Millepora alcicornis | |
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | Cnidaria |
Class: | Hydrozoa |
Order: | Anthoathecata |
Family: | Milleporidae |
Genus: | Millepora |
Species: | M. alcicornis |
Binomial name | |
Millepora alcicornis | |
Synonyms [2] | |
List
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Millepora alcicornis, or sea ginger, is a species of colonial fire coral with a calcareous skeleton. It is found on shallow water coral reefs in the tropical west Atlantic Ocean. It shows a variety of different morphologies depending on its location. It feeds on plankton and derives part of its energy requirements from microalgae found within its tissues. It is an important member of the reef building community and subject to the same threats as other corals. It can cause painful stings to unwary divers.
Millepora alcicornis is not a true coral in class Anthozoa but is in class Hydrozoa, and is more closely related to jellyfish than stony corals. Because of the variability in growth habit that this coral exhibits, it has been the subject of much confusion as to its taxonomy, being described under a number of different names from different localities. In 1898, Hickson decided that the variations in morphology were due to environmental factors and that Millepora alcicornis was the valid name for all these species. This conclusion has since been questioned. [3]
The species was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, but his type locality is unknown. [3] The scientific name comes from the Latin with Millepora meaning "thousand-pored" and alcicornis meaning "elk-horned". It seems likely that the type locality is in fact the West Indies. Explaining this in 1941 Crossland wrote "I cannot resist the remark that the one thing quite certain about the many forms of Millepora is that none of them have any resemblance to an elk's horn, except perhaps that from the West Indies". [3]
The morphology of Millepora alcicornis is very variable. Most colonies probably start as encrusting forms and adopt a branching structure as they grow. The encrustations can become established on a variety of structures, not only on coral reefs and rocks but also on dead corals and the hulls of wrecked ships. Later development is in the form of plates or blades in habitats with much water movement such as the surf-pounded outer edges of reefs. In calmer waters, such as in deep lagoons or more sheltered parts of the reef, a more upright, leafy or branched structure develops which can grow to 50 centimetres (20 in) tall. [4] [5] The habit of growth is also influenced by the inclination of the surface on which the fire coral grows. On vertical surfaces, the encrusting bases are larger with longer perimeters and the density of branching is lower than it is on horizontal surfaces. [6] The cylindrical branches usually grow in a single plane and span a range of hues from brown to pale, cream-like yellow, while branch tips are white. [4] [5]
Embedded in the calcareous skeleton are numerous microscopic polyps. They are connected internally by a system of canals and are concealed behind pores in the skeleton, the surface of which is smooth and lacks the corallites of true stony corals. The polyps have specialist functions, the gastrozooids processing and digesting the food caught by the dactylozooids which are grouped around them. The gastrozooids are small and plump and extend four to six tentacle stubs through their pores but are otherwise invisible. The dactylozooids have hairlike tentacles covered in cnidoblasts. Stings from the cnidocysts immobilize an item of prey and the tentacles thrust it through the mouth of an adjacent gastrozooid, from where it passes into the stomach for digestion. The polyps also extrude the coenosteum, the calcareous material of which the skeleton is composed. The coenosteum contains certain symbiotic microalgae called zooxanthellae. These are photosynthetic organisms which provide their hosts with energy and in return benefit from a protective environment in a well lit position. [4] About 75% of the fire coral's energy requirements are provided by the zooxanthellae. [7]
Millepora alcicornis is found in the Caribbean Sea, the Gulf of Mexico, Florida, the Cape Verde Islands and along the coast of Central and South America as far south as Brazil. It has also been found in Bermuda, but the morphology at that location is so different from that in the rest of its range that it may be a distinct species. [8] It grows at depths of up to 40 metres (130 ft) and is the only fire coral that often grows at depths greater than 10 metres (33 ft). [5]
Millepora alcicornis feeds on plankton. The tentacles of the dactylzooids are normally extended all the time. If an object is waved about above the coral, it will cause the tentacles to retract and then the coral can be handled without experiencing the painful stings caused by the cnidocytes. [7]
