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Lab 2: Phylum Cnidaria Name : Wan Nursyuhada Bt Wan Mohd Rozihas Matric No. : A155843 Lecturer’s Name : Dr. Wan Mohd Lotfi Bin Wan Muda Date : 1.0 – Introduction The Cnidaria is a group of animals are well known to many people under their common names, Sea Anemones, Corals and Jellyfish are all Cnidarians as are Hydras, Sea Whips, Sea Fans and Sea Pansies. They are linked together by their carnivorous feeding habits their simple anatomical design and the possession of nematocysts, though one species of Ctenophora possesses nematocysts as well. The name Cnidaria has now pretty much replaced the older term of Coelenterata which these days is often applied to both the Cnidaria and the Ctenophora together, these two phyla are also known as the Radiate Animals because they both have radial or biradial symmetry. The word Cnidaria refers to Cnidocysts, specialised cells which contain the Nematocysts, the stinging organelles that allow the Cnidaria to subdue their prey. The Cnidaria are the oldest of the true metazoan phyla. A fossil Hydrozoan from South Australia called Ediacara is 700 million years old, while numerous fossil Cnidarians exist from the Cambrian 500 million years ago. The Cnidarians, particularly the corals often make up an important component of the shallow marine fauna of tropical and subtropical seas. All the Cnidaria are aquatic and nearly all are marine. Corals because of their shallow marine environment and their habit of accumulating a mineralised skeleton (coralite) tend to fossilize well and we know quite a bit about their evolution. The Cnidarian body is basically a U shape with intact walls that surround a central digestive area and a mouth at the opening, generally surrounded by tentacles, there is no distinct anus. In Anemones the mouth faces up, and in Jellyfish it faces down. The Cnidarians show a more complicated arrangement of cell layers as well as a greater range of cell types than the Porifera. Their bodies show two distinct layers of cells and thus they are called 'Diploblastic animals'. The two cell layers are an outer Epidermis or Ectoderm, and an inner Gastrodermis or Endoderm. These two layers are separated by the mesoglea a non-cellular fibrous jelly like material that is thin in some groups such as the Hydras but can be quite thick in other such as the Jellyfish where it helps provide negative buoyancy (makes the animal more likely to float). The ectodermis consists of five basic cell types, Epitheliomuscular cells which supply some of the muscular capabilities of the animal, Interstitial cells which are basic cells that give rise to the other cell types, Cnidocysts (see below), Mucous glands and sensory or nerve cells. The endodermis consists of three or four basic cell types Gastromuscular cells which help digest food items and provide some muscle power, Gland cells that secrete enzymes for digestion, Mucous cells and in Anemones but not in Hydras, Cnidocytes. One of the most important distinguishing characteristics of the phylum are the Nematocysts. Nematocysts, and their enclosing Cnidocysts come in about 24 different forms, the differences play a functional role in the classification of the phylum. A Cnidocyst is a cell that secretes a nematocyst within it. A basic Nematocyst is a capsule made of something like chitin within which rest a coiled thread. This thread can be shot out of the capsule to encounter prey items, or in some cases to repel predators. The Cnidocyst has either a modified flagellum called a Cnidocil, or a cone as a sensory trigger. If this trigger is touched the nematocyst thread is rapidly ejected. Nematocyst threads come in 3 basic types. The fundamental nematocyst is a thin tubular thread with barbs at the far end, though there may be barbs near the base as well. When the nematocyst is discharged, the barbs penetrate the skin of the prey and a toxin can be injected. Ptychocysts are uncommon, occurring only in the Ceriantharians, they lack spines or barbs but are adhesive and can be used to line the tubes the Ceriantharians live in as well as to entangle prey. Spirocysts also lack barbs or spines, they are an enclosed tube that is adhesive, they are used to trap prey in a tangled net of sticky threads. The Cnidaria come in two basic forms, a 'Polyp' form typified by the Sea Anemones and a 'Medusa' form typified by Jellyfish. Generally speaking Polyps are tube shaped and sedentary with a ring of tentacles around the mouth, Medusae are umbrella or bell shaped, free living and have a central projection on the inside of the umbrella which supports the mouth and their tentacles around the rim of the umbrella. The Cnidarians are either carnivores or omnivorous filter feeders.The the carnivorous forms do not hunt their prey, instead they use various 'sit and trap' or 'float/swim and trap' strategies, using their Nematocysts, which are not only found on the stinging tentacles but can be all over the animals body, to stun and or kill their prey. There are about 10, 000 species of Cnidarians divided between 3 classes Hydrozoa, Scyphozoa and Anthozoa. 2.0 – Materials - Microscope Slides Cover slips Dissecting set Petri dish Clorox Rubber gloves 3.0 – Specimens Hydrozoa 1. Obelia 2. Millipora (Fire coral) Scyphozoa 1. Jellyfish (Moon jelly) Anthozoa 1. 2. 3. 4. 5. 6. 7. 8. 9. Sea Anemone Fungia (Mushroom coral) Acropora Montipora Pavona Sea pen Sea fan Sea whip Dendronephyta (Soft coral) 4.0 – Methodology Observation of polyps and corallites: 1. In the lab, we were provided with specimens which were Hydrozoa, Scyphozoa and Anthozoa. 2. For Hydrozoa, the specimens provided were Obelia and Millipora (fire coral). We observed the polyps of the specimens under the microscope and made important remarks about them. 3. For Scyphozoa, the specimen was jellyfish. Aurelia Aurita is the name of the jellyfish. Its common name is Moon Jelly. After placing it on the petri dish, we observed its gastric pouches, oral arms, mouth and tentacles. 4. The last one is Anthozoa. Under this class, there were many specimens provided and were observed. Extracting the spicules: 1. The soft coral was cut into a small piece and placed in a petri dish. 2. 5% of sodium hypochlorite solution (Clorox) was pipetted into the petri dish to dissolve the soft coral. 3. The soft coral was left for it to dissolve for 20-30 minutes. 4. The spicules were pipetted and dropped onto glass slide and was covered with a cover slip. The spicules were observed under a compound microscope. 5.0 – Results and Observation 1. Hydrozoa A) Obelia (Obelia longissima) The polyp is the asexual stage and the medusa the sexual stage. In such organisms the polyp, by budding, gives rise to medusae, which either detach themselves and swim away or remain permanently attached to the polyp. The medusae then produce new polyps by sexual reproduction. A medusa produces eggs or sperm, which are usually shed into the water; when an egg is fertilized, it develops into a swimming larva, which eventually settles and grows into a polyp. In addition to this elaborate means of reproduction, the polyp can form new polyps by budding. In some groups of coelenterates either the polyp or the medusa has become highly developed, with the reduction or complete loss of the other form. During the polyp stage, the mouth is situated at the top of the body, surrounded by tentacles. Its skeleton is composed of chitin. B) Millepora (Millepora alcicornis) – Fire coral The skeleton of a fire coral is calcareous and is made up of Calcium Carbonate. Branching adopts a calcerious structure which branches off, to rounded, finger-like tips. The gonophores in the family Milleporidae arise from the coenosarc (the hollow living tubes of the upright branching individuals of a colony) within chambers embedded entirely in the coenosteum (the calcareous mass forming the skeleton of a compound coral). Millepora and hard corals are different and Millepora cannot be classified as a hard coral because their polyps are different. Polyp of Millepora does not have a pharynx or tentacles. Its coralite too has no septa like those of in corals. 2. Scyphozoa - Jellyfish (Aurelia Aurita) – Moon jelly Scyphozoans usually display a four-part symmetry and have an internal gelatinous material called mesoglea, which provides the same structural integrity as a skeleton. The mesoglea includes mobile amoeboid cells originating from the epidermis. Aurelia undergoes alternation of generations, whereby the sexually-reproducing pelagic medusa stage is either male or female, and the benthic polyp stage reproduces asexually. It feeds by collecting medusae, plankton, and mollusks with its tentacles, and bringing them into its body for digestion. It is capable of only limited motion, and drifts with the current, even when swimming. 3. Anthozoa A) Sea Anemone (Metridium senile) The base of Metridium senile is considerably wider than the column and is attached to rock or another substrate. The column is long, smooth and cylindrical, of a fleshy consistency with a slimy surface lubricated with mucus. There are no warts or suckers and the column is topped by a parapet and deep groove. The oral disc is broad and deeply lobed into several curving sections that overhang the column. The slender, pointed tentacles are very numerous in larger specimens though fewer and relatively longer in smaller ones. Those near the margin are crowded and short whereas further into the disc they are longer and more dispersed. B) Fungia ( Fungia sp.) – Mushroom coral Corals in the genus Fungia are mostly solitary, some attaining 30 centimetres in diameter. However Fungia simplex is colonial. The juveniles attach themselves to rock but larger individuals detach themselves and become free living. They are found in various bright colours including white, pink, red, purple, blue and yellow and are popular with keepers of reef aquariums. The discs are either round or oval and the central mouth, which is surrounded by tentacles, may be a slit. The polypsits in a calcareous cup, the corallite. The septa are vertical skeletal elements inside the corallite wall and the costae join the septae and continue outside the corallite wall and underneath the coral. C) Acropora (Acropora sp.) Acropora is a genus of small polyp stony coral in the phylum Cnidaria. Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described. Acropora species are some of the major reef corals responsible for building the immense calcium carbonate substructure that supports the thin living skin of a reef. Acropora species may grow as plates or slender or broad branches. Like other corals, Acroporacorals are colonies of individual polyps, which are about 2 mm across and share tissue and a nerve net. The polyps can withdraw back into the coral in response to movement or disturbance by potential predators, but when undisturbed, they protrude slightly. The polyps typically extend further at night to help capture plankton and organic matter from the water. Acropora is most common in shallow reef environments with bright light and moderate to high water motion. Many small reef fishes live near their colonies and retreat into the thicket of branches if threatened. D) Montipora (Montipora sp.) Montipora is a genus of small polyp stony coral in the phylum Cnidaria. Depending on the species and location, Montipora may grow as plates or ridges, appearing to some as a bowl or flower. Undisturbed, the plates expand radially and may encrust over surrounding rocks, shells or debris. Members in this genus are usually thin corals that form leafy, plate-like, encrusting or semi-massive colonies. The colours vary greatly. The calices are less than 2 mm in diameter and are usually well separated by the coenosteum. The skeleton is lacy, the walls are indistinct and the septa, when present are small and in 2 cycles. The columella is rarely developed and the corallites are inconspicuous and appear empty as the polyps are very small. E) Pavona (Pavona sp.) Corals in this genus have a range of different forms including those that are massive, meandering, columnar, leaf-like, and plate-like. A single species may vary in form according to the current, wave action, lighting conditions, and depth of its location. Members of the genus are distinguished from other corals by having no walls to thecorallites, but having clearly delineated septocostae that connect each corallite to its neighbours, giving a flowerlike pattern on the surface of the coral. The corallites themselves are shallow depressions with central columella and may be separated by ridges. The polyps are only extended at night. The foliose and plate-like forms tend to be two-sided. F) Sea Pen (Pteroides sp.) Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 16 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide. Sea pens are grouped with the octocoralia ("soft corals"), together with sea whips or gorgonians. Although named after their feather-like appearance reminiscent of antique quill pens, only sea pen species belonging to the suborder Subselliflorae live up to the comparison. Those belonging to the much larger suborder Sessiliflorae lack feathery structures and grow in clublike or radiating forms. The latter suborder includes what are commonly known as sea pansies. Sea pens are colonial animals with multiple polyps (which look somewhat like miniature sea anemones), each with eight tentacles. Unlike other octocorals, however, a sea pen's polyps are specialized to specific functions: a single polyp develops into a rigid, erect stalk (the rachis) and loses its tentacles, forming a bulbous "root" orpeduncle at its base. G) Sea Fan (Gorgonia sp.) The structure of a gorgonian colony varies. In the suborder Holaxonia, skeletons are formed from a flexible, horny substance called gorgonin. The suborder Scleraxonia is one of the varieties of gorgonians which is supported by a skeleton of tightly grouped calcareous spicules. There are also species which encrust like coral.Most of Holaxonia and Sclerazonia, however, do not attach themselves to a hard substrate. Instead, they anchor themselves in mud or sand. Research has shown that measurements of the gorgonin and calcite within several long-lived species of gorgonians can be useful inpaleoclimatology andpaleoceanography, as the skeletal growth rate and composition of these species is highly correlated with seasonal and climatic variation. H) Sea Whip (Sinularia sp.) Colonies heavily branched, more or less in single planes; colonies up to 60 cm in height. Sea whip has long, flexible, quite flat and wide branches which are tapered somewhat from the base to the end. Polyps extend from a groove that runs along the thin edges. The color varies from purple, white to cream. Sea whips inhabit a wide range of inshore environments, from back reef areas of sand and rubble to patch reefs of moderate depth. I) Dendronephyta (Dendronephyta sp.) – soft coral Dendronephyta or soft corals, are an order of corals which do not producecalcium carbonate skeletons. Soft corals contain minute, spiny skeletal elements called sclerites, useful in species identification. Sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators. Unlike stony corals, most soft corals thrive in nutrient-rich waters with less intense light. Almost all utilize symbiotic photosynthesizing zooxanthella as a major energy source. However, most will readily eat any free floating food, such as zooplankton, out of the water column. They are integral members of the reef ecosystem and provide habitat for fish, snails, algae and a diversity of other marine species. Many soft corals are easily collected in the wild for the reef aquarium hobby, as small cuttings are less prone to infection or damage during shipping than stony corals. Nevertheless, home-grown specimens tend to be more adaptable to aquarium life and help conserve wild reefs. Soft corals grow quickly in captivity and are easily divided into new individuals, and so those grown via aquaculture are often hardier and less expensive than imported corals from the wild. Spicules of Dendronephyta