Urospora ovalis – coelomic gregarine from the White Sea polychaete Travisia forbesii
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| Year of publication | 2014 |
| Type | Conference abstract |
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| Description | Urosporids parasitize wide range of animals (echinoderms, annelids and ascidians) inhabiting coelom, intestine etc. Translocation within host causes changes in morphology and motility mode together with a structural modification of cortical zone. Particularly, gregarines of the family Urosporidae exhibit considerable morphological plasticity. This family comprises representatives inhabiting various host biotopes and showing different types of motility: gliding movement (Urospora travisiae), metaboly (Urospora ovalis) or peristalsis (Pterospora floridiensis), as well as immotile species (Urospora chiridotae, Lithocystis spp. and Gonospora spp.). Trophozoites of U. ovalis are spindle-shaped and lack any signs of cell polarity and show metabolic activity. TEM confirms that trophozoites are covered by a trimembrane pellicle. It forms numerous longitudinal epicytic folds that extend from one to another cell pole. In the apical part of these folds, two or three apical arcs can be poorly observed between the plasma membrane and the external cytomembrane. Just beneath the internal cytomembrane, there is a single rod of electron-dense material situated. Subjacent fibrillar layer can be found under pellicle. Micropores were found in between epicytic folds. In the region of cell constriction cortical zone forms superfolds. Superfolds are also covered by epicytic folds. Cytoplasm of gregarines subdivided into two regions: cortical zone with various filamentous structures, and endoplasm containing nucleus, majority of cellular organelles, amylopectin granules and other inclusions. New SSU sequences of U. ovalis belongs to the Lecudinoidea clade, however they affiliate not with other coelomic urosporids (Pterospora spp.) but with intestinal lecudinids. Our new obtained data confirm the theory on independent and parallel origin of coelomic gregarines. We also assumed parallel evolution of cell cortex morphological adaptations as a response to parasitism in different host biotopes. |
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