Oocysts and gametocyst morphology of extraordinary coelomic gregarine Urospora travisiae from marine polychaete
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| Year of publication | 2014 |
| Type | Conference abstract |
| MU Faculty or unit | |
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| Description | Apicomplexans represent successful group of unicellular parasites of vertebrates and invertebrates. They possess complicated life cycle, with sporogony, merogony and gametogony. The LC of eugregarines is characterized by a lack of merogony, but a presence of syzygy and gametocyst. Inside the gametocyst gametogony, fusion of gametes and sporogony take place. Way of gametocyst excystation and oocyst morphology are considered as key features in gregarine taxonomy, several detailed studies on terrestrial and marine gregarine species dealing with their architecture exist so far. We present our investigations on fine structure of gametocysts and oocysts found in marine polychaete Travisia forbesii. In the body cavity brown bodies comprising several white spheres, which were identified as gametocysts of Urospora travisiae, were found. Gametocysts are surrounded with several layers of flattened coelomocytes. Thick envelope of gametocyst consists of numerous membranous layers and thick hyaline layer with a lot of fibrils. Under this envelope, number of oocysts can be seen. Heteropolar spindle-shaped oocyst possesses a transparent conical collar situated at one end, and elongated, thin and curved tail. Under the SEM, the oocyst surface appears smooth. TEM reveals the presence of hair-like coating on oocyst surface. Occasionally, oocyst wall ruptures and 8 sporozoites can be seen. The cross-sections confirm the presence of 4 sporozoites at the both poles, with their apical ends oriented towards the oocyst’s poles. Sporozoites appear as banana-shaped and covered with a typical pellicle. Pellicle is underlined by 20 longitudinal microtubules. In the middle region sporozoites possess a large nucleus. Rhoptries and micronemes localize in anterior part of cell. Formation of sporozoites in different oocysts is asynchronous. This study provides completely new morphological data on gametocyst, oocyst and sporozoite of marine eugregarine U. travisiae. |
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