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Paramyxea
The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecular trees, which place them near the base of the Cercozoa. Both produce spores without the complex structures found in similar groups (such as polar filaments or tubules). Haplosporid spores have a single nucleus and an opening at one end, covered with an internal diaphragm or a distinctive hinged lid. After emerging, it develops within the cells of its host, usually a marine mollusc or annelid, although some infect other groups or freshwater species. The trophic cell is generally multinucleated. Paramyxids develop within the digestive system of marine invertebrates, and undergo internal budding to produce multicellular spores. A 2009 study concluded that ''Haplosporidium'' species form a paraphyletic group and that the taxonomy of the hap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marteilia
''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 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'' was discovered to be the cause of this decline in oyster (Grizel et al., 1974). Around the same time, '' Marteilia sydneyi'' was also found to be causing mortalities in Sydney rock oyster (''Saccostrea glomerate'') in Australia (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 primar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multinucleate
Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinated, synchronous manner where all nuclei divide simultaneously or asynchronously where individual nuclei divide independently in time and space. Certain organisms may have a multinuclear stage of their life cycle. For example, slime molds have a vegetative, multinucleate life stage called a plasmodium. Although not normally viewed as a case of multinucleation, plant cells share a common cytoplasm by plasmodesmata, and most cells in animal tissues are in communication with their neighbors via gap junctions. Multinucleate cells, depending on the mechanism by which they are formed, can be divided into "syncytia" (formed by cell fusion) or "coenocytes" (formed by nuclear division not being followed by cytokinesis). A number of dinoflagellat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |