| Fire coral | |
|---|---|
| Millepora dichotoma | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hydrozoa |
| Order: | Anthomedusae |
| Family: | Milleporidae Fleming, 1828 |
| Genus: | Millepora Linnaeus, 1758 |
| Species | |
|
|
| Fire coral range | |
Fire corals are colonial marine organisms that look rather like real coral. However they are technically not corals; they are actually more closely related to jellyfish and other stinging anemones. They are members of the phylum Cnidaria, class Hydrozoa, order Capitata, family Milleporidae.
Contents |
Fire corals have a bright yellow-green and brown skeletal covering and are widely distributed in tropical and subtropical waters. They appear in small brush-like growths on rocks and coral. Divers often mistake fire coral for seaweed, and accidental contact is common. Upon contact, an intense pain can be felt that can last from two days to two weeks. The very small nematocysts on fire corals contain tentacles that protrude from numerous surface pores (similar to jellyfish stings). In addition, fire corals have a sharp, calcified external skeleton that can scrape the skin.
Fire coral has several common growth forms; these include branching, plate and encrusting. Branching adopts a calcerious structure which branches off, to rounded finger-like tips. Plate adopts a shape similar to that of the smaller non-sheet lettuce corals; therefore erect, thin sheets, which group together to form a colony. The latter; "encrusting", is where the fire coral forms on the calcerious structure of other coral or gorgonian structures.[1]
The gonophores in the family Milleporidae arise from the coenosarc (i.e. the hollow living tubes of the upright branching individuals of a colony) within chambers embedded entirely in the coenosteum (i.e. the calcareous mass forming the skeleton of a compound coral).
Fire corals are found on reefs in the Indian, Pacific and Atlantic Oceans.[2] They form extensive outcrops on projecting parts of the reef where the tidal currents are strong. They are also abundant on upper reef slopes and in lagoons,[3] and occur down to depths of 40 metres.
The polyps of fire corals are near microscopic size and are mostly embedded in the skeleton and connected by a network of minute canals. All that is visible on the smooth surface are pores of two sizes: gastropores and dactylopores. In fact, Millepora means ‘many pores’. Dactylopores have long fine hairs that protrude from the skeleton. The hairs possess clusters of stinging cells and capture prey, which is then engulfed by gastrozooids, or feeding polyps, situated within the gastropores. As well as capturing prey, fire corals gain nutrients via their special symbiotic relationship with algae known as zooxanthellae. The zooxanthellae live inside the tissues of the coral, and provide the coral with food, which they produce through photosynthesis, and therefore require sunlight. In return, the coral provides the algae with protection and access to sunlight.[2]
Reproduction in fire corals is more complex than in other reef-building corals. The polyps reproduce asexually, producing jellyfish-like medusae, which are released into the water from special cup-like structures known as ampullae. The medusae contain the reproductive organs that release eggs and sperm into the water. Fertilised eggs develop into free-swimming larvae that will eventually settle on the substrate and form new colonies. Fire corals can also reproduce asexually by fragmentation.[4][5]
Fire corals face the many threats that are impacting coral reefs globally which include poor land management practices that are releasing more sediment, nutrients and pollutants into the oceans and stressing the fragile reef ecosystem. Overfishing has ‘knock-on’ effects that result in the increase of macro-algae that can out-compete and smother corals, and fishing using destructive methods physically devastates the reef. A further potential threat is the increase of coral bleaching events, as a result of global climate change.[6]
Most fire coral species have brittle skeletons that can easily be broken, for example, during storms, or by divers. Divers can easily break the branches of fire corals when diving for leisure, or when collecting fish for the aquarium trade. For instance, the yellowtail damselfish (Chrysiptera parasema) tends to dwell close to the branching fire coral colonies, and retreats into its branches when threatened. In Brazil, fire coral colonies are extensively damaged when harvesting the yellowtail damselfish, as the corals are often deliberately smashed and fishes hiding amongst the branches are ‘shaken out’ into plastic bags.[7]
Fire corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES).[8]
Thirteen species of Millepora are currently recognised:[9]
This article incorporates text from the ARKive fact-file "Fire coral" under the Creative Commons Attribution-ShareAlike 3.0 Unported License and the GFDL.
|
|||||||||||||||||||||||||