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TaiaroidaeGenus Siphonogorgia

Classification and Taxonomy

It must be understood that with respect to soft corals the taxonomy is presently in a state of confusion. (Of course anyone working on taxonomy in a group of living organisms would probably get a kick out of the previous statement since taxonomy in general is full of problems, but here we concentrate on the messy state of the soft corals). Seemingly different soft corals can be forms of the same species since many soft corals vary greatly as a result of environmental factors. Furthermore, seemingly identical corals may belong to different species, genera, or even families! Positive identification is often impossible without microscopic examination of the minute, sancl-like skeletal elements known as sclerites (spicules). Many species are still undescribed. Therefore,

Figure 1.1

Some typical sclerites

From Williams, 1993

A, B. Clavularia, C, D. Clad ¡ella, E, F. Lobophytum G, H, I. Sarcophyton J, K. Sinuiaria L, M. Dendronephthya


we are not always able to identify soft corals to species, and we feel that all that is really necessary to know is the genus. We have made every effort to assure the accuracy of the taxonomy we use and the names given in this book. Nevertheless future revisions of soft coral taxonomy will likely show that our book contains some identification errors. We have very deliberately avoided the unfortunate habit of some aquarium book authors who merely look at old books and copy the incorrect names found there for identifica-

tion of creatures in their "new" texts. The identifications in this book involved painstaking collection and preparation of tissue samples for examination by experts in soft coral taxonomy, and lots of correspondence.

Soft coral taxonomy is based on the study of the skeletal elements known as sclerites (sometimes referred to as spicules). The plasticity of form in soft corals makes the identification to species difficult or impossible without examination of the sclerites, which are usually more uniform in structure. The sclerites are taken from both the branches and the base since they vary depending upon their location in the colony.

Preparation of Sclerites for Examination

To examine the sclerites of a soft coral one must prepare a sample by dissociating the soft tissue from the calcium carbonate sclerites. This is done by simply excising a small (approx. 5mm x 5mm) sample of tissue with a scissors or scalpel and placing it on a microscope slide with a few drops of sodium hypochlorite (household bleach or Clorox). The solution dissolves the organic material away quickly, freeing the sclerites. A coverslip may then be added and the sclerites can be observed under low power. The sclerites can be rinsed with water in a vial to remove traces of sodium hypochlorite and clear away the cloudy dissolved organic material.

In the past, many soft coral taxonomists hardly knew how living colonies actually appeared, since they usually worked with preserved specimens from collections. The new school of soft coral taxonomists study living colonies. As aquarists, our photographic records and notes may serve to benefit the study of coral biology, and may help clean up the taxonomic mess that exists with respect to soft corals. We may also provide a valuable tool to taxonomists with our techniques for keeping and growing corals in captivity. Our living collections contain numerous undescribed species, particularly of soft corals. Unfortunately, growth in captivity can produce strange anomalies in the sclerites that can easily confuse the taxonomist. For example, Sinularia species typically have a concentration of long spindle shaped sclerites in the base. In captivity when branches are severed for the purpose o:i asexual propagation of the colony, the offspring often fail to develop this concentration of spindles in the base. Alcyonium (Colt Coral) also is frequently propagated by making cuttings. The colonies grown this way often lack sclerites, though the original parent colony had them, particularly in the base. Sometimes the

Table 1.1

Classification of Soft Corals After Bayer, 1981

We have not included all genera, particularly the sea pens, but all of the genera covered in this book are shown, in addition to other related genera not covered here. Items in brackets do not have formal taxo-nomical significance, but they are sometimes used as a matter of convenience by soft coral taxono-mists, for grouping some of the genera by some common morphological features.

Phylum Cnidaria (Coelenterata) Class Anthozoa

Subclass Octocorallia Haeckel. 1866

Order Helioporacea (=Coenothecalia)

Family Lithotelestidae: Epiphauxum (=Lithotelesto) Family Helioporidae: Heliopora Order Alcyonacea Lamouroux, 1816

[Suborder Protoalcyonaria]

Family Taiaroidae: Taiaroa [Suborder Stolonifera]

Family Cornulariidae: Cornularia Family Clavulariidae

Clavulariinae: Ciavuiaria, Bathytelesto, Rhodelinda, Scyphopodium Sarcodictyiinae: Sarcodictyon,Cyathopodium, Scleranihelia,

Tesseranthelia, Trachythela Telestinae: Telesto, Carijoa, Paratelesto, Teles tula Pseudocladochoninae: Pseudocladochonus Family Tubiporidae: Tubipora, Pachyclavuiaria Family Coeotogorgiidae: Coelogorgia Family Pseudogorgiidae: Pseudogorgia [Suborder Alcyoniina]

Family Paralcyoniidae: Maasella, Carotalcyon, Paralcyonium, Studeriotes Family Alcyoniidae: Alcyonium, Aero phylum, Anthomastus. Bathyalcyon, Bellonella, Cladiella, Lobophytum. Metalcyonium, Minabea, Maiacacanthus, Nidaliopsis, Parerythropodium, Sarcophyton, Slnularia Family Asterospiculariidae: Asterospicularia

Family Nephtheidae: Nephthea, Capnella, Coronephthya, Daniela. Dendronephthya, Drifa, Duva, Gersemia, Lemnalia, Lilophyton, Morchellana. Neospongodes Paralemnalia Pseudodrlfa, Roxasia, Scleronephlhya, Stereonephthya, Umbeliulifera Family Nidaliidae

Nidaliinae: Agaricoides. Nidalia

Siphonogorgiinae: Chlronephthya, Nephthylgorgia, Siphonogorgia Family Xeniidae: Anthelia, Ceratocaulon?, Cespitularia, Efflatounaria. Fungulus, Heteroxenia, Stereosoma, Sympodium, Xenia [Suborder Scleraxonia] Family Briareidae: Briareum Family Anthothelidae: Anthothelinae: Anthothela

