Skeletal eroding band

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Skeletal eroding band (SEB) is a disease of corals that appears as a black or dark gray band that slowly advances over corals, leaving a spotted region of dead coral in its wake. It is the most common disease of corals in the Indian and Pacific Oceans, and is also found in the Red Sea.

Coral diseases, comprising the diseases that affect corals, injure the living tissues and often result in the death of part or the whole of the colony. These diseases have been occurring more frequently in the twenty-first century as conditions become more stressful for many shallow-water corals. The pathogens causing the diseases include bacteria, fungi and protozoa, but it is not always possible to identify the pathogen involved.

Indian Ocean The ocean between Africa, Asia, Australia and Antarctica (or the Southern Ocean)

The Indian Ocean is the third-largest of the world's oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi). It is bounded by Asia on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean or, depending on definition, by Antarctica.

Pacific Ocean Ocean between Asia and Australia in the west, the Americas in the east and Antarctica or the Southern Ocean in the south.

The Pacific Ocean is the largest and deepest of Earth's oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west and the Americas in the east.

Contents

So far one agent has been clearly identified, the ciliate Halofolliculina corallasia . This makes SEB the first coral disease known to be caused by a protozoan. [ citation needed ] When H. corallasia divides, the daughter cells move to the leading edge of the dark band and produce a protective shell called a lorica. To do this, they drill into the coral's limestone skeleton, killing coral polyps in the process.

Ciliate phylum of protozoans

The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group and are variously used in swimming, crawling, attachment, feeding, and sensation.

Halofolliculina corallasia is a species of heterotrich ciliates identified as a cause of the syndrome called skeletal eroding band (SEB). It is the first coral disease pathogen that is a protozoan as well as the first known to be a eucaryote; all others identified are bacteria. Like other members of the folliculinid family, H. corallasia is sessile and lives in a "house" called a lorica, into which the cell can retreat when disturbed. The mouth is flanked by a pair of wing-like projections that are fringed with polykinetids, groups of cilia that work in groups to produce a current that draws food into the "mouth".

A disease with very similar symptoms has been found in the Caribbean Sea, but has been given a different name as it is caused by a different species in the genus Halofolliculina and occurs in a different type of environment.

Caribbean Sea A sea of the Atlantic Ocean bounded by North, Central, and South America

The Caribbean Sea is an American Mediterranean Sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico and Central America to the west and south west, to the north by the Greater Antilles starting with Cuba, to the east by the Lesser Antilles, and to the south by the north coast of South America.

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Symptoms and history

Skeletal eroding band is visible as a black or dark gray band that slowly advances over corals, leaving a spotted region of dead coral in its wake. [1] The spotted area distinguishes skeletal eroding band from black band disease, [1] which also forms an advancing black band but leaves a completely white dead area behind it. [2]

Black band disease coral disease

Black band disease is a coral disease in which corals develop a black band. It is characterized by complete tissue degradation due to a pathogenic microbial consortium. The mat is present between apparently healthy coral tissue and freshly exposed coral skeleton.

Skeletal eroding band was first noticed in 1988 near Papua New Guinea and then near Lizard Island in Australia's Great Barrier Reef, but was regarded as a gray variant of black band disease, as were instances off Mauritius in 1990. Surveys in 1994 in and around the Red Sea first identified the condition as a unique disease. [1] It is now considered the commonest disease of corals in the Indian and Pacific Oceans, especially in warmer or more polluted waters. [3]

Papua New Guinea Constitutional monarchy in Oceania

Papua New Guinea, officially the Independent State of Papua New Guinea is a country in Oceania that occupies the eastern half of the island of New Guinea and its offshore islands in Melanesia, a region of the southwestern Pacific Ocean north of Australia. Its capital, located along its southeastern coast, is Port Moresby. The western half of New Guinea forms the Indonesian provinces of Papua and West Papua. It is the world's 3rd largest island country with 462,840 km2 (178,700 sq mi).

Great Barrier Reef coral reef system off the east coast of Australia, World Heritage Site

The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef is located in the Coral Sea, off the coast of Queensland, Australia. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps. It supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN labelled it one of the seven natural wonders of the world. The Queensland National Trust named it a state icon of Queensland.

