Figure 1. A soft coral (believed to be a Sansibia species) is reproducing within an aquarium. Photo courtesy of Michael Pollock.

Soft corals reproduce asexually by a number of methods, including fragmentation, budding, fission and others, and hobbyists often exploit these in their coral propagation efforts (these methods were briefly reviewed at Part 2 of this series). See: http://www.advancedaquarist.com/2008/8/aafeature1

It is usually quite easy to make cuttings from many soft corals, and one large broodstock colony can easily become hundreds of colonies in a relatively short period of time. This will make most soft corals unlikely candidates for sexual reproduction in aquaria. However, there are many reports of soft coral spawnings within aquaria. This article should be of interest to those interested in what it would take to grow out the spawn. Perhaps more importantly, the information presented here brings home the message that we actually know very little about soft coral reproduction. Your observation could be the first on record, so it is important to make notes and photographs.

Octocoral Reproduction

Kahng reported at the 11^th ICRS that Lasker, Benayahu and he have sexual reproductive information on 155 octocoral species. Consider that there are about 100 octocorallia genera, and we quickly realize how limited research in this arena has been (and this should not be construed that the few soft coral taxonomists and researchers have done a poor job!). In addition, soft coral taxonomy seems to be in a state of constant rearrangement (bordering on chaos) making even recent references obsolete.

Soft Coral Identification Guides

The groupings listed below are from the latest source on octocorallia I have been able to locate Gary Williams Alphabetical List of Valid Octocoral Genera. This resource can be found on the internet at: http://research.calacademy.org/research/izg/OCTOGEN.htm. Photographs are available for some genera and it includes information from as late as 2007. A list of synonyms is also there.

Fabricius and Alderslades 2001 Soft Corals and Sea Fans (assists with identification to the genus level) is a good resource with many excellent photographs. It can be ordered at: http://www.aims.gov.au/docs/publications/bookshop.html

Good information is also found in Sprung and Delbeeks 1997 The Reef Aquarium, Volume Two. This volume is somewhat dated in its taxonomic groupings, but has excellent photographs of a number of invertebrates of interest to the marine aquarium hobbyist. This book is available through any well-stocked pet shop, or from any major internet retailer.

Of limited use, but still interesting, is Williams 1993 Coral Reef Octocorals – this work examines the soft corals of northern Natal.

Unfortunately, no guide to soft corals of the caliber of Verons Stony Coral ID exists. Perhaps this reflects the state of turmoil in soft coral taxonomy. Funding for research in this field is limited which perhaps explains the very limited number of younger soft coral taxonomists.

Hobbyists should be aware that soft coral identification sometimes requires microscopic examination of the calcium reinforcing rods (sclerites and spicules). Access to a microscope is of great advantage. Removing sclerites for examination is a bit of science and art. For an excellent free resource on soft coral examinations, visit this site: http://www.aquatouch.com/Research%20and%20Development.htm

Fabricius and Alderslades Soft Corals and Sea Fans (2001) also has good information on the details of examining soft corals in a laboratory, and many drawings of sclerites.

Anemone taxonomy used later in this article is based on Fautin and Allens 1992 Field Guide to Anemone Fishes and Their Host Sea Anemones. This is available for free online at: http://www.nhm.ku.edu/inverts/ebooks/intro.html

Glossary

Brooding

Where fertilized eggs are held internally (or sometimes on the surface of a parent colony) and are released as planula larvae.

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.

Sequential Hermaphrodite

Where one gender sex organ is produced during early life, and the second genders organs appear later.

Brooders (soft corals, hydrocorals and gorgonians):

• Anthelia glauca (Kruger and Schleyer, 1998)
• Clavularia koellikeri (Bastidas et al., 2002)
• Heliopora corulea (Harii and Kayanne, 2005)
• Heteroxenia fuscescens (Ben-David-Zaslow et al., 1999)
• Litophyton arboreum (Benayahu et al., 1992)
• Nephthea sp. (Benayahu, 1997)
• Paralemnalia thyrsoides (Benayahu, 1997)
• Parerythropodium fulvum fulvum (surface brooder, Barki et al., 2000)
• Stereonephthea cundabiluensis (Benayahu, 1997)
• Xenia macrospiculata (Benayahu and Loya, 1985)