Semperininae: Iciligorgia, Semperina, Solenocaulon Spongiodermatinae: Alertigorgia, Caliipodium. Dlodogorgia. Erythropodium, Homophyton, Titanideum. Tripalea Family Subergorgiidae: Subergorgia Family Sibogagorgndae (=Paragorgiidae): Paragorgia. Sibagorgia Family Coralliidae: Corallium, Pleurocoralloides? Family Melithaeidae: Melithaea, Acabaria, Clathraria.Mopsella. Wrightella Family Parisididae: Parisis (=Trinella) [Suborder Holaxonial

Family Keroeidae (=Keroeidididae): Keroeides, Ideogorgia. Lignelia Family Acanthogorgiidae; Acanthogorgia, Acalycigorgia, Anthogorgia. Calcigorgia,

Cyclomuricea, Muricella, Versluysia Family Plexauridae

[Plexaurinael: Plexaura, Anthoplexaura. Eunicea, Euplexaura. Muricea,

Muriceopsis. Plexaurella, Psammogorgia, Pseudoplexaura [Stenogorgiinae (=Paramuriceinae)]: Swiftia, Acanthacis, Aslrogorgia, Bebryce, Calicogorgia, Dentomuricea, Echinogorgia, Echinomuricea, Heterogorgia, Hypnogorgia, Lepidomuricea. Lytreia, Menella. Muriceides, Nicaule, Paracis. P'aramuricea, Placogorgia, Pseudothesea, Scleracis. Theses, Viliogorgia Family Gorgoniidae: Adelogorgia, Eugorgia, Eunicella, Gorgonia. Hicksonella,

Leptogorgia, Lophogorgia,Olindagorgia, Pacifigorgia. Phycogorgia, Phyllogorgia, Pseudopterogorgia. Plerogorgia, Rumphelia Family Ellisellidae: Ellisella, Ctenocella, Junceella. Nicella, Riisea. Toeplitzella, Verrucella Family Ifalukellidae: Ifalukella, Plumigorgia

Family Chrysogorgiidae: Chrysogorgia, Chalcogorgia, Distichogorgia, Helicogorgia. Iridogorgia, Isidoldes, Metallogorgia, Pleurogorgia, Radicipes. Stephanogorgia. Trichogorgia, Xenogorgia Family Primnoidae: Primnoa, Aimgmaptilon, Amphilaphis, Armadillogorgia.

Arthrogorgia, Ascolepis, Callogorgia, Callozostron, Calyptrophora, Candidella, Dasystenella, Narella, Ophidiogorgia. Paracalyptrophora, Parasienella, Plumarella, Primnoella. Pseudoplumarella, Pierosteneila Family Isididae

Isidinae: Isis, Chelldonisis Muricellisidinae: Muriceilisis Keratoisidinae: Keratoisis. Acanella, isidella, Lepidisis Mopseinae: Mopsea, Chathamisis, Circinisis, Echinisis, Minuisis, Peltastisis, Primnoisis Order Pennatulacea Verrill, 1865 Family Veretillidae Herklots. 1858 Cavernularia sclerites that form in captivity are malformed, or they change from the form they had when the colony was in the natural environment . While our aquariums are admittedly not the natural environment, they are similar enough to it that the sclerite changes occurring in our aquaria may also occur in the natural setting depending on environmental factors. If that is the case, then the study of sclerites may be of limited value in determining species (though they are certainly valuable for determining family and genus). At the moment such a notion is not a popular idea among soft coral biologists who specialize in learning the subtle differences between sclerites of different species.

Polyp Anatomy

The polyps of octocorals are distinctive from all other anthozoans in that they have eight tentacles per polyp. As we mentioned earlier, occasionally an exceptional "double polyp" occurs (something like a Siamese twin) that has more than eight tentacles, usually with two mouths (see photo). The tentacles tend to taper towards the end and each tentacle (usually, but not always) contains a number of short, pointed projections, usually in rows, called pinnules. These give the tentacles a feathered appearance. Sometimes the pinnules are not well developed, or are fused. In at least one species imported for aquariums, there are apparently no pinnules at all (see chapter seven, "unidentified stoloniferan number two").

Soft coral tentacles and pinnules are mobile, contractile, and hollow, their cavities being extensions of the gastrovascular cavities (Hyman, 1940). Octocoral polyps may be elongated (in some genera they extend several inches in length) and are topped with the flattened oral disc. At the center of the oral disc lies the oval mouth that opens directly into a pharynx (=actinopharynx). The pharynx can be smooth or grooved and extends down into the gastrovascular cavity. At one end of the oval shaped pharynx lies a groove lined by flagellated (=ciliated) cells known as the siphonoglyph (=sulcus) whose purpose is to drive water currents (and perhaps food particles) into the gastrovascular cavity.

There are three cellular layers that constitute the projecting portion of octocoral polyps. The outer layer, the epidermis, covers the exterior surface of the polyp and extends out over the body of the colony (coenenchyme). The epidermis that covers the polyps contains mucus cells, sensory cells and nematocysts, the last often in warts. The epidermis covering the coenenchyme contains fewer sensory cells and nematocysts (Hyman, 1940). The inner cell layer, the gastrodermis,

Figure 1,2 a

The internal anatomy of a typical octocoral polyp

After Hy man, 1940

Figure 1.2 b

Vertical section through the coenenchyme of Alcyonium, showing solenial network. Some polyps are expanded, some contracted.

After Hyman, 1940, based on Hickson, 1895



Nicella Morphology



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The COMPLETE guide to Aquariums

The COMPLETE guide to Aquariums

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