''Marteilia'' is a
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 ...
n genus of organisms that are
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s of
bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
s. It causes QX disease in
Sydney rock oyster
''Saccostrea glomerata'', is an oyster species belonging to the family Ostreidae.MolluscaBase eds. (2022). MolluscaBase. Saccostrea Dollfus & Dautzenberg, 1920. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/ ...
s and Aber disease in
European flat oyster
European, or Europeans, or Europeneans, may refer to:
In general
* ''European'', an adjective referring to something of, from, or related to Europe
** Ethnic groups in Europe
** Demographics of Europe
** European cuisine, the cuisines of Europe a ...
s. After being infected by ''Marteilia'', bivalves lose
pigmentation
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
in their
viscera
In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...
l tissue and become
emaciated
Emaciation is defined as the state of extreme thinness from absence of body fat and muscle wasting usually resulting from malnutrition.
Characteristics
In humans, the physical appearance of emaciation includes thinned limbs, pronounced and protrud ...
(Carrasco, Green, & Itoh, 2015).
History
In the late 1960s and early 1970s, there was a huge decline in European flat oyster (''Ostrea edulis'') population in
Brittany
Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo language, Gallo: ''Bertaèyn'' ) is a peninsula, Historical region, historical country and cultural area in the west of modern France, covering the western part of what was known ...
, France. This had a huge socioeconomic impact in Europe. ''
Marteilia refringens'' was discovered to be the cause of this decline in oyster (Grizel et al., 1974). Around the same time, ''
Marteilia sydneyi
''Marteilia'' is a protozoan genus of organisms that are parasites of bivalves. It causes QX disease in Sydney rock oysters and Aber disease in European flat oysters. After being infected by ''Marteilia'', bivalves lose pigmentation in their visc ...
'' was also found to be causing mortalities in Sydney rock oyster (''Saccostrea glomerate'') in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
(Perkins & Wolf, 1976).
There has been some success in breeding strains of Sydney rock oyster that are resistant to Marteilia ('QX disease').
Morphology
''Marteilia'' has a very peculiar morphology. The outermost cell is the primary cell. Within the primary cell, there is a
nucleus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
*Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucle ...
and between 3 and 16 secondary cells. Within a secondary cell, there is a nucleus and between 1 and 6
spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s. Within each spore, there is a nucleus and another spore, which has yet another nucleus and spore within. This spore within a spore within a spore is termed a