Suspected Parthenogenesis

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

• Alcyonium hibernicum, a temperate soft coral (Hartnoll, 1977)
• Plexaura sp. (Brazeau & Lasker, 1989)

Gonochoric Brooding

Gonochoric brooding involves broadcast spawning by males and internal or external fertilization of oocytes. It is known to occur in these soft corals:

• Anthelia glauca (Benayahu and Schleyer, 1998)
• Capnella gaboensis external brooder (Farrant, 1986)

Octocorals – Soft Corals (Subclass Octocorallia)

Order Alcyonacea – Stolonifera Group

Family Clavulariidae

1. Genus Carijoa (Snowflake Coral): Adult Carijoa colonies are rarely more than 20 cm in height.

2. Genus Cervera (also known as Cornularia): Cervera species without sclerites may be Clavularia.

3. Genus Clavularia (Clove Polyps)

4. Genus Cryptophyton: No information on sexual reproduction available.

5. Genus Paratelesto: No information on sexual reproduction available.

6. Genus Stereosoma: Only one species has been reported, but recent examination of the preserved specimen has tentatively placed it in Clavulariidae (Fabricius and Alderslade (2001). Williams does not recognize the genus in his updated internet database. No information on sexual reproduction is available.

7. Genus Telesto: No information on sexual reproduction available.

8. Genus Telestula: No information on sexual reproduction is available.

9. Genus Trachythela: No information on sexual reproduction available.

Figure 2. Tubipora musica is most well known for its red pipe organ skeleton and not its rather drab polyps. No information is available on reproductive habits. Photo by the author.

Family Coelogorgiidae

1. Genus Coelogorgia: No information is available on reproductive habits.

Family Tubiporidae

1. Genus Tubipora (Pipe Organ Coral)

Order Alcyonacea – Alcyoniina Group

Family Alcyoniidae

1. Genus Alcyonium: See Genus Klyxum for specimens from the tropical Pacific.

2. Genus Anthomastus

3. Genus Bellonella: No sexual reproduction information available.

4. Genus Cladiella (Finger Leather Coral)

5. Genus Dampia: Possibly a Sinularia species. No reproduction information available.

6. Genus Discophyton

7. Genus Eleutherobia: No sexual reproduction information available.

8. Genus Klyxum (Colt Corals)

9. Genus Lampophyton: No information is available on the sexual reproduction of this genus, erected by Williams in 2000.

10. Genus Lobophytum (Devils Hand)

11. Genus Paraminabea: Paraminabea is also called Minabea (for shallow water specimens only). No reproduction information available.

12. Genus Rhytisma: Rhytisma is sometimes referred to as Parerythropodium.

13. Genus Sarcophyton (Leather Coral)

Figure 3. In this instance, Sarcophyton glaucum was found in a male female ratio of 1 to 1.

14. Genus Sinularia (Soft Finger Coral)

Figure 4. Sinularia species are seen in a bewildering array of shapes. They are known to be broadcast spawners. Photo by the author.

15. Genus Thrombophyton

Family Nephtheidae

1. Genus Capnella (Kenya Tree Coral): The temperate water Australian Capnella gaboensis does not become sexually mature until it is 20 years of age (Farrant, 1987).

2. Genus Dendronephthya

3. Genus Lemnalia (Branch Coral): No information on sexual reproduction is available.

4. Genus Leptophyton: No information on sexual reproduction is available.

5. Genus Litophyton

6. Genus Nephthea: Some Nephthea specimens contain colored sclerites, and these may belong in genus Stereonephthea (Fabricius and Alderslade, 2001).

7. Genus Pacifiphyton: No information on sexual reproduction is available.

8. Genus Paralemnalia (Finger Leather Coral)

9. Genus Scleronephthya

10. Genus Stereonephthya

11. Genus Umbellulifera: No information is available on reproductive habits.

Family Nidallidae

1. Genus Agaricoides: No information on reproduction is available.

2. Genus Chironephthya: No reproduction information available.

3. Genus Nidalia: No reproduction information available.

4. Genus Nephthyigorgia: No reproduction information available.

5. Genus Pieterfaurea: No reproduction information available.

6. Genus Siphonogorgia: No reproduction information available.

Family Paralcyoniidae

1. Genus Studeriotes: No reproduction information available.

Family Xeniidae

1. Genus Anthelia

2. Genus Cespitularia (Blue Xenia)

3. Genus Efflatounaria

Figure 5. Oocytes (eggs) within the soft coral Heteroxenia. Histological photomicrograph courtesy of Michael P. Janes.

