The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.

中文翻译：

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Mithracidae（甲壳纲，十足纲，Brachyuura，Majoidea）成年卵巢周期的形态和超微结构

发育和卵黄生产过程中卵巢的超微结构在​​Brachyura和Majoidea中尤其鲜为人知。在这里，我们描述了来自三个不同属的四个Mithracidae物种的成年卵巢周期的组织学，组织化学和超微结构：hispidus，Mithrax tortugae，Mithraculus钳和Omalacantha bicornuta。所有物种均显示出相似的卵巢发育和卵黄发生模式。宏观上，我们检测到卵巢发育的三个阶段：基本阶段（RUD），发育阶段（DE）和成熟阶段（MAT）；但是，在组织学和超微结构分析中，我们确定了发展的四个阶段。在内源性卵黄形成过程中，处于RUD阶段的卵母细胞具有嗜碱性细胞质，充满了扩张的粗糙内质网。网状腔在不同的发育阶段显示出许多颗粒状至电子致密的物质。高尔基复合体仅在RUD阶段观察到，并负责释放融合到内源性或未成熟卵黄囊泡的囊泡。在早期DE阶段，油膜肿块在皮质处显示出许多包被的和内吞的囊泡。内吞囊泡与内源卵黄融合形成外源或成熟的卵黄囊泡，始终被膜包围，表征外源卵黄发生。外源卵黄囊泡包含糖蛋白，仅显示中性多糖。在DE晚期，仍会发生内吞作用，但是内源蛋黄的数量减少而外源蛋黄的数量增加。DE晚期的特征是微绒毛中绒毛膜开始产生。MAT阶段与晚期DE相似，但内源卵黄仅限于少数细胞质区域，卵浆充满外源卵黄，而卵囊中几乎没有包被的囊泡。在MAT阶段，绒毛膜完全形成并显示出两个电子致密层。就卵母细胞成熟过程中卵黄囊泡的组成，排列和增加而言，所研究物种的卵巢发育与鲜为人知的Majoidea有许多相似之处。主要区别在于卵黄发生过程，其中卵黄形成未成熟，而没有线粒体的直接参与，而是在内生阶段内质网的参与。oolemma的包被囊泡很少。在MAT阶段，绒毛膜完全形成并显示出两个电子致密层。就卵母细胞成熟过程中卵黄囊泡的组成，排列和增加而言，所研究物种的卵巢发育与鲜为人知的Majoidea有许多相似之处。主要区别在于卵黄发生过程，其中卵黄形成未成熟，而没有线粒体的直接参与，而是在内源性阶段内质网的参与。oolemma的包被囊泡很少。在MAT阶段，绒毛膜完全形成并显示出两个电子致密层。就卵母细胞成熟过程中卵黄囊泡的组成，排列和增加而言，所研究物种的卵巢发育与鲜为人知的Majoidea有许多相似之处。主要区别在于卵黄发生过程，其中卵黄形成未成熟，而没有线粒体的直接参与，而是在内生阶段内质网的参与。卵母细胞成熟过程中卵黄囊泡的排列和增加。主要区别在于卵黄发生过程，其中卵黄形成未成熟，而没有线粒体的直接参与，而是在内生阶段内质网的参与。卵母细胞成熟过程中卵黄囊泡的排列和增加。主要区别在于卵黄发生过程，其中卵黄形成未成熟，而没有线粒体的直接参与，而是在内生阶段内质网的参与。