Mauritius Island nation in the Indian Ocean

Mauritius, officially the Republic of Mauritius, is an island nation in the Indian Ocean about 2,000 kilometres off the southeast coast of the African continent. The country includes the islands of Mauritius and Rodrigues, 560 kilometres east of Mauritius, and the outer islands of Agaléga and St. Brandon. The islands of Mauritius and Rodrigues form part of the Mascarene Islands, along with nearby Réunion, a French overseas department. The area of the country is 2,040 square kilometres (790 sq mi). The capital and largest city is Port Louis.

The spread of the disease across an infected coral has been measured at 2 millimeters (0.079 in) in the Red Sea and 2 to 3 millimeters (0.079 to 0.118 in) around the Great Barrier Reef. [3] Corals of the families Acroporidae and Pocilloporidae are the most vulnerable to infection. A study in 2008 found that the infection spread at about 2 millimeters (0.079 in) per day in colonies of Acropora muricata, eventually wiping out 95% of its victims. However, experiments showed that the disease easily spread to already dead and dying areas of corals but did not attack undamaged corals. [4]

Acroporidae family of cnidarians

Acroporidae is a family of small polyped stony corals in the phylum Cnidaria. The name is derived from the Greek "akron" meaning "summit" and refers to the presence of a corallite at the tip of each branch of coral. They are commonly known as staghorn corals and are grown in aquaria by reef hobbyists.

Pocilloporidae family of cnidarians

The Pocilloporidae are a family of stony corals in the order Scleractinia occurring in the Pacific and Indian Oceans.

<i>Acropora</i> genus of cnidarians

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.

Halofolliculina corallasia

So far one agent has been identified, the ciliate protozoan Halofolliculina corallasia . Skeletal eroding band is the first recorded disease of corals that is caused by a protozoan, and thus the first known to be caused by an eukaryote – most are caused by prokaryotic bacteria. [1] For example, black band disease is caused by microbial mats of variable composition, [2] and White pox disease by the bacterium Serratia marcescens . [5] [6]

H. corallasia is a sessile protozoan that secretes a bottle-like housing called a lorica (Latin for cuirass, flexible body armor [7] ), that is anchored to a surface and into which the cells retract when disturbed. [8] When a mature individual cell division divides, it produces a pair of worm-like larvae that settle on undamaged coral just ahead of the black band. There each daughter cell secretes its lorica, at the same spinning to produce the lorica's flask-like shape. This spinning, combined with the chemicals that harden the lorica, crumble the coral skeleton and kill the polyps. The discarded loricae of the "parent" H. corallasia cells remain, leaving the distinctive spotted region in the wake of the living black band. [1]

"Caribbean ciliate infection"

A survey in the Caribbean Sea conducted in 2004 and published in 2006 reported a disease with very similar symptoms, affecting 25 species of coral within 6 families. Although the authors initially suspected H.corallasia, more detailed examination showed that the culprit was another species that was previously unknown and has not yet been formally named, although it is clearly a member of the same genus, Halofolliculina . [9] A follow-up analysis noted that the Caribbean infestations were commonest in oceanic waters, while those in the Indian and Pacific Oceans were more prevalent in coastal waters. Because of these two differences, the authors gave this new manifestation the name "Caribbean ciliate infection". Coral diseases are a relatively new topic of research, and the use of standardized terminology has not yet been fixed. [3]

See also

Related Research Articles

Polyp (zoology) One of two forms found in the phylum Cnidaria (zoology)

A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral end is attached to the substrate by means of a disc-like holdfast called the pedal disc, while in colonies of polyps it is connected to other polyps, either directly or indirectly. The oral end contains the mouth, and is surrounded by a circlet of tentacles.

Coral bleaching

Coral bleaching occurs when coral polyps expel algae that live inside their tissues. Normally, coral polyps live in an endosymbiotic relationship with these algae, which are crucial for the health of the coral and the reef. The algae provides up to 90 percent of the coral's energy. Bleached corals continue to live but begin to starve after bleaching. Some corals recover.

Cay small island formed on the surface of a coral reef

A cay, also spelled caye or key, is a small, low-elevation, sandy island on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans.