3. Genus Funginus: No reproduction information available. Williams believes Funginus is possibly synonymous with Heteroxenia.

4. Genus Heteroxenia (Pulse Coral)

Figure 6. Is Sansibia a brooder or slow extrusion broadcast spawner? Photo courtesy of Michael Pollock.

5. Genus Sansibia: Reproduction of a coral tentatively identified as a Sansibia species has been noted in an aquarium. There was successful recruitment and young colonies are present. It is believed by the author that Sansibia is a brooder, but this should be verified.

6. Genus Sarcothelia

7. Genus Sympodium

Figure 7. Sarcothelia edmondsoni colonies, endemic to Hawaii, are often seen as blue mats in areas of high water motion. Photo by the author.

8. Genus Xenia (Pulse Coral)

Figure 8. Xenia species are easily propagated by making cuttings, but they have been observed spawning in aquaria. Photo by the author.

Order Alcyonacea – Scleraxonia Group

Family Acanthogorgiidae (Suborder Holaxonia)

1. Genus Acanthogorgia: No information on reproduction available

2. Genus Anthogorgia: No information on reproduction available

3. Genus Muricella: No information on reproduction available.

Family Anthothelidae

1. Genus Altertigorgia: No reproduction information available.

2. Genus Erythropodium (Encrusting Gorgonian): No reproduction information available.

Figure 9. A Briareum spawns in an aquarium. Photo courtesy of Michael P. Janes.

3. Genus Iciligorgia: No reproduction information available.

4. Genus Solenocaulon: No reproduction information available.

Family Briareidae

1. Genus Briareum (Incorporates Pachyclavularia & Solenopodium. Star Polyps)

Figure 10. Briareum asbestinum, often called Corky Sea Fingers, is a Caribbean species, and sex ratios are skewed towards male colonies.

Family Chrysogorgiidae (Suborder Calcaxonia)

1. Genus Stephanogorgia: No information on reproduction available.

Family Corallidae

1. Genus Corallium

Figure 11. Junceella colonies. Photo courtesy of Michael P. Janes.

Family Ellisellidae (Suborder Calcaxonia)

1. Genus Ctenocella (Sea Whip or Harp Coral): No information on reproduction available.

2. Genus Dichotella: No information on reproduction available.

3. Genus Ellisella: No information on reproduction available.

4. Genus Heliania: No information on reproduction available.

5. Genus Junceella: No information on Junceellas sexual reproduction is available.

6. Genus Nicella: No information on reproduction available.

7. Genus Verrucella (also known as Umbracella): No information on reproduction available.

8. Genus Viminella: No information on reproduction available.

Figure 12. Junceella colonies often reproduce by fragmentation, as is shown in this photograph by Michael P. Janes.

Family Gorgoniidae (Suborder Holaxonia)

1. Genus Eunicella

2. Genus Gorgonia (Sea Fan): No information on reproduction available.

3. Genus Guaiagorgia: No information on reproduction available.

4. Genus Hicksonella: No information on reproduction available.

5. Genus Pinnigorgia (also known as Plexaura flava & Lophogorgia): No information on reproduction available.

6. Genus Pseudopterogorgia (Purple Frilly Gorgonian): This genus is found in the Pacific, but is one of the most common genera in the Caribbean/West Indies.

7. Genus Pterogorgia (Sea Blade or Sea Whip): No information on reproduction available.

8. Genus Rumphella (Sea Whip): No information on reproduction available.

Family Ifalukellidae (Suborder Calcaxonia)

1. Genus Ifalukella: No information on reproduction available.

2. Genus Plumigorgia: No information on reproduction available.

Family Isididae (Suborder Calcaxonia):

1. Genus Isis (Sea Fan): No information on reproduction available.

2. Genus Jasminisi: No information on reproduction available.

3. Genus Pteronisis: No information on reproduction available.

4. Genus Zignisis: No information on reproduction available.

Family Keroeididae (Suborder Holaxonia)

1. Genus Keroeides: No information on reproduction available.

Family Melithaeidae

1. Genus Acabaria

2. Genus Clatharia: See Acabaria

3. Genus Melithaea: See Acabaria

4. Genus Mopsella: See Acabaria

5. Genus Wrightella: See Acabaria

Family Parisididae

1. Genus Parisis: No information on reproduction available.

Family Plexauridae (Suborder Holaxonia)

