Scientific Nomenclature

The naming of living things follows a classification scheme known as scientific nomenclature that groups living organisms on the basis of their shared characteristics. Students remember the hierarchy of classification by means of a phrase like, ukeep party clean or father gets sore", each word beginning with the first letter corresponding to the terms kingdom, phylum, class, order, family, genus, species.

Coral taxonomists examine coral skeletal structure to group corals

Coral taxonomists examine coral skeletal structure to group corals and from fossils of extinct ones. Skeletal characteristics of stony corals vary among individuals of the same species from different regions of the world, or from different locations on the reef.

and from fossils of extinct ones. Skeletal characteristics of stony corals vary among individuals of the same species from different regions of the world, or from different locations on the reef.

Figure 3.1a

Scleractinian Family Tree

Showing the relationships between hermatypic families. After Veron 1986

Montastrea cavernosa from the Caribbean, photographed at The New York Aquarium for Conservation. J. Yaiulio and F. Greco.

Stony Coral Type Structure

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lifts

Figure 3.1b

Classification of Corals

Coenosteum

mm&

Order Zoanthidea

(Small anemone like anthozoans with no skeleton)

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Characteristics used for identification of genus and species may vary even on individual colonies! Coral taxonomists must familiarize ! i lemselves with the range of variation in species to be able to distinguish what defines the species as distinct from others. The relationships between the different coral genera, and the relationships between corals, anemones, and other cnidarians (coelenterates) is shown in figures 3-la & 3-lb. It is likely that as our understanding of the biology of these organisms increases, the accepted relationships between these groups of organisms will be modified, and revisions of coral relationships are already being made ( J. Veron, pers. comm.).

Polyp Anatomy

The structure of the parts of the living polyp and its skeleton help us to distinguish species, and to understand the relationships between genera and families. Familiarity with the appearance of different genera and the specific features of particular species makes it easy to identify many corals without close examination, or the need to view the skeleton. Still, some living corals are so similar to others, or have such an array of different morphologies as a result of environmental factors, that fine skeletal details must be observed for positive identification. We include here diagrams of some typical polyps, and their skeletal features that we often mention in the descriptions of the various species in chapter 13.

The Living Polyp

Externally there is not much to a coral polyp, but the repetition of structures and variety of shapes and colour make for a fantastic diversity of forms. On the typical coral polyp, tentacles surround a flat plane known as the oral disc, that surrounds the mouth. The mouth is usually distinguishable as a small pimple or cleft in the middle of the oral disc. The living tissue lying against the outside of the cup which holds the polyp, is called coenosarc. Living polyps typically form colonies, or exist as single individuals. However, in some corals the distinction between polyp and colony is vague, and there are individual coral polyps with many mouths, and colonies in which the individual polyps are connected so that it is impossible to say where one begins and ends unless one sees the skeleton.

In soft corals, Octocorallia, the tentacles have side branches called pinnules which give the tentacles an appearance like feathers. See fig. 3.2. Soft corals have eight tentacles as a rule, though occasionally a "double polyp'1 occurs, something like a siamese twin, that has more than eight tentacles, usually with two mouths. The biology and

Cnidocyte And Nematocyst

Figure 3.3

Cnidocyte with firing of the nematocyst

After Lange & Kaiser 1991

Figure 3.3

Cnidocyte with firing of the nematocyst

After Lange & Kaiser 1991

identification of soft corals will be covered in a separate text.

Stony coral tentacles vary in shape and size, Some tentacles have numerous ends with batteries of stinging cells, cnidocytes, loaded with the harpoon and coiled spring-like mechanisms known as nematocysts. Some tentacles merely have a single end, like a little ball. Most have nematocysts scattered across the tentacles, with the heaviest concentrations being at the tips.