Reproduction is by either asexual or sexual means. Parts of the coral may get detached from the colony by a storm or other means, and some of these fragments may end up in suitable locations to grow into new colonies which will be genetically identical to the parent colony. This fragmentation is probably the most frequent method of reproduction. [4] Alternatively, certain pores called ampullae contain polyps that bud off short-lived, jellyfish-like medusae, which separate from the colony. They produce gametes which, after fertilisation, develop into planula larvae. These drift with the currents as part of the zooplankton before settling out and developing into new colonies. [7]
A number of species of shrimp and fish take refuge among the branches of Millepora alcicornis, seemingly immune to the venom. Hawkfish in particular often perch on top of the fire coral, perhaps protected by their skinless pectoral fins. Perhaps unsurprisingly, Millepora alcicornis has few predators. The fireworm ( Hermodice carunculata ) sometimes grazes on it, but prefers other corals. Certain nudibranchs in the genus Phyllidia eat it as do filefish in the family Monacanthidae. [7]
It has been found that when Millepora alcicornis grows in close proximity to an arborescent gorgonian sea fan, the fire coral becomes aggressive. It produces "attack" branches which grow out sideways towards the sea fan, develop into hand-like structures and encircle and smother it. The fire coral then uses it as a substrate for new growth. Sometimes this new growth gets separated from the parent colony, and a new colony of fire coral is formed, genetically identical to the original one. This aggressive action is specific to gorgonians and does not happen in response to the close presence of other live or dead corals, other sessile invertebrates or open water. The fire coral seems to be able to detect the gorgonian's presence as a result of water flowing over the surfaces of both. [9]
Although not a true coral, Millepora alcicornis is subject to the same general threats that corals and coral reefs are facing. The greatest of these is global warming and the consequent rise in sea temperatures. Millepora alcicornis is one of the first corals to show bleaching as the symbiont zooxanthellae are killed. However, it is also more resilient than most and becomes re-established by recruitment earlier than the scleractinian corals. Other general threats to reefs include ocean acidification, pollution, sedimentation, invasive species and other changes in species dynamics, coral diseases, fisheries, leisure activities and tourism. Small quantities of Millepora alcicornis are gathered for sale to collectors. [1]
The cnidocytes of Millepora alcicornis are powerful enough to sting human skin. They can inject a venom that causes a painful burning sensation, skin eruptions, blisters and scarring. [4] The toxin has been investigated and is a water-soluble protein, 40 μg of which provides a median lethal dose to mice weighing 20 grams (0.71 oz). [10]
Millepora alcicornis has no commercial uses but is sometimes kept in reef aquaria. It requires high water movement and bright light to flourish and its health can be judged by its colour, a yellow hue showing health whereas a darker brown colour can indicate too little light. It can be difficult to control because it grows fast and spreads over other objects in the tank. [7]
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mouth is fringed with tentacles. Although some species are solitary, most are colonial. The founding polyp settles and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as 25 cm (10 in) across but in colonial species the polyps are usually only a few millimetres in diameter. These polyps reproduce asexually by budding, but remain attached to each other, forming a multi-polyp colony of clones with a common skeleton, which may be up to several metres in diameter or height according to species.
Alcyonacea are a species of sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Whilst not in a strict taxonomic sense, Alcyonacea are commonly known as "soft corals" (Octocorallia) that are quite different from "true" corals (Scleractinia). The term “soft coral” generally applies to organisms in the two orders Pennatulacea and Alcyonaceae with their polyps embedded within a fleshy mass of coenenchymal tissue. Consequently, the term “gorgonian coral” is commonly handled to multiple species in the Alcyonaceae order that produce a mineralized skeletal axis composed of calcite and the proteinaceous material gorgonin only and corresponds to only one of several families within the formally accepted taxon Gorgoniidae (Scleractinia). These can be found in order Malacalcyonacea (taxonomic synonyms of include : Alcyoniina, Holaxonia, Protoalcyonaria, Scleraxonia, and Stolonifera. They are sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Common names for subsets of this order are sea fans and sea whips; others are similar to the sea pens of related order Pennatulacea. Individual tiny polyps form colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across, but only a few inches thick. They may be brightly coloured, often purple, red, or yellow. Photosynthetic gorgonians can be successfully kept in captive aquaria.
