Coral polyp

Although coral looks like a plant, actually it is mainly comprised of (10) the limestone skeleton of a tiny animal called a coral polyp. While corals are the main components of reef structure, they are not the only living participants. Coralline algae cement the myriad corals, and other miniature organisms such as tube worms and mollusks contribute skeletons to this dense and diverse structure. Together, these (15) living creatures construct many different types of tropical reefs. 

Although perhaps not an attraction to nutrients in a strict sense, symbiotic dino-flagellates (zooxanthellae) have been known for some time to be attracted to host invertebrates (which ultimately provide them with nutrients), presumably via chemical cues from the hosts (Kinzie 1974 Fitt 1984). These cues may include ammonia and nitrate released from the host (Fitt 1984). Recently Pasternak et al. (2004) demonstrated chemoattraction by Symbiodinium sp. to cell-free homogenates of juvenile soft coral polyps, which did not previously have symbiotic zooxanthellae, but not to adult polyps, which did already have symbiotic algae. The attraction was subsequently shown to be a true chemotactic response with an additional chemoki-netic effect of the algae swimming slower in the presence of host chemical cues (Pasternak et al. 2006). 

Figure 3. Spectra of organic samples illustrating absorption features due to C-H (1)f 0-H (2), N-H (3), and organic pigments (4) (Halimeda spectrum offset vertically by 0.3 sapropel spectrum by 0.04> coral polyp by 0.04 gorgonian by -0.04> dead leaf by 0.04> and coral organics by -0.06. )...

Soft corals eggs contain terpenes such as 116, 117, and epoxypukalide 118 that are believed to play a defensive role.146,147 Extracts of Sinularia polydactyla larvae containing 116 and 117 are deterrent in assays with C. solandri which has been observed feeding on soft coral polyps in the field.147... 

The Ksp for calcium carbonate is 2.8 x 10 and the K value for calcium sulfate is 9.1 X 10. If coral polyps secreted calcium sulfate rather than calcium carbonate, how would this affect the formation of the coral reef ... 

Figure 1 Cross-section of coral polyp and skeleton.

Figure 7.1 As carbon dioxide dissolves in ocean water, carbonate ions are produced. Coral polyps capture these carbonate ions, producing crystals of calcium carbonate, which they secrete as an exoskeleton. Over time, the coral reef forms. A coral reef is a complex habitat that supports coral, algae, mollusks, echino-derms, and a variety of fishes. 

Palytoxin is a complex marine natural product containing 71 stereochemical elements (Fig. 5). The structure of PTX was elucidated by Moore. PTX is isolated from a zoanthid (order Zoanthidea) a type of soft coral commonly found in coral reefs all around the world. These animals come in a variety of different colonizing formations and in numerous colors. They can be found as individual polyps, attached by a fleshy stolon or a mat that can be created from pieces of sediment, sand and rock (soft coral). PTX is considered to be one of the most toxic nonpeptide substances known, second only to Maitotoxin. Typical symptoms of palytoxin poisoning are angina-like chest pains, asthma-like breathing difficulties, tachycardia, unstable blood pressure, hemolysis (destruction of red blood... 

Stimson, J., Stimulation of fat-body production in the polyps of the coral Pocillopora damicornis by the presence of mutualistic crabs in the genus Trapezia, Mar. Biol., 106, 211, 1990. 

Extracellular occurrence of MAAs is common in corals where these UV-absorbing compounds are found in the external mucus layer of the colony.163 176 MAA concentrations in mucus layers are closely matched to or occasionally less than the MAA concentrations in the coral tissues, indicating that MAAs are probably passively and nonselectively excreted.176 Consideration of the MAA content and optical path length of the mucus layer ( 1 mm) gives an estimated absorbance efficiency of approximately 7% of incident UV. Such low attenuation of UV radiation probably does not provide substantial protection for the living polyps, and it may be the antioxidant properties of mycosporine-glycine that are more important in the mucus layer (see also Section II.A.10). 

Today, coral is the name given to sea dwelling, soft bodied, carnivorous animals with polyps, most of which live in colonies. They belong to the phylum Coelenterata. There are thousands of different corals throughout the world s warmer seas. Coral is also the term used to describe the skeleton of the polyps, which may, in some cases, be used as a gem or ornamental material. 

The skeletons of other corals have a more spongy appearance, punctuated by a mass of holes. In these, the polyps have occupied the surface holes of the aragonite skeleton, and move further out as the colony grows and new layers of aragonite are laid down. 

Most of the gem corals belong to the subclass Octocorallia (previously called Alcyonaria). The polyps of all octocorals have eight tentacles. Another subclass, Ceriantipatheria, includes the homy corals, and the subclass Zoantharia includes fossilised corals. 

Coral reefs are made by tiny organisms known as polyps. They attach themselves permanently in one place and survive by eating tiny marine animals that swim past. 

Anatomical aspects. The skeletons of corals are formed of crystals of aragonite in an organic matrix. Calcification begins when the free-swimming larva attaches to the substratum. The larva then metamorphoses into a polyp which continues to deposit extracellularly CaCOs and organic matrix through the secretory activity of the calicoblastic epithelium. The epithelium is a layer of cells at the base of the polyp adjoining the skeletal area at which deposition takes place. 

Zooxanthellae symbiotic, unicellular algae in the endoderm of hermatypic coral (q.v.) polyps. 

Cnidarians are a group of animals that includes hydrozoids, sea fans, anemones, and jellyfish. All of the organisms in this group have simple, saclike bodies in the polyp or medusa forms (see Figure 3.3). The bell-shaped bodies of jellyfish are referred to as medusae, and the vaselike structures that are typical of coral and anemones are polyps. 

Several species of stalked, plantlike hydrozoans and octo-corals form small colonies in shallow intertidal waters. These organisms spend part of their lives as medusae and part as polyps. Like anemones, they gather food with their small tentacles. A less common but more conspicuous cnidarian along the shore is the jellyfish. Most jellyfish found in the intertidal zone are simply washed in, although the stalked jellyfish makes its home there. 

Corals may grow as solitary or colonial forms. The process of calcification in stony corals (sclerac-tinians) occurs in the lower portion of the polyp, producing a cup-like stmcture, the calyx, in which the pol3fp (typically 1-3 nun in diameter) sits. Stmctural elements of calyx comprise the surrounding walls (theca), the floor (basal plate), and, extending upwards from the basal plate a series of thin, radial elements (sclerosepta). 

The studied corals were collected alive Goniastrea from New Caledonia, Favia from Moorea island (Polynesia) and Merulina from New-Caledonia (Noumea lagoon). The polyp tissues were removed following a three-hour immersion in pure water that causes the cells to be destroyed, after which the remaining tissues are easily removed by a water-jet. In all cases, only the upper parts, i.e. the most recently formed skeleton, of the corallite structures were used to assess the structural and compositional properties of the skeletons. 

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