Reductions and new inventions dominate oogenesis of Strepsiptera (Insecta)

Jürgen Büning
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引用次数: 13

Abstract

The endoparasitic life of strepsipterans (Insecta), especially neotenic females, reduces to a great extent external and internal organs. Light and electron microscopic investigation of ovaries of Elenchus tenuicornis (Kirby) confirms the following: (1) somatic tissues of ovaries are totally reduced, with the exception of some cells surrounding germ cell clusters; (2) a previtellogenic growth phase of oocytes is reduced; (3) nurse cells remain diploid and their membranes degenerate at the onset of vitellogenesis; (4) vitellogenesis is reduced, vitellin and fat vacuoles contribute only 50% to the final egg volume; and (5) chorionogenesis is reduced to a vitellin membrane. However, some features of normal development remain, allowing classification of the ovary type as polytrophic meroistic: (1) germ cells undergo synchronized, incomplete divisions, following the 2n rule, where all former intercellular bridges become localized in one cystocyte, while the other has none; and (2) only one cell is determined as the oocyte, all other cystocytes serve as nurse cells and the surrounding somatic cells transform into follicular cells. Novel events in oogenesis of strepsipterans include fission of clusters during the phase of cluster mitoses, and protection of oocyte nuclei, while nurse cell nuclei degenerate in the same cytoplasm.

链翅目(昆虫亚目)卵发生主要是减少和新发明
链虫(昆虫科)的内寄生寿命,尤其是幼年雌性,在很大程度上减少了外部和内部器官。光镜和电镜观察证实:(1)除生殖细胞群周围的部分细胞外,卵巢的体细胞组织全部减少;(2)卵母细胞形成前的生长期减少;(3)卵黄发生时,乳母细胞仍为二倍体,膜退化;(4)卵黄发生减少,卵黄蛋白和脂肪液泡仅占最终蛋体积的50%;(5)绒毛膜生成被还原为卵黄蛋白膜。然而,一些正常发育的特征仍然存在,允许将卵巢类型分类为多营养分生类型:(1)生殖细胞进行同步的,不完全的分裂,遵循2n规则,其中所有先前的细胞间桥都定位在一个囊细胞中,而另一个则没有;(2)只有一个细胞被确定为卵母细胞,其他所有的囊细胞作为护理细胞,周围的体细胞转化为滤泡细胞。链霉菌卵发生的新事件包括在团簇有丝分裂阶段的团簇裂变和卵母细胞核的保护,而护理细胞核在同一细胞质中退化。
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