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Concept
Perkinsus marinus
Résumé
Perkinsus marinus is a species of alveolate belonging to the phylum Perkinsozoa. It is similar to a dinoflagellate. It is known as a prevalent pathogen of oysters, causing massive mortality in oyster populations. The disease it causes is known as dermo or perkinsosis, and is characterized by the degradation of oyster tissues. The genome of this species has been sequenced.
The species originally was named Dermocystidium marinum by Mackin, Owen and Collier in 1950.
P. marinus is a protozoan of the protist superphylum Alveolata, the alveolates. Its phylum, Perkinsozoa, is a relatively new taxon positioned between the dinoflagellates and the Apicomplexa, and is probably more closely related to the former. P. marinus is the type species of the genus Perkinsus, which was erected in 1978. When first identified in 1950, it was mistaken for a fungus.
The protist is about 2 to 4 μm long. The zoospore has two flagella, which it uses to swim in its marine habitat. It is ingested by its mollusc host, which is often an oyster of the genus Crassostrea. It then becomes a trophozoite, which proliferates in the tissues of the host. P. marinus often infests the hemocytes, cells in the blood of the host, analogous to malaria in vertebrates. It is also often seen in the cells of the intestine, connective tissues, digestive glands, and gills. Inside the cell, the trophozoite produces a vacuole that displaces the cell nucleus. The infested cell is referred to as a signet ring cell, because it is spherical and filled with the rounded vacuole, and resembles a signet ring. The mature trophozoite undergoes binary fission and up to 16 immature trophozoites are produced. These stay in the host animal and infest its tissues, or are released into the water in the feces or from a dead host. Trophozoites in the water mature and release flagellated zoospores.
The most economically important host is the eastern oyster (Crassostrea virginica). The parasite is also common in C. corteziensis, and the species C. rhizophorae, C. gasar, and C.
Source officielle
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