Skeletal Eroding Band
Encyclopedia
Skeletal eroding band is a disease of coral
s that appears 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 Ocean
s, and is also found in the Red Sea
.
So far one agent has been clearly identified, the sessile
heterotrich
(ciliate
) protozoan Halofolliculina corallasia
. This makes SEB the first coral disease known to be caused by a protozoan or any eucaryote. When H. corallasia divides
, the daughter cells move to the leading edge of the dark band and produce a "house" called a lorica
. To do this, they drill into the coral's limestone
skeleton
, killing the coral polyp
s in the process.
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.
, which also forms an advancing black band but leaves a completely white dead area behind it.
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. It is now considered the commonest disease of corals in the Indian
and Pacific Ocean
s, especially in warmer or more polluted waters.
The spread of the disease across an infected coral has been measured at 2 millimetre (0.078740157480315 in) in the Red Sea and 2 to 3 mm (0.078740157480315 to 0.118110236220472 in) around the Great Barrier Reef. Corals of the families and Acroporidae
and especially Pocilloporidae
are most vulnerable. A study in 2008 found that skeletal eroding band spread at about 2 millimetre (0.078740157480315 in) per day in colonies of Acropora muricata, eventually wiping out 95% of its victims. However, experiments showed that the disease easily infested already-dead areas of corals but did not attack undamaged corals.
protozoa
n Halofolliculina corallasia
. Skeletal eroding band is the first recorded disease of coral
s that is caused by a protozoan, and the first caused by a eucaryote – most are caused by bacteria
. For example, black band disease is caused by microbial mat
s of variable composition, and White pox disease
by the bacterium Serratia marcescens
.
H. corallasia is a sessile unicellular organism that secretes a bottle-like housing called a lorica
(Latin
for cuirass
, flexible body armor), that is anchored to a surface and into which the cells retract when disturbed. When a mature individual cell division
divides, it produces a pair of worm-like larva
e 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 polyp
s. The discarded loricae of the "parent" H. corallasia cells remain, leaving the distinctive spotted region in the wake of the living black band.
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. 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.
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s that appears 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
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s, and is also found in the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
.
So far one agent has been clearly identified, the sessile
Sessility (zoology)
In zoology, sessility is a characteristic of animals which are not able to move about. They are usually permanently attached to a solid substrate of some kind, such as a part of a plant or dead tree trunk, a rock, or the hull of a ship in the case of barnacles. Corals lay down their own...
heterotrich
Heterotrich
The heterotrichs are a class of ciliates. They typically have a prominent adoral zone of membranelles circling the mouth, used in locomotion and feeding, and shorter cilia on the rest of the body. Many species are highly contractile, and are typically compressed or conical in form...
(ciliate
Ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...
) protozoan Halofolliculina corallasia
Halofolliculina corallasia
Halofolliculina corallasia is a heterotrich ciliate identified as a cause of the syndrome called Skeletal Eroding Band . It is the first coral disease pathogen that is a protozoan as well as the first known to be an eucaryote; all others identified are bacteria...
. This makes SEB the first coral disease known to be caused by a protozoan or any eucaryote. When H. corallasia divides
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
, the daughter cells move to the leading edge of the dark band and produce a "house" called a lorica
Lorica (biology)
In biology, a lorica is a shell-like protective outer covering, often reinforced with sand grains and other particles that some protozoans and loricifera metazoans secrete. Usually it is tubular or conical in shape, with a loose case that is closed at one end. An example is the protozoan genus...
. To do this, they drill into the coral's limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
, killing the coral polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...
s in the process.
A disease with very similar symptoms has been found in the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
, but has been given a different name as it is caused by a different species in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Halofolliculina and occurs in a different type of environment.
Symptoms and history of discovery
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. The spotted area distinguishes skeletal eroding band from black band diseaseBlack band disease
Black band disease is characterized by complete coral tissue degradation due to a pathogenic microbial consortium that appears as a dark red or black migrating microbial mat. The mat is present between apparently healthy coral tissue and freshly exposed coral skeleton.-Appearance:Black Band disease...
, which also forms an advancing black band but leaves a completely white dead area behind it.
Skeletal eroding band was first noticed in 1988 near Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
and then near Lizard Island
Lizard Island National Park
Lizard Island is a national park on the Great Barrier Reef in Queensland , 1624 km northwest of Brisbane and part of the Lizard Island Group that also includes Palfrey Island.-Geology:...
in Australia's Great Barrier Reef
Great Barrier Reef
The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
, but was regarded as a gray variant of black band disease, as were instances off Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
in 1990. Surveys in 1994 in and around the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
first identified the condition as a unique disease. It is now considered the commonest disease of corals in the Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s, especially in warmer or more polluted waters.
The spread of the disease across an infected coral has been measured at 2 millimetre (0.078740157480315 in) in the Red Sea and 2 to 3 mm (0.078740157480315 to 0.118110236220472 in) around the Great Barrier Reef. Corals of the families and Acroporidae
Acroporidae
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...
and especially Pocilloporidae
Pocilloporidae
The Pocilloporidae is a family of corals in the phylum Cnidaria occurring in the Pacific and Indian Oceans....
are most vulnerable. A study in 2008 found that skeletal eroding band spread at about 2 millimetre (0.078740157480315 in) per day in colonies of Acropora muricata, eventually wiping out 95% of its victims. However, experiments showed that the disease easily infested already-dead areas of corals but did not attack undamaged corals.
Agent identified
So far one agent has been identified, the folliculinid ciliateCiliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...
protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n Halofolliculina corallasia
Halofolliculina corallasia
Halofolliculina corallasia is a heterotrich ciliate identified as a cause of the syndrome called Skeletal Eroding Band . It is the first coral disease pathogen that is a protozoan as well as the first known to be an eucaryote; all others identified are bacteria...
. Skeletal eroding band is the first recorded disease of coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s that is caused by a protozoan, and the first caused by a eucaryote – most are caused by bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. For example, black band disease is caused by microbial mat
Microbial mat
A microbial mat is a multi-layered sheet of micro-organisms, mainly bacteria and archaea. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces but a few survive in deserts. They colonize environments ranging in temperature from –40°C to +120°C...
s of variable composition, and White pox disease
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...
by the bacterium Serratia marcescens
Serratia marcescens
Serratia marcescens is a species of Gram-negative, rod-shaped bacterium in the family Enterobacteriaceae. A human pathogen, S. marcescens is involved in nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections and wound infections, and is responsible for 1.4% of...
.
H. corallasia is a sessile unicellular organism that secretes a bottle-like housing called a lorica
Lorica (biology)
In biology, a lorica is a shell-like protective outer covering, often reinforced with sand grains and other particles that some protozoans and loricifera metazoans secrete. Usually it is tubular or conical in shape, with a loose case that is closed at one end. An example is the protozoan genus...
(Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for cuirass
Cuirass
A cuirass is a piece of armour, formed of a single or multiple pieces of metal or other rigid material, which covers the front of the torso...
, flexible body armor), that is anchored to a surface and into which the cells retract when disturbed. When a mature individual cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
divides, it produces a pair of worm-like larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e that settle on undamaged coral just ahead of the black band. There each daughter cell secretes
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...
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
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
and kill the polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...
s. The discarded loricae of the "parent" H. corallasia cells remain, leaving the distinctive spotted region in the wake of the living black band.
Similar disease in Caribbean
A survey in the Caribbean SeaCaribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
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
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Halofolliculina. 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.