The Skeleton

Individual polyps are distinguished by a wall, the theca, which forms a cup called the corallite. The upper, open face of the corallite from which the living polyp protrudes is called the cálice, and the terms corallite and cálice are often used interchangeably, though only corallite refers to the whole cup. Flattened, plate-1 ike structures that divide the corallite radially into sections like a grapefruit are called septo-costae. Each septo-costa is composed of a costa, the part on the outside of the wall, and a septum, which lies on the inside. The septo-costae of many of the fleshy polyps

Figure 3.4

Stony Coral Polyp and Skeleton Anatomy: Longitudinal Section

Living Polyp

Tentacle

Corallite

Living Polyp

Tentacle

Corallite

Montastrea Cavernosa Skeleton

Paliform lobes

Corallite Wall

Coenosteum

Paliform lobes

Corallite Wall

Coenosteum

Nematocyst Operculum

Cnidocil

Cnidocyte And Nematocysts

Nematocyst Operculum

Cnidocil kept in aquariums have numerous sharp, tooth-like projections on them, resulting in the common name, "tooth coral1' for these species (e.g. Cynarina lacrymalis). Where the coral is attached to the substrate the skeleton is often smooth, appearing like a mantle. This structure is called the epitheca or peritheca, and it may ain all the way up the wall to the edge of living tissue. As the polyp grows upward, it may deposit epitheca over the costae. The junction between polyp and substrate that lies beneath the polyp (i.e. the lowest portion of the coral cup) in attached species is called the basal plate. In the center of the corallite in some species is the columella, an axial structure derived from upward growth of tangled calcified fibers from the innermost margins of the septa. Some species have a series of raised bumps derived from the inner margins of the septa, forming a ring surrounding the center or the columella if it is present. These are called paliform lobes or sometimes "pali". The plane and other structures between the corallites is called the coenosteum. The entire colony composed of these structures is known as the corallum.

Morphology of Corals

On the following page we present a table describing the different shapes of coral colonies, to assist in understanding the descriptions of the various species covered in this text. These forms are not mutually exclusive. Different forms are common to the same species and even individual colonies may show more than one type of colony formation. Some colonies stait as one form and become another as thev grow.

Table 3.5a Colony and

Polyp

Formation

Colony Formation Coral Morphology

Table 3.5b Colony forms

The growth form, referring to colony shape, not structure.

Cerioid - Corallites share common walls but do not form valleys, pressed so close together that the calyces often take on a polygonal shape, eg. Goniastrea spp.

Dendroid - Coral lites are tubular & colonies formed of branches with zig-zag alternation of corallites. eg. Duncanopsammia axifuga and Tubastrea micrantha.

Euphyllia Ancora

Flabellomeandroid -

Forming valleys which do not share common walls, eg. Euphyllia ancora and Cataiaphyllia jardinei.

Morfologi Euphyllia Ancora

Encrusting - Sheet-like growth form tightly adhering to the substrate and conforming to its shape. May also send growths upward, eg. Pontes spp.

Branching or Ramose -

Forming finger-like growths

(digitate) or branches like trees, eg. Acropora, Pontes, Seriatopora, Stylophora, Pocillopora spp.

Columnar - Forming prominent upright columns, eg. some Pontes spp.

Encrusting - Sheet-like growth form tightly adhering to the substrate and conforming to its shape. May also send growths upward, eg. Pontes spp.

Hillock Formation

Hydnophoroid - Formation in which the corallites are grouped around conical hillocks, eg. Hydnophoraspp.

Meandroid - Formation in which groups or series of corallites in valleys share common walls, eg. Leptoriaphrygia.

Hydnophoroid - Formation in which the corallites are grouped around conical hillocks, eg. Hydnophoraspp.

Meandroid - Formation in which groups or series of corallites in valleys share common walls, eg. Leptoriaphrygia.

Foliaceous Corals

Foliaceous - Leaf-like or forming thin, expanded sheets and whorls, eg. Turbinaria mesenterina.

Turbinaria Bell Shaped

Free Living - Colonies or single polyps typically unattached on sand, mud, or hardbottom. eg. Fungi a spp. and Trachyphyllia geoffroyi,

Foliaceous - Leaf-like or forming thin, expanded sheets and whorls, eg. Turbinaria mesenterina.

Free Living - Colonies or single polyps typically unattached on sand, mud, or hardbottom. eg. Fungi a spp. and Trachyphyllia geoffroyi,

Trachyphyllia Spp
Plocoid - Distinctly separated polyps, not united by their walls, but connected only by epitheca. eg. Barabattoia spp.
Massive Turbinates

Laminar - Growth like fiat plates or tiers.

eg. Pachyseris speciosa.

Laminar - Growth like fiat plates or tiers.

eg. Pachyseris speciosa.