White band disease coral disease

White band disease is a coral disease that affects acroporid corals and is distinguishable by the white band of dead coral tissue that it forms. The disease completely destroys the coral tissue of Caribbean acroporid corals, specifically elkhorn coral and staghorn coral. The disease exhibits a pronounced division between the remaining coral tissue and the exposed coral skeleton. These symptoms are similar to white plague, except that white band disease is only found on acroporid corals, and white plague has not been found on any acroporid corals. It is part of a class of similar disease known as "white syndromes", many of which may be linked to species of Vibrio bacteria. While the pathogen for this disease has not been identified, Vibrio carchariae may be one of its factors. The degradation of coral tissue usually begins at the base of the coral, working its way up to the branch tips, but it can begin in the middle of a branch.

Elkhorn coral species of cnidarian

Elkhorn coral is a prominent Caribbean reef-building coral, although current populations are still struggling to recover from white band disease outbreak. This species is structurally complex with many large branches. The coral structure resembles that of elk antlers. These branches create habitats for many other reef species, such as lobsters, parrot-fish, snapper shrimps and other reef fish. Elkhorn coral colonies are incredibly fast-growing, with an average growth rate of 5 to 10 cm per year and can eventually grow up to 3.7 m (12 ft) in diameter. The color of this coral species ranges from brown to a yellowish-brown as a result of the symbiotic zooxanthellae living inside the tissue of this coral species. Zooxanthellae are a type of algae which photosynthesize to provide the coral with nutrients. The zooxanthellae are also capable of removing waste products from the coral. Historically, the majority of elkhorn coral reproduction has occurred asexually; this occurs when a branch of the coral breaks off and attaches to the substrate, forming a new colony, known as fragmentation. The degree to which local stands reproduce by fragmentation varies across the Caribbean, but on average, 50% of colonies are the result of fragmentation rather than sexual reproduction. Sexual reproduction occurs once a year in August or September when coral colonies release millions of gametes by broadcast spawning.

White pox disease

White pox disease, first noted in 1996 on coral reefs near the Florida keys, is a coral disease affecting Elkhorn coral throughout the Caribbean. It causes irregular white patches or blotches on the coral that result from the loss of coral tissue. These patches distinguish white pox disease from white band disease which produces a distinctive white band where the coral skeleton has been denuded. The blotches caused by this disease are also clearly differentiated from coral bleaching and scars caused by coral-eating snails. It is very contagious, spreading to nearby coral.

Yellow-band disease coral disease

Yellow-band disease is a coral disease that attacks colonies of coral at a time when coral is already under stress from pollution, overfishing, and climate change. It is characterized by large blotches or patches of bleached, yellowed tissue on Caribbean scleractinian corals.

Environmental issues with coral reefs Factors which adversely affect tropical coral reefs

Human impact on coral reefs is significant. Coral reefs are dying around the world. Damaging activities include coral mining, pollution, overfishing, blast fishing, the digging of canals and access into islands and bays. Other dangers include disease, destructive fishing practices and warming oceans. Factors that affect coral reefs include the ocean's role as a carbon dioxide sink, atmospheric changes, ultraviolet light, ocean acidification, viruses, impacts of dust storms carrying agents to far-flung reefs, pollutants, algal blooms and others. Reefs are threatened well beyond coastal areas. Climate change, such as warming temperatures, causes coral bleaching, which if severe kills the coral.

<i>Acropora prolifera</i> species of cnidarian

Acropora prolifera, the fused staghorn coral, is a branching, colonial, stony coral found in shallow parts of the Caribbean Sea, the Bahamas and southern Florida.

<i>Dichocoenia</i> genus of cnidarians

Dichocoenia is a monotypic genus of stony coral in the family Meandrinidae. It is represented by a single species, Dichocoenia stokesii, which is commonly known as pineapple coral, elliptical star coral, or pancake star coral. It is found in the Caribbean Sea and the western Atlantic Ocean. Dichocoenia stokesii has irregular calyces and its form can be either a massive, hemispherical hump or a flat, platform-like structure.

Cymo melanodactylus, the furry coral crab, is a species of small decapod crustacean in the family Xanthidae. It is found in the Indo-Pacific Ocean and lives in crevices and on the surface of corals in the genus Acropora.

<i>Isopora palifera</i> species of Anthozoa

Isopora palifera is a species of stony coral in the family Acroporidae. It is a reef building coral living in shallow water and adopts different forms depending on the water conditions where it is situated. It is found in the Western Indo-Pacific Ocean as far east as Australia.