1. Genus Astrogorgia (also known as Muricella & Anthoplexaura): No information on reproduction available.

2. Genus Bebryce: No information on reproduction available.

3. Genus Echinogorgia: No information on reproduction available.

4. Genus Echinomuricea: No information on reproduction available.

5. Genus Eunicea (Knobby Candelabrum): No information on reproduction available.

6. Genus Euplexaura: No information on reproduction available.

7. Genus Menella (also known as Echinogorgia & Plexauroides): No information on reproduction available.

8. Genus Muricea (Spiny Sea Fan)

9. Genus Muriceopsis (Sea Plume)

10. Genus Paracis: No information on reproduction available.

11. Genus Paramuricea

12. Genus Paraplexaura: No information on reproduction available.

13. Genus Plexaura (Sea Rod)

14. Genus Plexaurella: No information on reproduction available.

15. Genus Pseudoplexaura

Figure 13. Pseudoplexaura porosa specimens demonstrated a male/female ratio of 1:1 (Lasker et al., 1996).

16. Genus Trimuricea: No information on reproduction available.

17. Genus Villogorgia: No information on reproduction available.

Family Primnoidae (Suborder Calcaxonia)

1. Genus Plumarella: No information on reproduction available.

Family Subergorgiidae

1. Genus Annella: No reproduction information available.

2. Genus Subergorgia: No reproduction information available.

Order Anthoathecatae (Fire Corals)

Family Milleporidae

1. Genus Millepora (Common Fire Corals)

Order Helioporacea

Family Helioporidae

1. Genus Heliopora (Blue Fire Corals)

Figure 14. An unidentified Hawaiian zoanthid. Photo by the author.

Subclass Hexacorallia: Including Order Actiniaria (Sea Anemones), Order Zoanthiniaria (Zoanthids)

1. Zoanthids

Order Zoanthiniaria

Family Zoanthidae

1. Genus Parazoanthus (Yellow Polyps)

Figure 15. Yellow Polyps (Parazoanthus species) offer a nice yellow color to an aquarium. Photo by the author.

2. Genus Sphenopus

3. Genus Epizoanthus

4. Genus Protopalythoa (Button Polyps)

5.Genus Zoanthus (Zoanthids)

5. Genus Palythoa (Sea Mat)

6. Genus Isozoanthus

7. Genus Isaurus (Snake Polyps)

Sea Anemones

Family Actiniidae

1. Genus Anthopleura

2. Genus Condylactis

3. Genus Entacmaea

4. Genus Epiactis

5. Genus Phymanthus

6. Genus Urticina

Family Aurelianidae

1. Genus Actinoporus

Family Sagartiidae

1. Genus Sagartia

Family Stichodactylidae

1. Genus Heteractis

2. Genus Entacmaea

Order Corallimorpharia

Family Actinodiscidae

1. Genus Discosoma (Mushroom Anemone)

Family Discosomatidae

1. Genus Rhodactis (Elephant Ear Mushroom Coral)

Subclass Ceriantipatharia: Including Order Anthipatharia (Black or Wire Corals)

Family Antipathidae

1. Genus Antipathes: It has been estimated that there are 23 Antipathes species. Overall, we know very little about their reproductive habits.

Figure 16. Sex ratio of the black coral Antipathes (Parker et al., 1997).

Size and Age of Antipathes fiordensis at Sexual Maturity

Antipathes fiordensis is sexually mature at an age of 31 years (with a corresponding height of approximately 70-105 cm). As Figure 16 shows, it is found in a male/female ratio of 1 to 1 (Parker et al., 1997).

Quick and Easy Reference Table

This concludes our observations of sexuality and reproductive habits among corals. Next time, well examine one of the most important environmental parameters in coral reproduction that of lighting. I have chosen to present the reference list at the end of this series. For those wishing an early copy, please email me at [email protected] and Ill send the complete reference list as a Word document.

Acknowledgements

I wish to thank Michael P. Janes for his generosity in sharing photographs and helpful comments. He often pointed me in the proper direction, especially with comments on classifications. However, any mistakes within the article are mine and mine alone. Also, aquarist Michael Pollock kindly shared the extraordinary introductory photo.