''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
parasites 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 oysters. After being infected by ''Marteilia'', bivalves lose
pigmentation in their
visceral tissue and become
emaciated (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, France. This had a huge socioeconomic impact in Europe. ''
Marteilia refringens
''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 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