Coral ReefTrachyphyllia Spp

Phaceloid - More dramatically separated polyps than plocoid. Polyps become like columns. Plocoid polyps may become phaceloid as they grow upward, eg. Caulastreaspp.

Intratentacular budding - New polyps bud from the oral disc, within the ring of tentacles, eg. Goniastrea spp.

Turbinaria Algae

Turbinate - Forming the shape of an inverted cone, eg. Turbinaria spp.

Massive - Colonies are thick, and similar in all directions, eg. Favia spp. and Favites spp.

Turbinate - Forming the shape of an inverted cone, eg. Turbinaria spp.

Coral Formations

Extratentacular budding - New polyps bud between polyps, from the coenosarc outside of the ring of tentacles of any polyp, eg. Montastrea spp.

Relationship Between Corals and Zooxanthellae

Coral reefs are relatively nutrient poor areas (see Chapter 2). Phosphate, nitrogen, iron and other essential nutrients are barely detectable in the clear water; clear because so little is growing in it (Benson, 1984). To compensate for this lack of nutrients, many invertebrates have developed symbiotic relationships with algae that they hold in their tissues. The larvae of hermatypic corals may already be "infected" with zooxanthellae from the parent polyp or colony (Veron, 1986). These algal cells produce energy that is used by the host. The host produces ammonia as a by-product of metabolism, and the algae use it as an energy source. Freshwater animals, such as Hydra, Spongil'la and Paramecium, contain a green alga known as Zoochlorella, while marine organisms generally contain brownish-gold dinoflagellates of the genus Symbiodinium, commonly termed zooxanthellae (Greek "xanthos" = yellowish-brown) (Gordon, 1977). Therefore, contrary to popular belief, zooxanthellae are not green algae but gold-coloured dinoflagellates.

At one point it was believed that there was only a single species of zooxanthellae, Symbiodinium microadriaticum, but it has been demonstrated that there are in fact several strains of zooxanthellae; some fast growing, some slow (Blank and Trench, 1985; Trench 1979). Using gel electrophoresis, Trench and Blank (1987) found that of four photosynthetic organisms studied, each had its own distinctive species of Symbiodinium. The mangrove jellyfish, Cassiopeia, incorporates S. microadriaticum. The Pacific hard coral Montipora has S. kawagutii. Symbiodinium goreauii was found in the Atlantic anemone, "Heteractis" lucida, and S. pilosum in the common Caribbean zoanthid, Zoantbus sociatus. Therefore it may no longer be appropriate to say that photosynthetic invertebrates contain S. microadriaticum, only that they contain Symbiodinium spp.

Zooxanthellae are found in most reef building stony corals, many Octocorallia (soft corals) including some gorgonians, sea anemones, zoanthids, Corallimorpharians (mushroom anemones), and tridacnid clams. Sponges and some ascidians (Sea Squirts) use different types of symbiotic algae, but their role is essentially the same as zooxanthellae (Gordon, 1977). Zooxanthellae are found in the second layer of cells below the outer layer of coral tissue, the epidermis; one algal cell per animal cell. They are important components of reef building corals because they provide them with nutrition, remove metabolic waste, and contribute to the production of calcium carbonate skeletons. Corals with zooxanthellae grow rapidly because they can deposit calcium carbonate 2 to 3 times

The COMPLETE guide to Aquariums

The COMPLETE guide to Aquariums

The word aquarium originates from the ancient Latin language, aqua meaning water and the suffix rium meaning place or building. Aquariums are beautiful and look good anywhere! Home aquariums are becoming more and more popular, it is a hobby that many people are flocking too and fish shops are on the rise. Fish are generally easy to keep although do they need quite a bit of attention. Puppies and kittens were the typical pet but now fish are becoming more and more frequent in house holds. In recent years fish shops have noticed a great increase in the rise of people wanting to purchase aquariums and fish, the boom has been great for local shops as the fish industry hasnt been such a great industry before now.

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Responses

  • edward
    Where is the cnidocil?
    8 years ago
  • Aman
    What do coral taxonomists exmine to group corals by family, genus, and species?
    7 years ago
  • Mary
    Where is this nematocyst on a coral?
    7 years ago
  • riitta
    What is the function of the cnidocil in the cnidarian?
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    What do coral taxonomist examine?
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    How to draw coral reefs?
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