Gametocyst and oocysts morphology of Urospora travisiae, an extraordinary eugregarine 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, few detailed studies on terrestrial and marine gregarine species dealing with their architecture exist. We present new data on morphology of gametocysts and oocysts found in marine polychaete Travisia forbesii. In body cavity brown bodies comprising gametocysts of Urospora travisiae were found. Gametocysts, whitish, round in shape surrounded with flattened coelomocytes. Envelope is thick and consists of numerous layers and hyaline cover. Under envelope, oocysts can be observed using light or electron microscopy. Spindle-shaped oocysts are heteropolar with a transparent conical collar situated at one end and elongated thin curved tail. Under SEM oocyst surface appears smooth. Damaged oocyst walls reveal 8 longitudinally oriented sporozoites. Cross-sections for TEM confirm presence of 4 sporozoites at both oocyst poles, with their posterior ends interdigitating in the middle of oocyst and apical ends oriented towards oocyst poles. Sporozoites appear banana-shaped and covered with a typical three-layered pellicle underlined by 20 longitudinal microtubules. Sporozoites possess a large nucleus. On longitudinal sections, anterior third is packed with rhoptries and micronemes. The nucleus is localized in the middle of the cell. Sporogony in different oocysts is asynchronous. Our light microscopic observations agree with original description of U. travisiae oocysts published by V.A. Dogiel, however, this study provides completely new data on gametocyst, oocyst and sporozoite architecture in U. travisiae. |
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