''Halofolliculina corallasia'' is a species of

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 ...

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s identified as a cause of the syndrome called skeletal eroding band (SEB). It is the first

coral disease 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 beco ...

pathogen that is a

protozoan Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

as well as the first known to be a

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

; all others identified are

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

. Like other members of the folliculinid

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

, ''H. corallasia'' is

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

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

polykinetid The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s, groups of

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

that work in groups to produce a current that draws food into the "mouth". This species is so far the only known agent causing skeletal eroding band, the most common disease of

coral 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 sec ...

s in the

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

and

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

s, and also found in the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

. A very similar disease was later discovered in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, but is caused by a different species of the same

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

and occurs in a different type of environment.

Description

''Halofolliculina corallasia'' was first observed in reefs near Motupore Island in

Bootless Inlet Bootless Inlet or Bootless Bay is a body of water in south-eastern Papua New Guinea, approximately southeast of Port Moresby. There are four islands in the bay: Motupore Island, Loloata Island, Manunouha Island, and Bunamotu Island. A barrier reef ...

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

in 1988, and named in 2001. The species name ''corallasia'' is a combination of "coral" and the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word ''lasios'' (λάσιος), which means "densely overgrown". ''H. corallasia'' is a member of the

group of

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

ns. Ciliates are among the most complex of single-celled

organisms, distinguished by three characteristics. First, it reproduces both by

cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

(splitting one cell into two) and by

conjugation Conjugation or conjugate may refer to: Linguistics * Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics * Complex conjugation, the chang ...

, in which two organisms temporarily join in order to swap DNA. Second, it has two

cell nuclei The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, h ...

. The larger, called the "macronucleus", carries out the normal work of the cell by

transcribing Transcription in the linguistic sense is the systematic representation of spoken language in written form. The source can either be utterances (''speech'' or ''sign language'') or preexisting text in another writing system. Transcription shoul ...

DNA into

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

, which is used to control the cell's functions. The smaller "micronucleus" is used only for reproducing the organism by cell division and by conjugation. And third, it has

at some stage in its life cycle. Heterotrichs, which are among the largest protozoans, have a spiral of polykinetids around their "mouths". These are groups of

that work in groups to produce a current that draws food into the "mouth". Members of the heterotrich family Folliculinidae are

, enclosing the rear ends in a lorica (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for

cuirass A cuirass (; french: cuirasse, la, coriaceus) is a piece of armour that covers the torso, formed of one or more pieces of metal or other rigid material. The word probably originates from the original material, leather, from the French '' cuira ...

, flexible body armor) that is anchored to a surface, and into which the cells retract when disturbed. The mouth is flanked by a pair of wing-like projections that are fringed with polykinetids. ''H. corallasia'' is smaller than other members of the same genus, having a flask-shaped lorica typically 220 µm long and 95 µm wide, and "wings" that are 175 to 200 µm long when fully extended. Its lorica, which is dark gray or black and made of a

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

-like substance, has flaps that close its opening when the cell is retracted.

Skeletal Eroding Band

Skeletal Eroding Band, the most common disease of corals in the

and

s and also found in the

, is the first recorded disease of

s that is caused by a protozoan, and the first caused by a

– most are caused by

. The disease is visible as a black band that slowly advances over corals, leaving dead coral in its wake. It is spread by cell division of ''Halofolliculina corallasia'', which produces a pair of worm-like

larva A larva (; plural larvae ) 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. The ...

e that settle on undamaged coral just ahead of the black band. There each 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 A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

and kill the polyps. The discarded loricae of the "parent" ''H. corallasia'' cells remain, leaving a spotted region in the wake of the living black band. This distinguishes Skeletal Eroding Band from

Black band 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 expo ...

, which leaves a completely white dead area behind it. ''H. corallasia'' is the first protozoan and the first

that is known to cause a disease in corals. A survey in the

conducted in 2004 and published in 2006 reported a disease with very similar symptoms as SEB, 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

, '' Halofolliculina''. A follow-up analysis noted that the Caribbean infestations were most common in oceanic waters, while those in the Indian and Pacific Oceans were more prevalent in coastal waters. Its authors therefore gave this new manifestation the name "Caribbean ciliate infection".

References

{{Taxonbar, from=Q15050695 Heterotrichea Coral diseases Coral reefs Protists described in 2001 Ciliate species