure 47. Size of adult colonies of the Atlantic coral Porites astreoides. It is a brooder.

Family Rhizangiidae

Genus Astrangia

Genus Culicia

No information available on this corals’ reproductive habits.

Family Siderastreidae

Many studies have been conducted on Siderastrea species from the Atlantic, some of which is listed here.

Genus Anomastraea

No information available on this corals’ reproductive habits.

Genus Coscinaraea

Genus Horastrea

No information available on this coral’s reproductive habits.

Genus Psammocora

Figure 48. Siderastrea sizes – note that 100 cm diameter may not be the largest colony size, it is the largest category (50-100 cm) listed by the researcher (Soong, 1993).

Genus Pseudosiderastrea

No reproductive information available.

Genus Siderastrea (Starlet Corals)

Legally-collected Caribbean Siderastrea colonies (S. siderea, S. stellata or S. radians) may be available in the future (Michael Janes, personal communication). S. radians is relatively small, and generally considered to be a brooder, making it an excellent candidate for captive propagation efforts.

Figure 49. Colony size and its relationship to sexual maturity of Siderastrea radians.

Figure 50. Males and females are found evenly in this case. It could be different in other areas due to any number of factors, but this has yet to be demonstrated for this coral species

Sex Ratios of Siderastrea radians

Siderastrea radians is found in male/female ratios of 1:1. (Lazar, internet resource, date unknown).

Comments on Siderastrea Reproduction and Longevity

Siderastrea radians is a protogynous hermaphrodite (Duerden, 1902, in Fadlallah, 1983).

Figure 51. Siderastrea species have been carefully studied by a number of researchers, resulting in information such as this.

Elahi and Edmunds (2007) report that Siderastrea siderea colonies can be at least 125 years old (based on a growth rate of 4mm (~1/6″) per year). Siderastrea siderea juveniles are less than 40mm in diameter, and mature colonies are 5.9 – 11.4 cm in diameter.

Family Trachyphylliidae

Genus Trachyphyllia

There are limited reports of this coral broadcast spawning in aquaria (Tyree, 1994).

In Closing

Figure 51. Suggested records for those observing a coral spawning.

As a matter of convenience (mostly mine), I have chosen to publish the reference list at the close of this series. If you like a copy earlier, please email me ([email protected]) and I’ll send this information in a Word document.

Next time, we’ll examine the reproduction habits of soft corals.

Acknowledgements

It would have been much easier to simply list the reproductive information of various stony corals. In fact, the initial draft of this article contained few photos. I felt this made the article a little too dry, so, I went, with hat in hand, to many sources asking for help – and thankfully a number of hobbyists and professional aquarists responded. Many thanks go to Dr. Bruce Carlson (once at the Waikiki Aquarium, but now at the Georgia Aquarium), Mitch (the King) Carl of the Henry Doorly Zoo, Omaha, Nebraska, Jake Adams (www.coralidea.com), Steve Ruddy (www.coralreefecosystems.com), Julian Sprung (www.twolittlefishies.com), master aquarist Tony Vargas, Michael P. Janes (www.aquatouch.com), and all the hobbyists across the country who extended a warm welcome to their homes and allowed me to take measurements
and photographs.