Montipora is a genus of Scleractinian corals in the phylum Cnidaria. Members of the genus Montipora may exhibit many different growth morphologies. With eighty five known species, Montipora is the second most species rich coral genus after Acropora.
Fire corals (Millepora) are a genus of colonial marine organisms that exhibit physical characteristics similar to that of coral. The name coral is somewhat misleading, as fire corals are not true corals but are instead more closely related to Hydra and other hydrozoans, making them hydrocorals. They make up the only genus in the monotypic family Milleporidae.
Millepora dichotoma, the net fire coral, is a species of hydrozoan, consisting of a colony of polyps with a calcareous skeleton.
Porites astreoides, commonly known as mustard hill coral or yellow porites, is a colonial species of stony coral in the family Poritidae.
Galaxea fascicularis is a species of colonial stony coral in the family Euphylliidae, commonly known as octopus coral, fluorescence grass coral, galaxy coral among various vernacular names.
Siderastrea radians, also known as the lesser starlet coral or the shallow-water starlet coral, is a stony coral in the family Siderastreidae. It is found in shallow parts of the western Atlantic Ocean as small, solid mounds or encrusting sheets.
Milleporasquarrosa is a species of fire coral that can be found in the Caribbean Sea as well as in the western Atlantic. They are very common on fringing reefs in patches. They have a smooth surface covered in tiny pores from which polyps protrude. They can reach up to 5 centimeters in height and can range from brown or tan in color with slight purple or red tints. It is commonly known as "box fire coral", which refers to its box-like structure and the stinging sensation felt when touched with a bare hand. These corals are important to reef-building.
Millepora platyphylla is a species of fire coral, a type of hydrocoral, in the family Milleporidae. It is also known by the common names blade fire coral and plate fire coral. It forms a calcium carbonate skeleton and has toxic, defensive polyps that sting. It obtains nutrients by consuming plankton and via symbiosis with photosynthetic algae. The species is found from the Red Sea and East Africa to northern Australia and French Polynesia. It plays an important role in reef-building in the Indo-Pacific region. Depending on its environment, it can have a variety of different forms and structures.
Plexaurella nutans, the giant slit-pore sea rod, is a tall species of soft coral in the family Plexauridae. It is a relatively uncommon species and is found in shallow seas in the Caribbean region.
Pseudoplexaura porosa, commonly known as the porous sea rod or the porous false plexaura, is a species of gorgonian-type colonial octocoral in the family Plexauridae. It is native to the Caribbean Sea and the Gulf of Mexico.
Platygyra daedalea, sometimes known as the lesser valley coral, is a colonial species of stony coral in the family Merulinidae. It occurs on reefs in shallow water in the Indo-Pacific region. It is a common species and the International Union for Conservation of Nature has assessed its conservation status as being of "least concern".
Millepora complanata, commonly known as blade fire coral, is a species of fire coral in the family Milleporidae. It is found in shallow waters in the Caribbean Sea where it is a common species. The International Union for Conservation of Nature has assessed its conservation status as being critically endangered.
Millepora tenera is a species of fire coral in the family Milleporidae. It is native to the Red Sea and the western Indo-Pacific region and is a zooxanthellate species with a calcareous skeleton. It was first described in 1949 by the Dutch zoologist Hilbrand Boschma.
Euphylliidae are known as a family of polyped stony corals under the order Scleractinia.
Briareum asbestinum, commonly known as the corky sea finger, is a species of a soft coral in the family Briareidae. It inhabits coral reefs and rocky bottoms in the Caribbean, Bahamas, and Florida, often growing to 30 cm at depths of one to 40 metres.
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