Corallivore

A corallivore is an animal that feeds on coral. Corallivores are an important group of reef organism because they can influence coral abundance, distribution, and community structure. Corallivores feed on coral using a variety of unique adaptations and strategies. Animals known to be corallivores include certain mollusks, annelids, fish, crustaceans, flatworms and echinoderms. The first recorded evidence of corallivory was presented by Charles Darwin in 1842 during his voyage on HMS Beagle in which he found coral in the stomach of two Scarus parrotfish.

Folliculinidae family of protozoans

The Folliculinidae are a family of ciliates in the class Heterotrichea, with the common name "bottle-animalcule".

Human behavior has a large impact on Jamaica's 479 square miles of coral reefs, which hosts 60 different species of coral. These reefs are a major tourist attraction for the country, accounting for 27 percent of its GDP. Due to Jamaica's economic reliance on its coastal reserves, the degradation of the coral reefs is much higher because of continuous habitat destruction.

Stony coral tissue loss disease Disease affecting corals

Stony coral tissue loss disease (SCTLD) is a disease of corals that first appeared off the coast of Florida in 2014. By 2019 it had spread along the Florida Keys and had appeared elsewhere in the Caribbean Sea. The disease completely destroys the soft tissue of many species of stony coral, killing them within weeks or months of becoming infected. The causal agent is unknown but is suspected to be a bacterium. The degree of susceptibility of a coral, the symptoms, and the rate of progression of the disease vary between species.

References

  1. 1 2 3 4 5 Antonius, Arnfried A., Lipscomb, Diana (2001). "First Protozoan Coral-killer identified in the Indo-Pacific" (PDF). Atoll Research Bulletin. Smithsonian Institution (481): 1–21. Archived from the original (PDF) on 2009-09-19. Retrieved 2009-08-15.
  2. 1 2 Richardson, L.L.; Yossi Loya (2004-06-14). "Black band disease". In Rosenberg, E.; Loya, Y. (eds.). Coral health and disease. Springer. pp. 325–336. ISBN   3-540-20772-4 . Retrieved 2009-08-16.
  3. 1 2 3 Rodríguez, S.; Cróquer, A.; Guzmán, H. M.; Bastidas, C. (March 2009). "A mechanism of transmission and factors affecting coral susceptibility to Halofolliculina sp. infection" (PDF). Coral Reefs. 28 (1): 67–77. doi:10.1007/s00338-008-0419-y. Archived from the original (PDF) on 2011-09-10. Retrieved 2009-08-16.
  4. ↑ Page, C.; Willis, B. (June 2008). "Epidemiology of skeletal eroding band on the Great Barrier Reef and the role of injury in the initiation of this widespread coral disease". Coral Reefs. 27 (2): 257–272. doi:10.1007/s00338-007-0317-8.
  5. ↑ Sutherland, Kathryn Patterson; Kim B. Ritchie. "White Pox Disease of the Caribbean Elkhorn Coral, Acropora palmata" (PDF). Archived from the original (PDF) on 2011-07-19. Retrieved 2009-08-22.
  6. ↑ Patterson KL, Porter JW, Ritchie KB, et al. (June 2002). "The etiology of white pox, a lethal disease of the Caribbean elkhorn coral, Acropora palmata". Proc Natl Acad Sci USA. 99 (13): 8725–30. doi:10.1073/pnas.092260099. PMC   124366 . PMID   12077296.
  7. ↑ Little, W.; Fowler, H.W; Coulson, J.; Onions, C.T. (1964). "Lorica". Shorter Oxford English Dictionary. Oxford University Press.
  8. ↑ Lynn, Denis H. (2008). "Subphylum 1, Postciliodesmatophora: Class2, Heterotrichea". The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature (3rd ed.). Springer. pp. 129–139. ISBN   1-4020-8238-X . Retrieved 2009-08-16.
  9. ↑ Cróquer, A.; Bastidas, C.; Lipscomp, D.; et al. (May 2006). "First report of folliculinid ciliates affecting Caribbean scleractinian corals". Coral Reefs. 25 (2): 187–191. doi:10.1007/s00338-005-0068-3.
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